LIBRARY 
 
 UNIVERSITY OF CALIFORNIA. 
 
 Deceived 
 Accessions No.V'<w. Class No. 
 
 i 
 
K . 
 
 A TEXT-BOOK 
 
 OF 
 
 ORDNANCE AND GUNNERY. 
 
 PREPARED' FOR THE USE OF CADETS OF THE 
 U. S. MILITARY ACADEMY. 
 
 BY 
 
 CAPTAIN LAWRENCE L. BRUFF, 
 
 ORDNANCE DEPARTMENT, U. S. ARMY,' 
 Instructor of Ordnance and Gunnery at the U. S. Military Academy^ 
 
 FIRST EDITION. 
 
 FIRST THOUSAND. 
 
 
 Of TBGi 
 
 'jmiB 
 
 NEW YORK: 
 
 JOHN WILEY & SONS. 
 
 LONDON: CHAPMAN & HALL, LIMITED. 
 
 1896. 
 
Copyright, 1896, 
 
 BY 
 LAWRENCE L. BRUFF. 
 
 ROBBRT DRUMMOND, ELECTROTYPER ANP PRINTER, NEW YORK. 
 
THE present text-book has been compiled with the object 
 of presenting as clearly as possible the elementary principles 
 of the course in Ordnance and Gunnery as taught at the 
 Military Academy, and of so arranging it that it can be 
 readily used for recitations in the section-room. For this 
 purpose it has been divided into separate subjects, each as 
 well denned as possible. In its preparation I -have followed 
 the lines laid down by my predecessor Capt. Henry Met- 
 calfe, U. S. A., retired, from whose labors in the same field I 
 have derived the greatest assistance. I am also under many 
 obligations to those who have kindly criticised and cor- 
 rected my work in many important particulars, and especi- 
 ally to Colonel Buffington, Captains Smith, Blunt, Birnie, 
 Mitcham and Crozier, Ordnance Department, and to Mr. 
 W. R. Quinan of the California Powder Company. 
 
 Lieut. Babbitt, Ordnance Department, my assistant at 
 the Military Academy, has made many valuable criticisms 
 and suggestions which have added greatly to the clearness 
 of the work. 
 
 WEST POINT, March 10, 1896. 
 
 iii 
 
TABLE OF CONTENTS. 
 
 PAGE 
 
 CHAPTER I. 
 
 GUNPOWDERAND INTERIOR BALLISTICS* I 
 
 CHAPTER II. 
 HIGH EXPLOSIVES AND SMOKELESS POWDERS.^ 105 
 
 CHAPTER III. 
 GUNS 136 
 
 CHAPTER IV. 
 PROJECTILES AND ARMOR 279 
 
 CHAPTER V. 
 FUZES and PRIMERS 328 
 
 CHAPTER VI. 
 EXTERIOR BALLISTICS '. 347 
 
 CHAPTER VII. 
 ARTILLERY CARRIAGES ; THEORY OF RECOIL , 389 
 
 CHAPTER VIII. 
 POINTING ; PROBABILITY OF FIRE 466 
 
 CHAPTER IX. 
 PORTABLE ARMS 528 
 
 CHAPTER X. 
 
 MACHINE AND RAPID-FIRE GUNS 589 
 
 INDEX 639 
 
[IHU7BRSITT] 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 CHAPTER I. 
 GUNPOWDER AND INTERIOR BALLISTICS. 
 
 GUNPOWDER. 
 
 1. Composition Manufacture. 
 
 COMPOSITION. Gunpowder is a mechanical mixture of 
 nitre, charcoal, and sulphur, in the proportions of 75 parts 
 nitre, 15 charcoal, and 10 sulphur. 
 
 The nitre furnishes the oxygen to burn the charcoal ancf 
 sulphur. The charcoal is the principal combustible body,, 
 and the smphur gives density to the grain and lowers its 
 point of ignition. 
 
 The nitre is purified by solution in water and crystalliza- 
 tion, the sulphur by distillation, and the charcoal is care- 
 fully prepared to make it as uniform as possible. 
 
 The distinguishing characteristic of charcoal is its color, 
 being brown when prepared at a temperature up to 280 
 Cent., from this to 340 red, and beyond 340 black. 
 
 Brown charcoal is now generally used for powder. 
 
 MANUFACTURE. The operations are : 
 
 r. Pulverizing, mixing, and incorporating the ingre- 
 dients. 
 
 2. Compressing this mixture to give it a proper density. 
 
 3. Dividing the dense mass into grains. 
 
 4. Finishing the grains. 
 
 Pulverizing and Mixing. The nitre is in fine crystals 
 when received; the sulphur is rolled in an iron barrel with 
 
TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 FIG. i. 
 
 iron balls ; and the charcoal also, or the latter may be 
 ground in a mill 
 
 The ingredients are mixed by hand or by machine. 
 
 Incorporating. To make the mixture thorough, the above 
 
 composition is moistened and incorporated in a wheel mill. 
 
 This mill consists of a pair of heavy cast-iron cylindrical 
 
 rollers running in a circular trough (Fig. i). By their 
 
 action they grind the products 
 together, and give a thorough 
 mixture. 
 
 This is the most important 
 operation in the manufacture, 
 and if not well done no subse- 
 quent operation can remedy it. 
 
 Pressing. The mill-cake which 
 comes from the " wheel mill " is 
 broken up, moistened, and placed, 
 in layers about 2 inches thick, 
 under a hydraulic press. The 
 
 layers are reduced to a thickness of about i inch and be- 
 come very dense and hard, and this is called " press-cake." 
 
 Graining. In ordinary powders, the press-cake is broken 
 up into grains of various sizes. The object of this is to 
 increase the surface of combustion, and to regulate it 
 according to the gun in which it is to be used. The grain- 
 ing is done by rollers acting on the press-cake, and the 
 grains are afterwards assorted with sieves. 
 
 Glazing. To remove the sharp angles, and give uniform 
 density to the surface, the grains are placed in a wooden 
 barrel revolving on its axis. They are thus made to rub 
 against each other, and accomplish, by their mutual attrition, 
 the objects mentioned. 
 
 Drying and Dusting. The excess of moisture in the 
 powder is now removed by a current of warm, dry air, and 
 the dust which has been formed on the grains is removed 
 by passing them through a revolving sieve. 
 
 Blending and Marking. Different lots of the same kind 
 of powder are mixed, to overcome, as much as possible, 
 irregularities of manufacture. In our service the powder 
 
GUNPOWDER AND INTERIOR BALLISTICS. 
 
 is packed in loo-lb. barrels and marked with certain letters, 
 as I. K. B., E. V. X., etc., the first two letters denoting the 
 kind of powder, or its use, and the third letter the lot. 
 
 In foreign services the letters indicate the use directly : 
 as, R. F. G., rifle fine grain ; P., pebble ; etc. 
 
 Government powder is purchased by contract. 
 
 2. Specific Gravity and Gravimetric Density. 
 
 THE SPECIFIC GRAVITY, or actual density, of gunpowder, 
 like that of any solid body, is the weight of a given volume 
 referred to that of an equal volume of water as unity. 
 Since water dissolves the nitre, mercury is used instead. 
 The instrument employed is called a mercury densimeter, 
 and consists of a glass globe a, Fig. 
 2, connected with an air-pump by 
 a rubber tube c. 
 
 The globe is exhausted of air 
 and its lower end immersed in 
 mercury in the dish d. 
 
 The mercury is allowed to rise 
 till it fills the globe and stands at 
 a certain height in the glass tube 
 . The globe is then detached 
 full of mercury and weighed. It 
 is then emptied, and a given 
 weight of powder placed in it, re- 
 turned to its original position, the 
 air again exhausted, and mercury 
 allowed to enter till it stands at 
 the same height as before ; the 
 globe with its mercury and pow- 
 der again detached and weighed. 
 The difference of the two weights 
 of mercury gives the weight of the mercury whose volume 
 is equal to that of the powder. 
 
 Let a = the weight of the powder; 
 
 P = the weight of the vessel and mercury; 
 
 P = the weight of the vessel, mercury, and powder ; 
 
 FIG. 2. 
 
4 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 S = the specific gravity of the mercury ; 
 $ = the specific gravity of the powder. 
 
 Then P' a =. the weight of the mercury and vessel 
 when the latter is partially filled with 
 powder ; 
 
 p P' -|- a = the weight of the volume of mercury 
 displaced by the powder. 
 
 Since the weights of equal volumes are proportional to 
 the densities, we have 
 
 a : P - P' + a : : S : S, 
 
 or 
 
 aS 
 
 The density varies between 1.68 and 1.85. 
 
 GRAVIMETRIC DENSITY is the name given to the density of 
 powder when the spaces between the grains are considered. 
 That is, it is the specific gravity of the powder in its natural 
 form. Suppose we have a solid piece of powder weighing 
 i Ib. If we determine its specific gravity, we will obtain a 
 value d given by formula (i). Suppose the same powder 
 broken up into grains. Its weight will not change, but its 
 volume will be greater than before. If we determine its 
 specific gravity under these circumstances, by comparing its 
 weight with the weight of an equal volume of water, we have 
 a particular value, called the " gravimetric density." 
 
 It is evident that the same powder will have only one 
 value for tf, but may have many values for gravimetric den- 
 sity according to its granulation. If the shape of the grain 
 is changed, the same weight of powder will occupy a greater 
 or less space according as the spaces between the grains are 
 greater or less. 
 
 Hence we say that gravimetric density measures the ca- 
 pacity of powder to pack, or measures the spaces between 
 the grains. 
 
 A cubic foot of powder is usually taken in determining 
 
GUNPOWDER AND INTERIOR BALLISTICS. 5 
 
 gravimetric density. A cubic foot of water weighs 62.425 
 Ibs. Hence we have 
 
 w 
 = 
 
 y denoting the gravimetric density, and w the weight of a 
 cubic foot of powder, y varies between 0.875 and i.oo. 
 
 The space actually occupied by the solid powder in a 
 Driven volume is determined as follows : 
 
 o 
 
 Let V = the total volume occupied by the powder; 
 
 v = the volume of the solid powder. 
 Since v6lumes are inversely as densities, we have 
 
 *=r ........ (3) 
 
 If Y = i-oo an d * '-8 (the ordinary values), we have 
 
 ....... (4) 
 
 That is, the volume occupied by the solid powder in a 
 charge is about .56 of the total volume of the charge. 
 
 3. Form of Grain. 
 
 Irregular Granulation. The processes of manufacture 
 are the same for all powders up to and including incorpo- 
 ration. 
 
 If the mill-cake be pressed into slabs, and these slabs 
 broken up into irregular grains by rollers, we have powders 
 of " irregular granulation." In our service the powders of 
 irregular granulation are : 
 
 (a) Small-arms poivder, used in the Springfield rifle and 
 carbine, and in small arms generally, and also as a bursting- 
 charge in field-shells. 
 
 (b) Mortar-powder, used in the 3.oo-inch wrought-iron rifle, 
 in the siege and sea-coast smooth-bore mortars, and in their 
 shells. 
 
 (c) Cannon-powder, used in the old 8- and lo-inch smooth- 
 bore guns. 
 
O TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 (d) Mammoth Powder, used in the 1 5-inch Rodman guns. 
 
 (e) I. K. Powder, used in the 3.2O-inch steel B. L. rifle,. 
 model ^7/1885, charge (3.50) Ibs. 
 
 All these powders may be regarded as having grains 
 which approach a sphere in shape, and whose mean radius 
 is determined as follows: 
 
 Let N = the number of grains in one pound of powder ; 
 r = the mean radius of the grain in inches ; 
 6 = the specific gravity of the powder. 
 The volume of one grain is 
 
 (5), 
 Its weight is (Michie, eq. i) 
 
 W= VSg', ........ (6) 
 
 g' being the weight of one cubic inch of water, or 
 
 62425 
 1728 ' 
 
 %nr*d X 62.425 . } 
 
 1728 
 
 Hence 
 
 and the weight of N grains is 
 
 N W = X 62.425 X^ ( 
 
 1728 
 
 ButNW = i. Hence 
 
 *7tr*d x 62.425 X N 
 
 1728 
 or 
 
 1.8766 
 
 Using this method, we find 
 
 2r = 0.04 small-arms powder ; 
 2r = 0.08 mortar powder ; 
 2r = 0.30 cannon powder; 
 2r = 0.75 mammoth powder; 
 2r = 0.24 I. K. powder. 
 
GUNPOWDER AND INTERIOR BALLISTICS. 
 
 -a 
 
 -a\ 
 
 Regular Granulation. Powders of regular granulation are 
 obtained by breaking up the mill-cake and pressing it be- 
 tween plates having depressions in them of regular shape, 
 such as a sphere or a pyramid. 
 
 Under this head we have the Dupont powders, viz.; 
 
 (a) The Hexagonal. The shape of the grains is that of 
 two hexagonal pyramids joined base to 
 
 base. The grains are connected by a thin 
 cake, which is broken off, and leaves a 
 rough surface at a, which facilitates ig- 
 nition. Used in the 8-inch converted rifle, 
 charge 35 Ibs. FIG. 3. HEXAGONAL. 
 
 (b) The Sphero-hexagonal, Fig. 4, which is the same as 
 
 the above, except that spheres are substi- 
 tuted for hexagonal pyramids. 
 
 This powder is now used for all the field 
 and siege guns and mortars. In the field 
 FIG. ^SPHERO- service it has replaced the I. K. powder used 
 HEXAGONAL. w ith the earlier model guns. 
 Molded Powder. This is made by reducing the mill-cake 
 to powder and pressing it into any required form, each grain 
 being made separately ; or a number of grains of powder of 
 irregular granulation may be compressed into a single large 
 grain ; the latter is also called concrete powder. Under 
 this head we have prismatic or brown powder, which is a 
 molded concrete powder made as above described. It is 
 called brown or cocoa powder from its color, which is due 
 to brown charcoal. 
 
 It is made in hexagonal prisms, Fig. 5, about I inch high 
 
 and 1.375 inches between opposite ^^^ 
 
 faces. Each prism is pierced by a 
 central hole parallel to the axis, and 
 about 0.40 inch in diameter. The 
 composition is generally given as 
 
 Nitre 81.5 per cent 
 
 Charcoal 15.5 per cent 
 
 Sulphur 3.0 per cent 
 
 FIG. 5. COCOA. 
 
 IOO.O 
 
8 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 It is a slow-burning powder, and is used in modern high- 
 power guns of large calibre. 
 
 4. Inspection and Proof of Powder History. 
 
 INSPECTION. The object is to see that the powder is 
 properly manufactured, and that it has certain required 
 qualities. 
 
 For small-arms powder 100 barrels are considered a lot, 
 and from them five barrels are taken, one pound of powder 
 from each barrel being selected for test. If the test is suc- 
 cessful, the lot is accepted. 
 
 For Granulation. All grains must pass through a sieve 
 with a mesh of 0.06 inch and none through a mesh of 0.03 
 inch. 
 
 Specific Gravity between 1.75 and 1.80 and gravimetric 
 density between 0.96 and i.oo. 
 
 Dust is detected by allowing a stream of powder to fall 
 rapidly two or three feet in a strong light. There must be 
 no dust. 
 
 Incorporation is tested by flashing 20 grains of powder on 
 a copper plate. There should be little residue, and no 
 globules of fuzed nitre on the plate. 
 
 Moisture is determined by exposing 1000 grains to a tem- 
 perature of 100 F. for 24 hours. The loss in weight should 
 be about 7 grains. 
 
 Capacity for absorbing moisture is tested by exposing 
 1000 grains to the vapor of water for 24 hours. The gain in 
 weight should be about 6 grains. 
 
 Fouling is tested by firing rapidly 100 rounds of rifle-ball 
 cartridges in series of 25 rounds each and weighing the rifle 
 after each series. In a moderately dry atmosphere the weight 
 of fouling from the 100 rounds should not exceed 15 grains. 
 
 For other powders the inspection will vary according to 
 the terms of the contract. 
 
 PROOF. The object of proving powder is to ascertain the 
 initial velocity it will impart to the projectile, the corre- 
 sponding pressure on the bore, and, for small arms, the 
 accuracy of the projectile. 
 
 The powder is always proved in the gun in which it is 
 
GUNPOWDER AND INTERIOR BALLISTICS. 9 
 
 to be used, and with service charges. The velocities and 
 pressures are measured with instruments to be described. 
 
 HISTORY. Gunpowder was first used in Europe early in 
 the fourteenth century, and in the form of powder or dust, 
 whence the name. The guns in which it was used were 
 weak, and the powder was suited to them, because it burned 
 slowly and gave low pressures. In the form of dust, how- 
 ever, it was difficult to load at the muzzle, as cartridges were 
 not used, and hence loading at the breech was introduced. 
 This failed because no gas-check could be devised that 
 would completely close the breech. As guns improved in 
 strength, better results were obtained by graining the pow- 
 der, but the grained powder became too strong for the guns, 
 and large guns were not made. No marked change in pow- 
 der was made until about 1860. 
 
 General Rodman, of the Ordnance Department, then 
 proposed to vary the size of the grain with the calibre, using 
 large-grained powder for large guns. He also advocated a 
 perforated powder, which was not used. His mammoth 
 powder, however, was adopted, and by an improvement in 
 the process of gun-construction, together with that of the 
 powder, he built smooth-bore guns up to 20 inches in calibre. 
 
 Following Rodman's plan, various forms of powder have 
 been adopted by other nations, the general idea being to so 
 modify the action that the gun will be strained less at the 
 beginning of the motion of the projectile, and more uni- 
 formly throughout the bore, than with the old powders. 
 The brown powder is the latest development of the old 
 nitrate powders. It has, however, many objections, and at 
 present smokeless powders are being developed, with the 
 prospect that they will supersede the others. 
 
 5. Combustion in Air Laws. 
 
 Explosion is the rapid conversion of gunpowder into 
 gases and solids with evolution of heat. It may be divided 
 into three parts, Ignition, Inflammation, and Combustion. 
 
 Ignition is the setting on fire of a part of the grain or 
 charge, and for this purpose a temperature of 300 C. is 
 required. 
 
10 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 Gunpowder may be ignited by electricity, by contact 
 with an ignited body, by friction, shock, or by chemical 
 reagents. 
 
 A gradual heat will decompose the powder by subliming 
 the sulphur, and the temperature of ignition will be raised 
 thereby. 
 
 Flame, owing to its slight density, will not ignite powder 
 readily. The time necessary for ignition will vary with 
 the condition of the powder. Thus damp powder ignites 
 less easily than dry ; a smooth grain less easily than a rough 
 one ; a dense grain less easily than a light one ; etc. 
 
 Powder is ordinarily ignited by a primer, by electricity, 
 or by contact with an ignited body. 
 
 Inflammation is the spread of the ignition from point to 
 point of the grain, or from grain to grain of the charge. 
 
 With small-grain powders, where the spaces between 
 grains are small, the time of inflammation is large as com- 
 pared with the time of combustion of a grain, but with 
 modern large-grain powders, the facilities for the spread of 
 ignition and the time of burning of the grain are so great, 
 that the whole charge is supposed to be inflamed at the 
 same instant, and the time of inflammation is not considered. 
 
 Combustion is the burning of the inflamed grain from the 
 surface of ignition inward or outward or both, as the case 
 may be. 
 
 LAWS. Experiment shows that powder burns in the air 
 according to the following laws : 
 
 1. In parallel layers, with uniform velocity, and the 
 velocity is independent of the cross-section burning. 
 
 2. The velocity of combustion varies inversely with the 
 density of the powder. 
 
 Hence if v denote the velocity of combustion, and 6 the 
 density of the powder, we have 
 
 (10) 
 
 the constant c depending on the nature of the powder. 
 
 3. The velocity decreases rapidly as the degree of moist- 
 ure in the powder increases. 
 
GUNPOWDER AND INTERIOR BALLISTICS. II 
 
 4. It increases with the amount of trituration of the in- 
 gredients, up to a certain limit. 
 
 5. For the same density, trituration, and moisture, the 
 greatest velocity of combustion is obtained with a powder 
 whose composition is 75 nitre, 15 charcoal, and 10 sulphur. 
 
 6. In air the actual velocity of combustion is from 0.4 to 
 0.6 inch per second. 
 
 7. The velocity varies with the pressure according to a 
 law which is expressed by the following formula of Sar- 
 rau: 
 
 ** 
 
 in which v is the velocity of combustion for the pressure 
 /, and v the velocity in open air corresponding to the at- 
 mospheric pressure p . 
 
 According to this formula, a powder which burns 0.6 
 inch per second in air would burn about 29 inches per 
 second in a gun .under a pressure of 35,000 Ibs. per square 
 inch. 
 
 6. Formula for Burning in Air of Grains of Different Shapes. 
 
 To deduce a formula for the amount of powder burned 
 at the time t y we proceed as follows : 
 
 The amount burned per unit weight or per unit volume 
 at any time / wijl evidently be a function of /, and may be 
 represented by <t>(t). Suppose 0(V) to be developed accord- 
 ing to the ascending powers of /, with constant coefficients, 
 which are to be determined. We may then write 
 
 + etc.), . . . . (12) 
 
 in which a, A, and /* are constants depending on the form of 
 the grain, and t is the total time of combustion of the grain, 
 and hence depends on its size. The negative sign is used be- 
 fore A. because the sign of this term is found to be negative 
 for all forms of grain in use. It is required to find values 
 for a, A, and // for all service grains. 
 
12 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 Spherical Grain. Let r be the radius of the grain ; 
 v the velocity of combustion ; 
 r the total time of combustion. 
 
 The original volume of the grain is f Trr*. At the end 
 of the time / the radial distance burned over is vt, and the 
 radius remaining unburned is r vt. Hence the volume 
 unburned at the end of / is f n(r z//) 3 . 
 The volume burned is then 
 
 |7rr 3 - ^n(r - */)', ...... (13) 
 
 or 
 
 But 
 
 *= ........ 05) 
 
 and substituting for - in (14) its value from (15), we have 
 
 (16) 
 
 The expression (16) is the actual volume burned at the 
 end of the time /. It is composed of two factors, the first 
 being the original volume of the grain, | nr 3 , and hence the 
 second factor must be the proportional part burned ; that is, 
 the amount burned per unit of volume, or per unit of weight, 
 in the time /, according as we consider volumes or weights, 
 and is denoted by <f>(i). Hence for this particular form of 
 grain we have 
 
 or 
 
 Comparing this with the general development in equation 
 (12), we see that 
 
 a = \=i w = 
 
GUNPOWDER AND INTERIOR BALLISTICS. 1$ 
 
 Since all powders of irregular granulation may be con- 
 sidered as spheres whose mean radii can be calculated by 
 equation (9), and since the hexagonal and sphero-hexagonai 
 may also be so considered, these values of a, A, and ^ apply 
 to ail such powders. 
 
 Values of #, A, and jw for Other Forms of Grain. By a 
 similar process we can find the values of a, A, and /* for all 
 service grains. These values are collected in the following 
 table. 
 
 Form of Grain. 
 
 a 
 
 A 
 
 n 
 
 Spherical ^ 
 
 ' 
 
 
 
 Cubical 
 
 a 
 
 I 
 
 I 
 
 Irregular f ' ' 
 
 
 
 3 
 
 granulation j 
 
 
 
 
 
 ! J-^-Lj, 
 
 * -f y + *y 
 
 xy 
 
 
 
 1 + * +y 
 
 i+-*-+y 
 
 Flat v 1t 
 
 I 1 2JC 
 
 IX -f X 9 
 
 X* 
 
 
 1 I *.* 
 
 I -f- 2* 
 
 1+2* 
 
 Flat, x y i 
 
 2 
 
 | 
 
 A 
 
 Pierced cylinder } 
 Pierced prism > 
 
 l4-ac 
 
 X 
 
 Q 
 
 
 
 
 
 Cocoa ) 
 
 
 i + x 
 
 
 Pierced cylinder; } 
 thickness of wall > 
 half of height 
 
 3, 
 
 2 
 
 I 
 
 ~3 
 
 
 OL OL 
 
 In this table ;tr = -Q, y , in which for the parallelopi- 
 
 / 
 
 pedon a, ft, and y are the lengths of the edges of the grain, 
 a being the least dimension ; also, for the pierced cylinder, 
 
 x = - , in which r is the exterior and r' the interior 
 
 radius of the cylinder, and h its height. 
 
 By substituting for a, A, and /* in the general formula (12), 
 the values given in the above table, the amount of powder 
 burned per unit weight, or per unit volume, for any of the 
 above-shaped grains, can be determined ; and this amount, 
 multiplied by the total weight or volume, will give the total 
 amount burned at any time /. 
 
14 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 7. Velocity of Emission Spherical Grain. 
 
 This is the rate of evolution of the gas of gunpowder ; 
 that is, the ratio of the part of the unit of weight of powder 
 burned in a small interval of time to that time. 
 Considering unit weight, let 
 
 v denote the velocity of combustion ; 
 5 the total surface burning at any time t ; 
 8 the density of the powder. 
 
 Then vdt is the space passed over by the burning surface 
 in the time dt, Svdt the volume burned, and Svddt the 
 weight, the value of g f being unity for French measures. Then, 
 from the definition, we have for the velocity of emission 
 
 Svddt 
 V= -ft- = * ....... (19) 
 
 This equation shows that the velocity of emission de- 
 pends upon 
 
 1. The total burning surface 5; 
 
 2. The velocity of combustion v ; 
 
 3. The density of the powder d. 
 
 But it has been found by experiment that in air 
 
 v8 c, (see equation (10).) 
 
 The velocity of emission in air depends, therefore, upon 
 the surface burning, and this surface depends on the form 
 and size of the grain. 
 
 We may obtain another expression for the velocity of 
 emission which is more convenient for discussion, as fol- 
 lows : 
 
 The proportional part of powder burned per unit weight 
 at any time t is, as we have seen, a function of /, and has 
 been expressed by 0(/). 
 
 The proportional part burned in the time dt is </[0(/)], 
 and by definition we have 
 
 The value of 0(*) lor different forms of grain can be de- 
 termined just as for the spherical grain, and knowing these, 
 
GUNPOWDER AND INTERIOR BALLISTICS. 1 5 
 
 we can determine the values of the velocity of emission for 
 different forms of grain. It is evident that the form of 
 grain whose velocity of emission is least at first will be 
 most advantageous, since, the rate of emission being small, 
 the gas will be given off gradually at first, and the press- 
 ure in the gun will increase slowly, and give time for the 
 projectile to move before the gun is overstrained. 
 
 We can therefore determine what form of grain is best 
 calculated to give the lowest pressure. 
 
 FOR SPHERICAL GRAIN. Differentiating equation (12) 
 with respect to /, we have 
 
 ~ I 4 4* \ 
 
 . . (20.) 
 
 dt 
 
 Substituting for a, A, and p their values for the spherical 
 grain, viz., a = 3, A= !,/* = , we have 
 
 At the beginning of combustion, when t = o, we have 
 
 ,-fi 
 
 and at the end, when / = r, 
 
 rj = o. 
 
 8. Velocity of Emission for Parallelopipedon and for Pierced Cyl- 
 inder. 
 
 FOR PARALLELOPIPEDON. Substituting the values of a, 
 A, and JM for the parallelopipedon in (20.), we have 
 
 w ""LTvyj * i ~ i j \ ] _ "\~ i j i ~j ) ^_ I *$ x y 
 
 i ~ Jj. _ V I I ^. ~ 
 
 When t = o, we have 
 
 ^ 
 and when t = T, 
 
1 6 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 For the flat grain whose thickness is one half its other 
 dimensions, x = y = . Hence for this grain we have at 
 the beginning of combustion 
 
 and at the end 
 
 or the velocity of emission is less at the beginning and 
 greater at the end for a flat grain than for a spherical one. 
 
 FOR PIERCED CYLINDER COCOA POWDER. Substitut- 
 ing the values of a, A, and /* for the pierced cylinder in (2O#)> 
 we have 
 
 _dWfj\_l+*t 2* /v 
 
 dT ~r\ r+^Tj" 
 
 When / = o, we have 
 
 ?=l<I+4r); 
 and when t = r, 
 
 r r' 
 For this grain x = - . If x = -J, as in the case of the 
 
 flat grain, the thickness of the walls is one half the height,, 
 and we have, for the velocity of emission at the origin, 
 
 2r r 
 and at the end, 
 
 -* 
 
 Comparing this with the spherical and flat grains, we see 
 that the velocity of emission for the pierced cylinder is less 
 at the beginning and greater at the end than for any other 
 form of grain. Hence, so far as velocit}^ of emission is con- 
 cerned, this is the best form of grain, and is the one now 
 used in large guns. 
 
GUNPOWDER AND INTERIOR BALLISTICS. 
 
 The results are shown in the following table : 
 
 Form of Grain. 
 
 Velocity of Emission 
 at Beginning. 
 
 Velocity of Emission 
 at End. 
 
 Spherical ) 
 Irregular grain \ ' ' 
 
 J3_ 
 
 T 
 
 
 
 Flat 
 
 2 
 
 ^5 
 
 Pierced cylinder . . 
 
 T 
 
 L5 
 
 T 
 
 r 
 
 J>_ 
 
 r 
 
 9. Size of Grain Density Progressive Powders. 
 
 SIZE. The velocity of emission depends on the surface in 
 combustion, and this, as has been shown, depends on the form 
 and size of grain. The effect of form has been discussed. 
 To show the effect of size, suppose we have two charges of 
 the same weight, composed of cubical grains. 
 
 Let a represent the edge of the grains in the first 
 
 charge ; 
 
 2a the edge of the grains in the second charge ; 
 N the number of grains in the first charge. 
 The surface of each grain in the first charge will be 
 
 and the total surface in the first charge 
 
 Since the weights are proportional to the cubes of the 
 edges of the grains, each grain in the second charge will 
 weigh 
 
 _ o 
 
 times as much as those of the first charge, and hence there 
 
 N 
 
 will be only grains in the second charge. 
 8 
 
 The surface of each grain in the second charge will be^ 
 (20? X 6, 
 
1 8 TEXT-BOOK OF ORDNANCE AND GUNNERV. 
 
 and the total surface in the second charge 
 
 or the total surface in the second charge will be only one 
 half that in the first; and since the velocity of emission 
 depends on the surface, it will be in the beginning one half 
 that of the first charge. 
 
 INFLUENCE OF DENSITY. Considering a single grain, if 
 we increase its density, the volume remaining constant, we 
 decrease the velocity of combustion according to the formula 
 
 vd = c, 
 
 and hence do not change its velocity of emission, since 
 77 = Svd. But considering a given weight of power, if we 
 increase the density of the grains without changing their 
 volume, we increase the weight of each grain, and hence de- 
 crease the number of grains contained in this weight. This 
 decreases the initial surface of combustion in the given 
 weight, and hence decreases the velocity of emission. 
 
 Ordinarily, for slow emission we increase at the same 
 time both the size and the density of the grain. The limit 
 of increase in size and density is reached when the grains 
 cannot be consumed in the gun before the projectile leaves 
 the bore. 
 
 PROGRESSIVE POWDERS. For this reason progressive 
 powders have been used. A progressive powder is one 
 which burns slowly at first, and afterwards more rapidly. 
 
 The Italian Fossano powder is an example. 
 
 The larger grains are in the form of a cube, each com- 
 posed of small dense grains united by a lighter powder. 
 
 The grain burns at first as a cube, with a small burning 
 surface, but the light powder which unites the dense grains 
 soon burns out, and the cube is then broken up into a 
 number of dense grains, by which the burning surface and 
 the velocity of emission are greatly increased. 
 
 The same progressive principle is found in nearly all 
 powders. With molded powders and those of regular 
 
GUNPOWDER AND INTERIOR BALLISTICS. ig 
 
 granulation the surface is more dense than the interior, 
 owing to the method of manufacture, and hence this surface 
 burns more slowly than the interior. In the molded pow- 
 ders especially, the ends of the prisms next the punches 
 which mold it, are most dense. Even in ordinary powders 
 of irregular granulation the same principle applies. 
 
 10. Combustion in a Close Vessel Chemical Formula Noble and 
 Abel's Experiments. 
 
 To determine the chemical composition of the products 
 of exploded gunpowder, and the various circumstances 
 attending its combustion, it is necessary to burn it in a close 
 vessel, and collect the products for examination and analysis. 
 
 CHEMICAL FORMULA. It is generally admitted that no 
 chemical formula will exactly represent the results of the 
 combustion of gunpowder under all circumstances, since 
 these results vary, for the same powder, with the conditions 
 under which it is fired. 
 
 The formula generally adopted is 
 
 4 KNO 3 + C 4 + S = K 2 CO 3 + K 3 SO 4 + N 4 + 2 CO 2 + CO. 
 
 According to this formula we should have for the solids 
 and gases of the exploded powder the following percentages 
 by weight : 
 
 K,CO, = 28.53 ) 
 K 9 S0 4 - 35.96 L Solids. 
 64.49 ) 
 
 N 4 = 11.56 
 
 >- Gases. 
 
 S = 18.17 
 C0= 5.78 
 
 35-51 
 
 It will be seen later that the percentage of solids is less, 
 and of gases greater, than the above, and also that the actual 
 constituents of both solid and gaseous products are different. 
 
 NOBLE AND ABEL'S EXPERIMENTS. Apparatus and 
 Methods. Numerous experiments have been made by Count 
 Rumford (1792), Bunsen and Schischkoff (1859), and b y 
 
20 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 Rodman (1863), upon the composition of the products of 
 fired gunpowder, the pressure produced by the gases, etc. ; 
 and while many of them are valuable, their results are not 
 strictly accurate, owing to defective apparatus and other 
 causes. 
 
 Captain Noble of the English Army, and Sir F. Abel, a 
 chemist of the British War Department, made a series of 
 experiments in 1874 and a second series in 1880, which are 
 accepted as authoritative on this subject. 
 
 Apparatus. The apparatus (see Fig. 6) was a strong steel 
 vessel of the shape shown, capable of resisting very high 
 
 n 
 
 FIG. 6. 
 
 pressures. The charge of powder was introduced into the 
 vessel through an opening a, which was then closed with a 
 tapering screw-plug. Besides this screw-plug there was 
 another, , carrying a crusher-gauge d for measuring press- 
 ures, and a third opening, e, was for the purpose of drawing 
 off the gases for analysis. The charge was fired by elec- 
 tricity. 
 
 Methods. Different powders were used in these experi- 
 ments, and for each kind of powder a series of experiments 
 was made. The volume of the explosion-chamber being- 
 constant, the quantity of powder in each experiment was 
 varied, starting with a very small charge and proceeding 
 till the chamber was filled. The maximum charge was 
 
GUNPOWDER AND INTERIOR BALLISTICS. 21 
 
 2.2 pounds (i kilogram). The results of all the experiments 
 were compared in order to deduce the general laws pertain- 
 ing to all the powders, and the variations due to particular 
 kinds of powder, form of grain, density, etc. 
 
 11. Density of Loading Object of Experiments. 
 
 DENSITY OF LOADING. It is evident that the amount of 
 powder fired in a given volume must greatly affect the re- 
 sulting pressures. 
 
 It is necessary, therefore, to determine accurately the 
 relation between this quantity and the space in which it is 
 fired. If gunpowder were always of the same density, and 
 of the same gravimetric density, we could compare the 
 volume of the powder with that of the space containing it. 
 But we know that both density and gravimetric density 
 vary, and hence if a vessel were one half full of two different 
 kinds of powder, while the volume of powder in the two 
 cases would be the same, the actual weights would be 
 different. By referring to gravimetric density, we see that 
 the weights of equal volumes of powder and water are 
 very nearly equal ; hence we compare the weight of the 
 powder fired with that of a volume of water which will fill 
 the chamber in which the charge is fired. 
 
 This is called " density of loading," and is a very impor- 
 tant ratio, which is constantly used in discussing the action of 
 gunpowder in guns or in any closed vessel. It may be de- 
 fined as " the ratio of the weight of the charge of powder 
 to that weight of water, at its maximum density, which will 
 completely fill the volume in which the charge is fired." 
 
 To determine an expression for it, let 
 
 A the density of loading : 
 c3 = the weight of the powder in pounds ; 
 C = the volume in which the powder is fired in cubic 
 inches. 
 
 One cubic foot of water weighs 62.425 Ibs.: hence one 
 pound of water occupies 
 
 1728 
 
 = 27.68 cubic inches. 
 
 62.425 
 
22 TEXT-ROOK OF ORDNANCE AND GUNNERY. 
 
 The number of pounds of water that will fill the volume 
 Cis 
 
 C 
 27.68' 
 
 and by definition 
 
 J = -A- = 27 - 68t5 . .... (2!) 
 
 6 7 
 
 27X58 
 
 French Measure of Density of Loading. In the metric 
 system the weight of the charge is expressed in kilograms, 
 and the volume of the chamber in litres or cubic deci- 
 metres. 
 
 Since a litre of water weighs one kilogram, the volume 
 of the chamber in litres expresses at once the weight in kilo- 
 grams of the water which would fill it, and hence the 
 density of loading is obtained simply by dividing the weight 
 of the charge by the volume of the chamber. Therefore 
 
 OBJECT OF EXPERIMENTS. The object of the experi- 
 ments was : 
 
 1. To determine the nature and composition of the pro- 
 ducts of combustion. 
 
 2. The effect of varying the size of the grain, and the 
 density and composition of the powder. 
 
 3. The amount of heat generated. 
 
 4. The volume. of the permanent gases. 
 
 5. The maximum pressure exerted by the gases, and the 
 laws of its variation, and from the data thus obtained to 
 calculate the effect in the bore of a gun. 
 
 12. Results Nature and Composition of Products. 
 
 NATURE OF PRODUCTS. In these experiments, for each 
 kind of powder the density of loading was varied by varying 
 the weight of the charge, starting with a density of 0.05, and 
 
GUNPOWDER AND INTERIOR BALLISTICS. 2$ 
 
 increasing by constant increments up to a density i.oo. For 
 the latter density the vessel was completely filled with the 
 powders used. The products were found to consist of per- 
 manent gases and solids. Noble and Abel supposed the 
 solid products to be liquid at the temperature of explosion, 
 and to be diffused in a finely divided state throughout the 
 gases. When the explosion chamber was opened after the 
 combustion of the charge, the residue was found collected 
 at the bottom in a solid form. The mass was compact and 
 hard, and of an olive-green color, changing to black on ex- 
 posure to the air. The volume of this residue when cold was 
 about 0.3 the original volume of the powder. 
 
 To ascertain the condition of the residue immediately 
 after the explosion, the following method was adopted. 
 
 One minute after the explosion, the vessel was inclined 
 quickly at an angle of 45. It remained in this position 45 
 seconds, and was then returned to its original position. 
 When the vessel was opened, the solid products were 
 found to be inclined to the walls at an angle of 45. 
 
 From this it follows that one minute after the explosion 
 the solid residue was in a liquid state, and 45 seconds after 
 this it had become solid. Moreover, a slight crust adher- 
 ing to the walls, and which had been partially broken by 
 the liquid when it took up its inclined position, showed 
 that the solidification had begun one minute after the explo- 
 sion. 
 
 The effect of high temperature on the solid residue was 
 tested as follows. It was exposed to a temperature of 
 1700 C. in a Siemens furnace. At first a slight efferves- 
 cence appeared, which disappeared immediately. At the 
 end of the experiment, a slight volatilization was visible. 
 When the crucibles containing the residue were removed 
 from the furnace, and allowed to cool, the increase in volume 
 of the solid products, as determined by marks left on the 
 walls of the crucibles, was about 78 per cent. 
 
 COMPOSITION. This was determined by chemical an- 
 alysis, and was found to be as follows for pebble powder. 
 The results differed slightly for different powders, and are 
 the percentages by weight. 
 
TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 K,CO, - 33 
 K 3 S0 4 = 7 
 
 K 2 S = 10 
 
 S= 4 
 
 Various = 2 
 
 * Solids. 
 
 Various = i 
 
 44 
 
 That is, 100 pounds of pebble powder, when fired, will 
 give 56 pounds of solid residue and 44 pounds of gases. 
 A mean of the results from all the powders gave 57 pounds 
 solids and 43 pounds gases. That is, the solid residue is 57 
 per cent and the gases 43 per cent of the original weight of 
 the charge. The theoretical reaction gives 64.49 P er cent 
 solids, and 35.51 gases. 
 
 13. Hesults Effect of Variations in Powder Amount of Heat 
 Generated Volume of Permanent Gases. 
 
 VARIATIONS. Slight variations in size and density of 
 grain were found to have very little effect upon the composi- 
 tion of the products of combustion, and no effect whatever 
 upon the pressures. Hence the pressure in a closed vessel 
 is independent of the size, form, and density of the grain, 
 and depends only on the density of loading or the quantity 
 of powder. The case is very different for a gun, as will be 
 seen later. 
 
 AMOUNT OF HEAT. The amount of heat generated by 
 the explosion was measured by immersing the steel ex- 
 plosion-vessel after discharge in a calorimeter containing a 
 given quantity of water at a known temperature, and noting 
 the rise of temperature of the water. 
 
 The mean result obtained was that 705 units of heat were 
 given off per unit weight of powder burned. Now if the 
 mean specific heat of the products of explosion were accu- 
 
GUNPOWDER AND INTERIOR BALLISTICS, 2$ 
 
 rately known, the temperature of these products at explo- 
 sion could be determined by the formula 
 
 in which Q is the quantity of heat, and c the mean specific 
 heat at constant volume. But this value of c is not known. 
 It is known that the specific heat of the solid products 
 increases with the temperature, but the law of increase is 
 unknown. Bunsen and Schischkoff found from their experi- 
 ments a value for c = 0.185. From this we should have 
 
 and 
 
 T, = T + 273 = 381 1 + 273 = 4084 C. 
 
 Noble and Abel believed this value to be much too large, 
 for the following reasons : 
 
 1. The specific heat of the solid products increases with 
 the temperature, hence 0.185 * s too small. 
 
 2. The heat measured by the calorimeter includes all 
 the heat absorbed by the explosion-vessel, as well as that of 
 the gaseous products. The heat absorbed by the vessel is 
 taken from the products of explosion, and- hence lowers the 
 temperature ; therefore 705 is practically too large. 
 
 3. A piece of platinum wire was enclosed in the explo- 
 sion-chamber, and when the chamber was opened after 
 explosion the platinum showed only slight signs of fusion. 
 As this metal fuses completely at 2000 C., it was thought 
 that if anything approaching a temperature of 4000 C. had 
 been attained the metal would have been entirely fused. 
 The temperature of explosion was therefore obtained by 
 calculation, as will be explained. 
 
 VOLUME OF PERMANENT GASES. This was determined 
 by collecting the gases in a gasometer, and observing their 
 volume at the ordinary atmospheric temperature and press- 
 ure, and afterwards reducing this volume to zero centigrade. 
 
 For the purpose of comparing the volumes of different 
 
26 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 gases the " specific volume " of each is used. For ordinary 
 gases this is the volume occupied by a unit weight of the gas. 
 at zero C. and under atmospheric pressure. For gunpowder, 
 it is the volume occupied by \hzgasfrom unit weight of powder 
 at the above temperature and pressure, and was found to be 
 280 times the original volume of the powder. That is, the gas 
 from i kilogram of powder occupies at zero Centigrade and 
 under atmospheric pressure a volume of 280 cubic decimetres. 
 
 14. Results Pressure of Gases Formula. 
 
 PRESSURE. For each kind of powder the pressure was 
 measured with the Noble crusher-gauge, for all densities of 
 loading from 0.05 to i.oo. The results were plotted; the 
 abscissas being the densities of loading, and the ordinates the 
 corresponding pressures. The resulting curve gave the law 
 connecting abscissas and ordinates. It was then necessary to 
 deduce the equation of this curve so as to express analyti- 
 cally the law connecting density of loading and pressure, 
 and afterwards to compare the results calculated by this 
 formula with those obtained by experiment. 
 
 FORMULA. To deduce the formula we proceed as follows: 
 The experiments had shown that the products of explosion 
 were partly solid and partly gaseous. Hence for a given 
 volume of explosion-chamber, it is evident that the volume 
 occupied by the gases at the moment of explosion is equal to 
 the total volume of the chamber minus the volume occupied 
 by the solid products. We can then calculate the pressure 
 due to this volume by Mariotte's and Gay-Lussac's laws. 
 
 Let 7" be the absolute temperature of the products at 
 the moment of explosion ; 
 
 7", the actual temperature of these products ; 
 
 P, the pressure in kilograms per square decimetre on 
 
 the walls of the chamber at the same instant ; 
 / , the normal atmospheric pressure (103.33 kilograms 
 per square decimetre) ; 
 
 V, the volume in cubic decimetres actually occupied 
 by the gases at the moment of explosion, corre- 
 sponding to the pressure P\ 
 
GUNPOWDER AND INTERIOR BALLISTICS. 2J 
 
 F , the volume in cubic decimetres occupied by the 
 same gases at zero Centigrade and at / pressure ; 
 
 c3, the weight of the charge in kilograms ; 
 
 z/ , the specific volume of the gases ; 
 
 a, the volume occupied by the solid residue of i 
 kilogram of powder at the temperature of explo- 
 sion ; 
 
 C, the volume of the explosion-chamber in cubic 
 
 decimetres. 
 
 Then we have (Michie, equation 823), from Mariotte's 
 and Gay-Lussac's laws, 
 
 = p ,F - (23) 
 
 fm w t\ IT > I V )/ 
 
 But 
 
 273+7-= T t ; 
 
 hence 
 
 f = * (24) 
 
 or 
 
 - 273^* 
 
 Now 
 
 F o = GW O , (26) 
 
 and 
 
 P 273 x v 9 
 
 but 
 
 - = constant /". (28) 
 
 Hence 
 
 p=f% (29) 
 
 Now F, the volume actually occupied by the gases, is the 
 difference between the volume of the chamber and that of 
 the solid residue. The volume of the solid residue is 
 
28 TEX'l-auUK OF ORDNANCE AND GUNNERY. 
 
 and hence 
 
 V C aw ......... (30) 
 
 The expression for density of loading is (see 22) 
 
 A _. . _ 
 - c . .. C- j 
 
 Substituting this value of C in (30), we have 
 
 F=Ji-/0, 
 and this value of Fin (29) gives 
 
 the equation required. 
 
 15. Discussion of Formula (31). 
 
 To compare the results of this formula with those ob- 
 tained by experiment it is necessary to know a and/. These 
 can be calculated by equation (31) by taking from the ex- 
 periments two values of A and the two corresponding values 
 of P, and substituting in (31). We will thus have two equa- 
 tions containing the two unknown quantities a and f from 
 which they may be determined. In this manner Noble and 
 Abel found for these constants the following values: 
 
 /= 291200 kil. per sq. dee. = 18.49 tons P er sc l- inch. 
 a = 0.57. 
 
 Taking Noble and Abel's numerical values, we have for 
 the French units 
 
 2QI200J 
 " I - 0.57^' 
 
 or for English units 
 
 ...... (33) 
 
 This value of a means that when the volume of the 
 charge is i cubic decimetre the volume of the solid prod' 
 nets is 0.57 cubic decimetre. 
 
GUNPOWDER AND INTERIOR BALLISTICS. 2$ 
 
 Referring to equation (4), it is seen that the volume of 
 the solid residue after explosion is nearly equal to that of 
 the solid powder in the charge before explosion. 
 
 If the charge is in kilograms, the volume of the solid 
 products is obtained by multiplying the number of kilo- 
 grams by 0.57. If the charge is in pounds, the volume of 
 the solid products is obtained by multiplying the number 
 of pounds by 27.68 and this by 0.57, or 
 
 Vol. of solid products = No. Ibs. X 27.68 X 0.57 ; 
 
 = No. Ibs. X 15 77- 
 
 When the chamber is full of powder the density of 
 loading for the powders used by Noble and Abel is i.oo. 
 
 In this case, since no more powder can be introduced, 
 we should get the greatest possible pressure which gun- 
 powder will give. This is sometimes called the " absolute 
 pressure." Its value is by (33), for A = i, 
 
 P= 43 tons per square inch. 
 
 16. " Force" of Powder Temperature of Explosion. 
 
 FORCE. Assume equation (31), 
 
 If in this equation we make 
 
 A 
 
 (34) 
 (34*) 
 
 (35) 
 
 Comparing this with the general expression for density 
 Of loading, 
 
 A & 
 
 "=' 
 
3 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 we see that when the weight of the powder is unity, and 
 the volume of the chamber in which it is fired is (i + a )> we 
 have, from (34*2), 
 
 p=f- 
 
 The quantity represented by f in these equations is 
 -see 28) 
 
 and is constant. This value of /is called the " force" of the 
 powder, and from (340) and (35) it may be defined as "the 
 pressure per unit of surface exerted by the gases from unit 
 weight of powder, the gases occupying at the temperature 
 of explosion a volume equal to unity." The volume of the 
 chamber is i + a, and a is the portion occupied by the solid 
 products. The value of f as determined by Noble and 
 Abel has been given. 
 
 This value of / is uncertain, and therefore it admits of 
 being modified to account for various resistances in a gun 
 which cannot be readily calculated. 
 
 It is found also that the values of /for different powders 
 are nearly the same. This arises from the fact that the 
 quantity of heat of a powder varies approximately inversely 
 as the specific volume of the gas ; and by (28) the product 
 of these two quantities measures the force of the powder. 
 
 TEMPERATURE OF EXPLOSION. Assume, (28), 
 
 from which 
 
 We have found 
 
 /= 291200 
 
 v. 280 ; 
 A = I03-33-. 
 
GUNPOWDER AND INTERIOR BALLISTICS. 
 
 Substituting in (36), we have 
 
 and 
 
 291200 X 273 8 o Q 
 
 103.33X280 
 
 T =2748 -273 = 2475 C. 
 
 These values agree well with the melting-point of plati- 
 num r and could be accepted if there were no doubt about 
 the value of/ 
 
 COMBUSTION IN A GUN INTERIOR BALLISTICS. 
 
 17. Action of Gunpowder in a Gun. 
 
 Suppose we have a charge of powder which completely 
 fills the chamber of a gun, the density of loading being 
 unity. If this charge be completely burned before the pro- 
 jectile moves, we obtain, by equation (33), 
 
 P 43 tons per square inch. 
 
 0' 0" A 
 
 FIG. 7. 
 
 In Fig. 7 let O be the position of the base of the pro- 
 jectile before firing, OX the axis of the bore, and OP the 
 axis of pressures. Lay off OP = 43 tons, and we have the 
 pressure corresponding to the instantaneous combustion of 
 
32 TEXT-BOOK OF ORDNANCE AND GUNN,ERY. 
 
 the charge. From this point P the gas will expand accord- 
 ing to the hypothesis adopted, and, acting on the projectile, 
 will cause it to move rapidly down the bore, the ordinates 
 of the curve Px representing the pressures at correspond- 
 ing abscissas of travel. The equation of this curve will be 
 deduced later. 
 
 Error in Supposition. It is evident that the assumption 
 that all the powder is consumed before the projectile moves 
 cannot be true in practice. As soon as the pressure rises 
 high enough to overcome the resistance of the projectile 
 and gun to motion, they will both move in opposite direc- 
 tions ; but for the present we will consider the motion of 
 the projectile alone. 
 
 Quick-burning Powder. Take a small-grained powder of 
 cubical form. The time of combustion of this powder is 
 small, and its velocity of emission at first great, as has been 
 shown. Let OP' represent the pressure which is sufficient 
 to start the projectile, and suppose the powder is all burned 
 when the projectile reaches A. Under these circumstances 
 the relation between the pressures and the travel of the 
 projectile, or the " pressure curve/' will be represented by 
 a curve such as OP ' P"abx. 
 
 Slow-burning Powder. Take the same weight of charge of 
 cocoa or slow-burning powder. The time of combustion 
 is comparatively great, and its velocity of emission at first 
 small. Let OP' represent, as before, the pressure required 
 to start the projectile, and suppose the powder all burned 
 when the projectile reaches B. 
 
 The pressure curve in this case will be OP ' P'"bx ; and 
 from these curves we may deduce the following conse- 
 quences : 
 
 a. The quick curve will rise above the slow one near the 
 origin, because the volume of gas given off in the same time 
 is greater with the quick powder. 
 
 b. The work done by the quick powder upon the pro- 
 jectile is greater than that done by the slow powder, be- 
 cause the area under the quick curve is greater than that 
 under the slow one. 
 
 c. The quick powder strains the gun more than the slow 
 
GUNPOWDER AND INTERIOR BALLISTICS. 33 
 
 one, because the maximum pressure O'P" > O"P" f , and this 
 maximum pressure is what determines the maximum strain. 
 That part of each curve from P' to a and b, respect- 
 ively, is called the combustion curve, because during this 
 time the powder is still burning and giving off gas. The 
 part from a and b to x is called the expansion curve, be- 
 cause from these points on the gas is expanding only. 
 
 18. Equation of Pressure Curve Noble and Abel's Method. 
 
 The equation of the true pressure curve is very difficult 
 to deduce, since at the origin, as we have seen, gas is being 
 evolved while the projectile is moving, and this renders the 
 problem very complex. 
 
 Noble and Abel deduced the equation of the curve Pabx, 
 Fig. 7, under the following hypotheses : 
 
 1. That all the powder is burned before the projectile 
 moves. 
 
 2. That the solid products of combustion give off heat 
 to the gases during the expansion. 
 
 Let , represent the specific heat of the solid products, 
 supposed constant throughout the expansion, and dT^ any 
 small change of temperature of the products of combustion. 
 
 Then c t dT 9 is the corresponding quantity of heat given 
 to the gases by the solid products per unit of weight. 
 
 Let w t represent the number of units of weight of the 
 solid residue- then the total quantity of heat given to the. 
 gases by the solid residue is wj^dT^. Let w^ be the number 
 of units of weight of the gases. These gases, by hypothesis, 
 receive the heat above found, and hence they receive per 
 unit of weight a quantity of heat dQ equal to 
 
 dQ=- Cl dT. = - ficJT., .... (37) 
 
 w, 
 
 
 ft being the ratio , and the negative sign being used since 
 
 7 1 , is a decreasing function of Q. 
 
 When the volume, pressure, and quantity of heat of a 
 gas change at the same time, we have a general law con- 
 
34 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 necting them, which is expressed by the following equation 
 (Michie, 832): 
 
 ( 38) 
 
 m which dQ is the elementary quantity of heat imparted to 
 
 the gases ; 
 dp and dv the elementary changes of pressure and 
 
 volume of the gas due to dQ ; 
 Cp and c, the specific heats at constant pressure 
 
 and volume, respectively. 
 
 Substituting in equation (38) for dQ its value given by 
 (37), we have 
 
 ftc^T^ = -^f v vdp -\- Cppdv) (39) 
 
 This equation contains T and R, while the equation of 
 the pressure curve should contain only /, v, and constants, 
 because the pressure curve is one showing the relation be- 
 tween/ and v. To eliminate T and R, assume the general 
 equation (823, Michie) connecting the pressures, volumes, 
 and temperatures of a gas. 
 
 pv = RT (40) 
 
 Differentiating, we have 
 
 RdT. = pdv -\-vdp, (40') 
 
 from which 
 
 _ pdv + vdp 
 
 Substituting this value of dT^ in (39), we have 
 
 -(A, + '4- = ( ^' + ^f (40") 
 
 For small changes of pressure and volume /?, c lt c p , and c v 
 are constant. Hence 
 
GUNPOWDER AND INTERIOR BALLISTICS. 35 
 
 /., /, z/,-, and v being the initial and any subsequent values 
 ot / and v. 
 
 Integrating, 
 
 -*3 
 
 Making 
 
 w^ =k ' (42) 
 
 we have 
 
 . J' < 43) 
 
 the equation of the pressure curve. 
 
 19. Application of Formula (43) Work of Gunpowder in a Gun. 
 APPLICATION. Assume equation (43) 
 
 /.=. 
 
 In this equation v f is the volume occupied by the gas at 
 the moment of explosion, and pi the corresponding press- 
 ure. To apply this equation to the case of a gun, the 
 original volume v t occupied by the gas, is the volume of the 
 chamber in which the charge is fired, minus the volume 
 occupied by the liquid products of the charge. The volume 
 it occupied by the gases corresponding to the pressure p 
 is the total volume to which the gas has expanded, including 
 that of the chamber, minus the volume occupied by the 
 liquid products. 
 
 Hence if v' denote the original volume of the chamber, 
 the density of loading being unity, av' is the volume occupied 
 by the liquid residue, and v { = v' av' = v'(i a). Also, 
 if v" represent any subsequent volume of the bore, at which 
 the pressure is/, the volume actually occupied by the gas is 
 
 v = v" - av'. 
 Making these substitutions in (43), we have 
 
 (44) 
 
36 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 Taking from the experiments the values of the constants, 
 we have 
 
 pi = 43 tons per square inch ; 
 
 ^=0.57; ft = 1.2957; 
 
 ^ = 0.2324; ^=0.1762; ^=0.45; 
 
 k' = 1.074, 
 and substituting in (44), we have 
 
 (45) 
 
 for use in practice. 
 
 WORK OF GUNPOWDER. The general expression for the 
 work done by a gas expanding from a volume v t to a volume 
 v is 
 
 = / pdv. 
 J*i 
 
 W= I pdv (46) 
 
 J*t 
 
 Substituting for / its value from (44) and changing the 
 limits to v" and v' y we have 
 
 or 
 
 Integrating, we have 
 
 ' 
 
 12 x ( 
 
 Multiply, and divide the second member by \v'(i a)Y'~ l : 
 
 - (49) 
 
 12 is used to reduce to foot-tons. This is Noble and Abel's 
 formula for work. 
 
 Taking the volume corresponding to the muzzle of the 
 gun, the corresponding work is obtained. If there were no 
 loss of energy due to the friction, resistance of rifling, etc., 
 
GUNPOWDER AND INTERIOR BALLISTICS. 37 
 
 the work thus calculated should be equal to the energy in 
 foot-tons possessed by the projectile at the muzzle, which is 
 
 2g X 2240 ' 
 
 w being the weight of the projectile in pounds, and V its 
 muzzle velocity in feet per second. But E is always less 
 than W, owing to the above causes ; and the ratio 
 
 is called the " factor of effect " for the particular gun and 
 charge. 
 
 Knowing this factor for any given gun we can find the 
 muzzle velocity for a given charge by calculating Wby (49), 
 multiplying it by F, and we have 
 
 _- = FW 
 
 2g X 2240 
 
 from which 
 
 ( 5 o) 
 
 Infinite Expansion. When the length of bore becomes 
 infinite, v" in (49) is infinite, and we have 
 
 /X(i-) , , 
 
 - I2(k' - I) ' 
 
 Using the constants as given above, and substituting for 
 v' its value, 27.68 cubic inches, the volume occupied by one 
 pound of powder, we have 
 
 W= 576.35 ft.-tons ...... (52) 
 
 for the work of one pound of powder expanded to infinity, 
 under Noble and Abel's hypothesis. 
 
 20. Equation of Pressure Curve Recent Hypothesis Expression 
 
 for Work under this Hypothesis. 
 
 EQUATION OF PRESSURE CURVE. In recent discussions 
 Noble and Abel's hypothesis is rejected, as it is believed that 
 
38 TEXT- BO OK OF ORDNANCE AND GUNNERY. 
 
 from the feeble absorbing power of gases generally, they re- 
 ceive only a very minute quantity of the heat radiated by the 
 solid products. The equation of the pressure curve Pabx> 
 Fig. 7, is therefore deduced under the following hypotheses: 
 
 1. That all the powder is burned before the projectile 
 moves. 
 
 2. That the gases expand without receiving heat from or 
 giving off heat to any external source, and that the work 
 done on the projectile is due to their own heat ; that is, the 
 expansion is adiabatic. 
 
 Assume the equation expressing the general law con- 
 necting the heat, volume, and pressure of a gas, as before v 
 (equation 832, Michie's Mechanics), 
 
 R 
 
 Since no heat is gained or lost externally, dQ Q and 
 we have 
 
 
 Making = k and integrating between the limits p t 
 
 9 
 
 and v, we have 
 
 (53> 
 
 or 
 
 rv>,~i* 
 
 (54) 
 
 which is the equation of the pressure curve, and differs from 
 that deduced under Noble and Abel's hypothesis only in 
 the value of the exponents k and k' y k' being 1.074 and k, for 
 powder gases, 1.30. 
 
 WORK. To deduce the' expression for work in this case, 
 we have, as before, equation (46), 
 
 r 
 
 W I pdv. 
 
GUNPOWDER AND INTERIOR BALLISTICS. 39 
 
 Substitute for p its value from (54), integrate, and we 
 have 
 
 (55) 
 
 When v = v { we have W = o, and C -~- - ; hence 
 
 w= 
 
 21., Work of Gunpowder in Terms of Force and Weight of Charge 
 Expression for it in Terms of Length of Travel of Projectile. 
 
 WORK IN TERMS OY FORCE AND WEIGHT. If & be the 
 weight of the charge in kilograms, the initial volume occu- 
 pied by the gas from each kilogram of powder, expressed in 
 cubic decimetres, will be 
 
 *> = ^ 
 
 GO 
 
 hence 
 
 pM^ppfi; ...... (57) 
 
 and from Mariotte's law we have 
 
 p.v^ = p"v" = C(a constant), 
 
 see equation (814), Michie's Mechanics. 
 
 Now if we make v" = i one cubic decimetre, p" be- 
 comes by definition the force of the powder, and hence 
 
 A", =/"=/; 
 
 and from (57), 
 
 p&i^fco. 
 
 *. 
 
 Substituting in (56) for/^,- this value, we have 
 
 in which W is expressed in terms of the " force of the 
 powder " and its weight. 
 
 In equation (58) the force of the powder is expressed in 
 kilograms per square decimetre, and the volumes in cubic 
 decimetres. Hence the work W will be expressed in kilo- 
 
40 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 gram-decimetres. It is usual, however, to express work in 
 kilogram-metres, and this is done by dividing by 10; and we 
 have 
 
 _ W J \ T 1 1 v fcrri 
 
 10 " ~ io(- 1) l \v> r 
 
 WORK IN TERMS OF LENGTH OF TRAVEL OF PROJECTILE. 
 We can place this expression for work under a still more 
 convenient form, as follows : 
 
 Reduced Length of Initial Air-space. The initial air-space 
 in the powder-chamber is equal to the total volume of the 
 chamber minus the volume occupied by the solid powder; 
 and the reduced length of this air-space is the length of a 
 cylinder whose volume is that of the initial air-space, and 
 whose area of cross-section is that of the bore proper. 
 To determine its value, 
 
 let A be the density of loading ; 
 #, the density of the powder; 
 GO, the area of cross-section of the bore ; 
 2, the reduced length of the initial air-space. 
 We have 
 
 GO CO 
 
 The volume occupied by the solid powder in cubic 
 decimetres is 
 
 hence the volume actually occupied by the gases, or the 
 initial air-space, is 
 
 . co GO 
 
 This volume divided by co, the area of cross-section of 
 the bore, gives 2 ; hence 
 
 GO I I l\ ff-^ 
 
 2 = ---/ ......... (DO) 
 
 AJ d/ 
 
GUNPOWDER AND INTERIOR BALLISTICS. 41 
 
 Having this value for z, we have (see page 29) 
 
 V i =G02' V=Go( Z + x) y . . . .(6Q0) 
 
 x denoting the length of travel of the projectile. 
 Substituting these values in (59), 
 
 ^_^| I _( - y-i . B 
 
 (61) 
 
 Taking k = 1.3 and /= 291,200, we have the constants 
 which enter (61), and W can be calculated for any length 
 of travel x of the projectile. When x = oo , the bore be- 
 comes infinite in length, the powder expanded to infinity, 
 and (61) becomes 
 
 - 
 
 io(k i)' 
 
 Making c3 = i, we have, for the work of one kilogram of 
 powder expanded to infinity under the adiabatic hypothesis, 
 
 W' = 97066 kil.-metres per kilogram, 
 = 142.2 ft.-tons per pound. 
 
 Comparing this with Noble and Abel's value for the 
 work of one pound, viz., 
 
 W 576.35 ft.-tons per pound, 
 
 we see that the work is much less under the adiabatic 
 hypothesis. 
 
 "22. Division of Work of Gunpowder Velocity of Recoil. 
 
 DIVISION OF WORK. Having the value of the total work 
 done by gunpowder, it is required to find how much of this 
 work is done upon the gun and how much upon the pro- 
 jectile, and thence to deduce values for the velocity of 
 recoil and of the projectile. 
 
 In this discussion we suppose : 
 
 1. That the gun recoils freely. 
 
 2. That gravity and resistance of the air can be neg- 
 lected in comparison with the great pressures considered. 
 
 Then we have, from mechanics : 
 
42 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 1. The total energy of the system is equal to the total 
 work done by the powder upon it. 
 
 2. Since the gun and projectile move in opposite direc- 
 tions with equal momenta, the sum of the quantities of 
 motion of the system is zero. 
 
 The energy of the system after the projectile has passed 
 over a given path x is composed of three quantities: ist, 
 the energy of the projectile ; 2d, that of the gun ; 3d, that 
 
 of the charge. The energy of the projectile is - , m de- 
 noting its mass and v its velocity of translation. To this 
 should be added the energy of rotation ; but this is so small 
 
 MV'* 
 that it may be neglected. The energy of the gun is , 
 
 M being the mass and v' the velocity. 
 
 The energy of the charge is unknown, since the velocity 
 of its particles is unknown. The velocities of these par- 
 ticles vary from zero, near the bottom of the bore, to v, 
 that of the projectile, for those in contact with the latter, 
 not taking into account irregular motions which also exist. 
 Hence the mean velocity of the particles is less than 
 
 that of the projectile. If j* be the mass of the charge, 
 
 would be its energy if the velocities above mentioned were 
 equal ; as they are not, we represent the energy of the 
 
 charge by X #, being a coefficient whose value is be- 
 tween zero and unity. 
 
 We have, then, as a first equation, 
 
 2lV= mi? + Mv* + Spi? (62) 
 
 The momenta of projectile and gun are mv and Mv'. 
 As before, the quantity of motion of the charge is not 
 known ; but, reasoning as above, we may represent it by 
 tffiv, and its sign will be +> because, as the centre of grav- 
 ity of the system is fixed, the greater part of the gaseous 
 mass moves in the same direction as the projectile. The 
 second equation is then 
 
 mv -f- 6' fAv Mv' = o (63) 
 
GUNPOWDER AND INTERIOR BALLISTICS. 43 
 
 The values of 6 and 6' are found by analytical methods 
 to be 
 
 VELOCITY OF RECOIL. From (63) we have 
 
 , m _L B'fJL 
 
 - 5 
 
 Make v = F the initial velocity, and we have v' V , the 
 velocity of the gun at the moment the projectile leaves the 
 bore. Making 0' = , and replacing masses by weights, we 
 have 
 
 t+- 
 
 V' = p--V. ....... (65) 
 
 Experiment shows that this formula gives correct values 
 for V at the instant the projectile leaves the bore, suppos- 
 ing the gun to recoil freely. But this value of V does 
 not represent the maximum velocity of recoil ; in fact, it 
 gives only about three fourths of the maximum, since it 
 applies only at the instant the projectile leaves the bore. 
 For slow powders the velocity of recoil is increased, since 
 the gas continues to act upon the piece after the projectile 
 has left the bore. 
 
 The subject of recoil will be further discussed under 
 Gun-carriages. 
 
 23. Velocity of Projectile Passive Resistances Limit of Length of 
 
 Bore Influence on Velocity and Maximum Pressures. 
 VELOCITY OF PROJECTILE. Substitute the value of v f 
 from (64) in (62), and we have 
 
 This equation gives the velocity of the projectile as a 
 function of the work of the powder. The third term in the 
 denominator, being generally small, may be omitted, and 
 we have 
 
 ..... (67) 
 
44 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 If we have a quick powder, and suppose it all burned 
 before the projectile moves, we may substitute for W in 
 (67) its value from (61), which gives 
 
 Making x = u, the total length of travel of the projectile, 
 becomes the initial velocity, and we have 
 
 For a long gun u would be large and - small, and 
 
 z -\- u 
 
 V* would become 
 
 (68) 
 
 The value of /in this equation must be found by experi- 
 ment, to compensate for the erroneous assumptions made in 
 deducing it. 
 
 PASSIVE RESISTANCES are those due to the forcing of 
 the band of the projectile into the grooves of the rifling, 
 friction, etc. 
 
 Let p denote the work done against these resistances 
 over the path x. In equation (62) this work is not ac- 
 counted for, and it is therefore not exact. Introducing it 
 into that equation, we have 
 
 2 ( W - P) = mv* + Mv'* + fyizf; ... (69) 
 and in equation (67) we have for the velocity 
 
 ...... < 
 
GUNPOWDER AND INTERIOR BALLISTICS. 45 
 
 LENGTH OF BORE. Although the value of p is unknown 
 we can use it as follows : Differentiate (70), v, W, and p being 
 variable. 
 
 v m -\- 
 
 In Fig. 8 let OX be the axis of the bore and OP that 
 
 X 
 
 of pressures. Suppose the bore divided into elementary 
 lengths dx. Then, since the length multiplied by the con- 
 stant area of bore is the volume, we may replace dx by dv, 
 the increment of volume, as in the figure. From equation 
 
 (46), 
 
 and each of the small areas bounded by the pressure curve, 
 the ordinates, and dv will be a value of dW. In the same 
 way 
 
 dp = Kdv, 
 
 K being a constant and equal to the constant pressure be- 
 tween projectile and rifling multiplied by the coefficient of 
 friction. Since K and dv are both constant, the values of 
 dp will all be equal, and they are bounded by the straight 
 line KK', the ordinates, and the axis of X. 
 
 As the projectile moves from toward X, the'increment 
 
46 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 of the work due to friction remains constant, while dW de- 
 creases and tends towards zero, since / constantly decreases. 
 There is some point, then, such as m, where 
 
 or dv = o. This value of X will be greater for a slow 
 powder than for a quick one, because, as we have seen, for 
 equal charges the slow powder gives a less maximum pressure, 
 and hence we can use larger charges of slow powder without 
 overstraining the gun ; and as these large charges give off 
 more gas, the pressure is kept up better along the bore than 
 with the quick powder, or the values of p are greater along 
 the bore, dp being independent of the nature of the powder. 
 When the point m is reached where dv = o, or the velocity 
 of the projectile ceases to increase, the limit of length is 
 reached. 
 
 With small arms this limit is attained more nearly than 
 with cannon ; and the above reasoning shows that slow 
 powder requires longer bores than quick powder. 
 
 INFLUENCE ON VELOCITY AND MAXIMUM PRESSURE. 
 Equation (70) shows that the passive resistances decrease the 
 initial velocity of the projectile ; but this is not always the 
 case. Certain passive resistances, such as the resistance of 
 the rifling, produce at first a more rapid combustion of the 
 powder on account of the rise in pressure due to the delay 
 of the projectile in moving off. Hence the powder acts as 
 a quicker powder, the work done by it over a given path is 
 increased, and this increase of work may more than com- 
 pensate for the resistance. It follows as a consequence 
 that the maximum pressure on the gun is increased. An 
 accidental resistance, such as wedging of the projectile, 
 may cause a great increase in pressure, and, if it cannot be 
 overcome, may burst the gun. 
 
 24. Sarrau's Formulas General Equation of Motion of Projectile 
 
 in Bore. 
 
 The formulas deduced above furnish approximations to 
 the initial velocity of the projectile, but are not exact for 
 many reasons. Among these are : 
 
GUNPOWDER AND INTERIOR BALLISTICS. 47 
 
 ist. The powder is supposed to be all burned before the 
 projectile moves. This is known to be incorrect. 
 
 2d. No account is takeii of the passive resistances. 
 
 3d. The kind of powder and the calibre of the gun are 
 not considered. 
 
 For these reasons it was customary to use empirical for- 
 mulas. These formulas gave good results so long as the 
 conditions under which they were deduced were not de- 
 parted from, but they were limited in their applications and 
 could not be generally used. 
 
 To obviate these difficulties, the subject has been dis- 
 cussed by M. Emile Sarrau, a distinguished French engineer 
 of powders, etc. In his discussion the following hypotheses 
 are adopted : 
 
 1. The inflammation of the charge is instantaneous. 
 
 2. The gases expand adiabatically. 
 
 3. The powder is not all burned before the projectile 
 moves. 
 
 EQUATION OF MOTION. At the end of any time / let 
 
 q be the weight of powder burned ; 
 x, the length of bore passed over by the projectile ; 
 p l , the mean pressure ; 
 
 v l , the volume of the bore in rear of the base of the pro- 
 jectile, minus the volume occupied by the solid 
 residue of the powder ; 
 v, the velocity of the projectile. 
 
 The gas which is formed at the time / expands adiabati- 
 cally, and we have, for any time t' after t (see equation 54), 
 
 (72) 
 
 / and v' being the mean pressure and volume at the time 
 /', and k the ratio of specific heats. 
 
 The total quantity of work done up to the time t' is, from 
 
 (46), 
 
48 TEXT-BOOK OF ORDNANCE AND GUNNERY.. 
 
 Substitute for /' its value from (72), integrate, and we- 
 ll ave 
 
 (73) 
 
 To find the value of the constant : When t' = /, we have 
 v' =. v l ; and if we consider the energy of the projectile 
 alone, W = \mv*\ hence 
 
 C = \mv* + , ' f , 
 
 K I 
 
 and consequently 
 
 - k 
 
 if- - - (74) 
 
 If we now suppose the bore to be infinite in length, z/ 
 becomes infinite, and W 7 becomes, from (61), 
 
 fq - 
 
 " io(k- i)' 
 and since k > I, 
 
 k- i 
 becomes zero. Hence 
 
 25. Transformation of Equation (75). Errors in its Deduction and 
 
 their Correction. 
 
 TRANSFORMATION. Equation (75) is transformed as fol- 
 lows : Make 
 
 dx 
 V = dt> 
 
 v l = GO(Z -f- x) ; (see equation 6oa ;) 
 
 This last equation expresses the fact that the total press^ 
 ure on the projectile,/,^, is equal to the accelerating force,. 
 
GUNPOWDER AND INTERIOR BALLISTICS. 49 
 
 While this is not exactly true, it is sufficiently accurate, 
 and can be corrected for, as will be explained. 
 
 Making these substitutions in equation (75) and including 
 the constant 10 in/, which is equivalent to changing the 
 unit in which the force of the powder is expressed, we have 
 
 fq _ mfd^V* d *x z-\- x 
 k i " " 2 \dt i ~ n d? k i* " ' ' ^ 
 
 ERRORS AND CORRECTIONS. In deducing this equation 
 certain errors have been made. These are : 
 
 1. The total work which a weight of powder is capable 
 
 of doing, when expanded to infinity, is not equal to j~- ,, 
 
 K -~ I 
 
 because part of the heat is absorbed by the walls of the 
 bore, and no allowance has been made for this loss. 
 
 On the contrary, we have supposed an adiabatic expan- 
 sion without gain or loss of heat. Hence -7 is too large 
 
 K I 
 
 and must be diminished. 
 
 2. At any time / the work of expansion is not equal to- 
 Jm^ 2 , but is equal to the total energy of the system, includ- 
 ing gun, projectile, charge, and gun-carriage. 
 
 To correct for this we must increase the term \m\- 
 
 3. We have assumed /,<*> = w-^-, or that the total press- 
 
 ure on the projectile is equal to the accelerating force. 
 
 This is not correct, because the force pja not only pro- 
 duces acceleration of the projectile, but overcomes the 
 passive resistances, such as forcing of the band, friction,, etc- 
 
 d*x 
 Hence, in order to make pja m ~~y we must in crease 
 
 Instead of correcting each term of equation (76) as in- 
 dicated, we can apply such a correction to the first member 
 as will make it a true equation. The numerical value of / 
 is uncertain, and we may therefore apply all the corrections 
 
1>O TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 to this quantity, and /then becomes a numerical coefficient 
 Avhose value must be determined by experiment. 
 
 26. Deduction of Final Equation of Motion of Projectile in Bore. 
 
 Value of q. The method of determining the value of/ 
 in equation (76) has been explained. It is necessary now to 
 find the value of ^, the quantity of powder burned at the 
 end of any time /. 
 
 The proportional part of powder burned in air at any 
 time / is given by the general expression, (12), 
 
 - + + etc -- . . . (77) 
 
 By multiplying this expression by the volume of the 
 grain or charge we obtain the volume burned (see equation 
 (16) ) ; and multiplying the same expression by the weight, 
 we have the weight burned at any time. 
 
 Hence, GO being the weight of the charge, we have 
 
 q = 0W ........ (78) 
 
 But the expression (77) applies to the burning of a grain 
 or charge in air. In a gun, the pressure varies and is much 
 greater than in air, and hence the velocity of combustion 
 varies and is much greater, as has been shown; and this 
 variation of velocity is expressed by Sarrau's formula 
 already given (equation n), 
 
 (79) 
 
 and the expression for <p(t) must be modified accordingly. 
 
 Spherical Grain. Take the simplest case, that of a spheri- 
 cal grain. When burning in air, we have found for the vol- 
 ume burned at any time t, equation (13), 
 
 Since v is no longer constant, owing to the variation of 
 pressure in the gun, the space burned in the time dt is vdt\ 
 
GUNPOWDER AND INTERIOR BALLISTICS. $1 
 
 /< 
 vdt, instead of vt t as in the case of 
 
 constant pressure. The above expression for the volume 
 of powder burned in the case of a spherical grain under 
 varying pressure becomes, then, 
 
 (8o) 
 
 and the value of 0(/) in equation (14) becomes 
 
 { i r f \ 3 
 0(0 =i-(i- ~J o vdt] (81) 
 
 If in this equation we substitute for v its value from (79), 
 we have 
 
 *=i- --:.! \&}#\> (82) 
 
 Now 
 
 r 
 r = , 
 
 the time of combustion of the grain in air under the normal 
 pressure, and 
 
 Substituting in (82), we have 
 
 Comparing this value of 0(0 with that for uniform 
 pressure, which is, equation (17), 
 
 (84) 
 
 we see that the only difference is the substitution of 
 
 (orr. 
 
52 TEXT-BOOK Of ORDNANCE AND GUNNERY. 
 
 Following the same method for other forms of grain, the 
 same results will be obtained. Hence we conclude that if 
 the combustion of powder under constant pressure is repre- 
 sented by 
 
 = f(i -*+>+ etc.), 
 
 the combustion under variable pressure will be represented 
 
 FINAL EQUATION. In equation (85) make 
 
 / =p l the mean pressure at the time /. 
 P^GD = *#-T- 3 - (see equation (75#)). 
 Whence 
 
 A = vW' 
 and we have for the value of the term J r^J dt, 
 
 and substituting this value in (85), we have 
 
 and for the value of <7, 
 
 q = c0(/) = (3 X 2d member of equation (87). . (88) 
 In equation (76) make 
 
 and it becomes 
 
GUNPOWDER AND INTERIOR BALLISTICS. 53 
 
 Substituting in this equation the value of q from (88), we 
 have the final equation desired, which is 
 
 ( \l m\* rtfd'xV,, , 
 
 i l ~r ) X b) *+ 
 
 , , 
 
 x l ~r * - J + etc 
 
 27. Integration of Equation (90) Practical Formulas for Velocity 
 and Pressure Values of A and ^Characteristics a and /3. 
 
 INTEGRATION. Equation (90) must be integrated before 
 it can be used practically. Sarrau has done this by the use 
 of auxiliary functions which are numerical and independent 
 of the variable elements of fire. As a final result of his 
 process, the general values for velocity and pressure are 
 expressed in the form of definite series, which are very con- 
 vergent. On this account it is necessary to consider only 
 two terms of the series in the expression for the velocity, 
 and only one term in the expression for the pressure. 
 
 BINOMIAL FORMULA FOR VELOCITY. Considering the 
 two terms of the series, Sarrau's formula for velocity is ex- 
 pressed as follows. It is called the binomial formula for 
 velocities, and is the result of the integration of equation 
 < 9 o) : 
 
 (9D 
 
 in which z> is the velocity of the projectile at the point , 
 and becomes the muzzle velocity when u is 
 equal to the total length of travel of the pro- 
 jectile in the bore ; 
 
 u, the length of bore passed over by the base of 
 the projectile in inches, measured from the 
 position occupied by it before firing. In 
 equation (90) this length is denoted by x, and 
 is changed to u in formula (91) ; 
 
 *, the calibre or diameter of the bore in inches ; 
 
 /, the weight of the projectile in pounds ; 
 
 (5, the weight of the charge of powder in pounds ; 
 
 A, the density of loading ; 
 
54 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 a and ft, two coefficients depending on the nature of the 
 powder used, and called the "characteristics" 
 of the powder; 
 
 A and B, two numerical coefficients which are independ- 
 ent of the elements of fire. 
 
 The values of a and ft are 
 
 in which /is the force of the powder; 
 
 a and A, coefficients depending on the form of the grain 
 of powder, and whose values for the different 
 forms of grain have been given ; 
 r, the total time of burning of the grain in air. 
 
 FORMULA FOR MAXIMUM PRESSURE ON BASE OF PRO- 
 JECTILE. In the same way, as the result of integration, the 
 expression for the maximum pressure on the base of the 
 projectile is 
 
 (93) 
 
 in which the quantities are the same as before, and K is a 
 constant whose value is to be determined as will be ex- 
 plained. 
 
 VALUES OF A AND B. If for a given powder we know the 
 values of a and ft, we can fire this powder from two differ- 
 ent guns, and measure the resulting initial velocities. This 
 will give v. The values of c, u, and p are known for the 
 two guns, and the values of c3 and A also, and, having two 
 equations containing A and B, they can be calculated. But 
 it is difficult to find exact values for a and ft, since they de- 
 pend on /and r, equation (92), and the values of these quan- 
 tities are uncertain. To avoid this difficulty, Sarrau adopts 
 a particular powder which he calls a type powder, and 
 assumes for it the values /= i, t =. i. 
 
 The values of a and A for the type powder are calculated 
 as explained previously. Hence all the quantities in (91) 
 are known except A and B, and they can now be calculated. 
 
GUNPOWDER AND INTERIOR BALLISTICS. 55 
 
 Since A and B are constants to be determined experimen- 
 tally, whatever errors we make in assuming the values of / 
 and r will be corrected for in the values of A and B as found 
 by experiment ; and since these values of A and B are inde- 
 pendent of all the elements of fire, they will be true for all 
 powders and all guns. A and B are found by experiment be- 
 cause they depend on v, which is determined by experiment. 
 
 In this way Sarrau found the values of A and B to be 
 
 log A = 2.56635 ; 
 log B = 2.30964. 
 
 CHARACTERISTICS a AND (3. Having the values of A and 
 B in (91), we must know the characteristics a and ft for any 
 powder before we can apply the formula to this powder. 
 The values of a and ft depend on /, a, A, and r (see (92) ). 
 a and A can be calculated, as before explained, for any grain 
 of ordinary shape, and their values for most service forms 
 have been given. The value of /is uncertain, and therefore 
 for simplicity Sarrau assumes / = i for all powders, the 
 same as for the standard powder. 
 
 We have seen that/ is practically constant for all pow- 
 ders, and hence the above assumption may be made. The 
 value of r cannot be accurately determined except by the 
 use of a formula not yet deduced, and hence the method of 
 determining it will be explained later. 
 
 28. Maximum Pressure on Breech of Gun Value of K. 
 
 MAXIMUM PRESSURE. Equation (93) gives the maximum 
 pressure on the base of the projectile, and in order to use 
 it K must be known. If we could measure accurately the 
 pressure on the base of the projectile, the value of K could 
 be found by firing a shot from a gun, since all the quantities 
 except K in (93) would be known, and hence it could be 
 determined. But this pressure cannot be accurately meas- 
 ured, and hence we determine first the maximum pressure 
 on the breech. 
 
 To do this assume equation (64) : 
 
56 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 Differentiate with respect to t : 
 
 dv' _ m + #'/* dv 
 ~dt'~ ~~M~~~dt' 
 
 M 
 Multiply both members by , co being the area of cross- 
 
 section of the bore : 
 
 M dv' 
 
 ..... (95) 
 
 Now denoting by P the maximum pressure per unit of 
 surface on the bottom of the bore, and by P the correspond- 
 ing pressure on the base of the projectile, we have 
 
 and substituting in (95), 
 
 (97) 
 
 Substituting weights for masses, and for 0' its value i, 
 
 (98) 
 
 This equation does not give true values for P , since in 
 placing the total pressure equal to the accelerating force, 
 equation (96), we have evidently neglected the force neces- 
 sary to overcome the passive resistances. Sarrau has there- 
 fore adopted, as more nearly agreeing with experiment, the 
 following formula : 
 
GUNPOWDER AND INTERIOR BALLISTICS. 57 
 
 Substituting for Pin (99) its value from (93), we have 
 
 *=4+l|)^. . . . (ioo) 
 
 Making 
 
 we have 
 
 Making 
 
 KK' = K 
 and 
 
 which is justified by experiment, w have finally, for the 
 pressure on the breech, 
 
 or reducing, 
 
 P, = KffJ ..... . . (103) 
 
 Since we can measure very accurately the pressure on 
 the breech of a gun, we fire with a given powder, measure 
 this pressure, substitute it for P 9 in (103), and, as all the 
 other quantities except K are known, we thus obtain its 
 value, which is 
 
 log K* = 4-25092. 
 
 VALUE OF K IN (93). Having the value of P , we substi- 
 tute it in (99) and find the corresponding value of P. This 
 value of P in (93), together with the known values of the 
 other quantities, will give K, whose value is 
 
 = 3.96197. 
 
58 TEXT-BOOK OF ORD NANCE AND GUNNERY. 
 
 Collecting the pressure formulas for convenience, we 
 have 
 
 P = Ko?A^ , on base of projectile 
 
 P t = Kjx*At--^-, on breech of gun. 
 
 log K= 3-9 6l 97; 
 
 log K, 4.25092. 
 
 29. Theoretical Maximum Velocity Time of Burning Correspond- 
 
 ing to the Maximum Velocity. 
 
 MAXIMUM VELOCITY. Assuming the binomial formula 
 for velocity, and replacing a and ft in it by their values, 
 equation (92), 
 
 we have 
 
 /AA ' " IUr -**=n ( I04 ) 
 
 If in this equation we make v and t the only variables, it 
 can be shown by the usual rules of calculus that v will have 
 a maximum value for a particular value of r. That is, as 
 i decreases in value, v will increase till it reaches a maxi- 
 mum. 
 
 But this ought not to be the case, because, theoretically, 
 as t decreases, or the powder becomes more quick, v should 
 increase; and this increase should continue up to the limit 
 where the combustion is practically instantaneous and rz=o. 
 
 Formula (104) gives this maximum value for v because it 
 is not absolutely correct, but only approximate. It will be 
 remembered that in its deduction it was stated that the 
 value for v was expressed in the form of a series, of which 
 the first two terms only were retained. But the function 
 represented by this series may go on increasing when r 
 decreases below the value which makes the sum of the first 
 two terms a maximum, provided the sum of the other terms 
 goes on increasing. 
 
GUNPOWDER AND INTERIOR BALLISTICS. 59 
 
 The value of r corresponding to the maximum of the 
 first two terms is nevertheless important, because it marks 
 the limit below which a decrease in r gives only a slight 
 increase in the velocity. It is not advisable to pass below 
 
 this value of t in practice, because a = f J enters the 
 
 pressure formulas (93) and (103) to the second power, and 
 r being in the denominator of the value of a, a small de- 
 crease in r causes a rapid increase in the value of a, and 
 hence in that of the maximum pressure, while the gain in 
 velocity, as shown by the previous discussion, is very small. 
 
 VALUE OF r CORRESPONDING TO THE MAXIMUM VALUE 
 OF v. The particular value of r which corresponds to this 
 maximum value of v is called the " time of the maximum." 
 
 Differentiating equation (104) with respect to r, placing 
 
 -r- o, and solving for r, we have, calling the resulting 
 
 value r l9 
 
 (I05 > 
 
 This shows that for a given form of grain, the value of r l 
 or the time of the maximum, depends on the calibre, weight 
 of projectile, and length of travel, and is independent of the 
 charge of powder and density of loading. 
 
 For the same powder, the weight of the projectile p is 
 proportional to the cube of the calibre, the length of travel 
 u to the first power of the calibre, and hence, since $B\ is 
 constant, we may write, from (105), 
 
 r = 
 
 (.06) 
 
 or the time of the maximum is proportional to the calibre of 
 the gun ; that is, to obtain the greatest velocity, the time of 
 burning should increase as tae calibre of the gun increases, 
 or large-grain powder should be used in large guns, which 
 proves the principle enunciated by Rodman. 
 
60 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 30. Modulus of Quickness Value of Modulus Velocity and Pres- 
 sure as Functions of this Modulus. 
 
 MODULUS OF QUICKNESS. Powders are called "quick" 
 or " slow " depending upon their action in a given gun. A 
 given powder may be "quick" when used in one gun and 
 " slow" when used in another. For example, the I. K. pow- 
 der which is used in the 3.2o-inch field-guns is " quick " when 
 used in the 8-inch rifle, and " slow " when used in the Spring- 
 field rifle. From equation (105) we can calculate the value of 
 r l , or the time of the maximum, for any gun and powder. 
 
 A powder whose time of combustion is much greater 
 than this is called a slow powder for this gun, and one whose 
 time of combustion is nearly equal to this is called a quick 
 powder for the same gun. 
 
 Also two powders fired in different guns are considered 
 equal, as regards their quickness, if their times of combus- 
 tion are proportional to the " times of the maximum" of the 
 two guns considered. Hence, if we make 
 
 ( I0 7) 
 
 and call this ratio x the " modulus of quickness " of the 
 powder, we can say that the quickness of a powder is meas- 
 ured by its modulus. 
 
 On this basis Sarrau classifies powders as follows : 
 
 x = i.o, very quick powder; 
 x = 0.9, quick powder ; 
 x ' = 0.8, medium powder ; 
 # = 0.7, slow powder ; 
 x 0.6, very slow powder. 
 
 VALUE FOR MODULUS, We have, from (107), 
 
GUNPOWDER AND INTERIOR BALLISTICS. 6l 
 
 Substitute for r^ its value from (105), and we have 
 
 and since from (92) 
 
 we have 
 
 x $Bfi^- (108) 
 
 VELOCITY AS A FUNCTION OF THE MODULUS x. To ex- 
 press the velocity as a function of the modulus, we have 
 for the subtractive term of the binomial formula (104) from 
 (1070), 
 
 and for r from the same equation, 
 
 xc 
 Substituting the value - for the subtractive term, and for r 
 
 I fsi\ \ 
 
 its value above, in the factor (^-J in the binomial formula, 
 we have 
 
 Making 
 
 we have 
 
 v = 
 
62 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 MAXIMUM PRESSURE AS A FUNCTION OF THE MODULUS 
 x. By a similar process the pressures on the base of the pro- 
 jectile and on the breech may be expressed in terms of x. 
 
 For the maximum pressure on the base of the projectile 
 we have 
 
 and for that on the breech 
 
 31. Limit of Use of Binomial Formula. 
 
 It has been shown that v in formula (91) becomes a max- 
 imum when t decreases to a particular value r t , and also 
 that v should not be a maximum for this particular value of 
 r, but should increase continuously as -c decreases. 
 
 It is also evident from (107) that when r becomes r l , x, 
 the modulus, becomes unity, or x i. That is, the velocity 
 is a maximum by formula (91) when x = i. 
 
 The value of x from (108) is 
 
 ("3) 
 
 and the subtractive term of the binomial formula is 
 
 ....... (,,4) 
 
 which is \ of x. Hence when v becomes a maximum in (91), 
 x becomes unity, and the subtractive term of (91) becomes \. 
 This value for the subtractive term would then mark 
 the limit of the use of the binomial formula, were it not for 
 the fact that as a function approaches its maximum it 
 changes its value very slowly, and hence before we reach 
 the value x = i, the binomial formula will cease to give cor- 
 rect results. For this reason Sarrau adopts the value x T T 
 for the particular value of the modulus at which it is best to 
 cease the use of formula (91). 
 
GUNPOWDER AND INTERIOR BALLISTICS. 63 
 
 When x = T 9 T , the subtractive term, being | of x, will be 
 i f TT - 2 73- Hence we have for determining the limit 
 of the use of the binomial formula the rule : Calculate the 
 value of the subtractive term in the binomial formula ; if it 
 is greater than 0.273, the binomial formula is not applicable ; 
 if less than 0.273, it is applicable ; or 
 
 > 0.273, do not use binomial formula ; 
 
 < 0.273, use binomial formula. 
 
 32. Monomial Formula for Velocity. 
 
 It is necessary, from what precedes, to have a formula for 
 velocity that can be used when the binomial formula ceases 
 to apply. 
 
 It is deduced as follows : The values of the modulus for 
 all powders in use vary between narrow limits (0.6 to i.o). 
 
 Hence, assuming the equation (1090), 
 
 A*) = 
 
 we may place 
 
 ........ (116) 
 
 since when a variable changes its value within narrow 
 limits, the function is proportional to some power of the 
 variable properly chosen. It is necessary now to find the 
 proper value of n in (116). 
 
 Differentiating (116), we have 
 
 r- //w = 
 
 L =;r /M [See(n6).] 
 
 Substituting for /(*) and fix) their values from (109*), 
 we have 
 
 for the value of n required. 
 
64 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 Assume equation (no); and substitute in it for f(x) its 
 value (116), and we have 
 
 Substitute for x its value (107^), and make 
 
 M =-A($By-*N, (119), 
 
 and we have 
 
 
 Formula (120) is a general form of the binomial formula 
 (104), and will give the same values for v as the binomial 
 formula, if the proper values for n be substituted. For the 
 particular case when x = T 9 T and n \ (120) becomes 
 
 This equation (121) is strictly applicable only to the par- 
 ticular case for which it was deduced ; that is, for x = T 9 T 
 and n = ; but by examining it we see that v increases con- 
 tinuously as t decreases, which should be the case, while in 
 the binomial formula, as already shown, v ceases to increase 
 as f decreases. 
 
 Hence if we use equation (121) for all values of x equal 
 to or greater than ^, we will obtain a value for v which is 
 correct for the value x T 9 T , and for all values of x greater 
 than T 9 T , values for v which will be more nearly correct than 
 those given by the binomial formula. 
 
 This is called the " monomial formula" for velocity, ana 
 we say that it is used whenever the subtractive term in the 
 
GUNPOWDER AND INTERIOR BALLISTICS. 65 
 
 binomial formula is greater than 0.273 ; since when that is 
 the case the binomial formula is no longer applicable. 
 
 When the subtractive term is nearly equal 100.273, either 
 formula can be used. 
 
 The monomial formula is usually written 
 
 (122) 
 
 by substituting a and /? for their values, equation (92). 
 
 To find M, Sarrau assumes a type powder as before, 
 making / = I, T: = i, and thus determines a and ft. The 
 powder is then fired in a given gun, v measured, and thus 
 everything is known in (122) except M, which may be cal- 
 culated. 
 
 Its value thus determined is 
 
 log M = 2.84571. 
 
 33. Calculation of the Value of T. 
 
 For the type powder t i, and under this supposition 
 the values of A and B are deduced. The values of r for all 
 other powders must therefore be expressed in terms of the 
 type powder as unity. That is, the value of r for any pow- 
 der is the ratio of its true time of burning to that of the 
 time of burning of the type powder. 
 
 The force of all nitrate powders is practically constant, 
 as has been shown ; and since /= i for the type powders, it 
 may be assumed as unity for all powders as an approximate 
 value. Making /= i in the binomial formula (104), we have 
 
 For any particular powder to which this formula is ap- 
 plicable, we could measure v and determine r, since all the 
 other quantities are known, if the equation could be solved 
 for r. But it is found that this solution is impossible. 
 
66 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 If the monomial formula applies to this particular pow 
 der, we have, making /= i, 
 
 (125) 
 
 In (125), placing 
 
 we have 
 
 a*X* 
 
 * = 
 
 and this may be easily solved and the value of r obtained. 
 For any powder, however, we do not know beforehand 
 whether the binomial or the monomial formula is applicable, 
 since r must be known to determine this point. Again, 
 while the value of f is very nearly unity for all powders, it 
 is not exactly unity for any except the type powder, and 
 hence the value of r determined as above by the monomial 
 formula would not be correct. 
 
 Under these circumstances we proceed as follows : The 
 value of r determined by (127) is approximate, but the 
 approximation is sufficiently correct to show which formula 
 is to be used. Substitute the value of r from (127) in the 
 subtractive term of the binomial formula 
 
 = B ~T O 2 *) 
 
 If the result obtained is greater than 0.273, the monomial 
 iormula applies ; if less than 0.273, the binomial. 
 
 Then calculate a by the pressure formula (103). Substi- 
 tute this value of OL in either the monomial or the binomial 
 formula according as the former or the latter applies, as de- 
 termined by the test, and solve for ft. This value of ft sub- 
 stituted in the formula 
 
GUNPOWDER AND INTERIOR BALLISTICS. 67 
 
 will give r. The value of r thus obtained, substituted in the 
 formula 
 
 together with the correct values of a and a, will give/. 
 
 34. Determination of the Characteristics a and ft. 
 ist Method. We have, equation (92), 
 
 Assuming /= i for all powders, we can calculate a and A, 
 for any service form of grain by the methods already ex- 
 plained, and illustrated in the case of the spherical grain ; 
 r can be calculated by the method explained above, in terms 
 of the type powder as unity, and hence we find a and ft. 
 
 2d Method. In the second method we find the values of 
 a and ft directly, without determining /, a, A, and r, as 
 follows : 
 
 The characteristics a and ft enter the binomial and mono- 
 mial formulas (91) and (122), and a enters the pressure for- 
 mula (103). Hence, for a given piece, powder, and projec- 
 tile, if we measure accurately the pressure, and substitute it 
 in (103), we can find #, and substituting the measured veloc- 
 ity and the value of a, just found, in either the monomial or 
 the binomial formula, whichever is applicable, we can find ft. 
 
 $d Method. In the third method two different guns are 
 used, and the velocities accurately measured under two dif- 
 ferent conditions of firing. The results being substituted in 
 the binomial formula, or in the monomial and binomial for- 
 mulas together, will give two equations, containing the two 
 unknown quantities a and ft, from which they may be ob- 
 tained. 
 
 The following table gives data with reference to Ameri- 
 can guns and powders, and was calculated from data fur- 
 nished from the Ordnance Proving Ground, Sandy Hook, 
 N.J. 
 
68 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 
 
 GO. 
 
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GUNPOWDER AND INTERIOR BALLISTICS. 69 
 
 35. Effect of Variation of Elements of Loading upon Velocity, and 
 
 Maximum Pressure. 
 The variable elements of loading for any gun are : 
 
 1. The weight of the charge of powder, c3 
 
 2. The density of loading, A. 
 
 3. The time of combustion of the grain, r. 
 
 The fixed elements are, : 
 
 1. The calibre, c. 
 
 2. The travel of the projectile in the bore, u. 
 
 3. The weight of the projectile,/. 
 
 For the same force of the powder and the same form of 
 grain, having c, u, and p constant, we may vary GO, A, and r 
 so as to obtain the same muzzle velocity with a different 
 maximum pressure on the breech, or the same maximum 
 pressure with a different muzzle velocity. In this discussion 
 the maximum pressure on the breech is alone considered, 
 since it is always greater than that on the base of the pro- 
 jectile. There are an infinite number of sets of values of 
 c5, J, and r which will satisfy these conditions, and the ques- 
 tion is to determine what set to use. 
 
 Assume equations (no) and (112), and regarding c3, J, 
 and r as variables, take the Napierian logarithms of both 
 members of each, differentiate, and we have 
 
 + fr; .... (I29) 
 
 A j(x 
 
 + "30, 
 
 Now 
 
 Hence 
 
70 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 We have also, from (1160), 
 
 Substituting these values in (129) and (130), we have 
 dv 3 d&> I dA dr 
 
 dJ\_$d dA_ dr 
 > -^" A" t' 
 
 These equations show that when c3 and A increase, v and 
 P 9 increase, and when r increases, v and P decrease ; and 
 this should evidently be the case. 
 
 36. Change of Velocity when Maximum Pressure remains Con- 
 stant Fixed Powder-chamber. 
 
 VARIATION OF VELOCITY. A gun, like any other struc- 
 ture, is built to stand a certain fixed maximum pressure, and 
 this pressure must not be exceeded. Therefore the most 
 important consideration is to find how the velocity will 
 vary for such changes in c3, A, and r as will keep the maxi- 
 mum pressure constant and within limits. 
 
 To do this we will consider the three variables GO, A, and 
 t in order, keeping one constant and varying the other two, 
 and find the effect upon the velocity, the pressure being 
 always constant and a maximum. 
 
 I st. GO constant, A and r variable. Since P and c3 are 
 constant, we have 
 
 and hence, from (133), 
 
 dA di 
 
GUNPOWDER AND INTERIOR BALLISTICS. fl 
 
 This condition must hold in order that P be constant. 
 Substituting the above value of -- in (132), we have 
 
 dv dA 
 
 --(t-) T ....... (134) 
 
 The value of n is, from (117), 
 
 2 3 x 
 
 When the modulus x > 0.6, which corresponds to a very 
 slow powder, n < J, and hence is positive and increases 
 
 with A. Therefore, when the weight of the charge is con- 
 stant, we see from (134) that we may increase the velocity 
 by increasing the density of loading ; but in order to keep 
 the pressure constant, (133^) shows that we must use a slower 
 powder. 
 
 2d. A constant, GO and t variable. P and A being constant, 
 we have 
 
 dP. = o ; 
 
 and from (133), 
 
 3 doo dr , 
 
 -- = ......... < I34a > 
 
 for the condition that P shall be constant. 
 
 Substituting this value of -- in (132), we have 
 
 The value of n is 
 
 (135) 
 
 V 4 \2 I GO 
 
?2 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 When x = o, n \. It is less than J for every other 
 value of x. Hence ( ri) is always positive, and - - in- 
 
 creases with c3. 
 
 Therefore when the density of loading is constant, (135) 
 shows that we may increase the velocity by increasing the 
 weight of charge, but (1340) shows that in order to keep the 
 pressure constant we must also use a slower powder. 
 
 This means that we can obtain an increase of velocity 
 with a constant maximum pressure, by increasing the size 
 of the chamber and using a larger charge of slower 
 powder, and this is the general method employed at present. 
 
 3d. t Constant, do and A Variable. P Q and r being con- 
 stant, we have 
 
 //V-o; 
 
 dr = o; 
 and from (133), 
 
 d& dA 
 
 for the condition that P shall be constant 
 
 dA . 
 Substituting this value of r- in (132), we have 
 
 dv d 
 
 Since this is always positive, (136) shows that for the same 
 kind of powder we may increase the velocity by increasing 
 the weight of charge, but (135^) shows that in order to keep 
 the pressure constant we must also decrease the density of 
 loading. 
 
 FIXED POWDER-CHAMBER. In the preceding discussion 
 it has been supposed that we could vary the size of the 
 powder-chamber. But in the ordinary case, with a gun 
 already built, the powder-chamber will be fixed and its 
 volume constant. In this case we have 
 
GUNPOWDER AND INTERIOR BALLISTICS. 73 
 
 Taking the Napierian logarithms of both members and 
 differentiating, we have 
 
 dA doo 
 
 ~A '-''-& (137) 
 
 Substituting this value of -j- in (132) and (133), we have 
 
 dv 5 doo dt 
 ^ = 8^~ -*7 
 
 dP Q _ 7 d& dr 
 ~ -~-'- 
 
 039) 
 
 The variables are thus reduced to two. Now if we sup- 
 pose cS and t to vary so as to keep P constant, we have 
 dP a o, and from (139) 
 
 dt 7 d(S 
 
 7" = 4 -' 04) 
 
 for the condition that P shall be constant. 
 Substituting this value of in (138), 
 
 dv 
 
 When x = 0.6, n = J (see 1350) ; and for larger values of 
 x, n becomes smaller ; therefore for all cases in practice the 
 second member of (141) is positive, and v increases with GO. 
 
 Hence (141) shows that when the powder-chamber is 
 fixed, we may increase the velocity by increasing the weight 
 of the charge, but (140) shows that in order to keep the 
 pressure constant we must use a slower powder. That is, 
 we use a larger charge of slower powder. 
 
 37. Relative Variation of Velocity and Time of Combustion Of 
 Velocity and Maximum Pressure Limits of Modulus Use- 
 ful Practical Formulas. 
 VELOCITY AND TIME OF COMBUSTION. To determine 
 
 the relative change in velocity for a given change in the 
 
74 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 time of combustion, suppose r to be the only variable in 
 equation (132). Then 
 
 dob = o ; d A = o ; 
 and the equation becomes 
 
 dv dr 
 -SB n . (142) 
 
 v t 
 
 As powder becoms slower x decreases. But as x de- 
 creases n increases (see 1350). In fact, n may be called the 
 "modulus of slowness," since it increases as the powder 
 becomes more slow, while x, or the " modulus of quickness," 
 increases as the powder becomes quicker. From (142) it is 
 evident that for the same relative change in the time of 
 burning the effect upon the velocity will be greater as the 
 powder becomes more slow, since n becomes greater. 
 
 This is one of the principal objections to using very 
 slow powder, because small irregularities of manufacture, 
 which are always apt to occur, affect r, the time of burning, 
 and cause irregularities in velocity. 
 
 VELOCITY AND MAXIMUM PRESSURE. In the same way, 
 to determine the relative change of velocity and maximum 
 pressure, suppose t the only variable in equation (133). 
 
 Then 
 
 dob = o ; dA = o ; 
 and the equation becomes 
 
 Tr*'-~r 043) 
 
 Substitute this value of in (142) and we have 
 
 dv dP, 
 
 =- (I44) 
 
 From this we see, generally, that with quick powders, 
 since n is small, a given increase of pressure gives only a 
 
GUNPOWDER AND INTERIOR BALLISTICS. 75 
 
 very small increase of velocity, and for slow powders, since 
 n is large, a given increase of pressure gives a considerable 
 increase of velocity. Hence it is advantageous on this 
 account to use slow powders. 
 
 LIMITS OF THE MODULUS. The preceding considera- 
 tions may be applied in fixing the inferior limit of the 
 modulus as follows : 
 
 Equation (144) shows that as x decreases, or n increases, 
 a given increase in the pressure will give a considerable 
 increase in the velocity, and hence it appears to be advan- 
 tageous to use a slow powder, for which n is large. But 
 (142) shows that for large values of n we have great irregu- 
 larities in v, as previously explained, and Sarrau has fixed 
 upon 0.6 as the value of x below which it is not expedient 
 to go in practice in order to avoid these irregularities. 
 
 For the superior limit, when x T 9 T or n = , equation 
 (144) shows that the relative increase of velocity is only one 
 eighth that of the maximum pressure ; and since the mono- 
 mial formula was deduced for this value, it was formerly 
 regarded as the superior limit of the modulus. Other con- 
 siderations, however, have led to an increase of this value 
 up to 1.2 for some powders. 
 
 USEFUL PRACTICAL FORMULAS. In practice it is fre- 
 quently required to find what change in velocity and press- 
 ure a given change in weight of charge will produce in the 
 same gun. For this purpose assume the monomial formula 
 for velocity 
 
 For any other charge of the same powder whose weight 
 is cS', all the quantities in the formula will remain constant 
 except z/, c3, and A. The value of A is 
 
 27.68c3 
 
 A = - = 
 
76 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 K being a constant. Raising both members to the one- 
 fourth power and multiplying by c3*, 
 
 Dividing the value of v by that of z/, we have 
 v c3* 
 
 t ? = e'i ........ (I45) 
 
 Similarly, for the pressures we have 
 
 Dividing as before, we have 
 
 ' = ........ 046) 
 
 These formulas are correct for quick powders and ap- 
 proximately correct for slow ones. The velocity formula 
 is useful where it is necessary to find the charge required 
 to give a certain velocity to a projectile at a target at re- 
 duced range, as in armor-plate experiments. 
 
 38. Pressure Curves in Guns Noble and Abel's Method Mayev- 
 ski's Method. 
 
 It is necessary in designing a gun to know the pressures 
 at different points along the bore, as the projectile moves 
 through it, under the action of the powder-gas, in order that 
 the gun may be given sufficient strength to withstand these 
 pressures. 
 
 The accurate solution of this problem is attended with 
 great difficulties, and can hardly yet be said to have been 
 successfully accomplished. Enough is known, however, to 
 
GUNPOWDER AND INTERIOR BALLISTICS. 77 
 
 furnish safe working limits in designing the strength of the 
 gun at different points. 
 
 NOBLE AND ABEL'S METHOD. They assumed an ex- 
 pression of the form 
 
 (I47) 
 
 in which x is the distance travelled by the projectile, t the 
 
 -+-H i * 
 
 irn n n 
 
 -J ' f 
 
 FIG. 9. 
 
 corresponding time, and a, a, /3, and y constants to be deter- 
 mined by experiment. 
 
 Wires were inserted into a gun through holes drilled at 
 short intervals, as shown in Fig. 9. These wires carried 
 currents of electricity, which were broken by the projectile 
 in its passage through the bore, and these breaks were re- 
 corded on the Noble chronoscope, which is an instrument 
 for measuring very small intervals of time. 
 
 The distance between the holes gave x, and the record 
 of the chronoscope /, and substituting the values thus ob- 
 tained in (147), the most probable values of the constants 
 were determined by the method of least squares. 
 
 Differentiating (147) with respect to / gives 
 
 and differentiating this with respect to / gives 
 
 d* x dv /T , 
 
 W = T t ........ (I49 
 
 the acceleration. 
 
 If W be the weight of the projectile and P the total 
 pressure on its base, we have 
 
/ TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 i 
 
 MAYEVSKI'S METHOD. General Mayevski assumed 
 
 x = At + /* + a 3 + Dt* + etc., . . . (151) 
 
 and by experiment determined /, having x given by the 
 nature of the experiments (see Fig. 10). His general plan 
 resembles that of Noble and Abel, but differs in the method 
 of conducting the experiments. 
 
 FIG. 10. 
 
 From these results values of A, B, C, and D were deter- 
 mined by the method of least squares. 
 
 Differentiating (151) with respect to /, we have 
 
 ., . (152) 
 
 for the velocity at any point. 
 From (152) we have 
 
 (I53) 
 
 for the acceleration ; and for the point where this is a maxi- 
 mum we have, from (153), 
 
 
 
 (154) 
 
 39. Longridge's Method. 
 
 Mr. Longridge, an English engineer, uses a combination 
 of Noble arid Abel's and of Sarrau's formulas as follows : 
 
 Noble and Abel's formula for the pressure curve is, see 
 (45), 
 
GUNPOWDER AND INTERIOR BALLISTICS. 79 
 
 in which p is the pressure corresponding to the volume 
 z/', v' is the volume of the powder-chamber supposed to be 
 entirely filled with powder, and v" any other volume of ex- 
 pansion. 
 
 E 
 
 Let AB, Fig 1 . 11, represent the reduced length of the 
 powder-chamber, that is, the length of a cylinder whose 
 diameter is that of the bore and whose volume is that of 
 the powder-chamber. 
 
 Suppose, according to Noble and Abel's hypothesis, that 
 all the powder is burned before the projectile moves from 
 its position B. Make v" v' in (155), and we have/ 43 
 tons. 
 
 This is the pressure that would exist in the chamber if 
 the powder were all burned before the projectile moved. 
 
 Lay off BB' = 43 tons. Assume different values for v" ', 
 corresponding to C, D, E, etc. Calculate the corresponding 
 ordinates from (155), and erect them at the corresponding 
 points. 
 
 The resulting curve B'C'D'E' will be Noble and Abel's 
 pressure curve. 
 
 Now it is known that the powder is not all burned before 
 
8O TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 the projectile moves, and hence the pressure BB' 43 tons 
 cannot exist in a gun. 
 
 The maximum pressure that does exist is given by Sar- 
 rau's formula for the maximum pressure on the breech. 
 
 P = A>M/V. 
 
 Calculate this pressure, lay off A A' at the breech equal 
 to it, and assume this pressure to be uniform from the breech 
 to the point of maximum pressure in the bore. Substitute 
 this value of P for p in (155) and find the corresponding 
 value of v" . This value of v" will give the point P in the 
 bore at which the maximum pressure occurs. The line A'P'' 
 will be parallel to AP, and the curve of pressures will be 
 A'P'C'D'E'. 
 
 Let ^, AB, the reduced length of the powder-chamber; 
 x = any other length measured from A. Then 
 
 and equation (155) becomes 
 
 ( 43 ) '- 074 
 
 which is more convenient for use. 
 
 The pressure at B is originally zero and rises to a maxiv 
 mum at P'. Hence the actual pressure curve has the form 
 BP'C'D'E'. 
 
 The form of the curve from B to P r is not important, as 
 its maximum ordinate only is required. 
 
 40. Pressure Curve by Sarrau's Formulas. 
 
 The pressure curve in a gun may also be obtained from 
 Sarrau's velocity formulas, as follows: 
 
 For a slow powder we have 
 
 v = 
 
GUNPOWDER AND INTERIOR BALLISTICS. 8 1 
 
 In (1560) u is expressed in inches. In (161), following, v 
 and g are in feet, and u must be expressed in feet in order 
 that, when du is substituted in (161), all the quantities may 
 have the same unit. 
 
 Hence in (156^) we write 
 
 u* inches = I2V feet; 
 
 and in the subtractive term 
 
 ( 
 
 * inches = I2** feet. 
 Place 
 
 v = au\i - 6u*) 9 ....... (157) 
 
 in which u is in feet, and 
 
 X 12* 
 
 From mechanics we have 
 
 du = vdt\ .'. dt = . 
 
 Substituting in the value of P f , we have 
 
 059) 
 
 g 
 
82 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 p being the weight of the projectile, and ;// it's mass ; and if GO 
 denote the area of the base of the projectile in square inches, 
 we have for the pressure in tons per square inch on its base, 
 
 . du t' 6 ') 
 
 Differentiating (157), we have 
 
 ^ v 3 -* 7 
 
 du ~ 8 a ' ~ 8 a H ' 
 
 and 
 
 vdv 357 
 
 ^7=8' Z "" : - 4*'*" 1 + gV*. (162) 
 
 Hence 
 
 P' 7 = / _ f~3^ 9 _ d _ 5_ , , j , 7 ; , , 8 t ~| 6 
 
 2240X<X^L8^ 4^ '8^ J* ( 
 
 For quick powders we have 
 
 71 
 
 * -' 
 
 which may be placed in the form 
 
 v = a'w\ ......... (164) 
 
 u being in feet as before explained, and 
 
 , Ma/3-*&4Vx 12* 
 
 -ph ~ ..... 
 
 Differentiating (164), we have 
 
GUNPOWDER AND INTERIOR BALLISTICS. 83 
 
 and 
 
 vdv 3 
 
 ~du = i6 a *' ...... ('6;) 
 
 Hence 
 
 Since these curves are obtained on the adiabatic hypothe- 
 sis, they may be considered as marking the interior limit of 
 pressures, and the true pressure curve probably lies between 
 the latter and those obtained by Longridge's method. 
 
 It must be remembered that the pressures given by these 
 equations (163) and (168) are those producing motion of the 
 projectile, and do not represent the total pressure on the 
 base. 
 
 41. Determination of Velocity by Experiment General Principles 
 Targets for Cannon For Small Arms. 
 
 In order to verify the formulas for velocity and pressure 
 previously deduced, it is necessary to determine accurately 
 by experiment the velocity of the projectile, and the pressure 
 in the gun, clue to a given charge of powder, under given 
 conditions of loading. 
 
 VELOCITY. The velocity of a projectile is determined by 
 measuring the time of its passage over a given distance. 
 
 Let A and B be two points whose distance apart is s, and 
 t the time of passage of the projectile over this distance. 
 Then, since 
 
 s 
 v = -, 
 
 v will be the mean velocity of the projectile over the dis- 
 tance s, or its velocity at the middle point between A and B. 
 In order that this may be true, the space s must be so small 
 that the motion of the projectile may be considered uniform 
 and in a right line. As neither of these conditions holds in 
 practice, v will not be the velocity at the middle point be- 
 tween A and B, but it will be sufficiently correct for all 
 practical purposes to assume that it is. 
 
84 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 GENERAL PRINCIPLES. In order that we may know ex- 
 actly the time of passage of the projectile over the distance 
 s, we must have first an accurate scale of time, and second, 
 we must mark on this scale the instant that the projectile 
 passes the two points A and B. The difference between the 
 times of passage of the points A and B will then give the 
 time of passage over the distance s, and knowing this time 
 we can find the mean velocity. The passage of the projec- 
 tile over the points A and B is marked on the time-scale as 
 follows : 
 
 Two targets are set up, one at A and the other at B. 
 Electric currents circulate through these targets, and 
 also through the instrument which furnishes the scale of 
 time. 
 
 When the projectile passes the target at A it breaks the 
 circuit, and this break is registered by the instrument. 
 When it passes B the same thing occurs. The differ- 
 ence between these breaks measured on the scale of 
 time, and corrected for errors, gives the time of passage 
 required. 
 
 TARGETS FOR CANNON. The functions of the targets are 
 then to mark the points in the path of the projectile between 
 which its velocity is to be measured, and to support the 
 wires carrying the electric currents which are to be broken 
 by the passage of the projectile. For cannon, the first target 
 is placed at such a distance from the muzzle that it will not 
 be injured by the blast. Call this distance x iy and the dis- 
 tance from the muzzle to the middle point between the tar- 
 gets x ; then 
 
 The velocity found by experiment is at the point ; that 
 
 which we wish to find is at the muzzle, or the initial velocity. 
 By formulas in " Exterior Ballistics " we can find the latter, 
 when the former, at the distance x i is known. 
 
 Each target for cannon generally consists of a frame of 
 wood carrying a number of small parallel copper wires. 
 
GUNPOWDER AND INTERIOR BALLISTICS. 
 
 FIG. 12. 
 
 The wires are so arranged that the current entering one 
 side of the target must traverse all of them before 
 passing out at the other side, so that the breaking 
 of any wire will break the current. The wires are 
 drawn as tight as possible in order that the break 
 may be abrupt, and the distance between them 
 depends on the diameter of the projectile, as it 
 must be impossible for it to pass through with- 
 out breaking at least one wire. The breaks are 
 repaired after each fire. 
 
 The target is shown in Fig. 12. 
 
 SMALL-ARM TARGETS. As there is practically no blast 
 
 with small arms, the first target is placed at the muzzle, and 
 
 consists of a single wire drawn tightly across it. To avoid 
 
 repairing the second target, it consists of a steel plate to stop 
 
 the bullets. On its rear face is 
 secured a spring insulated from 
 the plate (Fig. 13). This spring, 
 s, is fixed at one end to an insu- 
 lating substance, such as a block 
 of wood, w y and the other end 
 
 rests on a metallic pin,/. The current passes through the 
 spring and pin. When the bullet strikes the steel plate, the 
 shock causes the spring to leave the pin, and thus the current 
 is broken. The elasticity of the spring causes it instantly to 
 resume its former contact with the pin, and thus renders any 
 repairs unnecessary. 
 
 42. The Ballistic Instruments Description of the Le Bouleng6 
 Chronograph. 
 
 The functions of the ballistic instruments are to furnish 
 an accurate scale of time, and to record on that scale the 
 rupture of the targets by the passage of the projectile. 
 
 LE BOULENGE CHRONOGRAPH. The instrument gener- 
 ally used for this purpose was invented by Captain Le 
 Boulenge of the Belgian Artillery, and is called the Le Bou- 
 
 lenge Chronograph. 
 
 Scale of Time Its scale of time is furnished as follows : 
 Two rods are suspended vertically from electro-mag-' 
 
86 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 nets, and the currents which pass through the magnets, 
 pass also through the targets. Each electro-magnet has its 
 own current and its own target, and is independent of the 
 other. 
 
 When the first target is broken, one of the magnets is 
 demagnetized and its rod falls. When the second target is 
 broken, its magnet is demagnetized and its rod falls. The fall 
 of this second rod makes a mark on the first rod while it is 
 falling, and the distance h' from the origin of fall to this 
 mark is measured. Then we have, from the laws of falling 
 bodies, 
 
 which furnishes the scale of time. 
 
 Record of Breaking of Target 
 Description of Instrument. 
 The method of making the 
 record will appear from a de 
 scription of the instrument, Fig. 
 14. 
 
 Its principal parts are a ver- 
 tical column of brass, B, which 
 is supported by a triangular 
 bed-plate, C, and this bed-plate 
 rests upon a support or stand, 
 5. To the brass column are 
 attached two electro -magnets, 
 EE ' . The magnet E supports 
 the long rod a of the instru- 
 ment, called the chronometer. 
 This rod when in use is en- 
 veloped by a zinc or copper 
 tube, z, called the recorder, 
 upon which the mark is made. 
 The magnet E' supports the 
 short rod b, called the 
 trar. 
 
 regis- 
 FIG. 14. 
 
 Fig. 15 shows the details of the marker, or part of the. 
 
GUNPOWDER AND INTERIOR BALLISTICS, 
 
 instrument which makes the record of the breaking of the 
 target. It consists of a cir- 
 cular knife, m, on the end of 
 a spring, s, which causes it 
 to move to the right in the 
 figure. The trigger, /, is 
 supported in its fulcrum on 
 the bed-plate. Its right end 
 terminates in a catch, which 
 engages in a corresponding 
 one on the knife, and pre- 
 vents the latter from moving 
 to the right, under the action 
 of the spring, till the catch is 
 freed. The left end of the 
 lever is acted on by a spring 
 s', which presses it upwards, 
 and keeps the catch engaged 
 with the knife. The piece marked b is a disk which screws 
 into the left-hand end of the lever, and which may be raised 
 or lowered by means of the screw. 
 
 Above the disk is a tube or cup which retains the short 
 rod b after its fall. The record is made by the short rod 
 falling on the disk b, depressing it, and releasing the knife 
 ;;/ from the catch on the trigger. The knife then moves to 
 the right and, striking the long rod in its fall, makes the 
 required record. 
 
 43. Arrangement of Wires Working of Instrument Disjunction. 
 
 ARRANGEMENT OF WIRES. The arrangement of the 
 wires depends upon whether the time to be measured is 
 comparatively great or small. When great, the wires are 
 arranged as follows, Fig. 16. 
 
 The chronometer is supported by the upper magnet. The 
 first current comes from the battery to the upper magnet, 
 E\ from the magnet E to the disjunctor, whose functions 
 will be explained later ; from the disjunctor to the first target, 
 and from the first target to the battery. The course of the 
 second current is similar and can be readily followed. 
 
88 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 The instrument thus arranged i-s called a megagraph. 
 WORKING. When the first target is broken, the chronom- 
 eter falls ; when the second target is broken, the registrar 
 
 FIG. 16. 
 
 falls, and, striking the disk of the trigger, makes the record 
 on the chronometer, as at R, Fig. 14. 
 
 The point on the chronometer from which all heights 
 are measured is the mark O, Fig. 14, made on this rod by 
 the knife when the chronometer is susperided by its magnet. 
 Denoting the height OR by ti , the corresponding time is 
 
 and is the time which elapses from the fall of the chronom- 
 eter till the record is made. It is not, however, the time of 
 passage of the projectile between the targets, because 
 
 1. There is a certain time required for the demagnetiza- 
 tion of the magnet E. Hence the chronometer does not fall 
 at the instant the first target is broken, and the time is too 
 short by this amount, which we call /,. 
 
 Instead of making the record the instant the second 
 target is broken, there is a delay caused by 
 
 2. The time required to demagnetize E' = /,. 
 
GUNPOWDER AND INTERIOR BALLISTICS. 89 
 
 3. The time required for the registrar to fall to the disk 
 of the trigger = /,. 
 
 4. The time necessary to disengage the trigger, and for 
 the knife to move forward and make the record on the chro- 
 nometer = / 4 . 
 
 During these last three intervals the long rod is falling, 
 and hence the height of fall, and consequently the time, is 
 too great by their sum. Hence the true time is 
 
 and to find the true value of t it is necessary to find the 
 values of these times, since T is known. 
 
 To do this it is not necessary to find the value of each 
 single interval, since the total time can be readily obtained. 
 If we break both currents at the same instant, it is evident 
 that all the delays mentioned will still exist. The delay in 
 falling of the chronometer, and that of making the record 
 by the registrar, will be marked on the long rod as it falls, 
 and will be found at a certain height above O, as at D, Fig. 14. 
 This height is called " the disjunction," and the time corre- 
 sponding to this height is the algebraic sum of all the times 
 before named. 
 
 Let 
 
 * = (', + ', + O-'r 
 Then 
 
 in which h is the height OD. Hence 
 
 r _0_ A /^ /?* 
 V g \j g' 
 
 It must be remembered that difference of times and not 
 difference of heights is to be taken. 
 
 FIXED DISJUNCTION. For the velocity at the middle 
 point between targets we have 
 
90 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 Substituting for t its value, we have 
 
 v = 
 
 g 
 
 From this equation we see that if the values of s, and of 
 
 or the disjunction, be fixed, the values of v can be 
 g 
 
 calculated and tabulated for all values of h' within the 
 limits of practice. This has been done for the values 
 
 s= 100 feet and \/ = 0.15 second, and this value of 
 
 2h 
 
 \ -- = o- 
 
 V g 
 
 is called the fixed disjunction. If the above table is 
 g 
 
 not at hand, this fixed value of the disjunction avoids the 
 labor of calculating 6 or \ -- for each shot. 
 Hence in this case 
 
 /= T 0.15 sec. = A / 0.15. 
 
 V s 
 
 To fix the disjunction, the disk b on the trigger / may 
 be raised or lowered to regulate the height of fall of the 
 registrar till B = o. 1 5 sec. 
 
 44. Arrangement of Wires for Small Times Disjunctor Measur- 
 ing-rule. 
 
 ARRANGEMENT OF WIRES. Under ordinary conditions, 
 the distance between targets is so great, that the chronometer 
 acquires considerable velocity in falling, before the record 
 is made by the registrar. As the distance between targets 
 decreases there will be less interval between the breaking 
 of the two currents, and consequently between the fall of the 
 two rods. Hence the record will be made before the chro- 
 nometer has acquired much velocity, and small differences 
 
GUNPOWDER AND INTERIOR BALLISTICS. 
 
 in reading will correspond to considerable differences in 
 time. A small error in reading, therefore, will correspond 
 to a large error in time. As the distance between targets 
 decreases, the record will approach the disjunction circle, 
 and will fall on that circle when the distance is zero, or 
 when both currents are broken simultaneously. To measure 
 these short intervals of time accurately it is necessary to 
 allow the chronometer to acquire considerable velocity 
 before the record is made upon it. 
 
 This necessitates a new arrangement of wires and mag- 
 nets, as in Fig. 17. The magnet which supports the regis- 
 trar is changed from below to 
 above that which supports the 
 chronometer, and the first cur- 
 rent runs from the battery to 
 the registrar magnet, thence 
 to the disjunctor and to the 
 first target, so that the regis- 
 trar will fall first. With this 
 arrangement, if both currents 
 be broken simultaneously, the 
 " disjunction " will be made 
 near the top of the chronom- 
 eter at D, when its velocity is 
 greatest. When the registrar 
 falls first, as it does in actual 
 use in determining velocity, it 
 is evident that the record will 
 be made at some point be- 
 low the disjunction, as at R. 
 The same method is followed 
 in determining the time as be- 
 fore, except that the time cor- S~^ 
 responding to the record must" 
 be subtracted from that corre- 
 sponding to the disjunction, for the time of passage between 
 targets. The instrument thus arranged is called a mi< 
 
 .This instrument is used for breaking both 
 
 R 
 
 
 
 FIG. 17. 
 
92 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 currents simultaneously in order to determine the alge- 
 braic sum of all the times /,, t^, /,, etc. 
 
 It consists (Fig. 18) of two steel blades, nri , mounted on 
 
 FIG. 18. 
 
 a block of wood. These blades are attached at one end, 
 m m' , to the block, and carry binding-screws at this end. At 
 the other end they rest on two brass pins, b b' , and these 
 pins are connected with the binding-screws shown. Be- 
 tween these blades is a strong spring, r, with a knob, s, and a 
 spring-catch, g. At right angles to, and attached to this 
 spring r is a cross-piece, pq. The action is as follows : 
 
 When the spring r is pressed down by pushing on the 
 knob s, it is caught and held under the spring-catch g, and 
 the cross-piece is not in contact with the blades n n f . 
 
 Under these circumstances the blades rest on their pins 
 b b' , and the current from each battery enters its own blade 
 by the binding-screws and posts, and passes to its target. 
 
 But when the trigger or catch g is pulled back quickly, 
 the spring r is released, and, rising, its cross-piece/^ strikes 
 both blades n n' at the same instant, lifts them from the pins 
 b b', and breaks both circuits. 
 
 MEASURING-RULE. To facilitate measurements, the 
 heights corresponding to all velocities within the ordinary 
 limits of experiment are inscribed on a metal rule furnished 
 with a sliding index. The heights are in millimetres, and 
 must be reduced to feet for use with English measures. A 
 table of times corresponding to heights in millimetres has 
 been calculated, and by its use the above reduction may be 
 avoided. The sliding index has a knife-edge attached to it, 
 and, to obtain the reading, this knife-edge is placed on the 
 mark made by the marker on the chronometer, a pin on the 
 lower part of the scale having been inserted in a hole in the 
 
GUNPOWDER AND INTERIOR BALLISTICS. 93 
 
 chronometer at the lower end to bring the zero point of the 
 scale opposite the origin of fall. The height can then be 
 read off. 
 
 45. Adjustments Use Objections to the Instrument Br6ger's Im- 
 provements. 
 
 ADJUSTMENTS. The instrument must be properly 
 mounted on a stand at such a distance from the gun that it 
 will not be affected by the shock of discharge, and connected 
 with the batteries and targets, and be then adjusted for use. 
 
 The adjustments are three : 
 
 1. Levelling. The object of this adjustment is to make 
 the bed of the instrument level, and consequently the brass 
 column or standard vertical.*- The chronometer is used for 
 this purpose. The enveloping tube or recorder is first put 
 on, and when in place must rest closely against the bob. 
 Having cocked the knife, suspend the chronometer and 
 recorder from its magnet, and move the levelling-screws 
 which pass through the bed-plate, till the bob of the chro- 
 nometer rests in a square notch in the bed-plate. The stand- 
 ard is now vertical, 
 
 2. Regulating the Magnets. To regulate the strength of 
 the magnets, each of the rods is -provided with a weight 
 which is one tenth that of its rod. Place the proper weight 
 on the chronometer, and suspend it with this weight from its 
 magnet, the core of which is movable, and draw out this 
 core till the rod and weight fall. The strength of the 
 magnet is by this means regulated. Do the same for the 
 short rod, or registrar, and its magnet. 
 
 3. Fixing the Disjunction Reading. For the megagraph 
 this reading is at a fixed height, corresponding to 0.15 
 second. To make the adjustment, place the sliding index 
 on the rule at the mark " disjunction," and clamp it. 
 
 Place the pin of the rule in the hole in the bob of the 
 chronometer, bring the knife-edge of the rule to bear against 
 the copper tube on the chronometer, and turn this tube 
 around the chronometer. The knife-edge will describe a 
 circle on this tube, called the " disjunction circle," and the 
 disjunction reading must fall on this circle. To test it, 
 
94 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 suspend both rods from their magnets, and break both cur- 
 rents by means of the disjunctor. If the mark made by the 
 knife falls on the circle, no adjustment is necessary ; if 
 above the circle, the fall of the registrar is too great ; and 
 if below, the fail is too small. The height of fall of the 
 registrar is diminished or increased by raising or lowering 
 the disk on the left-hand end of the trigger /. The instru- 
 ment is now ready for use. 
 
 USE. In using it, first cock the knife or marker, suspend 
 the long and short rods, and take a disjunction reading. If 
 the disjunction is not exact, correct as above. If exact, 
 cock the knife again, suspend the rods, fire the piece, and 
 read the height with the rule. Find the time corresponding 
 to this reading, subtract from it the time corresponding to 
 the disjunction, which is 0.15 second when the instrument 
 is used as a megagraph ; or if used as a micrograph, sub- 
 tract the time corresponding to this height from that corre- 
 sponding to the disjunction, as previously determined, and 
 the remainder will give the time of passage of the projectile 
 between targets. Divide the distance between the targets 
 in feet by this time in seconds, and the quotient will be the 
 velocity of the projectile at a point midway between the 
 targets. 
 
 OBJECTIONS TO THE INSTRUMENT. The principal source 
 of error in the Le Boulenge arises from the fact that the 
 circuits are not broken similarly by the disjunctor and by 
 the projectile. 
 
 When the circuits are broken by the projectile, the re- 
 tardation of demagnetization is modified, and unequally so 
 for the two magnets, because they sustain different weights 
 and are consequently of different strength. 
 
 BREGER'S IMPROVEMENTS. This has led to modifications 
 of the instrument by Captain Breger (Fig. 19). The princi- 
 pal of these are, the two rods are made of exactly the same 
 weight, and consequently the electro-magnets are of the 
 same strength. Their axes are vertical instead of horizon- 
 tal. The parts generally are heavier and more firmly sup- 
 ported. 
 
 The height of fall of the registrar is regulated by raising 
 
GUNPOWDER AND INTERIOR BALLISTICS. 
 
 95 
 
 or lowering its magnet, ', and the disk of the trigger on 
 which the registrar strikes is fixed 
 with reference to the lever. The 
 knife is square instead of circular. 
 The disjunctor has been modified 
 so as to insure the simultaneous 
 rupture of the two circuits, and 
 the strength of the currents is reg- 
 ulated by resistance-coils. These 
 improvements render the instru- 
 ment much more accurate than 
 the old form. 
 
 E 
 
 E' 
 
 FIG. 19. 
 
 46. Schultz Chronoscope Marcel- 
 Deprez Registers Bashforth Tar- 
 gets. 
 
 SCHULTZ CHRONOSCOPE. The 
 Le Boulenge Chronograph meas- 
 ures velocity at one point only. 
 If the velocity of a projectile is to 
 be measured at several points, a 
 separate instrument is required for 
 each point, and this arrangement 
 would be troublesome, besides hav- 
 ing other objections. 
 
 It is frequently necessary to 
 measure the velocity of the same projectile at different 
 points, as in determining the laws of the resistance of the 
 air to its motion, and also it is sometimes required to deter- 
 mine its velocity at different points in the bore. For such 
 purposes an instrument must be used which will give a 
 scale of time of such an extent that all the phenomena may 
 be registered upon it. 
 
 There are several instruments of this class, and as a type 
 of them the Schultz chronoscope, one of the best known, 
 will be briefly described (Fig. 20). 
 
 Scale of Time. In this instrument a cylinder a revolves 
 by means of clockwork, and this cylinder has also, in the 
 older form of machines, a motion of translation parallel to 
 
9 6 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 its axis. In the most recent form the cylinder rotates only, 
 while the point b, which describes the scale, has the motion 
 of translation. 
 
 The point b is a quill attached to one branch of a tuning-, 
 fork, c. This point may be made to rest lightly against the 
 surface of the cylinder, or may be withdrawn from contact 
 with it. On each side of the tuning-fork is an electro- 
 magnet, d. 
 
 The object of the magnets is to start the fork vibrating, 
 to keep up this vibration during the experiment, and to 
 
 FIG. 20. 
 
 equalize the amplitude. The surface of the cylinder is 
 covered with lampblack before using. When the quill is 
 placed in contact with the coated cylinder, the latter is set 
 to rotating and the fork to vibrating. The quill-point will 
 then trace on the cylinder a sinusoidal curve, and, the 
 number of vibrations of the fork per second being known, 
 we have an accurate scale of time. If the time to be 
 measured is greater than can be registered on one revolu-. 
 tion of the cylinder, the cylinder or fork is given a motion 
 of translation along the axis, and the sinusoidal curve then 
 becomes a helix, and the whole length of the cylinder can 
 be used. 
 
 MARCEL DEPREZ REGISTERS. The record is made as fol- 
 lows: Small electro-magnets, ee, Fig. 21, are placed in front 
 
GUNPOWDER AND INTERIOR BALLISTICS, 
 
 97 
 
 They are provided 
 
 --A 
 
 of the cylinder, above the time-register, 
 with very light armatures, /, acted 
 on by a spring, g, which is almost in 
 equilibrio with the magnetic attrac- 
 tion. A point, //, connected with the 
 armature, rests against the surface of 
 the cylinder. When the current at 
 a target is broken, the correspond- 
 ing armature / yields to the action 
 of the spring g and is drawn aside 
 quickly, the point h recording the 
 motion on the cylinder by the side 
 of the time-scale. The number of 
 vibrations of the fork between any 
 two breaks divided by the number 
 per second gives the corresponding time. To assist in 
 counting vibrations, the quill b, Fig. 20, is first allowed 
 to trace a simple helix before the fork is put in vibra- 
 tion. The quill-point is then returned to its starting-point. 
 This line is called the mean helix. If the targets are at 
 such a distance apart that the current which is broken at 
 one point may be restored before the projectile reaches the 
 
 next, one register and one circuit 
 will be sufficient. If the targets 
 are too close together for this res- 
 toration of current, each target 
 must have its own current and 
 register. The registers have a 
 motion of translation in common 
 with that of the tuning-fork. 
 
 BASHFORTH TARGETS. For 
 restoring the current as above 
 described, the simplest device is 
 theBashforth target, invented and 
 used by the Rev. Francis Bash- 
 forth in his celebrated experi- 
 FIG! 22 ' merits on the resistance of the air 
 
 to the motion of projectiles. 
 
 This target (Fig. 22) consists of a series of wire springs, bd> 
 
9 TEXI^-BOOK OF ORDNANCE AND GUNNERY. 
 
 inserted in a board. On the front of this board are brass 
 plates, ace, having oblong holes in them through which the 
 springs pass. 
 
 The springs are held down in contact with the lower 
 side of the holes by weights, w w, attached to them by 
 strings. The current entering the plate a, will pass through 
 the wire spring b to the plate c, and so on. When one 
 of the strings is cut by a projectile, the corresponding 
 spring will fly up to the upper side of the hole in the brass 
 plate c, and the current will be broken during the passage 
 of the spring from bottom to top of hole, and will be made 
 again as soon as the spring strikes the top. 
 
 47. Determination of Pressures by Experiment Static Method 
 
 Discussion Conclusions. 
 There are two methods of measuring a force or pressure : 
 
 1. The Static Method, in which the unknown force is 
 balanced by a known resistance ; 
 
 2. The Dynamic Method, in which the unknown force is 
 determined by the acceleration which it communicates to a 
 given mass. Its measure is, from mechanics, 
 
 dv d l s 
 
 STATIC METHOD. General Principles. The general 
 method adopted in this case is to balance the unknown force 
 by the resistance which a body offers to deformation. If we 
 have a cylinder of metal of known length and diameter, and 
 uniform in quality, and apply to it a known force in the 
 direction of its length, the cylinder will be decreased in 
 length by a certain amount. We measure accurately this 
 decrease in length and note the force producing it. Pro- 
 ceeding in this manner we can form a table one column of 
 which will contain the decrease in length of the cylinder, 
 and the other the corrresponding pressure for all pressures 
 within the limits of experiment. From this table a curve 
 may be constructed whose abscissas give the pressures, and 
 the ordinates the corresponding compressions. 
 
 Such a curve is called the " tarage " of the cylinder. 
 
GUNPOWDER AND INTERIOR BALLISTICS. 99 
 
 If now a cylinder of the same material and dimensions be 
 subjected to the force to be measured, and this force be 
 applied in the same manner as that producing the " tarage," 
 it is only necessary to measure the compression produced 
 by the unknown force, and find from the " tarage," or from 
 the table, the corresponding pressure. 
 
 DISCUSSION. The pressure we wish to measure is that 
 of the powder-gas. This gas acts upon the cylinder to be 
 compressed, through the medium of a piston whose area is 
 exactly known. 
 
 This piston moves in a cylindrical channel, and its head 
 rests against the cylinder to be compressed, the gas acting 
 upon the opposite end of the piston (see Noble crusher- 
 gauge). In order that the results of the compression may 
 agree with those of the " tarage," the mass of the piston and 
 its velocity must be as small as possible. To show this: At 
 any instant let 
 
 P be the intensity of the force to be measured ; 
 
 R, the resistance to deformation offered by the cylinder ; 
 
 m, the mass of the piston ; 
 
 v, its velocity ; 
 
 x, the length of path passed over by it. 
 
 The work of the pressure on the piston over the path x 
 is 
 
 / 
 
 t/o 
 
 Pdx, 
 and that of the resistance over the same path 
 
 and the difference between these is the energy of the piston ; 
 hence 
 
 In order that P = R, which is the condition sought, we 
 must have at all times 
 
 = o. 
 
 L 
 
IOO TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 Now m cannot be zero, but it must be as small as possi 
 ble, and v must also be small. The former condition is 
 attained by making the piston small, and the latter by com- 
 pressing the cylinder before firing by a force nearly equal 
 to the value of P anticipated. 
 
 CONCLUSIONS. From numerous experiments Sarrau 
 concludes : 
 
 1. Gunpowder is the only explosive which under ordi- 
 nary conditions produces compressions agreeing with the 
 " tarage." 
 
 2. This conclusion is true only when the gauge is in rear 
 of the projectile. In the powder-chamber the pressure rises- 
 from zero to a maximum in a short time, but the time is ap- 
 preciable. Hence the application of the pressure resembles 
 in some degree that of the force producing the tarage. 
 When, however, the gauge is situated in front of the base of 
 the projectile, the gas suddenly strikes it, upon the passage of 
 the projectile, and we have a case similar to that of the high 
 explosives, and the same rule applies as with them. (See 3.) 
 
 3. For the high explosives, the rate of application of the 
 force is so great that as a general rule the maximum press- 
 ure is measured by the " tarage " corresponding to one half 
 the compression of the cylinder. 
 
 48. Rodman and Noble Gauges Advantages of Noble. 
 
 RODMAN GAUGE. The Rodman Pressure-gauge, Fig. 
 23, consists of a body or housing, H, which is a receptacle 
 for all the working parts. A copper disk, C, is placed in 
 the housing, and a knife, K, rests against it. The knife is 
 attached to the piston P, which fits accurately in the cylin- 
 drical hole in the housing. The housing is closed by a 
 screw-plug, /. 
 
 The gas acts on the end P' of the piston, and presses the 
 knife into the copper disk, causing it to make a cut,- whose 
 length measures the .pressure. A small copper cup, c, is 
 placed at the outer end of the piston to act as a gas-check, 
 and prevent the entrance of gas into the housing. This 
 gauge, when used, is placed in the centre of the bottom of 
 the cartridge-bag and tied to it with a string around the 
 
GUNPOWDER AND INTERIOR BALLISTICS. IOI 
 
 groove g. When in the gun, it must rest against the bottom 
 
 FIG. 23. 
 
 of the bore. The gauge may also be screwed into the 
 breech-block, or walls of the bore, 
 in which case it is threaded on the 
 exterior. 
 
 NOBLE CRUSHER GAUGE. This 
 has replaced the Rodman gauge gen- 
 erally, for reasons which will appear 
 later. It was used in Noble and Abel's 
 experiments. It consists (Fig. 24) of 
 a housing, H, closed by a screw-plug, 
 /, and forming a receptacle for the 
 working parts. 
 
 These consist of a piston, P, mov- 
 ing in a cylindrical channel as shown, 
 and a copper cylinder, C, to be com- 
 pressed, which is in contact with the 
 piston. The cylinder is central, and 
 kept in the axis of the housing by the 
 spring 5. 
 
 A copper cup, c, is used as a gas- 
 check as in the Rodman, and an- 
 other method for the same purpose, called " air-packing. 
 
102 TEXT- BOOK OF ORDNANCE AND GUNNERY. 
 
 is also employed. A series of grooves, a (Fig. 25), are 
 made around the piston. If gas enters between the piston 
 and its channel, it escapes into the 
 first groove, and by expanding, its ten- 
 sion is diminished. It may also escape 
 
 H 
 
 a 
 
 into the second groove, and so on, and 
 by each expansion its tension is still 
 FIG. 25. further reduced till it is unable to 
 
 penetrate into the body of the housing. The action of the 
 gauge is evident. In using it, the piston must always be in 
 contact with the copper cylinder. 
 
 ADVANTAGES OF NOBLE GAUGE. i. It is smaller than 
 the Rodman, since the copper cylinder is smaller than the 
 disk. It therefore takes up less room in the gun. The mass 
 of the piston is also less than that of the knife and piston in 
 the Rodman. 
 
 The advantage of this has been shown. 
 
 2. The knife of the Rodman is difficult to reproduce if 
 broken, while the piston of the Noble can always be dupli- 
 cated. 
 
 3. The copper disk offers very little resistance to motion 
 at first, while that offered by the cylinder is more nearly 
 uniform. 
 
 4. The cylinder can be given a preliminary. compression, 
 but a preliminary cut cannot be given to the copper disk. 
 
 49. Determination of Pressures by the Dynamic Method Noble and 
 Abel's Method -Letard's Apparatus Sebert's Velocimeter. 
 
 In this method the pressure is determined by the accel- 
 eration of a known mass. The mass may be either the pro- 
 jectile, the gun, or a piston lodged in the walls of the bore, 
 and communicating with it by a radial channel. 
 
 NOBLE AND ABEL'S METHOD. In this method the mo- 
 tion of the projectile is used, as already explained, page 77,. 
 and the result is given by equation (150), 
 
GUNPOWDER AND INTERIOR BALLISTICS. 103 
 
 the value oi ~ being determined by calculation from data 
 
 obtained by the experiment. 
 
 LETARD'S APPARATUS. To avoid piercing the walls of 
 the bore, as in Noble and Abel's method, this apparatus is 
 
 SHOT) 
 
 rCJ 
 
 FIG. 26. 
 
 employed. It consists (Fig. 26) of a body of wood, on the 
 front of which is a metallic ring, b. A metal bolt, a, passes 
 through the wood body and projects to the rear, its head 
 being in contact with the ring b. A pin, c, which is easily 
 broken, holds the bolt a in place. When in this condition 
 the current passes through the ring and bolt. 
 
 The wood body is attached to a second piece of wood, 
 and the whole is placed in the bore of the gun, and secured 
 against the wall with resin or cement. When the projectile 
 strikes the projecting end of the bolt a, the pin c is broken, 
 and the bolt driven out, thus breaking the circuit. 
 
 SEBERT'S VELOCIMETER. With this instrument the mo- 
 tion of the gun, or of the projectile, or of both, may be used. 
 The general principles are as follows: A ribbon of steel 5 
 (Fig. 27) is attached to the trunnion of the gun by the rod T 
 and the gun mounted so as to recoil with very little friction. 
 As recoil takes place, the ribbon has the same motion as 
 that of the gun. A tuning-fork, A, whose rate of vibration is 
 
104 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 known, is fixed, with reference to the gun, above the ribbon, 
 and carries a quill-point, b. The fork is made to vibrate by 
 electro-magnets, c, as in the Schultz Chronoscope, and dur- 
 ing recoil the quill-point traces on the blackened surface of 
 the ribbon a sinusoidal curve which is the scale of time. 
 In rear of the tuning-fork are placed several Marcel-Deprez 
 registers, R y connected with Letard interrupters in the gun. 
 When the projectile passes a point at which one of the inter- 
 
 FIG. 27. 
 
 rupters is situated, the break is registered on the steel rib- 
 bon beside the scale of time, and so for each successive 
 break. The number of vibrations between breaks, divided 
 by the number of vibrations per second of the fork, gives 
 the time of passage of the projectile over the distance be- 
 tween interrupters, and from this we can determine the 
 velocity. From these velocities we can determine the ac- 
 celerations, and hence the pressures, using the mass of the 
 projectile. 
 
 Since the ribbon contains a complete record of the mo- 
 tion of recoil of the gun, we can also determine velocities 
 and accelerations, and hence the pressures, using the mass 
 of the gun. 
 
CHAPTER II. 
 
 HIGH EXPLOSIVES AND SMOKELESS POWDERS. 
 HIGH EXPLOSIVES. 
 
 50. Definitions and Classification. 
 
 An Explosive is a substance which is capable of a sudden 
 change from a solid or liquid to a gaseous state, with evolu- 
 tion of great heat. 
 
 A High Explosive is one in which this change is very 
 rapid, and is accompanied by a crushing or shattering 
 effect. 
 
 A Low Explosive is one in which the change is relatively 
 slow, and accompanied by a propelling or pushing effect. 
 CLASSIFICATION. Explosives may be classed into 
 
 1. Explosive mixtures ; 
 
 2. Explosive compounds. 
 
 Explosive Mixtures are intimate mixtures of certain sub- 
 stances which are in themselves inexplosive, and which 
 undergo no chemical change till the moment of explosion. 
 They consist generally of a combustible body, such as car- 
 bon, and an oxidizing agent, such as potassium nitrate. 
 The best example is gunpowder, which has already been 
 discussed. 
 
 Explosive Compounds are chemical compounds, the mole- 
 cules of which are explosive in themselves. They contain 
 one or more combustible elements, such as carbon and hy- 
 drogen, together with the oxygen necessary to oxidize these 
 elements. 
 
 The constitution of the molecule is more or less unstable, 
 and when heated to a certain degree, the molecule breaks 
 up with the formation of the gaseous products of oxidation. 
 
 The most important explosive compounds are the or- 
 
 105 
 
106 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 ganic nitrates or nitric ethers, whose composition may be 
 represented by R-O-NQ 2 , and the nitro-substitution com- 
 pounds, represented by R-NO 2 , R in each case represent- 
 ing the hydrocarbon radical. 
 
 Both are derived from organic substances by the action 
 of nitric acid, th*e former from complex alcohols, such as 
 glycerine, etc.; the latter from certain hydrocarbons, by 
 the substitution in each case of NO 3 of the acid for H of the 
 alcohol or hydrocarbon. 
 
 Usually from each substance a series of explosive com- 
 pounds can be made, depending upon the number of atoms 
 of H replaced by NO 2 . 
 
 In the explosive mixtures, relatively great distances exist 
 between the atoms which are to combine, while in the com- 
 pounds each molecule constitutes a complete explosive, 
 and hence the transformation is much more rapid with the 
 latter. 
 
 51. Orders of Explosion Berthelot's TheoryDetonators. 
 
 ORDERS OF EXPLOSION. When gunpowder is fired in 
 the ordinary manner we have an explosion of the second 
 order; when it is mixed with nitro-glycerine and fired, we 
 may have an explosion of the first order, or a detonation. 
 
 The difference consists in the time necessary to produce 
 the chemical change. In the case of the explosion of the 
 "second order, the time is appreciable ; in the case of detona- 
 tion the change is practically instantaneous throughout the 
 whole mass of the body. 
 
 BERTHELOT'S THEORY. Berthelot, the great French 
 authority, accounts for the difference in these orders as fol- 
 lows : Every explosion is caused by heating some part of 
 the substance to the temperature of decomposition, and 
 this temperature is transmitted successively to all parts of 
 the body. 
 
 In the case of explosions of the second order, the portion 
 of the substance first heated explodes ; but if the gases have 
 space in which to expand, they are cooled to a certain ex- 
 tent, and heat only a small additional portion of the ex- 
 plosive body to the temperature of explosion. This new 
 
HIGH EXPLOSIVES AND SMOKELESS POWDERS. TO/ 
 
 portion then explodes, and the cooling again takes place; 
 and so on, the explosion being propagated successively 
 from layer to layer. This is the ordinary case with gun- 
 powder. 
 
 Suppose, now, that a violent shock is given to any part 
 of the explosive body, and that the pressures resulting from 
 this shock are too great to be transmitted throughout the 
 mass of the explosive. 
 
 The energy of this shock will be transformed into heat, 
 and this heat will affect the first layers of the explosive 
 body and cause them to be suddenly converted into gas, or 
 will produce detonation. This gas being suddenly pro- 
 duced, the body causing the shock will not have time to be 
 displaced, and therefore the expansion of the gas thus pro- 
 duced will cause a new shock, more violent than the first, to 
 the layers below. 
 
 The energy of this shock will be transformed into heat, 
 and will cause the second layer to detonate, and so on. 
 
 Hence we have an alternate conversion of energy into 
 heat and of heat into energy, and this conversion resembles 
 the propagation of a sound-wave in a given medium, except 
 that its rate of travel is much greater. We may also have 
 a combination of these orders of explosion, so that the dis- 
 tinction between the two cannot be sharply defined. 
 
 Every explosive seems capable of producing the two 
 different orders of explosion, according to the manner in 
 which the initial heating or shock is given. The high ex- 
 plosives give ordinarily the first order of explosion, the low 
 explosives the second order. 
 
 DETONATORS. The order of explosion generally de- 
 pends on the intensity of the initial shock. If this is not 
 great enough, the explosive may burn quietly, or give an 
 explosion of a lower order. To produce this initial shock, 
 a small quantity of some violent explosive, called a detona- 
 tor, is required. 
 
 The principal detonating agent in use is fulminate of 
 mercury,, which, on account of its great force, gives rise to a 
 high temperature when the initial shock is converted into 
 heat. 
 
108 TEXT-BOOK OF ORDNANCE AND GUN AERY. 
 
 52. Modes of Producing Explosion Fuzes Detonation by Influence. 
 An explosion of the second order may be produced by 
 shock, friction, the direct application of heat, by electricity 
 or by an ordinary primer, and by certain chemical or physical 
 changes; but to produce detonation a special fuze, called a 
 detonating fuze, is generally employed. The material used in 
 these fuzes is ordinarily mercuric fulminate,and one 
 form is shown in Fig. 28. A is a copper shell ; B, 
 the chamber filled with mercuric fulminate ; C, 
 the electric wires ; D, the ends of these wires ; E y 
 \"D the platinum bridge which is heated by the cur- 
 rent ; F, the sulphur cement holding the wires and 
 fulminate in place. This fuze is placed in the 
 mass of the explosive, as its effect is weakened if 
 a layer of air is interposed. Other varieties of 
 fuzes are used. Those fired by electricity are 
 classed as high and low tension, according to the 
 kind of current used with them. 
 
 Mass of Fuze. -- The mass of the detonator 
 should bear a certain proportion to that of the 
 explosive. If it is too weak, it produces a low 
 order of explosion ; if too strong, it may scatter 
 the explosive. 
 
 The exception to the rule is nitro-glycerine, 
 which detonates equally well with a small or a 
 large primer ; but it holds for gun-cotton, and for 
 those explosives which have been rendered less 
 sensitive by various means. 
 
 DETONATION BY INFLUENCE. If a series of 
 cartridges of dynamite or gun-cotton be placed at certain 
 distances apart, and one of them be detonated by a fulminate 
 primer, the others will also detonate. This is called " deto- 
 nation by influence " or "sympathetic" detonation. It ap- 
 pears to be governed by the following laws : 
 
 i The distance apart at which detonation occurs de- 
 pends on the envelope of the cartridges, and the nature of 
 the material on which the cartridges rest. If the initial 
 cartridge is enveloped in a non-resisting material, such as 
 a paper envelope, the influence extends much further than 
 
HIGH EXPLOSIVES AND SMOKELESS POWDERS. 109 
 
 with a resisting envelope. If the cartridges rest on a re- 
 sisting material, as an iron rail, the effect is propagated to a 
 greater distance than if they rest upon the ground. 
 
 2. The envelope of the secondary charges should be as 
 thin and elastic as possible, in order to oppose the minimum 
 resistance to the shock. 
 
 3. An explosion thus propagated will become weaker 
 from cartridge to cartridge, and may even change its order. 
 
 4. Similar effects are observed under water. 
 
 5. The shock is better transmitted by a liquid than by a 
 gas. 
 
 6. The density of the secondary charges should be as 
 great as possible, in order that the effect may not be reduced 
 by motion among the particles. 
 
 53. Strength of an Explosive Potential Force Rapidity of 
 Reaction. 
 
 STRENGTH. An explosive must be considered as exert- 
 ing pressure and having potential energy, and in order to 
 estimate its strength, and its value for different purposes, 
 we must be able to determine the relative values of the pres- 
 sure and potential for each explosive. 
 
 Water in freezing exerts ^reat pressure if confined, and 
 may burst the walls of the containing vessel. The frag- 
 ments, however, will not be projected to any distance. 
 
 In this case we have a great pressure, but no potential 
 energy or capacity to do work. If instead of water a high 
 explosive be confined in the envelope and detonated, two 
 effects will be observed : the walls will be ruptured, and the 
 fragments thrown violently in all directions. In this case 
 we have the pressure required to rupture the walls, and the 
 potential energy necessary to project the fragments. 
 
 Again, if we compare equal weights of large and small 
 grained powder of the same composition, exploded in a 
 closed vessel, it is evident that the potential is the same for 
 both, since the products and the quantity of heat dis- 
 engaged are the same ; the force or pressure is also the 
 same, since this depends solely on the density of loading. 
 The effect of these powders is, however, very different. 
 
110 TEXT-BOOK OF ORDNANCE AND GUNNERY 
 
 The small-grained powder, if exploded in a shell, will 
 burst it into many fragments and project them to great dis- 
 tances, while the large-grained powder will give few frag- 
 ments and small propelling force. Similar effects are ob- 
 served with different classes of high explosives, and depend 
 on the rapidity of the reaction by which they are converted 
 into gas. 
 
 The strength of an explosive, then, depends on 
 
 1. Its force or pressure; 
 
 2. Its potential ; 
 
 3. The rapidity of its reaction or conversion. 
 
 FORCE OR PRESSURE. The force of an explosive, as 
 already defined in the case of gunpowder, is the pressure ex- 
 erted by its gaseous products per unit of surface, when unit 
 weight of these products is confined in unit volume. The 
 expression for it in the case of gunpowder is, equation (28), 
 
 /_ A^o^o. 
 
 f ~ ~ 
 
 and the same expression measures the lorce of any explosive, 
 v t being the specific volume, / the atmospheric pressure, 
 and T the absolute temperature. 
 
 POTENTIAL. The potential energy of an explosive is the 
 total work it can do, when the products are indefinitely ex- 
 panded without loss of heat, all the heat being expended in 
 the performance of work. 
 
 Let E be the potential energy of unit weight of the ex- 
 plosive, J the mechanical equivalent of a heat-unit, T 9 the 
 absolute temperature of explosion, and K the mean specific 
 heat of the products. Then 
 
 RAPIDITY OF REACTION. This depends on the rapidity 
 with which the chemical transformation is propagated 
 throughout the mass of the explosive. Certain explosives, 
 such as nitro-glycerine and gun-cotton, have very great 
 velocities of conversion, and they may be regarded as un- 
 dergoing an instantaneous change. 
 
HIGH EXPLOSIVES AND SMOKELESS POWDERS. Ill 
 
 This change being so rapid, the heat is employed almost 
 entirely in expanding the gases and performing mechanical 
 work. Hence these substances are violent explosives, and 
 shatter everything in their path. 
 
 The transformation is made to take place less rapidly by 
 removing the particles to a greater distance from each other, 
 as in the case of gunpowder, which then decomposes com- 
 paratively slowly and exerts a pushing effect rather than 
 that of a blow. 
 
 It is evident that the choice of an explosive depends upon 
 the relative values of these three elements. If an explosive 
 is required for a shell, we need one having the greatest pos- 
 sible potential to scatter the fragments, a relatively small 
 force, so as not to break it into very small fragments, and 
 gVeat rapidity of reaction in order that all the gases may 
 be formed before the shell breaks. For mining, we require 
 moderate force, small potential, and moderate rapidity of 
 reaction, etc. 
 
 54. Principal Explosives Gun-cotton. 
 
 PRINCIPAL EXPLOSIVES. Gunpowder may be regarded 
 as a type of the explosive mixtures, and as its properties are 
 possessed to a greater or less extent by all these mixtures, 
 the high explosives only will be considered in what follows. 
 
 The principal ones in use for military purposes are : 
 
 1. Gun-cotton; 
 
 2. Nitro-glycer ine; 
 
 3. Dynamites; 
 
 4. Picric acid and picrates ; 
 
 5. Fulminates ; 
 
 6. Sprengel safety mixtures ; 
 
 7. Smokeless powders. 
 
 GUN-COTTON. Its chemical formula is C 6 H T O,(ONO,),, 
 and it is formed from cotton wool by the action of strong 
 nitric acid. The reaction is 
 
 C.H A(OH). + 3 HN0 3 - C.H t O,(ONO,). + 3H.O. 
 
 Cellulose. Nitric Acid. 
 
 Sulphuric acid is added to the nitric to take up the water 
 and prevent the dilution of the later acid, which would give 
 
112 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 the lower orders of nitration, such as collodion cotton. The 
 method of preparing it is described in chemistry. 
 
 In the earlier processes of manufacture the long fibres 
 of cotton were used. These became filled with the acids, 
 and being capillary tubes, it was found impossible to wash 
 them out, and hence the product was unstable and liable to 
 spontaneous decomposition. Abel, however, improved the 
 process of manufacture by selecting the cotton waste, and 
 cleaning it with alkaline washing, and especially by cutting 
 up, or pulping the gun-cotton after it had been partially 
 freed from the acids employed in its manufacture. By this 
 operation the long fibres were reduced to very short tubes 
 which could be thoroughly washed. A final washing in 
 alkaline water completed the neutralization of free acids. 
 
 Forms. Gun-cotton occurs ordinarily 
 
 1. In the form of wool, like the original cotton; 
 
 2. In compressed cylinders and slabs. 
 
 The first form is that in which the cotton was used up to 
 the time of Abel's improvement. It was sometimes twisted 
 into strands, and woven, to regulate its rate of burning. 
 
 The compressed cylinders are made by the action of a 
 hydraulic press upon the pulped and washed gun-cotton. 
 
 Properties Density. Its density is about 0.2 for the wool 
 form and i.i for the dry compressed. 
 
 Solubility. It is insoluble in water, alcohol, or sulphuric 
 ether, but is soluble in acetone and acetic ether. This in- 
 solubility in alcohol and sulphuric ether distinguishes it 
 from the lower orders of nitrated cellulose, which are soluble, 
 giving collodion. 
 
 Effect of Foreign Substances. The addition of water de- 
 creases the sensitiveness to explosion. The addition of 
 paraffine has a similar effect, with the advantage that it does 
 not evaporate. The reason for this decrease in sensitiveness 
 is that the water or paraffine gives a certain elasticity and 
 solidity to the gun-cotton, so that the initial shock of the 
 detonator is propagated through a much greater mass, and 
 consequently its local energy is diminished. 
 
 Nitre is sometimes added to increase the supply of 
 oxygen, which is deficient. 
 
HIGH EXPLOSIVES AND SMOKELESS POWDERS. 113 
 
 Free Acids. These cause spontaneous decomposition, 
 with elevation of temperature and increased sensitiveness, 
 so that explosion frequently results. 
 
 The presence of these acids formerly caused many acci- 
 dents. 
 
 Effect of Heat and Cold. As a general rule, the sensitive- 
 ness of a high explosive increases with the temperature. If 
 wet, the application of heat will cause the evaporation of the 
 water and thus increase the sensitiveness of the gun-cotton. 
 
 Cold will cause the freezing of the wet compressed gun- 
 cotton and its consequent flaking and disintegration. 
 
 Ignition. A temperature of about 180 C. is required. 
 If the cotton is dry and unconfined, the application of flame 
 will cause it to burn quickly. If the mass is large, an explo- 
 sion may occur, but it will be ordinarily of a low order. If 
 wet, the cotton will burn when unconfined, only in successive 
 layers as they become dry. 
 
 Detonation. Dry gun-cotton is detonated by a fulminate 
 fuze. 
 
 Wet or paraffined gun-cotton requires a large detonator or 
 an initial priming charge of dry cotton with a fulminate fuze. 
 
 Reaction. The reaction on explosion is 
 
 2C.H 7 1 (ONO,) i = ;H 2 + 3CO, + 9CO + 6N. 
 
 There is evidently a deficiency of oxygen, and hence of 
 potential energy, and therefore nitre is sometimes added as 
 before stated. 
 
 Use in Blasting. From the CO given off it is disadvan- 
 tageous in blasting unless a nitrate be added. It has also 
 the disadvantage of being of comparatively low density and 
 solid, and hence it cannot be introduced so readily into bore- 
 holes, nor in such large quantities as other explosives which 
 are plastic or have higher densities. It is, however, very safe. 
 
 Use for Military Purposes. -It has been used for charging 
 torpedoes, for bursting charges for shell, and for destroying 
 obstacles such as walls, palisades, guns and carriages, etc. 
 
 Storage. It is best stored wet, as under these conditions it 
 is perfectly safe. It should not, however, be exposed in this 
 state to a freezing temperature on account of disintegration.. 
 
114 TEXT BOOK OF ORDNANCE AND GUNNERY. 
 
 55. Nitre-glycerine. 
 
 Its chemical formula is C.,H r , ( ()NO a \ , and it is formed by 
 the action of strong nitric acid upon glycerine. 
 
 The reaction is 
 
 C.H.(OH). + 3 HN0 3 = C.H.(ONOJ. + 3 H,O. 
 
 Glycerine Nitric acid 
 
 Sulphuric acid is added to the nitric, as in the case of 
 gun-cotton, to take up the water formed in the reaction. 
 
 The method of preparing it is to add the glycerine slowly 
 to the mixture of acids ; to keep the mixture cool by cooling 
 coils in the vessel, and by passing a current of air through it, 
 which also insures a thorough mixture ; and to wash the pro- 
 duct thoroughly with water to which a small quantity of 
 alkali is added, to insure the removal ot free acid. 
 
 Form. Nitroglycerine when hrst made is in the form of 
 an opaque, white, oily liquid, becoming colorless with time. 
 
 Properties Density. Its density is 1.6. 
 
 Solubility. It is very slightly soluble in a large quantity 
 of cold water. It is freely soluble in alcohol, ether, chloro- 
 form, and slightly in glycerine. 
 
 It has a sweet, pungent, aromatic taste ; is poisonous, and 
 causes headache. 
 
 Heat and Cold. It freezes at4.4 C. to a white crystalline 
 solid, and is almost inexplosive in this condition by ordinary 
 means, unless a small mass be acted upon by a shock. 
 
 When frozen, it is thawed at a temperature of 37. 7 C. by 
 placing the vessel containing it in another of water at this 
 temperature. 
 
 Free Acids. These cause its decomposition, as in the 
 case of gun-cotton, and render it more sensitive to friction 
 and percussion, and hence they must be carefully removed. 
 
 Ignition. Its temperature of ignition is about the same 
 as that of gun-cotton, 180 C. 
 
 If unconfined and subjected to a blow, the particle struck 
 will explode, and scatter the remainder. 
 
 If confined and struck, it will detonate ; when unconfined, 
 in small masses, the application of flame causes it to burn 
 rapidly without explosion. 
 
HIGH EXPLOSIVES AND SMOKELESS POWDEKS. 11$ 
 
 Detonation. It is detonated by mercuric fulminate, and 
 the detonator should be placed in the liquid. If frozen, it 
 may also be detonated, but the action is generally less 
 violent, owing to incomplete conversion. 
 
 Reaction. The reaction on explosion is 
 
 2C 3 H 6 (ONO a ), - 6C0 2 + 6N + 5 H,O + O. 
 
 Here we have an excess of oxygen, and the reaction, 
 following a general law, is always stable. 
 
 Use in Blasting. Nitro-glycerine is one of the strongest 
 of the high explosives, possessing great force, potential, and 
 rapidity of reaction. Owing to its liquid form it can be 
 poured into holes of any shape, provided they do not com- 
 municate with fissures, and from its great rapidity of re- 
 action, the depth of the hole may be decreased, and no tamp- 
 ing except water is required. It is therefore a valuable 
 agent for blasting, but owing to its liquid form it is very 
 unsafe in handling, as it is liable to leak, and thin films of it 
 may be easily exploded. For this reason, except for special 
 purposes, it is now generally replaced by dynamite. 
 
 Use for Military Purposes. The same remarks apply in 
 this case as for blasting. 
 
 Storage. If possible nitro-glycerine should be kept frozen, 
 and should be transported and handled in this state, being 
 thawed before using. 
 
 Test for Purity. Free acid may be detected by using blue 
 litmus-paper. The acid will redden it. 
 
 56. Dynamite With Inert Base. 
 
 Owing to the dangers involved in the transportation, 
 handling, and storage of nitro-glycerine as previously noted, 
 efforts were made to find an absorbent for it, so that it could 
 be given a solid form. The addition of these absorbents has 
 given rise to dynamite and various other derivatives of 
 nitro-glycerine. 
 
 Absorbents Classified. These may be classified into: I. 
 Inert ; 2. Chemically active. 
 
 INERT ABSORBENTS DYNAMITE No. i. The most im- 
 portant of the inert bases is kieselguhr, a siliceous infusorial 
 
Il6 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 earth which is porous, and will absorb and retain about three 
 times its weight of nitro-glycerine. 
 
 When it absorbs about 75 per cent of nitro-glycerine, the 
 product is called dynamite No. I. 
 
 Form. It is either granular, or in compressed cylinders, 
 wrapped in paraffined paper. 
 
 Properties Density. Its density is about 1.5 to 1.6. 
 
 Heat and Cold. Dynamite freezes at 4.4C., and in this 
 condition is detonated with great difficulty when solid, but 
 when loose it may be detonated, the explosion being less 
 violent. If frozen, it must be thawed before exploding, and 
 this should be done very carefully, as in common with all 
 preparations of nitro-glycerine it becomes more sensitive as 
 it is heated. At all high temperatures the nitro-glycerine 
 exudes, and hence the dynamite becomes dangerous. 
 
 Free Acids. These are very dangerous, and the same re- 
 marks apply as to nitro-glycerine. 
 
 Detonation. A fuze of fulminate of mercury is used, which 
 must be placed in the mass of the cartridge. 
 
 Reaction. This is the same as for nitroglycerine. 
 
 Use in Blasting. It has been found very useful in blasting 
 on account of safety in handling. The potential is dimin- 
 ished by the presence of the silica, and hence its action is 
 less violent, and its effects more distributed. By regulating 
 the percentage of nitro-glycerine present, this effect may be 
 still further modified. 
 
 Use for Military Purposes. In the U. S. service, Dynamite 
 No. i is used for charging torpedoes, and may be regarded 
 as the standard high explosive for this purpose. General 
 Abbott of the U. S. Engineers has made a series of researches 
 upon this subject, and has deduced formulas for the inten- 
 sity of different explosives when used under water. (See 
 " Professional Papers, Corps of Engineers," No. 23 1881.) 
 
 Storage. Dynamite No. i is stored in boxes of wood, in 
 magazines free from dampness, and no fulminate caps or 
 primers should be stored with it. 
 
 57. Dynamite with Chemically Active Bases. 
 
 Instead of an inert base, a combustible one may be used, 
 
HIGH EXPLOSIVES AND SMOKELESS POWDERS. 11? 
 
 which is capable of combining with the excess of oxygen of 
 the nitro-glycerine and thus increasing the potential. 
 
 Various substances have been used for this purpose. 
 
 90 per cent of nitro-glycerine and 10 per cent of charcoal 
 form carbo-dynamite. Sawdust, treated with superheated 
 steam, becomes a jelly, and is capable of absorbing a large 
 quantity of nitro-glycerine. Other- compounds of the same 
 class are also found. 
 
 On the other hand, by using a nitrate or chlorate mixture 
 as a base, additional effect is obtained by inducing a higher 
 order of explosion in the base. When gunpowder is used 
 as an absorbent, the detonation of the nitro-glycerine causes 
 the detonation of the powder. Potassium-chlorate mixtures 
 are also used for this purpose, but are generally regarded as 
 dangerous. 
 
 High Explosive Bases. The most important of these com- 
 pounds is explosive gelatine or " gum-dynamite." 
 
 It has been shown that when gun-cotton detonates, there 
 is a deficiency of oxygen, and in the case of nitro-glycerine 
 there is an excess of it. 
 
 If these two explosives are mixed in such proportions as 
 to have the excess of oxygen in the one, neutralize the defi- 
 ciency in the other, we have a considerable increase of 
 potential. The result is best realized in a substance called 
 explosive gelatine or gum-dynamite, which was invented by 
 the Swedish engineer Nobel. 
 
 It is made by dissolving 7 parts of a special grade of 
 soluble gun-cotton in 93 parts of nitro-glycerine, by the aid 
 of heat. 
 
 For military purposes about 4 per cent of camphor is 
 added to decrease its sensitiveness. 
 
 Form. It is a translucent jelly of a yellowish or dark 
 brown color, which may become in time hard and opaque. 
 
 Properties Density. Its density is 1.6. 
 
 Solubility. It is insoluble in water and is unaffected by 
 it. 
 
 Heat and Cold.\i heated slowly to 204 C, it explodes; 
 and it freezes at low temperatures. 
 
 Ignition. When ignited unconfined it burns readily, but 
 
 
Il8 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 does not explode ; but if confined, explosion occurs. It is not. 
 affected by shock, and bullets have been fired through it 
 without producing explosion. 
 
 Detonation. For detonation a special primer is required, 
 and the strength of the primer must be increased as the 
 sensitiveness of the gelatine is decreased. 
 
 Use for Military Purposes. It has been tried as a bursting 
 charge for shells; but as it requires a large primer, the ad- 
 vantages of the decrease in sensitiveness of the explosive 
 are lost by the increase of sensitiveness of the primer. 
 
 Storage. Some doubt exists as to the stability of this 
 compound, and the effect upon its sensitiveness of the evap- 
 oration of the camphor. 
 
 58. Picric Acid and Picrates Fulminates. 
 
 The chemical formula for picric acid or tri-nitro-phenol 
 is C 6 H 2 (NO 2 ) 3 OH, and it is formed by the action of nitric 
 acid on carbolic acid. The reaction is 
 
 C.H.OH + 3 HNO, = C.H.(NO,).OH + 3H.O. 
 
 Form. It occurs in yellow crystals which are slightly 
 soluble in water. It explodes when heated rapidly, but is, 
 ordinarily not used as an explosive by itself, and is only of 
 importance from its compounds. 
 
 Potassium Pier ate. This salt is a violent explosive. 
 Mixed with nitre and charcoal and grained, it forms Desig- 
 nolle's powder, which has been used for small arms and 
 cannon, and also for torpedoes, with good results, but it is 
 expensive, and some cases of premature explosions have been 
 noted. 
 
 Ammonium Pier ate. This is less sensitive than the potassa. 
 salt, and burns without explosion in the air. Mixed with 
 nearly equal parts of nitre, it forms Brugere's powder, which 
 has about twice the strength of ordinary gunpowder, but is 
 expensive, somewhat hygroscopic, and too violent for small 
 arms. 
 
 The picrates form the bases for certain smokeless 
 powders. 
 
 Emmens Acid. This acid is said to be formed by the 
 action of nitric acid upon picric acid. 
 
HIGH EXPLOSIVES AKD SMOKELESS POWDERS. 1 19 
 
 Emmcnsitc is a mixture of emmens acid and sodium or 
 ammonium nitrate. It is yellow and crystalline in appear- 
 ance, and is used in mining and as a substitute for gun- 
 powder, both as a propelling agent and for charging shells. 
 It is much stronger than gunpowder, is smokeless, and 
 almost insensitive to shock. 
 
 It is hygroscopic, and its stability after long storage is 
 not yet well settled. It was invented by Dr. Emmens, and 
 is stHl undergoing trial. 
 
 Melinite. This French explosive is generally supposed 
 to be a mixture of gun-cotton with picric and cresylic acids 
 dissolved in ether. 
 
 FULMINATES. The most important is mercury fulminate, 
 the chemical formula for which is HgC s N Q O 2 . It is formed 
 by the action of alcohol upon mercury nitrate. The reac- 
 tion is rather complex, and may be found in the chemistry. 
 
 Form. It is in fine gray crystals. 
 
 Properties Density. Its density is 4.42. 
 
 Solubility. It is insoluble in water, not affected by the 
 air, and is poisonous. 
 
 Water. When saturated with water it is inex plosive, 
 and hence it is always kept under water for safety. 
 
 Detonation. When dry it is very sensitive to a blow and 
 detonates with violence, and also when heated to 182 C. 
 or when subjected to friction, or to contact with any ignited 
 body, or to the action of the electric 'spark. 
 
 Reaction. The reaction on explosion is 
 
 t The great value of this explosive is as a detonator 
 for the other high explosives. Its effects are due to its great 
 force, since the volume of gas given off is very great ; and 
 also to its high density, in consequence of which a large 
 mass is contained in a small volume. The gases also are 
 not subject to dissociation, and hence impart all their energy 
 to the explosive to be detonated. It is said to have ten 
 times the force of gunpowder. Being comparatively low 
 in potential, an oxydizing agent is sometimes added when 
 the primer is at a distance from the charge. 
 
120 TEXT- BO OK OF ORDNANCE AND GUNNERY. 
 
 Storage. It must be kept under water for safety, and 
 must not be allowed to come in contact with a metallic sur- 
 tace, as it then tends to decompose. Hence percussion-caps 
 are varnished before it is placed in them. It must not be 
 stored with high explosives. 
 
 59. Nitro-Benzines Sprengel Safety Mixtures. 
 
 NITRO-BENZINES. These are formed by the action of 
 nitric acid on benzine, and we have the mono-, di-, and tri- 
 nitro-benzines resulting. 
 
 They are not explosive, but are used in the manufacture 
 of a class of explosives called Sprengel safety mixtures. 
 
 SPRENGEL SAFETY MIXTURES. These were invented by 
 Dr. Sprengel ; the idea being to mix an oxydizing with a 
 combustible agent at the time it is to be used, the constituents 
 being each non-explosive before mixture, and therefore safe 
 to handle and transport. 
 
 Rack-a-rock is a Sprengel mixture of liquid mono-nitro- 
 benzine and potassium chlorate. If the cartridges are kept 
 awhile, their sensitiveness to friction or percussion increases. 
 This explosive was used at Hell Gate in 1885 ; 240,000 Ibs. 
 of it being exploded together with 42,000 Ibs. of dynamite. 
 
 Hellhoffite is a mixture of di-nitro-benzine and nitric acid. 
 It has been used as a bursting charge for shells, by plac- 
 ing the components in separate vessels in the shell, and caus- 
 ing their mixture automatically, either during its flight or on 
 impact. 
 
 Bellite is a mixture of tri-nitro-benzine with ammonium 
 nitrate. It is not sensitive to blows or friction, is chemically 
 stable, and can be stored and transported without change or 
 danger. 
 
 Another class of explosives of the same kind are the 
 flameless explosives, which when confined and detonated, 
 evolve gases which quench any flame. They are especially 
 useful in mines where fire-damp is prevalent. 
 
 Roburite is one of the class of flameless explosives, made 
 by mixing ammonium nitrate and chlorinated di-nitro-ben- 
 zine, and is a yellowish powder. It is flameless because the 
 ingredients are so proportioned as to cause complete oxida- 
 
HIGH EXPLOSIVES AND SMOKELESS POWDERS, 121 
 
 tion, and the products of combustion are carbon dioxide, 
 water, nitrogen, and HC1; the gases given off quenching any 
 flame that may be produced. 
 
 Many other explosives of this class are made, and their 
 composition may be found in " The Dictionary of Ex- 
 plosives," by Major J. P. Cundill. 
 
 SMOKELESS POWDERS. 
 
 60. Changes in Black Powders Early History of Smokeless 
 Powders. 
 
 CHANGES IN BLACK POWDERS. A general idea has been 
 given previously of the history of gunpowder, and the 
 changes made in it. It was found to be too strong even for 
 modern guns in the small-grained form, and hence Rodman 
 conceived the idea of suiting the grain to the calibre. 
 
 His perforated powder was also designed with the idea 
 of burning on an increasing surface, and thus decreasing the 
 volume of the gas emitted at first, and hence the maximum 
 pressure. 
 
 No change had been made in the components of the 
 powder. Later still these changes in form were combined 
 with changes in the nature of the materials, and their pro- 
 portions. In the cocoa-powder the nature of the charcoal 
 was changed, as were also the proportions of nitre, sulphur, 
 and charcoal, and certain carbo-hydrates were introduced. 
 
 While these changes made the powder slower, they 
 necessitated larger charges. This increased the cost, oc- 
 cupied a greater volume of bore, and thus reduced the path 
 over which the gases worked, and necessitated long bores, 
 and also gave great volumes of smoke. 
 
 With small arms, when the calibre was reduced to 0.30, 
 the length of the bullet remaining the same, it became neces- 
 sary, in order to obtain an increase in velocity, to increase 
 the mean pressure per unit of area of the projectile, and 
 hence to adopt some agent having better ballistic qualities 
 than the old powders. Increased charges of compressed 
 black powders were first tried, but they gave high and 
 
122 TEXT- BOOK OF ORDNANCE AND GUNNERY. 
 
 irregular pressures and relatively lower velocities than with 
 the old charges. 
 
 EARLY HISTORY OF SMOKELESS POWDERS. To obviate 
 these defects a new explosive was sought, which would in- 
 crease the velocities, without increasing the pressures beyond 
 safe limits. Naturally the high explosives were tried, and 
 of these the most promising was gun-cotton. It was known 
 that this gave no smoke, that it burned freely when uncon- 
 fined, but that it detonated when confined. Attempts were 
 therefore made to regulate its burning, by twisting it into 
 strands and winding these on the exterior of a hollow wood 
 cylinder, so that the cartridge thus made would fit the 
 chamber of the gun. It was supposed that when sufficient 
 pressure was developed, the cylinder would crush, and thus 
 give a very much larger volume for the gases to expand in, 
 and hence prevent detonation. It w r as found, however, that 
 detonation did occur, with destruction of the gun, and 
 attempts in this direction were abandoned. 
 
 Another method was to mix gun-cotton with ordinary 
 cotton. The two were after mixture subjected to a strong 
 compression, but it was difficult to obtain a homogeneous 
 mixture, the velocities were not increased, and the gun- 
 cotton still detonated. 
 
 An attempt was also made to place a charge of black 
 powder in front of the charge of gun-cotton. The projec- 
 tile was started by the burning of the black powder, and 
 then the gun-cotton was inflamed. 
 
 This plan gave excessive pressures in practice, and was 
 soon abandoned. 
 
 Abel's compressed cotton was also tried with the same 
 results, and gun-cotton was then abandoned as a propelling 
 agent. This was about 1884. 
 
 61. Modification of Gun-cotton Effect of Calibre. 
 
 MODIFICATION OF GUN-COTTON. In all the early trials 
 of gun-cotton no essential modification of its physical con- 
 dition was attempted. 
 
 The fibres of the gun-cotton were not compact, and on 
 being subjected to the action of a highly-heated gas, the 
 
HIGH EXPLOSIVES AND SMOKELESS POWDEKS, 12$ 
 
 flame readily penetrated all parts of the mass, raising it to 
 the temperature of explosion, and detonation followed. 
 
 In 1884 ^ was proposed to dissolve the gun-cotton in 
 some solvent, which could afterwards be evaporated, leav- 
 ing a compact horny substance, which would resist the 
 penetration of flame, and burn regularly. This was the 
 first step in the successful manufacture of smokeless powder. 
 
 EFFECT OF CALIBRE. With black or nitrate powders, as 
 has been shown, the size of the grain must increase with the 
 calibre for all large guns, but for all small arms the same 
 powder (small-arms) may be used with good results. 
 
 With smokeless powders, however, each change in 
 calibre of the small arm requires a change in the powder 
 used. This may be explained as follows : As the calibre 
 decreases, the length of the bullet remaining constant, while 
 its weight decreases, it is necessary to increase the initial 
 velocity of the projectile to obtain superior ballistic results, 
 and this increase of velocity can only be obtained by an in- 
 crease of pressure per square inch of the powder-gas. 
 
 To obtain this increase the physical qualities of the 
 smokeless powder are modified so as to obtain a quicker 
 powder, and this is accomplished by stopping the solution 
 of the cotton at the proper point, and by decreasing the 
 thickness of the grain. For the larger calibres the solution 
 of the cotton is more complete and the grains thicker. 
 
 Those physical qualities, therefore, which principally 
 affect the velocities and pressures given by the powder are : 
 
 1. Its degree of solution or density ; 
 
 2. Its thickness, or least dimension of grain ; 
 both of which regulate its burning. 
 
 In order to increase the -pressure per unit of area, a 
 proper combination of these qualities is required for each 
 particular calibre, and this requires a special powder for 
 each gun. 
 
 62. Operations in the Manufacture of Smokeless Powder Solution. 
 
 OPERATIONS. The principal operations in the manufac- 
 ture of a smokeless powder of the nitro-cellulose class are : 
 
 I. Preparation of the nitro-cellulose; 
 
124 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 2. Solution of the nitro-cellulose in a proper solvent ; 
 
 3. Compression of the material after evaporation of the 
 solvent ; 
 
 4. Rolling into sheets or pressing into rods or tubes ; 
 
 5. Cutting up the sheets, rods, or tubes into grains ; 
 
 6. Drying the grains. 
 
 SOLUTION. The principal precautions to be taken in 
 this operation are, to avoid the formation of lumps or undis- 
 solved particles of nitro-cellulose ; to have the solvent act 
 regularly ; and to prevent the cotton from collecting in 
 masses, so that the solvent cannot readily penetrate it. If 
 the powder is to be quick, the cotton must not be com- 
 pletely dissolved, and hence the operation must be stopped 
 at the proper time, which requires great delicacy in manip- 
 ulation. 
 
 In the operation, the gun cotton must not be plunged in 
 the solvent, but the latter must be poured over the cotton. 
 For this purpose the cotton, which is finely divided, is 
 placed in layers of the proper thickness, in ebonite pans of 
 slight depth. These are enclosed in a glass vessel, and the 
 solvent added in the form of a spray. The gun-cotton 
 gradually dissolves, or rather becomes gelatinized ; the sup- 
 ply of the solvent is then stopped, and the solution allowed 
 to proceed to the proper degree. A current of warm air is 
 then passed over the gelatinized gun-cotton, carrying off the 
 solvent in a state of vapor, which is afterwards condensed 
 in a cool vessel. In this manner the drying of the powder 
 is assisted, and the solvent which is removed can be used 
 again. The cost of these powders depends principally 
 upon the solvent, and hence it is important to collect as 
 much of it as possible. 
 
 63. Compression and Rolling Cutting Up Drying. 
 
 COMPRESSION. During the evaporation of the solvent, 
 bubbles are formed, the effect of which is to render the 
 mass more or less porous in places. This causes irregular 
 density, and hence in the same sheet some parts would burn 
 more quickly than others. It is necessary, therefore, to 
 get rid of these bubbles. 
 
HIGH EXPLOSIVES AND SMOKELESS POWDERS. 12$ 
 
 The thickness of the sheet, after the solvent has evapo- 
 rated, is not uniform, as it is impossible to spread the cotton 
 regularly before it is acted on by the solvent. This thick- 
 ness is very important, as affecting the ballistic properties of 
 the powder. 
 
 To get rid of the bubbles and at the same time regulate 
 the thickness, the sheet is subjected to strong pressure, 
 which is kept up for some time. This pressure has also the 
 effect of completing the solution of certain parts which were 
 not completely dissolved. 
 
 ROLLING. The sheet is then passed between two rolls of 
 polished bronze. The upper roll must be so arranged that 
 its weight will not rest upon the sheet. In this way when 
 the sheet has reached its proper thickness it will not be 
 reduced further. 
 
 The reduction to the required thickness is gradual, so as 
 not to tear the surfaces. In general three or four successive 
 passes through the rolls are necessary. 
 
 CUTTING UP. Black powder is grained, but this opera- 
 tion is impossible with smokeless powder, which is tough 
 and flexible and cannot be broken. It is therefore cut into 
 the required form by special machines, or pressed, while still 
 pasty, through holes in a die, thus forming strings or cords. 
 
 DRYING. The sheets are cut while still saturated with 
 the solvent, and the drying accomplished after the powder 
 is reduced to grains. 
 
 This operation should take place slowly, and at a rela- 
 tively low temperature. Without this precaution there is 
 danger of evaporating the remaining solvent too rapidly, 
 which would cause disintegration of the material and in- 
 crease the porosity. 
 
 Smokeless powders are difficult to dry, especially when 
 thick, and hence when considerable thickness is required, as 
 with cannon-powder, several thin sheets previously dried 
 are placed on each other, and the whole compressed to the 
 required thickness by hydraulic pressure. 
 
 The drying should not be complete, a certain quantity of 
 the solvent being left ; as in the case of black powders, a 
 
126 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 certain quantity of moisture is retained. This tends to di- 
 minish the pressure and to keep up the normal velocity. 
 
 The great difficulty in the manufacture of smokeless 
 powder has been to make it in large quantities by machinery, 
 so that it shall give uniform results as to velocity and pressure. 
 It is not difficult to make small quantities in a laboratory, 
 but very difficult to reproduce them on a large scale. 
 
 64. Classification of Smokeless Powders Classes 1, 2, and 3 Wet- 
 
 teren Powder. 
 
 The manufacture described above applies only to the 
 nitro-cellulose classes of smokeless powders; but as the 
 others are generally mixtures of different substances, in the 
 state of powder, their preparation resembles that of gun- 
 powder and requires no special description. 
 
 CLASSIFICATION. Smokeless powders are generally 
 classed as: 
 
 1. Those derived from picric acid and the picrates; 
 
 2. Those derived from ammonium nitrate ; 
 
 3. Those derived from nitro-cotton or from mixtures of 
 nitro-glycerine and nitro-cotton, with the addition of cer- 
 tain agents which act to modify the rate of burning. 
 
 Class i. Picric-acid Powders. Of these Designolle's and 
 Brugere's powders have already been described. This class 
 is no longer of much importance, as it has been abandoned 
 for powders of class 3. 
 
 Class 2. Ammonium-nitrate Poivders. The objection to 
 this class of powders is that they are all highly hygroscopic, 
 and they are no longer used. 
 
 Class 3. There are a few well-known powders of this class. 
 Very little is known about their actual composition, and 
 hence only a general description of them can be given. 
 
 WETTEREN POWDER. This is made in Belgium. It is 
 said to be composed of nitro-cotton dissolved in acetic ether, 
 with the addition of nitrate of baryta. Another composition 
 given is nitro-cotton dissolved in acetic ether, with the 
 addition of nitro-mannite, which is formed by the action of 
 nitric acid on manna-sugar. The grains are hard, square in 
 form, and of a slate color. 
 
HIGH EXPLOSIVES AND SMOKELESS POWDERS. I2/ 
 
 To protect it irom moisture the grains are varnished 
 with a special collodion. 
 
 The defects of this powder are, it is expensive ; the acetic 
 ether does not thoroughly dissolve the nitro-cellulose ; and 
 after the solvent is evaporated, white scales are formed on 
 the surface. In time this powder loses its compact struc- 
 ture, and under the influence of shock reduces to dust in the 
 cartridge-case, and this dust will cause excessive pressures. 
 Also the acetic ether is difficult to evaporate, and hence 
 different parts of the powder may contain different amounts 
 of the solvent, and this gives rise to irregular ballistic quali- 
 ties. This powder is now being tried in the U. 8. cal. 30 
 rifle, charge 37 grains, muzzle velocity 2000 ft.-secs. 
 
 65. Powder B. N. F.Ballistite Cordite. 
 
 POWDER B. N. F. This powder is used in France in the 
 Lebel rifle. Its composition is unknown, but it is supposed to 
 be a mixture of cottons of different degrees of nitration, gela- 
 tinized by suitable solvents. It is first formed into plates, 
 these are rolled into sheets, which are cut up into grains for 
 small arms or into strips for large guns. It has a grayish or 
 yellowish color, is difficult to ignite, and is said to be very 
 regular in its action and not affected by change of climate. 
 
 BALLISTITE. This powder is used in Germany and Italy, 
 and is the invention of Alfred Nobel. It was the first success- 
 ful smokeless powder made by uniting nitro-glycerine and 
 nitro-cellulose. By acting upon a soluble gun-cotton with 
 nitro-glycerine in the proportions previously given, Nobel 
 produced explosive gelatine. By increasing the proportions 
 of the nitro-cellulose to 30 or 40 per cent and reducing the 
 nitro-glycerine to 60 or 70 per cent, the resulting mixture 
 becomes a horny compact mass capable of definite granula- 
 tion. About 7 per cent of camphor dissolved in the nitro- 
 glycerine is found to assist the process. In the manufacture, 
 benzole is mixed with the nitro-glycerine, to render the 
 nitro-celiulose temporarily insoluble in order to facilitate 
 its equal distribution and absorption. The benzole is then 
 evaporated and the material repeatedly passed through 
 steam-heated rolls and made into sheets. These are after- 
 
128 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 wards cut up into cubical grains which are dark brown in 
 color and are horny and translucent when cut. It has about 
 three times the ballistic force of black powder, and its effects 
 are very regular. 
 
 CORDITE. This powder is used in England and is the 
 invention of Sir F. Abel and Professor Dewar. It is very 
 similar to ballistite, except that a highly nitrated gun-cotton 
 is used. 
 
 As this is insoluble in nitro-glycerine, to obtain a stable 
 union with the latter it is necessary to dissolve the gun- 
 cotton in a solvent. Acetone is used. Various slowing 
 agents have been tried. Tannin is called for in the patent, 
 but at the present time about 10 or 15 per cent of vaseline 
 is preferred. 
 
 These powders are perfectly smokeless, and give high 
 velocities with safe pressures. They are said to deteriorate 
 rapidly, the manufacture is dangerous, and in some samples 
 the nitro-glycerine exudes, rendering the powder sensitive. 
 They give great heat on explosion, and this may, it is 
 thought, injuriously affect the bores of guns. They are also 
 difficult to explode. 
 
 66. Leonard Powder Peyton Powder. 
 
 LEONARD POWDER. This is an American powder whose 
 composition is gun-cotton dissolved in acetone, a large per- 
 centage of nitro-glycerine, and a slowing agent. 
 
 In shape it resembles cordite for large guns, the diam- 
 eter of the cord increasing with the calibre of the gun. For 
 small arms the cords are very small, and are cut in short 
 pieces, so that the powder is granular in appearance. 
 
 This powder has given good results in proof, and it is 
 now undergoing trial. The grains are rather soft. 
 
 PEYTON POWDER. This is also an American powder, 
 manufactured by the California Powder Works. It is a 
 gelatinized mixture of nitro-glycerine 38 per cent and gun- 
 cotton 40 per cent, acted on by acetone, with certain other 
 substances added. 
 
 The mixture is incorporated in a small wheel-mill, cov- 
 ered to prevent loss of solvent. After incorporation the 
 
HIGH EXPLOSIVES AND SMOKELESS POWDERS, 129 
 
 plastic mass is pressed by hydraulic pressure through a hole, 
 in the centre of which is a rod. This forms the mass into a 
 hollow cylinder or pipe. As the cylinder passes out of the 
 hole, it is cut open longitudinally by a cutter, and is spread 
 out into a flat sheet, about 10 inches wide and \ inch thick. 
 This sheet is run through a set of rollers with transverse 
 grooves and ridges. By this means the sheets are cut into 
 a series of strips, but the strips are not entirely separated, as 
 they are still united by a thin film of the material, so that 
 the sheet can be handled as a whole. These sheets are then 
 passed under a cutter, acting at right angles to the strips, 
 by which they are cut into grains. The length and width 
 of the grains are about equal. By this operation most of 
 the grains will be separated from each other. Those that 
 stick are rubbed on a sieve or rolled in a barrel. The 
 grains are then dried at a temperature of about 5i.6C., to 
 drive off the solvent, which is collected, and are finally 
 polished and glazed. The size of the grain increases with 
 the calibre ol the gun, and must be determined by experi- 
 ment for any particular gun. 
 
 The above particulars were furnished by Mr. W. R. 
 Quinan of the California Powder Company. 
 
 This powder is also being tried by the United States, ai 
 lot of 5000 Ibs. having been purchased for the cal.-3O rifle. 
 
 Mr. Longridge gives the following as the relative energies 
 in foot-tons developed by equal weights of the three powders 
 given below, the energy of brown powder being unity: 
 
 Cordite 4-i6 
 
 Ballistite 3-44 
 
 Poudre B. N 2.48 
 
 67. Conditions to be Fulfilled by Smokeless Powders Smokeless- 
 ness Velocities and Pressures Stability. 
 CONDITIONS. Smokeless powders should fulfil the fol- 
 lowing conditions : 
 
 1. They should be approximately smokeless. 
 
 2. They must give high and uniform velocities, with safe 
 and regular pressures. 
 
 3. They must be chemically and physically stable, under 
 varying conditions of moisture, temperature, and age. 
 
130 TEXl^-BOOK OF ORDNANCE AND GUNNERY. 
 
 4. They must not cause excessive fouling, or excessive 
 heating of the gun. 
 
 5. They must not be sensitive to friction or shock. 
 
 6. The manufacture should not be difficult or danger- 
 ous, or the ingredients very expensive. 
 
 7. The products of combustion should not be noxious, 
 and should not corrode the gun. 
 
 8. There must be no chemical action upon the cartridge- 
 case. 
 
 9. They should give the required ballistic results with 
 reduced weight of charge, and the charge should not 
 occupy a large volume, and should be so grained as to be 
 loaded in the ordinary loading-machine. 
 
 SMOKELESSNESS. Nearly all the powders introduced 
 satisfy this condition. Those of class 3, however, are the only 
 ones which are in general truly smokeless, but the smoke from 
 the others is rapidly dissipated. In most of them a slight 
 mist is visible, since the water formed in the explosion is 
 condensed by the air, and the priming or lubricant or the 
 slowing agent also produces visible smoke. 
 
 VELOCITIES AND PRESSURES. Very few of the powders 
 fulfil this condition. 
 
 Experiment shows that, especially for small arms, a very 
 slight variation of size of grain, weight of charge, or density 
 of loading gives a great variation of pressure. For instance, 
 a variation of weight of one grain in the small-calibre rifle 
 increased the pressure from 44,740 to 51,620 Ibs. per square 
 inch, while the velocity was increased only 88 ft.-secs. 
 
 CHEMICAL AND PHYSICAL STABILITY. This is another 
 point about which there is great doubt. Most of these 
 powders are of such recent date that sufficient time has not 
 elapsed to test their stability. They are generally made as 
 wanted for purposes of experiment, and used in a short time. 
 Tests are being made, however, upon this subject by all 
 countries. 
 
 Cordite has been tested as to changes of climate in India 
 and Canada with good results. 
 
 Ballistite has been soaked in water, dried and fired, with 
 very little change in ballistic qualities. 
 
HIGH EXPLOSIVES AND SMOKELESS POWDERS. 13! 
 
 68. Fouling Sensitiveness Safety and Cost of Manufacture 
 Character of Products of Explosion Chemical Action 
 Weight of Charge and Specific Gravity. 
 
 FOULING. As a rule there is very little fouling with 
 smokeless powders. The fact that they are smokeless in- 
 dicates at once the absence of the residue of solid particles 
 which causes fouling with ordinary black powders. This 
 absence of fouling, however, has proved to be a disadvantage 
 in small arms, owing to the increased friction between the 
 bullet and the bore, which the fouling prevented, by acting 
 as a lubricant. This friction has sometimes been so great as 
 to strip the covering off the bullet and leave it in the bore. 
 
 Various lubricants have been tried to overcome this 
 defect, but none of them have proved satisfactory, and the 
 defect has been overcome by using a proper covering for 
 the bullet, either of copper, nickled steel, or German silver. 
 
 SENSITIVENESS. All the powders are safe in this respect, 
 and have been pretty thoroughly tested. The difficulty lies 
 in the opposite direction, as they are so insensitive that they 
 are difficult to explode, and for most of them, special primers, 
 or more powerful ones, are required. 
 
 Nitro-cellulose powders are specially insensitive. 
 
 SAFETY AND COST OF MANUFACTURE. The principal 
 danger arises in the manufacture of the ingredients, nitro-gly- 
 cerine and gun-cotton, and in handling the former. While 
 explosions sometimes occur, the manufacture can hardly be 
 considered more dangerous than that of gunpowder. The 
 question of cost is subordinate to that of efficiency, and 
 would only enter in deciding between two or more powders 
 of equally good ballistic properties. 
 
 CHARACTER OF PRODUCTS. The character of the gaseous 
 products differs very little from those of gunpowder, being 
 principally CO, CO.", H 2 O, and N, and hence no danger is to 
 be apprehended from them, and they should not corrode the 
 gun. Corrosive effects have been noticed, but they are due 
 to the great heat of the gases. 
 
 CHEMICAL ACTION. So far as is known, these powders 
 do not act chemically upon the cartridge-cases. 
 
 WEIGHT OF CHARGE AND SPECIFIC GRAVITY. These 
 
132 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 powders have much higher ballistic qualities than the old 
 nitrate powders, and hence a much smaller charge will give 
 greater velocities. The weight of the charge, for the .30- 
 cal. rifle is 37 grains, and that of the projectile 220 grains. 
 That of the old cal.-45 rifle was, powder 70 grains, bullet 
 500 grains. 
 
 This reduction in weight of cartridge has an important 
 bearing upon the number of rounds carried by the soldier. 
 It is evident that with a magazine arm the number of car- 
 tridges used will be greatly increased, and the reduction 
 in weight enables them to be carried with ease. 
 
 The specific gravity and gravimetric density of the new 
 powders are less than those of the old, and hence they oc- 
 cupy a greater volume for the same weight ; but as the 
 weight necessary to give the same or better results is less 
 for each charge, the decrease in density occasions no diffi- 
 culty. 
 
 69. Cause of Ballistic Superiority of Smokeless Powders. 
 
 The superior effects of the smokeless powders may be 
 explained by considering their potential, force, and rapidity 
 of reaction. 
 
 1. Potential. This is much greater than with the old ni- 
 trate powders, as the quantity of heat evolved in the com- 
 bustion of gun-cotton and nitro-glycerine is very much 
 greater than that of ordinary powder. This heat measures 
 the quantity of work which the gases can do upon the pro- 
 jectile, and hence the energy of the latter is much greater, 
 and we have higher velocities. 
 
 2. Force. This is also greater than with the old powders, 
 as the specific volume of the gases and their temperature 
 are higher. 
 
 The specific volume is greater because all the powder is 
 converted into gas. This force tends to increase the press- 
 ure exerted by the gases upon the gun at the origin, and 
 hence this pressure would be very great if it were not 
 that 
 
 3. The Rapidity of Reaction is very much decreased, so 
 that the gas is given off slowlv, and allows the projectile 
 
HIGH EXPLOSIVES AND SMOKELESS POWDERS. 133 
 
 to start from its original position before this pressure has 
 reached too great a value. 
 
 These powders burn very slowly in air, but, like the ni- 
 trate powders, their rate of burning increases very rapidly 
 with the pressure, and probably if this pressure were very 
 high they would detonate. 
 
 Another circumstance concurs to prevent this, however, 
 and that is that the powder has no solid residue, and hence 
 all the space in the powder-chamber and in rear of the pro- 
 jectile is occupied by the gas. In ordinary powders about 
 .57 of this space, or more than half, is occupied by solid 
 residue. Hence the pressure is kept down at first, and, 
 owing to the high temperature and great volume of the gas, 
 it is maintained better along the bore than with the old 
 powders. 
 
 We have therefore in the new powders a propelling 
 agent which for less weight gives safe pressure at first, 
 more gas, more heat, and more sustained pressure than the 
 old powders, and hence their ballistic superiority. 
 
 TABLE OF HIGH EXPLOSIVES AND SMOKELESS 
 POWDERS. 
 
 (From Cundill's " Dictionary of Explosives.") 
 
 I. NITRATE MIXTURES. 
 
 NAME. COMPOSITION. 
 
 f Nitre, 101 parts 
 
 Amide Powder ] Ammonium nitrate, 80 
 
 ( Charcoal, 4 " 
 
 II. CHLORATE MIXTURES. 
 
 , j Chlorate potash, 3 parts 
 
 1 Mono-nitro-benzine, i part 
 
 III. NITRO COMPOUNDS. 
 
 j Gun-cotton 
 Abel's Glyoxiline j Nitro . glycer i ne 
 
 i Gun-cotton 
 
 Also < Potassium nitrate 
 ( Nitro-glycerine 
 
134 TEXT-BOOK OF ORDNANCE AND GUNNERY, 
 
 ( Nitro-glycerine, 15 to 65 parts 
 JEtna. Powder ............. -j Sodium nitrate 
 
 f Wood-pulp 
 
 f Sodium nitrate, 2 parts 
 
 Wood fibre, 21 " 
 Magnesium carbonate, 2 
 
 Nitro-glycerine 75 " 
 
 Ammonium nitrate 8^ " 
 . _ , . 
 Tn-mtro-benzme 17 
 
 Blasting Gelatine .......... Di-nttro-cellulose dissolved in nitro- 
 
 glycerine 
 Borland Powder } j Nitro-glycerine, 90 parts 
 
 ( 
 Belhte ................... 1. 
 
 ( 
 
 I Ic" 
 
 Carbo-dynamite ) ( Charcoal, 10 
 
 ( Nitro-glycerine, so " 
 
 Dittmar Powder ) \ * 
 
 .. [ 4 Sawdust, 30 
 
 Dualme j J _ 
 
 I Potassium nitrate 20 
 
 Dynamite No. i \ Nitro-glycerine, 7 5 
 
 ( Kieselguhr, 25 " 
 
 Giant Powder (See Dynamite.) 
 
 Judson Powder Gunpowder coated with mtro-glycerine 
 
 Lithofracteur (See Rendrock.) 
 
 ( Sugar of manna 
 Nitro-mannite J Nitric acid 
 
 ( Sulphuric acid 
 
 f Potassium nitrate, 40 parts 
 
 Rendrock J Nitro-glycerine, 40 " 
 
 | Wood-fibre, 13 
 
 t Paraffine, 7 " 
 
 Ammonium nitrate 
 Chlorinated di-nitro-benzine 
 
 ( Nitro-lignin 
 
 I Potassium nitrate 
 
 Shultze Powder <{ Barium nitrate 
 
 (a sporting powder) Sawdust 
 
 I Paramne 
 
 , . ( Gun-cotton 
 
 Tonite } , 
 
 /u . , x { Barium nitrate 
 
 (blasting-powder) 
 
 IV. PICRIC POWDERS. 
 
 ( Ammonium picrate, ^4 parts 
 Brugere s Powder . * 
 
 ( Potassium nitrate, 46 
 
 ( j 
 Roburite ' -j 
 
 ( v^l 
 
HIGH EXPLOSIVES AND SMOKELESS POWDERS, 135 
 
 ( Potassium picrate, 9 parts. 
 
 Designolle's Powder < Potassium nitrate, 80 " 
 
 ( Charcoal, n " 
 
 ( Gun-cotton dissolved in ether 
 Melinite I Picric acid 
 
 ( Cresylic acid 
 
 V. SPRENGEL MIXTURES. 
 
 ( Di-nitro-benzine 
 
 Hellhoffite ] XT . . 
 
 ( Nitric acid 
 
 Rack-a-rock (See ante.) 
 
 VI. MISCELLANEOUS. 
 
 ( Chlorate potash 
 Caps for Toy Pistols . . . . j A houg phosphorus 
 
 f Fulminate mercury, 6 parts 
 j Potassium chlorate, 6 " 
 Percussion-caps <j Antimony su i ph i de , 4 
 
 [ Ground glass, 2 
 
 \ f Mercury 
 
 Mercury f ) Nitric acid 
 
 Fulminate J ' ( Akohol 
 
 c Tin cases filled with powder and hav- 
 
 Railroad Fog-signals ] ing cones with ordinary percus- 
 
 ( sion-caps. 
 
CHAPTER III. 
 
 GUNS. 
 
 GUN-STEEL. 
 
 70. Definition of Gun-steel Chemical Composition Different Con- 
 stituents and their Effect. 
 
 DEFINITION. Steel is an alloy of iron and carbon, the 
 percentage of the latter being from o.io to 2.5. This per- 
 centage, however, does not always serve to classify steel, as 
 it runs into wrought iron on the one hand, and into cast-iron 
 on the other. It is distinguished from cast iron by its 
 quality of becoming hard when heated to a certain tern- 
 perature and cooled quickly, and of having this hardness 
 reduced by a process called tempering. 
 
 It is distinguished from wrought iron by this same qual- 
 ity, and also by being cast into molds or ingots, which is not 
 possible with wrought iron, the latter not being fluid except 
 at very high temperatures. In gun-steel the proportion of 
 carbon is low, not exceeding 0.5 per cent as a rule. 
 
 CHEMICAL COMPOSITION. Upon this point there is great 
 difference of opinion. Steel is called an alloy of iron and 
 carbon, but the exact condition of the carbon is not known. 
 
 It is sometimes called dissolved carbon for the harder 
 steels, and undissolved for the softer; also "hardening" 
 and " cement " carbon, for the harder and softer steels re- 
 spectively. More recently it is called " fixed " carbon for 
 the hard, and " free" carbon for the soft steels. These two 
 carbons may be changed from the one to the other, as the 
 result of special treatment. 
 
 OTHER CONSTITUENTS. Besides the carbon, there are 
 always other substances present, some of which are bene- 
 
 136 
 
GUNS. ! 3 7 
 
 ficial and others injurious to its quality. Among the prin- 
 cipal of these substances are : 
 
 1. Sulphur. This is injurious to the steel, as it makes it 
 difficult to forge, producing " hot-shortness," or brittleness 
 when hot. 
 
 2. Phosphorus. This is also injurious, as it has the effect 
 of making steel brittle when cold, or " cold-short." 
 
 3. Manganese. This when added in proper proportions 
 improves the quality of the steel, rendering it hard and 
 tough. 
 
 4. Silicon. Is valuable, as it forms a fusible slag with the 
 iron oxide in manufacture, and prevents the formation of 
 gas, and consequently of blow holes in the steel. If in too 
 great quantity, it causes brittleness. 
 
 5. Chromium. Gives great hardness to steel without 
 brittleness, and hence the best forged steel projectiles are 
 made of chrome-steel. 
 
 6. Nickel. This gives great toughness to steel, so. that 
 armor-plates made of nickel-steel resist racking very well. 
 
 Nickel-steel is also being experimented with for guns, at 
 present. 
 
 71. Physical Qualities Hardness Toughness Elastic Limit 
 Hooke's Law Tensile Strength. 
 
 HARDNESS. Gun-steel should be sufficiently hard to re- 
 sist deformation from blows, and also the action of the pro- 
 jectile and the powder-gases; but hardness is generally 
 accompanied by an undesirable quality, brittleness, and 
 hence a modification called toughness is sought in this metal. 
 
 TOUGHNESS is the quality which enables a metal to under- 
 go considerable change of form under the action of a force, 
 without rupture, and with great resistance to that change. 
 
 ELASTICITY AND ELASTIC LIMIT. When a tensile stress 
 or force is applied to a piece of steel, it will elongate a cer- 
 tain amount. 
 
 This total elongation, divided by the original length, wil 
 give the elongation per unit of length. When the stress or 
 force ceases to act, the steel will recover its original length, 
 provided the stress is not too great. If an additional force 
 
138 TEXT- BOOK OF ORDNANCE AND GUNNERY. 
 
 be applied, a similar effect will be obtained, the elongation 
 per unit of length being greater in this case, and the metal 
 returning again to its original length when the stress ceases 
 to act. The same effects will be observed till the stress 
 reaches a certain amount, when the metal will not return to 
 its original length, but will acquire a permanent set. If the 
 stress next below the one which produces the permanent set 
 be measured, and be divided by the area of cross-section of 
 the metal, it will give the elastic limit of the metal ; and if the 
 elastic limit be divided by the corresponding elongation per 
 unit of length, the result will be the modulus or coefficient 
 of elasticity of the metal. 
 
 Let a be the area of cross-section of the metal ; 
 
 /, its length ; 
 
 K, the total elongation ; 
 
 W, the stress acting at the elastic limit ; 
 
 , the modulus of elasticity ; 
 
 0, the elastic limit. 
 
 Then 
 
 ?=?= 
 
 F - JL 
 
 ~~ K ~~ ' 
 
 Denoting by A the elongation per unit length, we have 
 
 and 
 
 HOOKE'S LAW. The ratio of stress to elongation remains 
 constant up to the elastic limit, and this constant ratio is the 
 modulus of elasticity E. This is expressed as follows : 
 
GUNS. 
 
 Within *the elastic limit of a metal, the stress is proper- 
 tional to the strain. This is called Hooke's law. 
 
 If we compare two kinds of steel, one having a high per- 
 centage ol carbon, and the other a low percentage, it will 
 be found that the steel high in carbon has a high elastic 
 limit, and that low in carbon a low limit. Since the modulus 
 of elasticity for all steel is nearly constant, and equal to 
 about 30,000,000 Ibs. per square inch, the high steel will 
 elongate more at the elastic limit than the low (equation 
 169)). From this alone it would appear that the high steel 
 is best for gun-construction, since it enables the metal to 
 yield more to the stresses of the powder-gas, and to recover 
 its original form without permanent set. 
 
 The reason why high or hard steel is not used is, that it. 
 is liable to flaws, strains, or incipient cracks, produced in 
 manufacture, especially in large pieces. A hard steel is 
 also dangerous, because after passing its elastic limit, it has 
 very little remaining strength, and breaks easily, and with 
 little warning, while the soft steel yields considerably with- 
 out fracture, after passing the elastic limit, exhibiting the 
 quality of toughness, previously defined. 
 
 TENSILE STRENGTH. By this is commonly understood 
 the stress per unit area required to rupture the metal. It is 
 not of great importance in gun-steel, although limits are 
 prescribed for it in the tests, since we consider the elastic 
 limit only in gun-construction. 
 
 For clearness, a tensile stress only has been considered. 
 
 The same relations hold, however, for compression or 
 torsional stress, and each has its corresponding elastic limit 
 and modulus. 
 
 72. Structure of Steel Defects Blow-holes Pipes. 
 
 STRUCTURE. Steel is always a crystalline metal, and has 
 no fibrous structure like wrought iron. These crystals are 
 generally small, and vary in size and appearance with the 
 treatment the metal receives after casting. They are very 
 small in the best steels, and may be so small that the frac- 
 ture will lose its crystalline appearance. 
 
TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 DEFECTS. These are common to all cast metals, and 
 steel has some in addition peculiar to itself. 
 
 Slow Cooling in large masses gives large crystals, and 
 consequently a weak steel. It also causes a lack of uni- 
 formity in the steel. This being an alloy of iron and car- 
 bon, and the carbon being combined in different proportions 
 throughout the fluid mass, the alloys highest in carbon are 
 the lightest, and will rise to the top. Hence the hardest 
 steel is found here. For the same reason, the softest will 
 be at the bottom of the ingot. The middle portion of the 
 length will therefore give the best steel. As the fusibility 
 of the steel increases with the percentage of carbon, those 
 portions low in carbon will solidify first, and hence, in the 
 same cross-section, the part high in carbon will be near the 
 centre, where the mass remains fluid longer. 
 
 BLOW-HOLES. This defect is peculiar to steel, and is due 
 to the gases in the melted metal, which, being unable to es- 
 cape, are imprisoned in the casting, and form holes. These 
 blow-holes are causes of weakness in steel, as it is impossible 
 to discover them, and forging or compression only changes 
 their form, but does not remove them. Various theories 
 have been advanced to account for their presence, and at- 
 tempts made to get rid of them. They are more prevalent 
 in the Bessemer than in the open-hearth steels, by which 
 latter process gun-steel is made. 
 
 The lower the temperature at which the steel is cast, the 
 more apt are these blow-holes to occur, because the metal 
 hardens before the gas has time to escape. 
 
 PIPES. These are cavities formed in the axis of the 
 ingot, due to internal strains from cooling. They generally 
 occur when the metal is cast too hot. Thus on the one 
 hand too low a temperature causes blow-holes, and too high 
 a temperature pipes. 
 
 To avoid these defects in gun-steel, 6 per cent of the 
 total weight of the cast ingot is cut from the bottom and 
 33^ per cent from the top, the remainder being used for the 
 lorging. The piping and weak metal in the centre of the 
 ingot are removed by boring or cutting out the central part 
 of the ingot. Blow-holes can be prevented only by careful 
 
GUNS. 
 
 141 
 
 treatment in casting, arid their presence cannot be detected 
 except by subsequent working, and not then if they are 
 beyond the reach of the tools employed. 
 
 73. Working Qualities of Steel Fusibility Malleability and 
 Ductility Welding Annealing. 
 
 FUSIBILITY. This quality enables steel to be cast into 
 various shapes, and into ingots for gun-forgings. It re- 
 quires, however, a relatively high temperature, and has 
 caused the introduction of various special processes for 
 obtaining this temperature. In the Bessemer process, the 
 heat necessary is obtained, by blowing air through a melted 
 mass of cast iron, by which the carbon and silicon are oxi- 
 dized, and a high temperature produced. In the open- 
 hearth process, the high temperature is ootamed by the use 
 of gaseous fuel, and by storing up the waste heat of the fur- 
 nace in chambers of fire-brick, through which the gaseous 
 fuel passes, and by which it is raised to a high temperature. 
 
 MALLEABILITY AND DUCTILITY. Steel, when heated to 
 a red heat, possesses the property of malleability, and it is 
 due to this fact that it can be forged into any shape. When 
 cold, owing to its ductility, it can be drawn into wire, which 
 is used in wire guns and for various other purposes. 
 
 WELDING. Ordinarily steel cannot be welded except 
 when very low in carbon, and approaching wrought iron. 
 Lately, however, the process of electric welding has been 
 introduced, and by it the welding can be readily accom- 
 plished. 
 
 ANNEALING This is a very valuable property possessed 
 by steel. By heating it to a certain temperature and allow- 
 ing it to cool slowly, a piece of hard steel will become soft, 
 so that it can be readily worked in the lathe. After work- 
 ing, it can be returned to its former hard condition, by 
 heating it again, and cooling it quickly. After forging or 
 working steel, it generally has internal strains due to these 
 processes, and' these strains may be removed by annealing. 
 By cooling in oil, the tensile strength and elastic limit of 
 steel are greatly increased, and these qualities, especially 
 elasticity, are very valuable in gun-construction. 
 
142 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 74. Manufacture of Gun-steel Open-hearth Process Gas-producer 
 and Regenerators. 
 
 OPEN-HEARTH PROCESS. All gun-steel at the present 
 day is made by this process, which derives its name from the 
 fact that the receptacle in which the steel is melted is open 
 at the top, and exposed to the flame of the fuel which plays 
 over the surface, and performs a principal part in the forma- 
 tion of the steel. It is also called Siemens or Siemens-Martin 
 steel, according to the ingredients used to form the steel. 
 
 APPARATUS. The furnace used is that invented by Dr. 
 Siemens, and a general description of it is given. It con- 
 consists of the following essential parts : 
 
 1. The gas-producer ; 
 
 2. The regenerators ; 
 
 3. The furnace proper. 
 
 THE GAS-PRODUCER. The fuel used in the Siemens fur- 
 nace is gaseous, and is obtained from ordinary fuel, by sub- 
 jecting the latter to a preliminary process in the gas-produ- 
 cer. This apparatus, Fig. 29, consists of a rectangular 
 
 FIG. 29. 
 
 chamber of fire-brick, one side, B, being inclined at an angle 
 ol 45 to 60. A is the grate. The fuel, which may be of 
 any kind, is fed into the producer through the hopper C. 
 As the fuel slowly burns, the CO 2 rises through the mass 
 above it, and absorbs an additional portion of C, becoming 
 converted into 2CO. This gas passes out of the opening D, 
 into a flue. In order to cause it to flow towards the furnace, 
 it is led through a long pipe, E, where it is partially cooled, 
 
G UNS. 
 
 143 
 
 and it then descends the pipe /Heading to the furnace. The 
 gas in F being cooler than that in E and D, a constant flow 
 of gas from producer to furnace is maintained. 
 
 THE REGENERATORS. The gas entering the furnace is, as 
 has been stated, CO. To burn it to CO 2 , air must be mixed 
 with it. This mixture is made in the furnace proper, the 
 CO and air being kept separate till they reach the point 
 where they are to burn. The CO is cooled to some extent, 
 as shown, before being admitted to the furnace. 
 
 To heat both air and CO before they are mixed and 
 burned, and to accomplish this economically, and raise them 
 to a high temperature, the waste heat of the furnace is em- 
 ployed. This is the object of the regenerators, Fig. 30. 
 
 They consist of four large chambers below the furnace, 
 tilled with fire-brick, piled so that there are intervals be- 
 tween the bricks to allow the gas and air to pass through. 
 Their action is as follows : When the furnace is started, 
 CO is admitted through A and air through B, both A and 
 B being cold. These pass up through the fire-bricks in A 
 and B and through flues at the top, and flow into the fur- 
 nace proper, where they are lighted. The products of 
 combustion are caused to pass through C and D, which are 
 similar chambers. In doing so these products heat the fire- 
 bricks in C and D. After some time, about one hour gen- 
 erally, by the action of valves controlled by the workmen, 
 the CO and air are caused to enter the furnace through C 
 
144 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY, 
 
 and D respectively, and the products of combustion to pass 
 out through A and B. In this case the CO and air entering 
 the heated chambers C and D are raised to a high tempera 
 ture before ignition, and the temperature of the furnace 
 thereby greatly increased. It is also evident that A and B 
 will be more highly heated than C and D were, and hence 
 when the next change is made the gas and air passing 
 through A and B will be more highly heated than when 
 passing through C and D, and so on. 
 
 The action of the furnace is therefore cumulative, and 
 its only limit in temperature is the refractoriness of the 
 material. By regulating the proportions of gas and air, 
 which is readily done, the temperature may be kept con- 
 stant. 
 
 75. Manufacture of Steel The Furnace Operation Crucible 
 
 Process. 
 
 THE FURNACE. The furnace proper consists (see Fig. 
 31) of a dish-shaped vessel D of cast iron, supported so that 
 
 FIG. 31. 
 
 the air can circulate freely around it and keep it from melt- 
 ing. This is lined with refractory sand S; and in order to 
 repair it when necessary, the pan D is generally arranged so 
 that it can be run out of the furnace. This allows it to cool 
 quickly. The pan is placed over the regenerators, and the 
 gaseous fuel and air enter by the flues F, and the products 
 of combustion escape by the flues JF', or the reverse, ac- 
 cording to the position of the regulating-valves. 
 
 The arrows show the direction of these currents. The 
 
GUNS. 145 
 
 roof R is lined with fire-brick, and by its shape deflects the 
 flame over the metal in the hearth. At opposite ends of 
 the furnace are a charging-door for admission of the metal,, 
 and a tap-hole for drawing off the finished steel. These are 
 not shown in the drawing. 
 
 OPERATION. The principle of the process is that when 
 wrought-iron or steel scrap is added to melted cast iron, the 
 percentage of carbon is thereby reduced till it reaches that 
 required for steel. The charge consists of pig-iron heated 
 red-hot in a separate furnace, and then placed on the hearth 
 of the Siemens furnace. By the action of the furnace this 
 pig-iron is soon melted. Scrap wrought iron or steel is then 
 added in suitable proportions, till the percentage of carbon 
 is low. When it has reached the proper point, the percent- 
 age is made exact by adding a pig iron containing a known 
 percentage of carbon, such as Spiegeleisen or ferro-manga- 
 nese, or by the addition of ore. The percentage of carbon 
 is judged of during the process by taking samples from 
 the melted metal, cooling them, observing their fracture 
 on breaking, and by dissolving portions of the specimen in 
 HNO 3 and comparing the color with that of standard solu- 
 tions of steel in HNO 3 containing different percentages o 
 carbon. In this way the composition of the steel can be 
 exactly regulated, as the metal can be kept in a melted 
 state without damage for a considerable time, and the char- 
 acter of the flame made oxidizing or reducing at will, ac- 
 cording to the relative amounts of air and CO admitted. 
 
 The operation ordinarily lasts about eight hours for 
 each charge. 
 
 When the steel has attained its proper composition, the 
 furnace is tapped and the metal cast into ingots, ready for 
 the succeeding operations. 
 
 CRUCIBLE PROCESS. This is used by Krupp. The in- 
 gredients of the steel are melted in crucibles, and the result- 
 ing steel from the crucibles is poured into a common reser- 
 voir from which the ingots are cast. 
 
 The Bessemer process, though important and producing 
 large quantities of steel, is not as yet used in making, 
 steel. 
 
146 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 76. Casting Ingots Ladle Crane Ingot-mold Pouring Sink- 
 ing Head. 
 
 After the proper percentage of carbon is obtained, the 
 steel is cast in ingots. 
 
 LADLE. The first step is to tap the furnace and draw 
 off the steel into a ladle. This ladle is made of boiler-iron 
 lined with refractory sand. It has two trunnions on the 
 exterior which support it, and around which it revolves 
 
 when tipped, to pour the metal into 
 the mold ; or it may have a tap- 
 hole at the bottom closed with a 
 plug of fire-clay, which is lifted by 
 an iron rod covered with refractory 
 material. 
 
 In Fig. 32, T is the tap-hole, T 
 the trunnions, R the rod, and S its 
 casing. The advantage of tipping 
 is that it is quicker, and of the tap- 
 hole, that it gets rid of scoria and impurities on the surface 
 of the melted steel, and keeps them out of the mold. 
 
 CRANE. This is used to convey the ladle to the molds, 
 or, more generally, for handling the ingots and molds 
 after the casting. It is very 
 often found more convenient 
 to run the ingot-molds on 
 cars under the ladle, or under a 
 spout attached to the furnace. 
 INGOT-MOLDS. These are 
 generally made of cast iron, 
 and are circular in cross-sec- 
 tion, to insure uniform cooling. 
 They are in one piece, and 
 slightly conical on the inte- 
 rior, so that the ingot, after 
 casting, may be readily with- 
 drawn. They may also be 
 made in halves, parting on 
 an axial plane ; but in this 
 case they are liable to open at the joint, due to warping. 
 
 J0L 
 
 J0L 
 
 SOLID. 
 
 SPLIT. 
 
G UNS. 
 
 '47 
 
 The interior surface is protected by a wash of clay or 
 plumbago. Melted steel poured into an ingot-mold will 
 not adhere to the sides, while melted cast iron will adhere. 
 The reason is that the steel chills and contracts away 
 from the mold, while the iron cools more slowly and fuses 
 the mold. The general shape of the ingot-molds is shown 
 in Fig. 33. 
 
 POURING. If the steel is very hot, it must be poured 
 slowly into the molds in a thin stream. This allows the 
 gases time to escape. If at a lower temperature, it may be 
 poured more quickly. 
 
 The ingot-molds may be warmed before casting to pre- 
 vent undue cooling and consequent strains, and also the 
 formation of pipes. 
 
 After the steel is cast, the molds must be covered to ex- 
 clude air and cause slow cooling. 
 
 SINKING-HEAD. In all castings, whether of iron, steel, or 
 other metal, an excess of metal, called the sinking-head, is 
 left at the top of the mold. This column of metal acts by 
 its weight to give greater density to the lower portions of 
 the ingot ; it also serves to collect the scoria and impurities 
 which rise to the top, and it fills any cracks or cavities that 
 may form in the cooling of the ingot. It is necessary to 
 keep this sinking-head fluid as long as possible, and hence 
 it is generally cast in a sand-mold for gun-ingots. 
 
 77. Whitworth's Process of Fluid Compression. 
 
 Thi^ process was invented by Sir Joseph Whitworth of 
 England, and gives by hydraulic pressure, the same effect 
 as that due to the sinking-head. It may be regarded as an 
 artificial sinking-head of great height. The process con- 
 sists in forcing the piston of a hydraulic ram down upon 
 the melted steel in the mold, and maintaining the pressure 
 till the steel solidifies. The ingot-mold used in this process 
 must be very strong to withstand the great pressure, and it 
 has a peculiar arrangement by which the gases driven out 
 by the pressure are allowed to escape. Fig. 34 gives the 
 general arrangement. 
 
 The mold consists of a strong cast-steel cylinder, A, 
 
148 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 % 
 
 ff 
 
 s 
 
 * 
 
 
 - 
 
 = 
 
 
 
 I 
 
 
 = 
 
 - 
 
 -E 
 
 
 
 
 
 
 
 -D 
 
 
 = 
 - 
 
 
 
 
 7= 
 = 
 = 
 
 A 
 
 
 L 
 
 
 B 
 
 
 u 
 
 
 with its bottom', B. This cylinder is lined with rectangular 
 bars of wrought iron, C, which have 
 grooves, D, cut at intervals along their 
 faces in a radial direction. Their rear 
 edges are also cut off longitudinally so 
 that when placed side by side and forming 
 a lining for the cylinder A they have con- 
 tinuous longitudinal channels, E, parallel 
 to the elements of the cylinder. The 
 grooves D communicate with the channels 
 , and thus allow the gas to escape at the 
 top and bottom of the mold. The interior 
 of the mold is lined with refractory sand. 
 Action. When the melted steel is 
 poured into the mold and the ram R 
 forced down upon it, the hot metal is at 
 first forced through the openings O be- 
 tween ram and mold. But the metal 
 quickly cools and forms a solid mass, 
 completely closing these openings O. The 
 gas is forced out through the channels as shown, and 
 the effect of the pressure and shrinkage is to shorten the 
 ingot about ij inches for each foot of length. 
 
 Theory. It appears at first that the metal, as well as the 
 gases, would be expelled through the channels, and also 
 that, since fluid pressure is equal in all directions, there is no 
 reason why this pressure should force the gas out of the 
 melted metal. Dr. Siemens suggests as an explanation that 
 the steel cools first on the exterior where it is in contact 
 with the mold, and offers a greater resistance here to the 
 motion of the ram. It is broken up in consequence by the 
 pressure, and becomes porous. The interior of the mold 
 remaining fluid, and offering less resistance than the outside, 
 receives consequently more compression, and hence the re- 
 sult will be to force the gas outward through the porous 
 exterior. This porous exterior, while allowing the gas to 
 escape, retains the fluid metal. It is also claimed that the 
 pressure increases the solvent action of the metal upon the 
 gases. Krupp maintains, however, that this process of 
 
 FIG 
 
GUNS. 
 
 I 49 
 
 fluid compression simply closes up the cavities but does not 
 -expel the gas. 
 
 78. Treatment after Casting Testing Reheating Forging 
 Cranes Hammer. 
 
 TESTING. After the ingot is cast and cooled, specimens 
 of it are tested chemically to determine its composition, 
 and also in the testing-machine to determine its physical 
 qualities. The ingot is graded according to these tests, 
 and a hole is then bored through it parallel to its axis, re- 
 moving the central part of the ingot. This hole is for 
 purposes of forging, as will be explained. 
 
 If the ingot is short, this hole may be punched ; and for 
 small tubes or any solid forgings the hole is not necessary. 
 
 REHEATING. For forging, the ingot is then reheated in 
 a furnace which is a modification of the Siemens. In the 
 reheating, care must be taken to apply the heat slowly and 
 regularly, so as to avoid overheating the exterior before 
 the interior is brought to the proper temperature. If the 
 heat is applied too quickly, the ingot is liable to crack from 
 unequal expansion, and the exterior to be overheated or 
 " burned." 
 
 CRANES. The ingots when heated to the proper temper- 
 
 FIG. 35- 
 
 ature are handled by heavy cranes, which remove them from 
 the furnace and carry them to the hammer or press. They 
 
TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 are slung from the crane by a chain called the sling-chain,, 
 and are balanced by the addition of extra weights at the 
 cool end, so that they may be readily swung by the work- 
 men, and turned axially under the hammer. Fig. 35 shows 
 the general arrangement for forging an ingot under a ham- 
 mer. H is the hammer, A the anvil, C the crane, E the in- 
 got, 5 the sling-chain, P the porter-bar ; the handles K are 
 used for rotating the ingot under the hammer. 
 
 HAMMER. The steam-hammer is used in forging ingots, 
 except where hydraulic pressure is preferred. These ham- 
 mers consist of a heavy head or tup attached to the piston 
 of a steam-cylinder. The cylinder is vertical and is sup- 
 ported by two legs, and the hammer thus formed is called 
 an A hammer, from its general appearance. When the 
 steam raises the hammer, and is then exhausted, and the tup 
 allowed to fall by its own weight, we have a single-acting 
 hammer ; when the steam acts also to drive the tup down, 
 we have a double-acting hammer. The foundation for the 
 anvil is separate from the hammer to diminish the effect of 
 the blow upon the latter. 
 
 Since the same energy may be obtained from a light 
 hammer moving quickly or from a heavy hammer moving 
 slowly, the latter is preferred for heavy masses, as the effect 
 of the blow is better distributed through the mass. Armor- 
 plates are generally made by hammering, as the effect of 
 the blow is felt more on the face and less in the interior, and 
 it is important to have a good quality of face. With gun- 
 forgings both hammer and hydraulic pressure are used 
 with excellent results, the hydraulic press, however, being 
 preferred, as it is more slow in its action and distributes, 
 the effect throughout the mass. 
 
 79. Whitworth's Hydraulic Forging The Press Mandrels. 
 
 In this process the ingot is drawn into shape by the 
 pressure of a powerful hydraulic ram. As the action is slow, 
 it is claimed that the effect is better distributed throughout 
 the mass, as before stated, and consequently produces a 
 better effect upon the metal as a whole. 
 
 THE PRESS. This is a large hydraulic ram so arranged 
 
GUNS. 1 ^ l 
 
 that it may be quickly adjusted to any size of ingot. The 
 general arrangement is represented in Figs. 36 and 37 
 although the ram actually has many arrangements for ad- 
 justment, etc., not shown. 
 
 THE MANDRELS. With this press a secondary or mov- 
 able anvil, called a mandrel, is used. It is shown in Figs. 36 
 and 37, and its use is as follows : 
 
 If the ingot is to be drawn out into a long forging such 
 as a gun-tube, it is first bored out on the interior. It is 
 then heated, and the mandrel passed through the bore. The 
 ingot is now placed under the forg ing-press, resting on the 
 fixed anvil as shown in Fig. 36. When pressure is applied 
 
 I 
 
 'FRONT. ELEVATION. 
 
 SIDE ELEVATION. 
 
 FIG. 36. 
 
 under these circumstances, the effect will be to lengthen the 
 ingot, keeping its interior diameter unchanged. On the 
 other hand, if the ingot is to be forged into a hoop, it is 
 bored as before, heated, and the mandrel passed through 
 the bore ; but in this case the ends of the mandrel are sup- 
 ported as shown in Fig. 37, the ingot being allowed to swing 
 on the mandrel. 
 
 When the pressure is applied under these conditions, it 
 is evident that the walls of the ingot will be compressed, 
 the interior diameter increased, and the length of the ingot 
 will remain practically unchanged. 
 
 In the first case we have a fixed mandrel, and in the 
 second a swinging mandrel. A current of water sometimes 
 
152 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 circulates through the centre of the mandrels to keep them 
 cool, and in the case of the fixed mandrel, it is withdrawn 
 from the forging by a second hydraulic press acting on it. 
 
 Comparing the hammer and press, it is claimed for the 
 hammer that its effects are more local, and therefore that it 
 
 FRONT ELEVATION- 
 
 SIDE ELEVATION. 
 
 FIG. 37. 
 
 is better for armor-plates ; that the effect of its blows is to 
 heat the metal, and therefore the temperature may be lower 
 in forging ; and that it uncovers defects in the metal, while 
 the press conceals them. 
 
 80. Gun-forgings Treatment after Forging Annealing Boring 
 and Turning Oil-tempering Re-annealing Tests. 
 
 GUN FORCINGS. The principal gun-forgings are the 
 tube, the jacket, and the hoops. 
 
 The forging of the tube and hoops has been explained, 
 and that of the jacket is exactly similar. 
 
 ANNEALING. After forging, the hammer or press leaves 
 certain strains in the metal, and they must be removed. 
 This is done by annealing. This process consists in heating 
 the forging carefully to a certain temperature, which is de- 
 termined by experience, and allowing it to cool slowly, in 
 the furnace, the latter being allowed to cool naturally. 
 By this process the steel becomes soft, and all strains are 
 removed. 
 
 BORING AND TURNING. The forging is now placed in a 
 
GUNS. 153 
 
 lathe and bored and turned to near its finished size. Pieces 
 are also taken off the ends as specimens, and tested, to de- 
 termine the qualities of the metal and as a guide to subse- 
 quent treatment. 
 
 OIL-TEMPERING. The object of this process, to which 
 the forging is now subjected, is to give the peculiar prop- 
 erty called " toughness" to steel. The practical effect is 
 that it increases the elastic limit and tensile strength, and 
 reduces the elongation before rupture. 
 
 Process. The forging is slowly heated and carefully 
 inspected, till all the parts have acquired the same tem- 
 perature, which is judged by the color. A long forging is 
 generally heated vertically to avoid warping. When at 
 the proper temperature, it is raised by a crane and lowered 
 vertically into a tank of oil, a current of which is caused to 
 flow through the bore. The oil is surrounded by a water- 
 jacket to keep down the temperature. 
 
 Being a poor conductor of heat, the oil allows the steel 
 to cool correspondingly slowly, and thus gives the particles 
 time to adjust themselves, and the result is a considerable 
 increase in elasticity and tenacity, and it acquires the prop- 
 erty of toughness already defined. 
 
 RE-ANNEALING. The process of oil-tempering causes 
 internal strains in the metal, and these are removed by 
 reannealing as before. This annealing process reduces 
 slightly the elastic limit and tensile strength and increases 
 the elongation before rupture. 
 
 TESTS. The physical qualities of the metal are now 
 tested. For this purpose specimens are cut from the 
 breech and muzzle ends of each tube, jacket, or hoop forg- 
 ing, and the results of these tests compared. No great 
 difference in quality must exist between breech and muzzle 
 specimens, as this would indicate a variation in quality of 
 the metal from breech to muzzle. In the U. S. service the 
 requirements of the Ordnance Department are about as 
 follows : 
 
 Elastic limit, 46,000 to 50,000 pounds per square inch ; 
 
 Tensile strength, 86,000 to 93,000 pounds per square 
 inch ; 
 
154 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 Elongation at rupture, 15 to 17 per cent in a length of 3 
 inches. 
 
 81. Brinell's Experiments. 
 
 To determine the effects of heating and cooling on the 
 change of structure and the hardening of steel, Mr. J. A. 
 Brinell, a Swedish engineer, made a series of experiments. 
 
 Taking a certain kind of steel which contained about the 
 same percentage of carbon as gun-steel, he heated bars of 
 it to different temperatures and cooled them at different 
 rates. After heating and cooling, the bars were broken 
 and the fracture carefully examined, and chemical tests 
 were made to determine the condition of the carbon. He 
 found that there were two states of the carbon one which 
 he called free carbon and which was associated with soft 
 steel, and the other, fixed carbon, associated with hard 
 steel. In general the soft steel had a crystalline structure 
 and the hard steel an amorphous structure, or one in 
 which the crystals were so small as to lose their crystalline 
 appearance. 
 
 His conclusions were as follows : 
 
 1. For each steel, hard and soft, there is a certain tem- 
 perature, called the critical temperature, to which if the 
 steel be heated, and be suddenly cooled, all the carbon will 
 become fixed, and the structure will be amorphous. This 
 is the hardest condition of steel ; and hence, to harden it, it 
 is heated to this temperature and cooled suddenly. 
 
 2. Hard steel, if heated to this critical temperature and 
 cooled slowly, will acquire the crystalline structure, and all 
 the carbon will become free. Soft steel heated to this tem- 
 perature and cooled slowly undergoes no change. This is 
 the softest condition of steel, and hence, to anneal it, it is 
 heated to this critical temperature and cooled slowly. 
 
 3. If hardened steel, or steel which has been subjected 
 to the first process, be heated to any temperature below 
 the critical temperature, it becomes softer as the tempera- 
 ture increases. That is, with hard steel, as the critical tem- 
 perature is approached, more and more of the fixed carbon 
 becomes free, and if the steel be cooled either slowly or 
 
GUNS. 155 
 
 quickly after having been heated to any temperature below 
 the critical one, the hardness of the steel is diminished. 
 This process is called tempering, and by it the degree of 
 hardness can be regulated to any extent. It is the process 
 commonly employed by the blacksmith in tool-making. 
 The less the steel is heated the harder it will be. 
 
 4. When steel is heated to the critical temperature and 
 cooled very quickly, as by immersion in mercury or acidu- 
 lated water, it becomes harder than if cooled by immersion 
 in ordinary water ; and on the other hand, if cooled more 
 slowly, as in oil, it acquires less hardness but more elas- 
 ticity. 
 
 MACHINES USED IN GUN-MANUFACTURE. 
 
 82. General Principles of Machines Definition How Motion is 
 Transmitted and Modified. 
 
 In order to understand the operations in the manufac- 
 ture of a modern gun, some knowledge of the general 
 principles of machines is necessary, since all the operations 
 upon the gun after the forgings are received, are conducted 
 in a machine-shop, and the success of the modern gun as a 
 machine for propelling projectiles, depends upon the accu- 
 racy with which the machine-work is done in building it. 
 
 DEFINITION. A machine is any instrument or device 
 designed to receive energy from some source, and to over- 
 come certain resistances in transferring this ene'rgy to other 
 bodies. (Michie, p. 246.) 
 
 The mechanical principles of machines are discussed in 
 the Mechanics, pages 246-281, and it is intended here to. 
 give the practical application of these principles as seen in 
 the shops. 
 
 Another definition of a machine is, an assemblage of 
 moving parts for the purpose of transmitting and modify- 
 ing motion and energy. 
 
 How MOTION is TRANSMITTED AND MODIFIED. A 
 machine receives its motion from some source of energy 
 such as the steam-engine, water-wheel, etc., and transmits it. 
 
156 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 through a series of wheels, sliding surfaces, etc., to the 
 point where the work is done. 
 
 The source of motion is called the driving-point or prime 
 mover ; the parts through which the motion is transmitted, 
 the train ; and the point where the work is done, the working- 
 point. 
 v Motion may be transmitted and modified by : 
 
 1. Rolling contact of two or more surfaces ; 
 
 2. Sliding contact, as in gear-wheels, screws, etc. 
 
 3. Belts or bands ; 
 
 4. Linkwork ; 
 
 5. Cords or ropes ; 
 
 6. Hydraulic connection. 
 
 83. Rolling Contact Different Forms of Pieces in Rolling Contact. 
 ROLLING CONTACT. Let A and B, Fig. 38, represent two 
 wheels whose axes are parallel. When 
 motion is communicated to B it will impart 
 this motion to A by the friction of the two 
 surfaces in contact at the point a. These 
 FIG. ?8. circles in contact at a are called the pitch- 
 
 circles, or pitch-lines ; the point of contact a, the pitch-point. 
 The line cd joining the centres of the wheels is called the 
 line of connection, and is the line along which the velocity of 
 the moving pieces is zero. 
 
 The general principle which governs the motion of the 
 pieces in rolling contact is that each pair of points in the 
 pitch-lines which are in contact at any instant, must at that 
 instant be moving in the same direction, and with the same 
 velocity. 
 
 This principle leads to the following results : 
 Since each pair of points in contact must move in the 
 same direction at the same instant, the axes of the wheels 
 and their points of contact must lie in the same plane, be- 
 cause the motion of the points of contact is at right angles 
 to the axis of each wheel ; and since the velocities of their 
 points of contact must be equal, the angular velocities of 
 the wheels must be inversely as their radii. 
 
GUNS. 157 
 
 DIFFERENT FORMS OF PIECES IN ROLLING CONTACT. 
 Besides the circular wheels, we may have 
 
 1. A wheel, A, and rack, , Fig. 39, 
 
 2. Two wheels with intersecting axes, Fig. 40 ; 
 
 3. Two wheels with axes which are neither parallel nor 
 intersecting. This case will not be considered. 
 
 FIG. 39. 
 
 For the wheel and rack, since all points in the wheel move 
 at right angles to its axis, while all points of the rack move 
 parallel to itself, or at right angles to the axis of the wheel, 
 the general principle that the points of contact shall be moving 
 in the same direction requires that the axis of the wheel and 
 all points of contact must lie in a plane perpendicular to the 
 motion of the rack, and that, since the points of contact must 
 have the same velocity, the actual velocity of the rack must be 
 equal to the product of the angular velocity of the wheel by 
 its radius. For the two wheels with intersecting axes, if the 
 line ac joining the point of contact a with the intersection of 
 the axes be regarded as the line of contact of two cones, 
 whose axes are those of the wheels, it is evident that, as the 
 surfaces of the cones come into contact along this line, each 
 pair of points in contact will be moving at that instant in 
 the same direction and with the same velocity. Hence the 
 surfaces of two wheels whose axes intersect, are frusta of 
 cones, whose element of contact passes through the point of 
 intersection of the axes. 
 
 84. Sliding Contact Principles of Teeth Figures of Teeth- 
 Action. 
 
 SLIDING CONTACT. In the method of communicating 
 motion by rolling contact, it is evident that no great force 
 
IS TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 can be transmitted without danger of the slipping of one 
 wheel on the other. If this happens, the velocity ratio of 
 the two wheels is not constant, and hence this method will 
 not answer for accurate work. Where an exact ratio is to 
 be maintained between the velocities transmitted by two 
 wheels, these wheels must be so connected that one cannot 
 move without the other. 
 
 This connection is usually made by means of projections 
 on each wheel called teeth. 
 
 PRINCIPLES OF TEETH. Their construction and opera- 
 tion depend on the following- general principles : 
 
 Let A and B, Fig. 41, represent two wheels whose axes 
 are a and b, and suppose these wheels 
 in contact at c. 
 
 Then the circumferences in con- 
 tact are the pitch-circles, as before 
 explained. Let i, 2, 3, etc., represent 
 teeth formed upon the wheel A. 
 Then the pitch of the teeth is the 
 distance de along the pitch-circle 
 from the front of one tooth to the front of the next. Hence 
 
 1. In wheels which rotate continuously for one revolu- 
 tion or more, the pitch must be some aliquot part of the 
 pitch-circle, in order that it may be contained in that circle 
 an even number of times. For a rack, or a wheel which 
 does not perform a complete revolution, this condition is 
 not necessary. 
 
 2. In order that two wheels, or a wheel and rack, may 
 work correctly together, the pitch must be the same in each. 
 
 3. Hence, in a pair of wheels which work together, the 
 number of teeth in each wheel is directly as the circumfer- 
 ence or radius, and therefore inversely as the number of 
 revolutions in a given- time. 
 
 FIGURES OF TEETH. These are regulated by the prin- 
 ciple that the velocity ratio given by the teeth sliding on 
 each other shall be the same as that given by the pitch- 
 circles rolling on each other. 
 
 ACTION OF TEETH. To give a general idea of this ac- 
 tion, let Fig. 42 represent the teeth of two wheels in contact. 
 
GUNS. 
 
 '59 
 
 DRIVEN 
 
 DRIVER 
 
 FIG. 42. 
 
 The tooth a of the lower wheel first touches b of the 
 upper at the point c. These teeth then slide towards each 
 other till the point d is reached, 
 when they slide away from each 
 other and finally lose contact at e. 
 This process continues for all the 
 teeth, the arc cd being the arc of 
 approach, and de the arc of recess, 
 the whole curve cde representing 
 the various positions occupied by the point of contact dur- 
 ing the action of the teeth. 
 
 The method of describing the figures of teeth is too ex- 
 tensive for discussion here. 
 
 85. Belts or Bands Rounded or Crowning Pulleys Speed-Cones 
 Starting and Stopping. 
 
 BELTS. When teeth are used to communicate motion, 
 they possess the great advantage of preserving always the 
 same velocity ratio between two wheels. They have, how- 
 ever, the disadvantage of being a rigid connection, so that 
 they do not allow for starting or stopping, or sudden 
 changes of speed. Hence for the transmission of energy 
 from the engine or other prime mover to the different ma- 
 chines in a shop, belts are almost universally employed. 
 After the energy has been received at any machine, the 
 parts of that machine are connected by gearing, or teeth, if 
 accurate velocity ratios are required. 
 
 Belts are generally made of leather or gutta percha, and 
 are broad and flat, and hence require correspondingly shaped 
 pulleys. 
 
 The velocity ratio of two pulleys connected by a belt 
 follows the same principle as in the case of rolling or sliding 
 
 FIG. 43. FIG. 44. 
 
 contact, viz., the actual velocities of all points along the 
 belt are the same, and hence the angular velocities of the 
 
i6o 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 \ 
 
 .1 
 
 pulleys are inversely as the radii. If the pulleys are to 
 move in the same direction, the belt must be open, Fig. 43 ; 
 if in opposite directions, the belt must be crossed, Fig. 44. 
 
 ROUNDED PULLEY. To prevent the belt from leaving 
 the pulley, the latter is made crowning or rounded, Fig. 45. 
 j A belt always moves toward that part 
 
 of the pulley whose radius is greatest, and 
 the reason is as follows : When the belt 
 3 moves to one side of the pulley, the side 
 ab of the belt becomes compressed, Fig. 
 45. The resistance of the side ab to this 
 compression produces a force in the direc- 
 tion of the arrow e, which straightens the 
 belt and causes it to move to the highest, 
 part of the pulley. 
 
 SPEED-CONES. To vary the velocity 
 ratio communicated between a pair of par- 
 allel pulleys or shafts by a belt, without stopping the mo- 
 tion of the machinery, speed-cones are used. These may 
 be either continuous cones, 
 Fig. 46, or stepped cones, Fig. 
 47. In the first case we can 
 obtain a gradual variation of 
 speed, and in the second, cer- 
 tain fixed variations only. 
 
 The second method is gen- 
 erally used. 
 
 STARTING AND STOPPING. 
 
 j 
 
 Q- 
 
 FIG. 46. 
 
 FIG. 47. 
 
 As individual machines require to be started or stopped 
 without interfering with the source of power, each machine 
 is in general provided with two pulleys. 
 
 These pulleys are mounted on an independent shaft called 
 a counter-shaft, and one of them is fixed to this shaft, while 
 the other turns freely upon it. When the machine is to be 
 stopped, the belt is shifted to the " loose pulley," as it is 
 called ; and when started, to the fixed pulley. 
 
 86. Linkwork Cords and Ropes Hydraulic Connection. 
 
 LlNKWORK. When two rotating pieces are connected 
 
GUNS. l6l 
 
 by a rigid bar, as the driving-wheels of a locomotive, this 
 bar is called a link. It may also connect a rotating piece 
 and a sliding piece, as the piston-rod and crank of a steam- 
 engine, which are connected by a link. In the case of link- 
 work, the velocity of all points of the link being the same 
 at any instant, the angular velocities of the rotating pieces 
 are inversely as the perpendiculars let fall from the axes of 
 rotation to the link. 
 
 In the case of a rotating and a sliding piece, as in Fig. 
 48, every point of the sliding piece is moving at a given in- 
 stant perpendicular to the line ab, 
 and at the same instant the point 
 c is moving perpendicular to be. 
 Hence a line through the point b, 
 perpendicular to the plane of the 
 paper at the intersection of these 
 two lines, is at this instant the in- 
 stantaneous axis about which the 
 two points a and c are moving. 
 
 Their velocities are therefore 
 directly as their distances from this 
 axis, or 
 
 v : v' :: ab : cb. FIG. 48. 
 
 The same principle may be applied to linkwork in gen- 
 eral. The actual velocity of the point a becomes zero when 
 the point c reaches the positions i and 2, and these points 
 are called " dead-points." In the steam-engine the stored-up 
 energy of the fly-wheel carries the point c over the dead- 
 points. 
 
 CONNECTION BY CORDS. This connection is principally 
 made between blocks, forming a block and fall, or block and 
 tackle. 
 
 Although very useful, it is not employed to any extent 
 in machine construction. Wire ropes are sometimes used 
 instead of belts to transmit power, in which case grooved 
 pulleys are required to keep the rope from slipping off. 
 
 HYDRAULIC CONNECTION. This is of great importance 
 in modern machinery, as the gun-steel is forged by a hydrau- 
 
102 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 lie press, and hydraulic cranes are employed for lifting- the 
 heavy weights. The general principle of these machines is 
 explained in mechanics, and depends on the fact that if two 
 cylinders fitted with pistons are in hydraulic communication, 
 the volume of liquid forced out of one is equal to that forced 
 into the other. As this volume is the product of the length 
 of the cylinder by its area of cross-section, it follows that 
 the velocities of the pistons are inversely as their areas. 
 From this principle we can obtain a slow motion and great 
 power, as in the hydraulic press, or a quick motion and less 
 power, as in the hydraulic crane, by regulating properly 
 the size of the cylinder. 
 
 87. General Arrangement of Machine-shops Distribution of 
 
 Energy. 
 
 GENERAL ARRANGEMENT. All machine-shops are ar- 
 ranged upon the same general principles, though differing 
 greatly in details, depending on the work to be done. 
 
 In general, there is first a source of energ}% as a steam- 
 engine or water-wheel. This source of energy may be 
 regarded as the reservoir from which energy is drawn as 
 required ; and as different amounts of energy are needed at 
 different times, according as different machines are working 
 or not, some arrangement must be made to regulate the 
 amount of energy. Without this regulation, if several 
 machines are suddenly stopped, the energy will be in excess, 
 and the remaining machines will increase in speed. This is 
 injurious to the work and to the machines. The reverse 
 will happen when machines are suddenly started. To regu- 
 late the energy of the prime mover, a fly-wheel and governor 
 are used. The fly-wheel stores up energy and gives it out 
 when it is suddenly required, and prevents sudden changes 
 in speed, and the governor regulates the supply of steam, 
 etc., to the engine. 
 
 The principles are explained in mechanics. 
 
 DISTRIBUTION OF ENERGY. To distribute the energy 
 from the prime mover to the various machines, any one of 
 the methods previously described may be used. Belts are 
 generally preferred. 
 
 The pulleys which carry these belts run upon lines of 
 
GUNS. 
 
 163 
 
 -shafting. Extending lengthwise through the shop, there is 
 a " main shaft," a, Fig. 49. 
 
 The motion is communicated directly from the prime 
 mover b to this main shaft, by a belt. The shaft is supported 
 by hangers, c, bolted to the beams or walls. At intervals 
 along the main shaft are pulleys, d, each of which carries 
 the belt for a particular machine. 
 
 d 
 
 d 
 
 FIG. 49. 
 
 Over each machine is a short shaft, e, called a counter- 
 shaft. 
 
 This carries at least three pulleys, the first running loose 
 upon the shaft, the second fixed to it, and the third also fixed, 
 and driving the machine. Their use has been explained. 
 
 In addition to affording a means of starting and stopping 
 any machine without interfering with the main shaft, the 
 counter-shaft affords a means of increasing or decreasing the 
 speed of any machine, by decreasing or increasing the size 
 of the pulleys as compared with those on the main shaft 
 which transmit the power. 
 
 88. Machine-tools Shearing Cutting Scraping Drills Reamers 
 
 and Milling-cutters. 
 
 In every machine the working point, or part by which 
 the work is actually done, is called a tool. Machine-tools 
 
164 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 may be classified according to the manner in which they 
 act, as 
 
 1. Shearing- tools ; 
 
 2. Cutting or paring-tools ; 
 
 3. Scraping-tools. 
 
 SHEARING-TOOLS. These tools act to divide a plate or 
 bar of the material operated on, by causing the parts to 
 separate from each other by sliding or shearing. This class 
 includes also punches and dies. They are not used to any 
 extent in gun-construction. 
 
 CUTTING-TOOLS. These cut a thin chip or shaving from 
 the surface of the work and thus produce a new surface. 
 
 SCRAPING-TOOLS. These tools scrape off small particles 
 from the surface of the work, and correct any irregularities 
 that may have been left by the cutting-tool. 
 
 ACTION OF CUTTING AND OF SCRAPING-TOOLS. The 
 general method of the action of these tools is shown in 
 Figs. 50 and 51. 
 
 E 
 
 In each case the tool is acting upon a cylindrical piece 
 of work which is rotating in the direction of the arrow. 
 
 The angle DAE is called the cutting angle of the tool ; 
 DAC, the angle of relief, the line AC being tangent to the 
 face of the work at the point A. The angle CAE is the 
 working angle, and is equal to DAC ' + DAE. 
 
 In cutting-tools the angle CAE is always acute ; in 
 scraping-tools the angle CAE is either right or obtuse : and 
 the tools are thus distinguished by their working angles. 
 
 The hook F is given to the tools in order that the cutting 
 edge A shall not be above the axis or centre line of the tool. 
 
 If this were the case, any springing of the cutting edge 
 
G UNS. 
 
 I6 5 
 
 caused by excessive resistance of the material, would move 
 the edge A further into the work, or cause it to " dig into " 
 it, while as arranged the cutting edge will spring away 
 from the work. In plan, the tool may be of various shapes, 
 as shown in Fig. 52, these shapes depending on the nature 
 of the work. 
 
 c 
 
 FIG. 52. 
 
 DRILLS AND REAMERS. For making cylindrical holes, 
 drills and reamers are used. The ordinary drill is shown in 
 Fig. 53, the cutting edge being adb\ 
 the reamer in Fig. 54. 
 
 The reamer consists of a num- 
 ber of parallel cutters forming a 
 cylinder, and is used to finish a 
 cylindrical hole that is required to 
 be very true and smooth. Drills 
 and reamers rotate about the ver- 
 tical axis cd and have generally a 
 motion in the direction of this axis. 
 
 MILLING-CUTTERS. These may 
 be used to form surfaces of almost 
 any shape, and they vary greatly in 
 form. The general method of their 
 operation is indicated in Fig. 55, in 
 which the irregular surface abed is cut by the milling-cutter 
 A rotating on the axis B. 
 
 ^ 
 
 d 
 
 FIG. 53. 
 
 FIG. 54. 
 
 FIG. 55. 
 
 The work C moves along a plane director at right angles 
 to the axis B. 
 
i66 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 89. Machines in General Use The Lathe Parts. 
 
 MACHINES IN GENERAL USE. The machines in general 
 use are 
 
 The lathe ; 
 The planer ; 
 The shaper ; 
 The drill-press; 
 The milling-machine. 
 
 THE LATHE. This machine is intended principally to 
 produce accurate surfaces of revolution. Its general ar- 
 rangement is as follows: 
 
 A piece of metal or wood is caused to revolve about one 
 of its lines as an axis. A cutting- or scraping-tool is made to 
 bear against the metal or wood. As the latter, which is 
 called the " work," revolves, the tool is caused to move 
 either parallel or perpendicular to the axis of the work, or 
 
 FIG. 56. 
 
 in a direction which is compounded of these two motions. 
 The tool cuts a chip or shaving from the surface of the 
 work, and by a continuation of its action produces either a 
 cylinder, a plane surface, a cone, or any other surface of 
 
GUNS. 
 
 I6 7 
 
 revolution which may be formed by combining the two 
 motions at right angles to each other. 
 
 PARTS. The principal parts of the lathe, Fig. 56, are the 
 bed, consisting of two parallel ways or guides, a, of a A- 
 shaped cross-section. 
 
 On these guides slides the support for the tool, which is 
 thus made to travel parallel to the axis of the work. At one 
 end of the ways is fixed a heavy block of metal, b, called the 
 head-stock. This forms a support for the spindle c. To this 
 spindle (see Fig. 57) is attached the face-plate d, by means 
 of a screw, d ', on the end of the spindle. This spindle is 
 hollow at one end, and in this hollow fits a conical piece of 
 metal, e, called the live-centre. The spindle also carries a 
 speed-cone,/, and a gear-wheel, g. The gear-wheel is fixed 
 to the spindle, while the cone revolves freely upon it. The 
 gear-wheel^ and cone /may be connected by a bolt, i, pass- 
 ing through g. The small end of the speed-cone terminates 
 in a gear-wheel, //, which is a part of the cone, and hence 
 runs free on the spindle, but revolves with the same angular 
 velocity as the cone. Parallel to the lathe-spindle c is an- 
 other axis, k, Fig. 57, carrying two toothed wheels, k' and/". 
 
 k 
 
 U 
 
 FIG. 57- 
 
 This axis k is mounted in eccentric bearings, and may be 
 moved so that its wheels, k'k" , will engage or disengage with 
 those on the lathe-spindle c. The arrangement of the axis 
 k and wheels k' and k" is called the back gear. At the op- 
 posite end of the lathe-bed is a second block of metal, b' r 
 resting on the ways, called the tail-stock. It also supports 
 a spindle, called the dead-spindle, and this spindle termi- 
 
1 68 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 nates in a conical piece of metal, e r , called the dead-centre or 
 back centre. The tail-stock may be moved to any position 
 along the ways, and clamped there, and the dead-spindle 
 has a sliding motion parallel to the axis of the lathe, which 
 enables the distances between the centres e and e' to be very 
 accurately adjusted. These centres e and, /, form the axis 
 of revolution for any work in the lathe ; and if they are re- 
 moved, the prolongation of the axis of the live and dead 
 spindles forms this axis. 
 
 BO. The Lathe Slide-rest Feed Action. 
 
 SLIDE-REST. This forms the support for the cutting- 
 tool, and through it motion is given to the tool in any direc- 
 , t tion. It consists (Fig. 58) of a 
 
 slide or bed, /, resting upon the 
 ways, a, of the lathe, and ca- 
 pable of travelling along them 
 by the action of the feed- 
 screw m. Upon this slide 
 rests a second or cross slide, n, 
 which moves at right angles 
 to the first slide, and hence at right angles to the axis of 
 the lathe. This cross-slide carries a tool-holder, o. 
 
 FEED. The screw m is called the feed-screw. It passes 
 through a nut, m' ', on the slide-rest, and this nut is made in 
 halves which can be separated, thus freeing the nut from 
 the feed-screw, and stopping the longitudinal travel of the 
 slide-rest. The cross-feed is given by hand or automati- 
 cally by gearing, by means of the screw ri. On one end of 
 the feed-screw m is fixed the gear-wheel / (Fig. 56). At- 
 tached to the lathe-spindle is a second gear-wheel, /', and 
 upon an axis fixed to the head-stock or some convenient 
 part of the lathe-bed is a third gear-wheel, p" . This ar- 
 rangement may be varied according to circumstances, and 
 is intended to regulate the velocity ratio of the lathe-spindle 
 and that of the feed-screw. .Suppose, for example, it is re- 
 quired to cut a screw having ten threads to the inch, and 
 that the feed-screw of the lathe has this number. Then it 
 is evident that the work must turn ten times while the tool 
 
GUJVS. 169 
 
 moves one inch, and also that, in order to move the tool one 
 inch, the feed-screw must turn ten times. In other words, 
 the velocity ratio of the feed screw and of the work is 
 that of equality. Hence, from what has been stated under 
 Toothed Wheels, it follows that p and p' must have the 
 same number of teeth. The number of teeth upon p" will 
 not affect the velocity ratio, since, being a lever of equal 
 arms, it receives and transmits the motion from / to/' with- 
 out change. 
 
 ACTION OF LATHE. Motion is imparted to the lathe 
 from the belt running on the speed-cone /. By placing the 
 belt on the different steps of this cone considerable varia- 
 tion of speed may be obtained. If a slower speed than that 
 given by the cone is desired, the back gear is used. The 
 action of the back gear is as follows : 
 
 When the back gear is in gear with the lathe, the cone- 
 pulley is detached from the large gear g by removing the 
 bolt, z, Fig. 57. The cone-pulley then rotates, and its small 
 gear h drives the large wheel k' of the back gear. The 
 speed of the back-gear shaft is thus* reduced in the inverse 
 ratio of the numbers of teeth of h and k' , and with this 
 reduced speed the gear k" drives g, which in turn drives 
 the lathe-spindle. The speed is again reduced here in the 
 inverse ratio of the numbers of the teeth of g and k". 
 
 The action of the feed-screw is evident. By throwing 
 the feed-screw out of action and causing the cutting-tool to 
 move at right angles to the axis of the lathe by the screw 
 ri a plane surface will be formed, and by combining the 
 longitudinal and transverse motions in various ways any 
 surface of revolution may be produced. 
 
 91. The Planer Parts Action. 
 
 The object of this machine is to make a flat surface, 
 as nearly plane as possible. Its general principles are as 
 follows : 
 
 A large table is made to slide along two parallel plane 
 surfaces. Upon this table is fixed the work. Above the 
 table the cutting-tool is firmly supported. As the table 
 slides, the tool bears against the work, and cuts a chip or 
 
TEXT-BOOK Of ORDNANCE AND GUNNERY. 
 
 shaving, leaving a surface which is an exact copy of the 
 parallel plane guiding surfaces of the table. The table and 
 work then slide back, and at the end of this motion the cut- 
 ting-tool is moved sidewise an amount equal to the width 
 of the cut. This side motion is called the feed. The table 
 with the work again moves forward, and the tool makes a 
 second cut, and these operations are repeated till the work 
 is finished. 
 
 PARTS. The machine (Fig. 59) consists of a bed, a, which 
 is essentially two parallel beams or cheeks having on the 
 
 FIG. 59- 
 
 upper surfaces two V-shaped grooves, which are the guide- 
 grooves. The table b has two corresponding projections 
 on its under side which fit into these guide-grooves. Along 
 the middle of the under side of the table is a rack, c, into 
 which gears a toothed wheel,//, by which the table is driven. 
 Two vertical standards, e, support a cross-slide, f, and this 
 cross-slide carries the tool-holder /' and tool. The cross- 
 slide can be raised or lowered upon the standards by the 
 screws g, acted on by the bevel gears h. A feed-screw, k, 
 
GUNS. 171 
 
 runs through the cross-slide, and gives the feed motion 
 already spoken of to the tool. 
 
 ACTION. The machine is driven by two belts passing 
 over pulleys, /. As the motion is reversed at every stroke, 
 one of the belts is open and the other crossed, as previously 
 explained. 
 
 The gearing is also arranged so that the backward 
 movement of the table after the cut is much quicker than 
 the forward motion, when the tool is working. This is to 
 save time. The action of the machine is automatic both as 
 to motion of table and feed, and can be set to any length of 
 stroke. At the end of the forward travel of the table a pro- 
 jecting arm on it moves a lever, and this shifts the belts on 
 the pulleys, bringing the reversing-belt into action. At the 
 end of the backward motion of the table the feed is brought 
 into action, and the tool prepared for its next cut. To pre- 
 vent breaking the cutting edge of the tool by dragging it 
 over the cut in the backward motion of the table, the tool- 
 holder is hinged so that it allows the tool to rotate in the 
 direction of the return stroke, but holds it firmly against 
 rotation in the opposite direction. The same principle will 
 be found later in the rifling-tool. 
 
 92. The Shaper Parts Action. 
 
 There are certain objections to the planer which have 
 led to the introduction of a modified form of the machine 
 called the shaper. For small work, or for short strokes of 
 the tool, power is wasted in moving the heavy bed of the 
 planer, and when it is necessary to stop the stroke of the 
 tool at some definite point, as at a shoulder, it is difficult to 
 do this with the planer on account of the delay in shifting 
 the belts. The shaper remedies these defects. 
 
 PARTS. It consists of a bed, a (Fig. 60), along which 
 slides a head, b. This head carries a ram, c, upon which the 
 cutting-tool is fixed. This ram moves backward and for- 
 ward at right angles to the bed, and this transverse motion 
 is given by a link, d, attached at one end to the ram and 
 at the other to an arm, e, upon the toothed wheel/. The 
 work is supported upon the tables g or //, as the sliding- 
 
I7 2 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 head may be moved to any position along the bed ; or if 
 the work is too long for either table, it is supported at each 
 end by them, i is an arbor or shaft attached to the bed, 
 and intended for cylindrical surfaces. The tables g and h 
 
 FIG. 60. 
 
 can be adjusted vertically by screws, one of them being 
 shown at j. 
 
 ACTION. The machine is driven by a belt on the speed- 
 cone k. Motion is communicated from this cone to a back 
 shaft m through the gear-wheel m' . On this back shaft is a 
 small pinion splined to the shaft, so that it will slide freely 
 along the latter and yet turn with it. The toothed wheel 
 /"is driven by this pinion, and this gives motion to the arm 
 e y and this to the link d and ram c. A feed-screw, n, is con- 
 nected with the sliding head b, and is driven by the toothed 
 wheel m" on the back shaft m. This gears into a pinion on 
 the feed-screw, and by means of proper gears any feed can 
 be given to the sliding head. 
 
 By this arrangement the sliding head is fed along the 
 bed a a certain distance, just before the beginning of each 
 stroke. By changing the point of attachment of the link d 
 nearer to or further from the centre of e y the length of stroke 
 of the ram may be decreased or increased, and by changing 
 
GUNS. 
 
 173 
 
 its point of attachment to the ram the position of the tool 
 may be regulated. The speed is varied by the cones. 
 There is also a very ingenious mechanical device invented 
 by Sir Joseph Whitworth to cause a slow forward motion 
 of the tool while cutting, and a quick backward motion. 
 
 93. The Drill-press Parts Action. 
 
 This machine is used for making cylindrical holes of 
 comparatively small size. For large sizes, such as the inte- 
 rior of tubes, gun-hoops, etc., a boring-mill, or boring lathe, 
 is used. 
 
 PARTS. The principal parts, Fig. 61, are the frame a, 
 which supports all the parts ; the table b, upon which the 
 work is held ; the speed-cone c, which gives motion to the 
 drill and the other parts of the machine ; the spindle d, 
 which holds the tool e ; the feed-screw/, which gives a ver- 
 
 FIG. 61. 
 
 tical motion to the drill-spindle and its tool ; the feed-shaft 
 g, which carries at its lower extremity a hand-wheel, h, and 
 
1/4 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 at its upper end a pinion, i-\ this pinion gears into a toothed 
 wheel, k, whose hub or centre forms a nut through which 
 the feed-screw f passes ; this wheel and nut are held in a 
 collar, so that it can rotate freely but cannot change its po- 
 sition vertically ; the bevel gears II' give a motion of rotation 
 to the spindle d. 
 
 ACTION, When motion is communicated to the speed- 
 cone c by a belt, it drives the bevel gear /', and this drives /. 
 
 The hub of the bevel wheel / is hollow, and the drill- 
 spindle d passes through it. By means of a spline, the 
 spindle can slide freely through the hub of /, but is com- 
 pelled to rotate with it no matter what its position verti- 
 cally may be. The work rests on the table b, and the tool 
 e is in contact with it. As the drill rotates, the tool is 
 pressed down upon the work by the action of the feed-screw 
 /, which rests upon the upper end of the drill-spindle and is 
 connected with it by a collar, so that the spindle can turn 
 without causing rotation of the feed-screw. As the work 
 progresses, the tool is fed down or pressed down by turning 
 the hand-wheel /z, which causes the pinion i to rotate, and 
 this in turn rotates the toothed wheel k. When the work 
 is finished, a reverse motion of the hand-wheel h causes the 
 feed-screw / to rise, carrying with it the drill-spindle and 
 drill. 
 
 In all ordinary drills the feed is both automatic and by 
 hand. 
 
 94. The Milling-machine Parts Action. 
 
 The milling-machine is a development of the principle 
 of the lathe, and is used for forming any irregular surface 
 whose elements in one direction are parallel to a plane di- 
 rector. In this machine the cutter rotates, while the work 
 moves at right angles to the cutter and along a plane sur- 
 face. 
 
 PARTS. The machine, Fig. 62, consists of the bed a, 
 which supports a frame, #, carrying a spindle and cone, c, 
 with back gear, d, as in the lathe. To the frame is attached 
 a horizontal arm, e, for the support of the outer extremity of 
 the axis or arbor of the milling-tool/. This tool is fixed 
 
GUNS. 
 
 175 
 
 upon an axis or arbor, one end of which is supported by 
 what may be called the live-centre, and the other end by 
 the dead-centre at the extremity of the horizontal arm e. 
 Below the cutter is a table, g, which moves at right angles 
 
 -rf 
 
 FIG. 62. 
 
 to the axis of the milling-cutter. This table is capable of 
 adjustment vertically by the screw k, and is fed trans- 
 versely by the feed-screw i driven by the worm-gear j 
 through the shaft k and cone-pulleys //'. 
 
 ACTION. Motion is communicated to the cone-pulley c 
 by a belt, and this causes the cutter f to rotate. Feed-motion 
 is also communicated to the table g from the cone-pulley c 
 through gear wheels to the cone /, and thence by a belt to 
 /'. From I' it is communicated to the shaft k which drives 
 the worm-wheel/, and this drives the feed-screw t. 
 
 With this machine it is not necessary to have a constant 
 velocity ratio between the motion of the tool and that of 
 the work, and hence belts instead of gearing are used for 
 the feed. Also, since the cut is heavy owing to the large 
 
176 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 tool employed, a slow but powerful feed is required, and 
 this is obtained with the worm-gear/. It is evident that 
 the profile of the cutter may be of any figure within wide 
 limits. Many varieties of these machines are used, and they 
 are largely employed in the manufacture of the minor 
 parts of small arms. 
 
 GUN-MANUFACTURE. 
 
 95. General Description of Modern Guns Parts Th 
 Division of Operations. 
 
 DESCRIPTION. All modern high-power guns are made 
 of steel, and are composed of several parts united to form 
 a whole, and the parts are so arranged as best to support 
 the stresses upon them. The gun is therefore called a 
 " built-up " gun. 
 
 PARTS. The principal parts are (Fig. 63): the tube, T> 
 
 A 
 
 A T- A 
 
 .2 c 
 
 ~ D~*> 
 
 
 '' ^5 
 
 
 J ^ = ^- 
 
 
 tt 
 
 P Tl 1 R 
 
 FIG. 
 
 63- 
 
 1 
 
 which lorms the interior of the gun and supports the 
 other parts. This contains the powder-chamber, P, and the 
 rifling, R. The jacket, /, is the next larger forging, and 
 rests upon the exterior of the tube, carrying in rear the 
 base-ring in which the threads of the breech-block en- 
 gage. The hoops may be divided into two classes, the chase- 
 hoops, C and D, and the reinforce hoops, A. The trunnion- 
 hoop, T ', belongs to the latter class, and there may be one 
 or more layers of each class according to the size of the gun. 
 The hoops are arranged to break joints when two layers 
 overlap, or to lock into each other when stiffness is required, 
 as in the chase-hoops. The interior diameters of the jacket 
 and hoops are less than the corresponding exterior diame- 
 ters of the tube and the parts enveloped. This difference 
 
GUNS. 177 
 
 of diameters is called the shrinkage, and its amount, and the 
 reason for using it, will be discussed later. These cylinders 
 are put in place by heating them till they will pass over the 
 part to be enveloped, and then cooling them in place. 
 
 FORCINGS. The manufacture of the forgings and their 
 treatment has been explained. At the gun-factory they are 
 finish-bored, turned, and assembled to form the gun, and 
 after assembling, certain operations are required upon the 
 gun itself before it is ready for service. 
 
 DIVISION OF OPERATIONS. The mechanical operations 
 in gun-building are therefore naturally divided into : 
 
 1. Operations before assembling ; 
 
 2. Operations after assembling. 
 
 96. Operations before Assembling Tube Warping First Boring: 
 Tool Second Boring Tool. 
 
 WARPING. As received from the manufacturers, the 
 tube is liable to be bent or warped, due to the oil-tempering. 
 
 The amount of this warping is ascertained by mounting 
 the tube in a lathe, the ends being centred ; and as the tube 
 rotates, the deflection at the middle, or at the point where it 
 is greatest, can be measured. If found to be considerable, 
 it may require a readjustment of the axis of the tube in the 
 lathe, or it may be so great as to cause rejection of the tube, 
 though this latter seldom occurs. 
 
 FIRST BORING. The tube is bored before being turned, 
 in order that when turned there may be a uniform thickness 
 of metal at every point in the same circumference. The 
 first boring is done with a tool so arranged that it will run 
 straight. This is necessary, because when received the 
 bore of every tube is irregular to some extent, and the tube 
 is generally warped or bent slightly. The bore must be ex~ 
 actly parallel to the axis of the lathe, as, in case of deviation 
 from this line, the tool may run so far to one side as to spoil 
 the tube. A deviation of about 0.25 inch in a length of 
 20 feet would reduce the thickness of metal on one side so 
 much that the tube would be useless. 
 
 TOOL. The tool used for this purpose is a semi-cylinder 
 of cast iron, A, Fig. 64, carrying a cutting-tool of steel, B, \\\ 
 
TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 front. This semi-cylinder exactly fits a hole in the bore of 
 the tube, which hole is previously bored very accurately 
 with a small lathe-tool. The tool A is supported by a long 
 
 FIG. 64. 
 
 bar, C, called a boring-bar, which is pushed forward by a 
 feed-screw, as in the ordinary lathe. 
 
 The tube is caused to rotate while the tool is pushed for- 
 ward ; and since the semi-cylinder A accurately fits the hole 
 in the bore at starting, and is constantly forced down against 
 it by the presssure of the cut on B, it produces a cylindri- 
 cal surface along which A slides, without deviation. The 
 length of A, being about three times the diameter of the 
 bore, also corrects any tendency to deviation. 
 
 SECOND BORING. The first boring gives a straight hole, 
 but it is not smooth or regular. It is necessary now to use 
 a tool which will remedy these defects. 
 
 TOOL. The tool used for this purpose is called a wood 
 reamer. It consists, Fig. 65, of a flat cast-iron head, A, car- 
 
 _XA_ J\ 
 
 -jlL.^i J 
 
 FIG. 65. 
 
 rying two cutters, b b, so that a cut is made at opposite ex- 
 tremities of a diameter. DD are two pieces of hard wood 
 bolted to the cast-iron head, and turned to a diameter 
 slightly greater than that of the hole to be made by the cut- 
 ters bb. This packing D, guides the cutters, and keeps them 
 steady, and being thoroughly oiled it polishes the bore. 
 The cutters are slightly wedge-shaped or conical, so that 
 
GUNS. 
 
 179 
 
 FIG. ob. 
 
 they tend always to move towards the axis of the hole 
 already bored. By having two cutters, each 
 of them does one half the work of a single 
 cutter, and hence the tool travels compara- 
 tively rapidly down the bore ; and from this 
 fact, and also because a light cut is taken, 
 and the cutting-edge of the tool is long, so 
 that the work is well distributed, it follows 
 that the wear of the tool is slight, and the 
 bore very smooth and uniform. Fig. 66 illustrates this, be- 
 ing exaggerated to show the principle. 
 
 The tool is supported in the same bar, C, and fed forward 
 as with the first tool, the tube rotating. 
 
 97. Boring and Turning Lathes Back Eests Bore of Tube- 
 Turning. 
 
 LATHES. In all these operations the tube is mounted in 
 a boring and turning lathe. These lathes consist, Fig. 67, of 
 the bed B, made very strong and much larger than is the 
 ordinary lathe ; the head-stock and cone-pulley C\ the face- 
 
 FIG. 67. 
 
 plate F\ the slide-rest S, carrying a turning-tool; the back 
 rests R R, forming intermediate supports for the tube T '; 
 the boring-bed O, supported on the bed proper, B, and car- 
 rying the boring-bar P with its tool Q ; the feed-screw V, 
 which lies inside the boring bar P\ and the gears W, by 
 which the feed-screw is driven. 
 
 Motion is communicated to all the parts by the belt X, 
 acting on the cone-pulley. This causes the tube to rotate, 
 and also communicates motion to a long shaft, not shown in 
 figure, upon the end of which is the lower gear-wheel, W". 
 The motion is transmitted through W to W, and thence to 
 the feed-screw V, and by changing the gears any ratio be- 
 tween the velocity of rotation of the tube and that of trans- 
 
180 TEXTBOOK OF ORDNANCE AND GUNNERY. 
 
 lation of the tool Q can be obtained. The back rests R R 
 can be adjusted to any diameter of forging, and the boring- 
 bar moved forward or backward. It is necessary that there 
 be only one source of motion, since if the feed-screw or slide- 
 rest were driven independently of the cone-pulley, a change 
 in speed of one would not cause a corresponding change in 
 the others, and hence damage to tools, tube, or machine 
 might result. 
 
 The slide-rest is driven by a second feed-screw not shown. 
 
 In this lathe, the work may be turned on the exterior 
 while boring is in progress. It is best, however, not to 
 make a heavy cut on the exterior during boring, as it may 
 cause bending of the tube and consequent irregularity of 
 bore. Each lathe is supplied with an oil-pump, by means of 
 which a stream of oil is forced into the bore while the work 
 is in progress. The chips or cuttings come out at the op- 
 posite end of the tube from that at which the tool enters. 
 The same machines in general are used for boring and turn- 
 ing jackets and hoops, with some slight changes necessitated 
 by the difference in size of the forgings. 
 
 BORE OF TUBE. Before assembling, the tube is bored 
 below its finished size, as the cooling of the jacket and hoops 
 causes irregular contraction of the bore, and metal enough 
 must be left to remove these irregularities and give a uni- 
 form bore. 
 
 TURNING. After or during boring, the exterior. of the 
 tube is turned to the proper diameter. The exterior of the 
 jacket and hoops is not turned before assembling, as changes 
 in these diameters are caused by the shrinkage, and it is 
 preferable to finish them after assembling. 
 
 98. Assembling Furnace Expansion Cooling. 
 
 The parts having been turned and bored as explained are 
 carefully measured to see that their dimensions are correct. 
 A variation of 0.003 m ch is allowed from prescribed diam- 
 eters. If the dimensions are correct, the parts are ready for 
 assembling. 
 
 FURNACE. The jacket is first placed on the tube. To 
 do this the jacket must be expanded sufficiently to allow the 
 
GUNS. 
 
 181 
 
 tube to pass readily through it. As a general rule, an ex- 
 pansion of 0.004 inch per inch of diameter is sufficient. 
 That is, if the interior diameter of the jacket be 15.00 inches, 
 it is to be expanded 
 
 15.00 X .004 = 0.06 inch, 
 
 and the expanded diameter will be 15.00 + .06= 15.06 
 inches. 
 
 To obtain this expansion the jacket is heated in a furnace. 
 This furnace consists essentially of a vertical cylinder of cast 
 or wrought iron closed completely except at the top, where 
 the forging is introduced and removed. This cylinder is 
 surrounded by a fire-box so arranged that the heat shall be 
 as uniform as possible at all points. This uniformity of 
 heating is essential to prevent warping of the forging and 
 consequent difficulty of assembling. The forging is pro- 
 tected from direct contact with the fuel, to insure uniformity 
 of heating, and also to prevent dirt from collecting on it, as 
 this would be difficult to remove. 
 
 EXPANSION. The amount of expansion has been stated. 
 The heat necessary to obtain this expansion varies slightly 
 with different forgings, but ordinarily it 
 does not exceed 600 F. LI 
 
 The requisite expansion is determined ^f 
 
 by noting the colors which form on the 
 polished surface of the steel, as these colors 
 pass through a regular gradation, from pale 
 yellow to purple, blue, and black. The 
 latter color is seldom exceeded. 
 
 Gauges are also made of the exact diam- 
 eter to which the bore should expand. When 
 the color indicates the proper expansion, the 
 gauges are tried, and when they will enter 
 the bore, the requisite expansion has been 
 attained. 
 
 ASSEMBLING. The furnace door is now 
 opened, the jacket hoisted vertically out of 
 the furnace by a crane, and placed on a 
 casting, as shown in Fig. 68. This casting stands in a pit of 
 
 -TUBE. 
 
 -JACKET. 
 
1 82 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 E 
 J 
 
 FIG. 69. 
 
 sufficient depth to contain the tube. The tube is lowered 
 slowly through the jacket till it is in place. 
 
 COOLING. The heated forging is now 
 cooled by the application of water as follows: 
 Fig. 69 shows a section of the tube of 8" 
 gun with hot jacket in place ; J is the jacket, 
 T the tube resting against a shoulder, C, in the 
 jacket ; D is a ring formed of pipe bent into 
 a circle, the inside being perforated with 
 small holes about f inch apart. 
 
 This pipe is placed above the shoulder C, 
 so that the jacket in cooling may contract or 
 " draw " toward this shoulder, and hence in- 
 sure a tight joint there. A current of water 
 circulates through the pipe, and issues from 
 the small holes on its interior against the hot 
 jacket. By this means the cooling can be 
 readily effected, the ring being gradually 
 moved upward, toward the breech, as the 
 cooling progresses. It is important that the parts below 
 E be cooled first, as otherwise the jacket will grip at E, and 
 on cooling and contracting longitudinally, it will compress 
 the tube in this direction, and produce great longitudinal 
 strains. The same process applies to hoops, the water being 
 applied first at the joint between the cooled and the hot 
 hoops, in order to cause contraction toward the joint, and 
 keep the latter closed. 
 
 99. Operations after Assembling Finish-boring Rifling Rifling- 
 machine Rifling-tool. 
 
 FINISH BORING. The gun after assembling is placed in 
 the boring-lathe, and finish-bored up to the true diameter. 
 The wood reamer is used for the final boring. The powder- 
 chamber, and the slope connecting this with the bore, are 
 also finished. 
 
 RIFLING. The next operation is rifling, or cutting the 
 spiral grooves in the bore for giving rotation to the pro- 
 jectile. This operation requires a special machine and tool. 
 
 RIFLING-MACHINE. This resembles to some extent the 
 
G UNS. 
 
 183 
 
 boring and turning lathe already described, but differs in 
 the following respects : 
 
 1. The gun does not rotate ; 
 
 2. The cutting-tool has a motion both of rotation and of 
 translation. 
 
 FIG. 70. 
 
 Fig. 70 shows the outlines of the rifling-machine. The 
 gun is supported on a bed as for boring, Fig. 67, and the 
 rifling-bar m is supported as in boring the tube. 
 
 The feed-screw b gives the motion of translation to the 
 rifling-bar m and tool g. 
 
 To the side of the rifling-bed is bolted a table, o, which is 
 horizontal, and on this table is bolted a " guide bar" e, made 
 of flexible steel, and whose shape is that of the developed 
 groove of the rifling. A toothed wheel or gear, c, is fixed to 
 the rifling-bar, and a toothed rack, d, engages with this gear. 
 At the outer end of the rack are two small rollers,//', em- 
 bracing the steel guide-bar e. The rifling-bar m is free to 
 turn about its axis while moving forward. 
 
 The action is as follows : When the rifling-bar is driven 
 forward by its feed-screw b, it carries with it the toothed 
 rack d. 
 
 The outer end of this rack travels along the guide-bar e y 
 and as the roller /bears against this guide-bar, the rack is 
 pushed inward or to the left in the figure. This causes the 
 gear c to rotate to the right, carrying the rifling-bar with it, 
 and thus the rifling-tool is caused to cut the proper groove 
 in the gun. 
 
 RIFLING-TOOL (Fig. 71). This is a cylindrical head, c, oi 
 metal accurately fitting the bore. Four radial arms, d, slide 
 in grooves in the front face of the cylinder, and carry the 
 cutters k on their outer ends. 
 
184 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 The inner ends rest on a wedge, e, which has a sliding 
 motion parallel to the axis of the cylinder. By sliding this 
 wedge forward the radial arms and cutters are pushed out, 
 and by sliding it backward they are pulled in. By this 
 means the depth of the cut or feed is regulated. 
 
 
 
 TUBE. 
 
 
 
 
 
 
 , 
 
 
 
 
 
 
 RIF 
 
 .ING BAR. I 
 
 e I F==yH^\ 
 
 
 
 
 
 
 cm 
 
 II 1 e II r 
 
 ; 
 
 i j 
 
 
 1 
 
 
 HJ1 
 
 ri^kr^ 
 
 
 
 
 
 
 
 CL" IfU /c 
 
 
 
 
 
 
 
 
 
 
 
 
 FIG. 71. 
 
 When the tool reaches the end of the groove in the gun, 
 the projecting end of the sliding wedge strikes a rod, r, in 
 the bore, and the cutters are thus drawn back, which pre- 
 vents breaking them by dragging them over the cut ; the 
 motion of the machine is then reversed and the tool drawn 
 out of the bore. As the rifling-bar and tool move forward, 
 a stream of oil is forced on the cutters by a pump. 
 
 Arriving at the end of the cut, the cutters are automati- 
 cally withdrawn as explained ; and as the motion of the 
 rifling-machine is reversed the bar and tool return, being 
 guided in their return motion by the bearing of the roller/', 
 Fig. 70, upon the outside of the guide-bar. The sliding 
 wedge is then adjusted for the next cut, and pushed out to 
 the front,, raising the cutters, and so on till the groove is fin- 
 ished. To cut the next groove, the rifling-bar is turned in 
 its bearings a distance equal to the width of one land of the 
 rifling, and the new groove cut as above described. 
 
 The remaining operations are finish-turning, inserting the 
 breech-screw, fitting the, mechanism, marking, and weighing, and 
 are not different from the ordinary operations of a machine- 
 shop. 
 
GUNS. 185 
 
 ELASTIC STRENGTH OF GUNS. 
 
 100. Definitions Case Considered Radial Stress and Strain. 
 
 DEFINITIONS. In the following discussion stress means 
 the force acting in pounds or tons per square inch, and strain 
 the effect of this force ; this effect being either extension or 
 compression, and expressed in inches per inch of length. 
 
 Elastic Strength. The elastic strength of a cylinder or 
 gun is the greatest stress to which it can be subjected 
 without straining any part of the cylinder or gun beyond its 
 elastic limit. 
 
 CASE CONSIDERED. To show the stresses acting upon a 
 cylinder, and the strains produced by them, let us consider 
 the case of a single cylinder, closed at both ends, and acted 
 upon by an interior pressure only, the exterior pressure 
 being that of the atmosphere, and consequently so small 
 that it may be neglected. This case corresponds to that of 
 a gun composed of a single piece of metal, closed at one end 
 by the breech, and at the other by the projectile, and acted 
 on by the pressure of the powder-gas. It is evident that a 
 normal stress is acting upon all parts of the interior of this 
 cylinder, including the ends. 
 
 RADIAL STRESS AND STRAIN. Take a ring of this cyl- 
 inder, whose length is unity, Fig. 72, and consider a cube of 
 this ring whose edges are unity. 
 
 Let p represent the normal 
 stress upon the inner surface of 
 this cube. Then the effect of 
 this stress is to compress the 
 cube in the direction of the 
 radius, and to decrease the thick- 
 ness of the wall of the cylinder. 
 It also increases the length of 
 the radius. Since the same is 
 true for every unit-cube into 
 which the ring may be divided, FIG. 72. 
 
 we conclude : 
 
 (i) That one effect of an interior stress upon a closed 
 
1 86 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 tube is to strain the wall of the tube in the direction of the 
 radius ; 
 
 (2) That this stress decreases the thickness of the walls 
 of the tube, and increases the interior radius. 
 
 This is called the radial stress, and its accompanying- 
 strain is the radial strain. 
 
 It must remembered that for the particular case con- 
 sidered the effect is as stated. But we may have both an 
 interior and an exterior stress acting at the same time, or 
 we may have an exterior stress acting alone, the interior 
 stress being zero. 
 
 According to the relative values of the stresses acting- 
 we may have therefore a radial strain of extension or of 
 compression, as will be shown later. 
 
 101. Tangential Stress and Strain Longitudinal Stress and Strain 
 Conclusions. 
 
 TANGENTIAL STRESS AND STRAIN. Consider again the 
 same ring of metal as before, whose length is unity, and take 
 any particular unit cube, as a, Fig. 73. 
 
 The stress p acts normal to 
 the diametral plane be, and its 
 effect is to separate the cylinder 
 into two halves along this plane. 
 Hence the edges of the cube a 
 parallel to the direction of the 
 stress or normal to the plane be 
 are strained by this stress, and 
 this is true for the whole cube; 
 hence the effect is to elongate 
 the cube in this direction. This 
 
 is called the tangential or circumferential stress, or the 
 hoop tension, and it produces a corresponding strain. Its 
 amount is obtained by multiplying the intensity of the 
 stress by the area over which it acts. The intensity is 
 />, and for each side of the ring the area over which it 
 acts is r X I = r. Hence the resultant tangential force 
 is pr. This force is resisted by the elasticity of the fibres, 
 and it produces a corresponding stress in these fibres, 
 which at any point is represented by /. Since the 
 
 .FIG. 73- 
 
GUNS. ig/ 
 
 same may be shown for each of the unit cubes, the total 
 effect of this stress is to strain or elongate the interior cir- 
 cumference of the cylinder in the direction of the tangent. 
 This also increases the length of the radius. Hence we 
 conclude : 
 
 (1) That another effect of the interior stress upon a closed 
 tube is to strain the wall of the tube in the direction of the 
 tangent. 
 
 (2) That the stress increases the interior radius of the 
 tube. 
 
 As in the case of the radial stress, it must be remembered 
 that this stress may decrease the circumference of the interior 
 layer, or shorten the radius, depending upon the resultant 
 of the forces acting. 
 
 It appears from the above discussion that the radius is 
 changed by both the radial and the tangential stresses, and 
 the two cases must not be confused. 
 
 LONGITUDINAL STRESS AND STRAIN. In addition to 
 the radial and tangential stresses acting on the unit cube, 
 there is a third stress due to the pressures on the ends of 
 the cylinder. This stress acts parallel to the axis of the 
 cylinder, and its effect is to strain the elementary cube in 
 the direction of this axis. Since this is true for each cube, 
 the resultant strain is an elongation of the tube in this direc- 
 tion. 
 
 This is called the longitudinal stress, and it produces a 
 corresponding strain. 
 
 CONCLUSIONS. If we follow the same method of discus- 
 sion for the case of an exterior and an interior stress acting 
 at the same time, or for the case of an exterior stress acting 
 alone, the interior stress being zero, similar results will be 
 obtained. 
 
 Hence we conclude in general that when a single cyl- 
 inder is acted on by exterior and interior stresses, their effect 
 is to produce in the cylinder : 
 
 1. A radial stress,/, and its corresponding strain; 
 
 2. A tangential stress, /, and its corresponding strain; 
 
 3. A longitudinal stress, q, and its corresponding strain ; 
 
1 88 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 and that all these stresses exist at the same time and at 
 every point of the cylinder. 
 
 102. Relations between Stresses and Strains when all the Forces 
 
 are Tensions Application to Cube in Gun-cylinder. 
 RELATIONS BETWEEN STESSES AND STRAINS. Since all 
 the stresses /, /, and q exist at the same time, and each pro- 
 duces its own strain, it is required to find the resultant strain 
 due to these three stresses acting together. 
 
 For this purpose it is more simple to consider at first, 
 three stresses of the same kind. 
 
 If a cubical elastic solid be acted on by a given stress in 
 a direction normal to one of its faces, experiment shows 
 that it produces a corresponding strain in that direction, 
 
 and that it will also produce con- 
 trary strains in the two direc- 
 tions at right angles to the first, 
 equal to one-third the first strain. 
 Thus, Fig. 74, if the force / act 
 on the cube in the direction 
 shown, it will elongate the edges 
 aa, bb, etc., and will contract the edges ac, ab, and this con- 
 traction will be one third the elongation of aa, bb. 
 
 This law holds only within the elastic limit. Consider 
 the general case of a cube acted on by the three stresses X, 
 F, and Z, at right angles to the faces of the cube, and sup- 
 pose these stresses to be tensions. 
 
 Let A be the resultant strain in the direction of the stress 
 
 M, that in the direction of F; 
 v, that in the direction of Z; 
 E the modulus of elasticity of the cube. 
 The stress X, by a preceding principle (see equation 
 (169)), produces a strain in its own direction equal to 
 
 E 
 
 The stress F decreases this strain by the amount 
 
GUNS. 
 
 I8 9 
 
 and the stress Z by the amount 
 
 \_ Z 
 3^0* 
 
 Hence the total strain in the direction of X\s 
 
 *. = TrUr---- . 
 
 In the same way we have for the total strains in the 
 direction of Fand Z 
 
 * Z \. 
 
 ~ 3 ~~3'' 
 
 i( 7 X Y\ 
 
 = -~\Z J. 
 
 ' 
 
 APPLICATION TO CUBE IN GUN-CYLINDER. Referring 
 now to the unit cube in the gun-cylinder, we have the same 
 case, except that one of the stresses is a compression. 
 Hence, substituting in the above equations / for X, p for 
 F, and q for Z, we have 
 
 3 3 
 
 . . . (170) 
 
 
 In these equations A is the strain in the direction of the 
 circumference or tangent, p the strain in the direction of 
 the radius, and v the strain in the direction of the axis of 
 the cylinder, due to the action of the three forces /, t, and q 
 at any point. These strains may be extension or compres- 
 
1 90 TEXT-BOOK OF ORDNANCE AND GUNNERY, 
 
 sion according to the relative values and directions of the 
 forces. 
 
 103. Lamp's First Law Connecting /, /, and q. 
 
 In equations (170) the values of A, /*, and v are unknown, 
 and they are expressed in terms of /, /, and q, which are also 
 unknown. 
 
 Hence in order to find the values of A, /*, and v in known 
 terms it is necessary to establish certain equations of condi- 
 tion, by means of which /, />, and q may be replaced by 
 known terms. This has been done by what are known as 
 Lame's formulas, from the name of the distinguished in- 
 vestigator of the subject of the elasticity of solid bodies, 
 M. Lame. 
 
 To deduce the first law it is assumed that the longitu- 
 dinal stress q is constant throughout the cross-section of 
 the cylinder. 
 
 This is not exactly true, but the results obtained upon 
 this hypothesis are sufficiently exact in practice. 
 
 Assume the last of equations (170), 
 
 v 
 
 In this equation q is constant by hypothesis, and the 
 value of v varies only with / and p. One third of the dif- 
 ference of these quantities is the only variable in the above 
 equation ; and since / and / vary together at different points, 
 
 the variations in the value will be small, and may be 
 
 O 
 
 neglected in comparison with q. 
 
 Hence we may assume without material error that v is 
 constant throughout the cross-section of the cylinder. 
 
 From this we have 
 
 tp = $(q vE ) = constant, . . . (171) 
 or 
 
 tp = constant (172) 
 
GUNS. 
 
 19- 
 
 Th eref ore 
 
 in which T , P OJ 7",, and P, are the values of / and p at the 
 interior and exterior of the cylinder respectively. 
 
 From this we have Lame's First Law : 
 
 The difference between the tension and the pressure is the 
 same at all points. 
 
 104. Lamp's Second Law. 
 
 The second law, or second equation of condition for/, /, 
 and q, is deduced as follows : 
 In Fig. 75 
 
 Let R^ be the interior radius of the cylinder ; 
 RV the exterior radius ; 
 r, the radius of any circle of the section ; 
 r', the radius of a circle of 
 the section, exterior and 
 near to that whose 
 radius is r\ 
 
 p, t, and q, the radial, tangential, and 
 longitudinal stresses, re- 
 spectively, at any point 
 of the circle whose 
 radius is r\ 
 P and T , the values of / and t for 'FIG. 75- 
 
 the interior of the cylinder ; 
 P, and r,, the values of / and / for the exterior of the cylia 
 
 der; 
 
 q, constant for all parts of the cross-section ; 
 " the modulus of elasticity. 
 
 Consider the cylindrical ring whose radii are r and r } 
 and whose length is unity. 
 
 The interior pressure p, as previously shown in the dis- 
 cussion of tangential stress, produces a tangential stress on 
 the interior of the ring equal to pr. 
 
 For the circle whose radius is r' the pressure p becomes 
 /', and the force causing tangential stress on the exterior of 
 the ring is p'r 1 . 
 
I9 2 TEXT- BOOK OF ORDNANCE AND GUNNERY. 
 
 There, is therefore a difference in tension between the 
 two parts of the ring equal to 
 
 and this difference of tension is balanced by the product of 
 the thickness of the ring r' r, and the mean stress along 
 bb' , or along any other part of its thickness. 
 
 We have therefore the following equation for the whole 
 ring, since the tension and pressure have opposite signs. 
 
 2 p' r > _ 2/r = _ 2l (r> _ r ), . . . . (i;4 ) 
 
 r being the mean stress throughout the thickness of the 
 ring. From which 
 
 (I75) 
 
 Passing to the limit by making r' = r, in which case r 
 becomes /, we have 
 
 limit of ( r) r , = r = t ...... (177) 
 
 Hence 
 
 From (171) we have 
 
 *=/+3(?- ") ...... (179) 
 
 Substituting the second member for / in (178), we have 
 
 Differentiating ; / and r being variables, 
 
 pdr 4- rdp 
 
GUNS. 193 
 
 Reducing, 
 
 dr_ ___ dp_ _ 
 ~ := -' 
 
 Integrating, 
 
 Substituting the value of / + 3(0 r ) from (179), we 
 have 
 
 ...... (184) 
 
 or 
 
 (t + pY = 7=1 = constant. . . . (185) 
 
 From which we can write 
 
 
 and from these we have Lame's Second Law : 
 
 The sum of the tension in the direction of the circumference? 
 
 and of the pressure in the direction of the radius, varies inversely 
 
 as the square of the radius. 
 
 Formulas (172) and (185) are known as Lame's formulas. 
 
 105. Curve of Stresses in a Cylinder Discussion. 
 
 Lame's formulas enable us to determine the stresses ex- 
 isting- at every point of the cross-section of a cylinder sub- 
 jected to the action of exterior and interior forces. A curve 
 showing the relation between the radii and the stresses for 
 all points of the cross-section is called a curve of stress, and 
 is thus determined. 
 
 Assume equations (173) and (186) : 
 
 *=:( 7; 
 t-p = T,-P,: 
 
 -/ - T.-P, 
 
194 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 Combining these equations, and eliminating .T, , r o ,and 
 /, we obtain 
 
 - , ,.. 
 
 R* - R* AY - AY r *' 
 
 Combining again and eliminating T l , T , and /, we have 
 
 R t 'R.\P. - P.) i 
 
 p= ~ R; - R: &: - R: ? (lk 
 
 Since q is assumed constant throughout the cross-section 
 it is not considered in this discussion. 
 
 Equations (187) and (188) give the values of / and / at 
 any circumference whose radius is r. From these equations 
 we can construct the curves of stress. To illustrate, take 
 equation (187). 
 
 Differentiating, we have 
 
 dr R: - R: r 3 * 
 
 Differentiating (189), we have 
 
 & =6R> K; ( -X t ' P -? ('9) 
 
 From (187), we have for the values of / for the interior 
 and exterior of the cylinder, by making r = R and r R l , 
 respectively, 
 
 7^ o p o 3 it y- _ /> _? L _; e (191) 
 
 7^ p <L_ r> \ i" o / /T^O\ 
 
 ^ i 'o TTi r> a * i ~^^ D~a~. \ 1 9 2 ) 
 
 AJ ^ yv:, K O 
 
 Now considering the two forces P and /*, , we may have 
 the following cases: 
 
 3. p. < p,' 
 
 First. P, > P t . 
 
G UNS. 
 
 195 
 
 Equation (189) shows that - < o ; hence / decreases 
 algebraically as r increases. Equation (190) shows that 
 -j-: t > o ; hence the curve of stress is concave upwards. 
 
 If we lay off values of r along the axis OX, and of / along 
 OY, the resulting curve will be the 
 curve of stress for the particular 
 stress considered, and may be any 
 one of the curves b, d, c, a in Fig. 
 76. If J" and J 1 , are both positive, 
 we have curve b, which is the gen- 
 eral case. If T = T l , we have 
 curve d. If 7" o, we have curve c. 
 If T and T t are both negative, 
 we have curve a. 
 
 Second. P = P,. 
 
 In this case 
 
 dt^_ d^_ 
 
 and the curve of stress becomes a 
 right line parallel to the axis of OX. 
 
 Equation (191) shows that T < o, FIG. 76. 
 
 and hence the right line will be below the axis of OX, as 
 in Fig. 77. 
 
 FIG. 77. 
 
 FIG. 78. 
 
I 9 6 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 Third. /></>. 
 
 In this case 
 
 dt 
 
 dr* 
 
 hence / increases algebraically with r, and the curve is 
 convex upwards. Equation (191) shows that T < o, and 
 hence the curve will be as in Fig. 78. 
 
 106. Conclusion from Curves Method of Strengthening Cylinder. 
 CONCLUSION. Similar results will be obtained by dis- 
 cussing equation (188), and an examination of all the curves 
 
 thus obtained will show that in general the greatest stresses 
 
 are at the interior of the cylinder, and the object of modern 
 
 gun-construction is to strengthen this interior layer. 
 
 METHOD OF STRENGTHENING CYLINDER. Take a gun 
 
 composed of one piece of metal, such as the old cast-iron 
 guns. When fired, the interior pressure is 
 P 9 , and the exterior pressure is zero, since 
 the pressure of the air may be neglected. 
 
 Then P >P t , and the curve of tensions 
 is b, Figs. 76 and 79. If P is great, the 
 inner layer may be deformed or ruptured 
 before the exterior layers are brought to 
 their limit of endurance. Suppose, how- 
 FIG. 79. ever, that before firing we cause a pressure, 
 
 P 1 , to act upon the exterior of the cylinder. Then we have 
 
 the case where P < P l , and the state of 
 
 stress in the cylinder before firing is as in 
 
 Figs. 78 and 80. That is, all the layers 
 
 are compressed, those at the interior 
 
 more than those at the exterior. 
 
 Now when the gun is fired, we have 
 
 the condition P > P l , and the curve of 
 
 tensions would be b, Fig. 79, were it not 
 
 that we have already a curve of tensions,/ 
 
 Fig. 80, in the cylinder. 
 
 Hence the new curve of tensions is the resultant of the 
 
 two curves b and/ or AB, Fig. 8:. 
 
GUNS. 
 
 I 9 7 
 
 A 
 
 That is, before the inner layer can be put in tension, a 
 force must be exerted sufficient to overcome the preliminary 
 -or initial compression, and after this any 
 excess of the force will produce tension. 
 The result is shown in Fig. 81. A' B' 
 is the curve of tensions, supposing no 
 previous stress acting on the cylinder. 
 CD is the curve of initial compression ; 
 AB is the resultant curve, which is ob- 
 tained by taking differences of ordi- 
 nates, and is the curve representing 
 the actual tensions. 
 
 This method is called the method of 
 initial compression, and is now universally used in guri-con- 
 struction. 
 
 107. Values of the Strains at any Point in a Cylinder in Terms of 
 the Radii and Pressures. 
 
 The general laws of the stresses in a cylinder have been 
 determined, and the curves of stress constructed. The ob- 
 ject of the present discussion is to find the values of the 
 strains A, yw, and v at any point in a cylinder in terms of the 
 exterior and interior pressures and radii, and of the modulus 
 j 0J these strains being within the elastic limit of the metal. 
 For this purpose assume equations (170) : 
 
 FIG. 81. 
 
 -- 
 
 It may be shown analytically, and the result has been 
 proved by actual experience in gun-building, that in con- 
 sidering the resistance of the cylinder we can simplify the 
 problem by neglecting the longitudinal force q, and consid- 
 ering at first only the forces / and /, and afterwards con- 
 .sider separately the force q, when the longitudinal strength 
 
TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 of the gun is to be determined. This is equivalent to mak- 
 ing q = o in the above equations. These equations then 
 become 
 
 Substitute the values of t and / from (187) and (188) in 
 (193), and we have 
 
 . - , 4 t ,- J_ . 
 
 : > ' - ~ 
 
 _ 4R:x:(P, - P t ) _L 
 
 " ' * > ' 
 
 These equations are general and give the values of the 
 strains A, /*, and v at any point r in a cylinder. 
 
 To find the values of the strains at any particular point 
 we substitute for r the value of the radius at that point. 
 
 Thus for the interior of the cylinder, substitute R ti for r,. 
 and for the exterior R l for r. 
 
 108. Maximum Values of Strains in a Cylinder. 
 
 If any part of a gun-cylinder is subjected to a stress 
 beyond its elastic limit, this part becomes deformed. 
 
 Hence other parts will be called upon to bear stresses 
 different from those for which they were calculated, and 
 the result will be that after a few rounds the whole structure 
 may be deformed or destroyed. We then use the following- 
 principle, which is the foundation of the modern theory of 
 gun-construction : 
 
 No fibre of any cylinder in the gun must be strained, under 
 any circumstances, beyond the elastic limit of the metal of that 
 cylinder. 
 
GUNS. 199 
 
 From this principle we can determine the maximum 
 stress to which a cylinder can be subjected. 
 
 It has been shown that the inner layer of a cylinder is 
 subjected to the greatest stress. Hence if this layer does 
 not pass its elastic limit, every other layer, and consequently 
 the cylinder itself, will be safe. 
 
 The strains at the inner layer will be obtained from (194) 
 and (195) by making r A^ . Considering for the present 
 only A and j*, since v is constant, we have, making r = R^ , 
 
 .. > 
 
 ~p7^e7); ' (I97) 
 ( 4 tf, 2 - 2R a ')P, - 2 R,'P l 
 
 *=-- ^R?^}T " (I98) 
 
 These are any strains within the elastic limit. 
 
 Let be the elastic limit of the cylinder for tension ; 
 
 P , the elastic limit for compression, in pounds or 
 tons per square inch. 
 
 Then, by equation (169), the elongation at the elastic 
 limit will be 
 
 A 
 
 ,' 
 
 and the compression at the elastic limit 
 
 and, by the principle previously stated, these are the 
 maximum strains that can be allowed. Since, in general, A, 
 is extension and /* compression, A and ^ must be equal to 
 
 ~- and --, respectively, at the limit. If, however, A becomes 
 
 ^0 ^0 
 
 compression and /* extension, A must be placed equal to 
 
 a 
 
 -, and u to -^, 
 
 ^0 ^0 
 
 ing these values, 
 
 a 
 
 -, and u to -^, as will be seen later. We have then, equat- 
 
 
200 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 .y.-2*.v. 
 
 109. Limiting Interior Pressures Discussion. 
 
 LIMITING INTERIOR PRESSURES. Solving (199) and (200) 
 for P a , we find the pressures which will produce the strains 
 
 A = -=?- and /* = ~-, and these will be the maximum interior 
 
 A. 
 
 pressures which the cylinder will stand. These values are 
 
 ,p*. P. l i ' ( 201 ) 
 
 
 ? - 2R: 
 
 P o9 will cause the inner layer of the cylinder to elongate 
 till it reaches the elastic limit , and P op will cause the 
 inner layer to be compressed radially till it reaches the 
 elastic limit p . 
 
 These values of P 0& and P op will differ, and the smallei 
 value marks the limit of stress to which the cylinder can b( 
 safely subjected. 
 
 For instance, if P o9 < P op , the limit # will be reached. 
 while that for compression p will not be. The cylinder has 
 therefore more compressive strength than can be used, since 
 if we increase P o till it is equal to P op , we pass the limit , 
 which is contrary to the principle stated. 
 
 DISCUSSION. In a single cylinder the most common case 
 is that in which P t , the exterior pressure, is that of the 
 atmosphere, and may be neglected. P l is therefore zero, and 
 under this condition equations (201) and (202) become 
 
 
 Since for all metals used in gun-construction # = or < 
 P., Po will always be less than P QP , and hence it alone will 
 be considered. 
 
GUNS. 201 
 
 (i) Required the thickness of wall necessary to resist a 
 given interior pressure P 00 . Solving (203) for (JK, R o ), the 
 thickness, we have 
 
 -' ' ' (205) 
 
 (2) To show the relation between the thickness of the 
 cylinder and its resistance, we have from (203) 
 
 (206) 
 
 Suppose the cylinder to be one calibre thick. Then 
 
 K.-SX., 
 
 and 
 
 /U = *3.. 
 
 If the cylinder be of infinite thickness, R l = oo , and 
 
 which shows that an increase in thickness from one calibre 
 to infinity, increases the strength of the cylinder only from 
 
 .63^0 to .7500- 
 
 Hence we conclude that a single cylinder is not materi- 
 ally strengthened by increasing its thickness beyond one 
 calibre, and also that the greatest possible value for the 
 interior pressure in a single cylinder without initial com- 
 pression is less than 
 
 110. Limiting Exterior Pressures Thickness of Cylinder Exterior 
 Strains. 
 
 LIMITING EXTERIOR PRESSURES. It has been shown 
 that, in order to strengthen the cylinder, we apply an exte- 
 rior pressure P lf and produce a compression of the cylinder; 
 this compression being greatest at the interior. 
 
 What is the limiting value of this exterior pressure? 
 
 Its limiting value is that which will compress the inner 
 layer up to its elastic limit ; and it is determined as follows: 
 
202 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 The interior pressure being zero, or P 9 = o, the strains A 
 and JA at the interior become, from (197) and (198), 
 
 ( 2O 7) 
 
 1^- (-S) 
 
 The first, being negative, shows that the inner layer is 
 compressed tangentially ; the second, being positive, that 
 the wall of the cylinder is extended in a radial direction or 
 increased in thickness. As before, the limiting compressive 
 strain is 
 
 and that for extension 
 
 E.' 
 
 and the values of A and // must not exceed these respectively. 
 Hence 
 
 , . = _n._. 
 
 E. (R; - R?)E, ' 
 
 .. 
 
 - , - ' ' 
 
 Solving for P v we have 
 
 ,_(R^_R^P.. 
 IP 2R ' ..... V 2O 9; 
 
 The negative sign is omitted in (209), as it indicates com 
 pression simply. These equations are useful in determining 
 the limiting value of the exterior pressure which the tube or 
 inner cylinder will support, when we are considering what 
 pressure P l can be applied to its exterior to strengthen it ; 
 
G UNS. 2O3 
 
 and since P IP is generally less than P l9 , equation (209) only is 
 used. 
 
 THICKNESS OF CYLINDER TO RESIST EXTERNAL PRES- 
 SURE. From equation (209) the thickness of wall of cylinder 
 necessary to resist a given exterior pressure P IP may be 
 obtained. 
 
 Solving it for R t R H' y the thickness, we have 
 
 STRAIN AT EXTERIOR OF CYLINDER. The only strain 
 of importance at the exterior of the cylinder is that in the 
 direction of the circumference, or A.. Referring to the gen- 
 eral value for it at any point r, equation (194), and making 
 r = R, , we have for its value at the exterior 
 
 A = 
 When P = o, 
 
 x = -*'+ 
 
 a contraction. 
 When P J = o, 
 
 * = (je 2 f je') * (2I4) 
 
 an extension. 
 
 111. Longitudinal Strength. 
 
 To determine this, suppose the cylinder closed at one 
 end by the breech, and at the other end by the projectile, as 
 in a gun. The total pressure acting on the bottom of the 
 cylinder is then 
 
 The area of cross-section of the cylinder is 
 
204 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 and the pressure nR*P Q is resisted by the elasticity of this 
 cross-section. Supposing the pressure to be uniformly dis- 
 tributed, the stress per unit area of cross-section is 
 
 TtR^P, P.R? 
 
 3 ^ - * ' 
 
 Substitute in the third of equations (170) for t and/ their 
 values from (187) and (188), and for q its value from (215), 
 and we have for the value of the strain v in the direction of 
 the axis of the cylinder, 
 
 (2I6) 
 
 The maximum value of this strain must be equal to 
 
 n 
 
 FT- as before, hence 
 
 _ 
 
 - : 
 
 Solving for P , we have 
 
 P o = ^-^ ^ 2 - L - i - . . . (217) 
 If/>=o, 
 
 p n * = 
 
 For the thickness of wall necessary to resist the pressure 
 P acting parallel to the axis, we have, solving (218) for 
 
 R, - R = H" = R.(\/. P * + o 3 ^ - i\ . (219) 
 
 This discussion applies to the older guns made of a single 
 piece of metal. With modern built-up guns the breech- 
 block is in an outer cylinder or jacket, and a new formula 
 must be deduced for the longitudinal strength in such a gun. 
 
GUNS. 205 
 
 112. General Principles of Built-up Guns Method of Applying Ex- 
 terior Pressure. 
 
 GENERAL PRINCIPLES. It has been stated, in discussing- 
 the resistance of a single cylinder, that it may be strength- 
 ened by applying a force /*, to the exterior of the cylinder. 
 This force, as shown, produces a compression of all the lay- 
 ers of the inner cylinder, the interior layer being compressed 
 to the greatest extent, as it should be, since it is extended 
 more than any other layer by the action of the powder-gas. 
 
 The layers of the cylinder being thus subjected to tan- 
 gential compression, this compression must first be over- 
 come before the inner layers can be brought to a state of 
 tension. Hence part of the powder-pressure is exerted to 
 bring the inner layers to a neutral state of strain, and any 
 excess of pressure over that required for this purpose will 
 cause tension in the inner layers. It is evident, however, 
 that since the cylinder will safely support a certain interior 
 pressure P Q0 or P op without this preliminary compression, it 
 will support a much greater interior pressure with the aid 
 of this compression. 
 
 METHOD OF APPLYING EXTERIOR PRESSURES. The 
 method of applying this exterior pressure is by placing over 
 the inner cylinder an exterior one, whose interior diameter 
 is slightly less than the exterior diameter of the inner cylin- 
 der. The exterior cylinder is applied as has been explained 
 in Gun-construction. Upon cooling it contracts upon the 
 inner cylinder, and if the difference of diameters is properly 
 regulated it will produce the required pressure. 
 
 It is evident, however, that in compressing and strength- 
 ening the inner cylinder, the outer cylinder is itself extended 
 and weakened ; but this extension or weakening of the outer 
 cylinder, when properly regulated, can be supported with- 
 out damage to the structure. 
 
 According to Lame's second law the sum of the tension 
 and pressure varies inversely as the square of the radius. 
 Hence a value of (T + P ) which would be large at the 
 interior would be very much diminished at the radius ^,. 
 This principle is applied to any number of cylinders placed 
 one over the other. The differences of diameters of any 
 
206 
 
 TEX 'T- BOOK OF ORDNANCE AND GUNNERY. 
 
 two adjacent cylinders is called " the shrinkage," the re- 
 sulting gun a built-up gun, and the cylinder a compound 
 cylinder. 
 
 113. Calculations for Compound Cylinder States Considered 
 
 Nomenclature. 
 
 CALCULATIONS. Suppose the cylinders assembled with 
 the proper shrinkage. It is required 
 
 1. To calculate the maximum resistance of the com- 
 pound cylinder ; 
 
 2. To calculate the shrinkage, so that when assembled 
 the pressure exerted by the exterior upon the interior cyl- 
 inders shall be such as to give to the compound cylinder its 
 maximum resistance. 
 
 STATES OF CYLINDER. When the powder-pressure is 
 acting, the cylinder is said to be "in action;" when the 
 powder-pressure ceases to act, the cylinder is " at rest." It 
 is evident, however, that the system is not free from stress 
 when at rest, owing to the shrinkage ; and it is necessary to 
 consider the stresses both in action and at rest, as will be 
 seen later. 
 
 NOMENCLATURE. For simplicity of discussion, consider 
 that the compound cylinder is made up of two cylinders 
 
 only. The inner cylinder will be 
 designated as the tube, and the 
 exterior as the jacket. 
 
 In Fig. 82 let 
 
 R , R lt R^ be the radii of the inte- 
 rior, middle, and ex- 
 terior surfaces of the 
 cylinders, R l being 
 the radius of the sur- 
 face of contact be- 
 tween the tube and 
 jacket ; 
 
 /* , P lt P,, the normal pressures at 
 the interior, middle, and exterior surfaces, re- 
 spectively, when the system is in action ; 
 A A > A variations in / > ,/ > 1 ,/ > a , produced by any cause 
 
 FIG. 82. 
 
GUNS. 207 
 
 whatever, such as a change from a state of 
 action to that of rest ; 
 # , B lt elastic limits of tube and jacket, respectively, for 
 
 tension ; 
 
 p , p lf same for compression; 
 
 , moduli of elasticity of tube and jacket respec- 
 tively. These are generally assumed as equal, 
 hence = E^ ; 
 
 /Y, the normal pressure acting at the surface of con- 
 tact of the two cylinders when the system is at 
 rest. 
 
 For a single cylinder the radii have been denoted in the 
 previous discussions by R^ and R l , and the pressures by P 
 and P,. 
 
 As a general rule, if n denote the number of the cylinder, 
 counting from the interior, its radii and pressures are n i 
 and n, for the interior and exterior respectively. Thus, for 
 the fourth cylinder we have R 3 , 1? 4 , P 3 , and P 4 , and by 
 applying this rule the equations deduced for two cylin- 
 ders may be applied to any number. 
 
 114. Resistance of Compound Cylinder in Action. 
 
 In the case of a compound cylinder in action the tube 
 is acted on by an interior pressure P 9 and by an exterior 
 pressure /*. The jacket is acted on by an interior pressure 
 P l and by an exterior pressure P a , which is that of the at- 
 mosphere, and therefore regarded as zero. The jacket is 
 therefore a single cylinder acted on by an interior force, P lt 
 and its resistance is given by equation (203). 
 
 Making, in (203), 
 
 P*9 * if> ^o ^i 
 
 *, = *;, .= 
 
 we write 
 
 P l9 being alone considered, because, as previously shown, 
 it is always less than P lf . (See equations (203), (204).) 
 
 This pressure P l9 will extend the inner layer of the 
 
2O8 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 jacket to its elastic limit, and hence it is the greatest 
 pressure which can be safely applied to the interior of this 
 cylinder. 
 
 The pressure P l9 just found also acts upon the exterior 
 of the tube, and P acts upon the interior. Hence we have 
 the case, already discussed, of a cylinder acted upon by two 
 forces, and equations (201) and (202) apply, viz., 
 
 _oo i 
 
 *R? + 2R: 
 
 -^o>o+2^,* 
 
 4*; - 2R; 
 
 The smaller value must be selected, and this value 
 marks the limiting pressure which the tube, and conse- 
 quently the compound cylinder, will safely support. 
 
 When this interior pressure acts, it raises the inner layer 
 of the tube to its elastic limit for tension or compression, 
 according as P o or P op is the less. At the same time it 
 produces the pressure P l9 at the surface of contact. Hence 
 when the maximum interior pressure is acting it raises the 
 inner layers of both cylinders to their elastic limits. 
 
 Equation (220) is solved first, since it contains only known 
 quantities in the second member. The resulting value, P l& , 
 is then substituted in both (221) and (222), and both of these 
 equations can then be solved, the smaller value being taken 
 as explained. 
 
 - Collecting these equations for convenience, we have for 
 calculating the maximum pressures which a compound 
 cylinder composed of a tube and jacket will safely support 
 in action 
 
 .. , 
 
 * + 2R: 
 
 .>. + 2*.-/, 
 
 - (222} 
 
G UNS. 209 
 
 115. Longitudinal Strength of Compound Cylinder. 
 
 In a gun composed of two cylinders the jacket carries 
 the breech-block, in order to free the tube as much as pos- 
 sible from longitudinal stress. 
 
 The total pressure upon the breech-block is, as before, 
 
 This acts upon the area of cross-section of the jacket, 
 which is n(R* R*} ; hence the stress per unit area of this 
 cross-section is 
 
 __ ( , v 
 
 " n(R? - R?} ~ R? - R*' ' 
 
 The values of t and / from (187) and (188) become for 
 the outer cylinder, by making the following changes in the 
 nomenclature, 
 
 /> = o, R, = R, ; 
 
 ' 
 
 -' 
 
 Substituting these values of /, /, and q in the third of 
 equations (170), we have 
 
 _ _ 
 
 3 (/?;-^), 
 
 The maximum safe longitudinal strain upon the jacket is 
 
 e 
 
 --. If the value of v calculated by (226) is less than this, 
 
 *h 
 
 the jacket will not be overstrained longitudinally by P . If 
 f\ 
 
 greater than -~, the pressure P must be reduced. 
 
 "i 
 
 The limiting value for the pressure is obtained, as before, 
 by placing 
 
2IO TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 Solving for P , we have 
 
 3 w - RW + 2PR? 
 
 ~ 3*." 
 
 116. The System at Rest Reasons for Considering It Variations 
 of Pressure. 
 
 The formulas previously deduced give the maximum 
 pressures which the .compound cylinder will safely support 
 in action ; and in order that these pressures may exist, the 
 jacket must be applied by shrinkage upon the tube. The 
 pressure thus produced on the tube will strengthen it. 
 
 It may be, however, that this pressure which is applied 
 to the exterior of the tube will be so great that when 
 the powder-pressure ceases to act it will compress the 
 inner layer of the latter to such an extent as to cause this 
 layer to pass its elastic limit. Thus the tube may be injured 
 by the exterior force which is applied to strengthen it. 
 
 It follows, therefore, that although the compound cyl- 
 inder would support certain pressures in action if the req- 
 uisite exterior pressure could be applied, it may be im- 
 possible to apply this pressure to the exterior of the tube at 
 rest, and therefore, before we can determine whether equa- 
 tions (220), (221), and (222) represent allowable pressures in 
 action, it is necessary to consider the effects of the pressure 
 at rest upon the tube. 
 
 When the powder-pressure acts, we have the forces P 9 
 at the interior and P l at the surface of contact of the cyl- 
 inders. 
 
 These can be calculated by (220), (221), and (222). 
 
 When the powder pressure ceases to act, the interior 
 pressure becomes zero, and the variation of pressure at the 
 interior is from -|- P to o. This difference between the 
 pressure in action and at rest gives the variation of press- 
 ure. Hence for the interior we have 
 
 A = 0-P , or p = -P (228) 
 
 This is further evident by considering that the algebraic 
 sum of the pressure in action and the variation of pressure 
 must be the pressure at rest. 
 
GUNS. 211 
 
 For the surface of contact of the two cylinders the 
 pressure at rest is P/ and in action it is P t - hence the varia- 
 tion of pressure /, at that surface is, as before, 
 
 >>/'->, ....... (229) 
 
 117. Limiting Value of Exterior Pressure on Tube System at 
 
 Rest. 
 
 The limiting value of the exterior pressure upon the 
 tube for the state of rest is that value which will compress 
 the inner layer of the tube to its elastic limit, and it is given 
 by equation (209). 
 
 and no greater pressure than this can be allowed to exist at 
 the exterior surface of the tube at rest. 
 
 Now the pressure actually existing at this surface "at 
 rest" is, from (229), 
 
 />/=+>, ...... (230 
 
 This value of /y depends on P lt the pressure at the ex- 
 terior of the tube " in action," and also upon p lt the variation 
 of the pressure at that surface in passing from the state of 
 action to that of rest. It is necessary therefore to calculate 
 /y by (231) and compare it with P IP , the maximum admis- 
 sible pressure calculated by (230). If /Y > P^, it follows 
 that it will strain the tube at rest beyond its elastic limit, 
 and hence it cannot be allowed. The value P 1P must then 
 be adopted in place of P/ and be substituted for it in (231). 
 This substitution in (231) will produce a corresponding 
 change in the value of P lt and this change in P, will also 
 change P . (See equations (220), (221), (222).) On the other 
 hand, if /y, from (231), be less than P IP from (230), P, f must 
 be used and not P 1P , because although the tube will support 
 the pressure P IP > /y at rest, if this value of P IP be sub- 
 stituted for /y in (231) it will cause an increase in the value 
 of P, , the pressure on the exterior in action. 
 
 But it has been shown previously that the value of P l 
 from equation (220) represents the greatest pressure which 
 the jacket will endure in action without passing its elastic 
 limit. 
 
212 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 Hence this pressure must not be increased. 
 
 We are therefore limited on the one hand to the value 
 P 1P , equation (230), which must not be exceeded at rest, and 
 on the other to the values P and P t , equations (220), (221), 
 (222), in action which must not be increased. 
 
 118. Calculation of p v in Equation (231). 
 
 In order to calculate P t ' from (231) we must know /,, 
 since '/>, is given by (220). To calculate /, we proceed as 
 follows : 
 
 When variations of pressure occur at any surface they 
 produce corresponding changes in the dimensions of the sur- 
 face at which they act, and these changes depend directly 
 upon the variations of pressure which cause them. The 
 changes of dimensions in the direction of the circumference 
 of the cylinder are the greatest (see equations (194) and 
 (195) ), and hence it is only necessary to consider these. 
 
 For the jacket, the exterior pressure is always zero, and 
 the variation of pressure at the interior is/,. Equation (197) 
 gives the change of the inner layer of a cylinder in the direc- 
 tion of the circumference due to the forces P and />,. 
 
 In the present case /*,=/,, and P l = o. Also R, = R^ , 
 R = R l , = ,, hence 
 
 A = . .. 
 
 ' ' 
 
 For the tube we have the variation of pressure /, acting 
 upon the exterior surface, and / upon its interior. Equa- 
 tion (212) gives the tangential change at the exterior of a 
 cylinder due to the two forces P and P r To adapt it to 
 the present case make 
 
 Making these substitutions, we have 
 
 Since the exterior surface of the tube and the interior 
 surface of the jacket are in contact, they form virtually but 
 
GUNS. 213 
 
 one surface, and whatever change occurs in one will occur 
 also in the other. Hence the two values of A in (232) and 
 (233) are equal. 
 
 Equating these and solving for/ x , we have, since JS 9 = 
 
 And since, from (228), 
 
 we can find /, in terms of P from 234. 
 
 119. True Value of P.. 
 
 The true value of P 9 is that which is safe for the system 
 both in action and at rest. 
 
 It has been shown that if Pf < P 1P , the values of P given 
 by (221) and (222) are safe. 
 
 If /Y> P 1P , these values are not safe and the true value 
 of P is calculated as follows : 
 
 The equation expressing the limiting value for the exte- 
 rior pressure system at rest is 
 
 (235) 
 
 in which the value of P lf is obtained from equation (230). 
 Hence 
 
 />, = />-* ..... (236) 
 
 Substituting the value of / t from (234), in which / = P , 
 pp 4- ^ 2 (^' ' R *} p <> 
 
 lp ^ ' 
 
 The equations expressing the limiting values of the in- 
 terior pressure for the state of action are (221) and (222). 
 
 Substituting the value of P, from (237) in (221) and (222) 
 and taking the smaller value, we have the true value of P , 
 which will be safe both in action and at rest, since it has 
 been obtained by combining two equations which contain 
 the conditions of safety both for action and for rest. 
 
214 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 The results of the substitution are 
 
 />.*= 
 
 2R:} - 
 
 ^ (A> 
 
 - 2R?) - 
 
 F 1 *-- ' ' (B) 
 
 Having the true value of P from (A) or (B), we find the 
 true value of /, from (234), and this value of p l in (235), with 
 the value of P 1P from (230), will give the true value of P r 
 
 120. Calculation of the Shrinkage. 
 
 Shrinkage is the difference of diameters of two adjacent 
 cylinders. This is called the actual or absolute shrinkage. 
 Dividing the absolute shrinkage by the diameter, we have 
 the shrinkage per unit of diameter, or the relative shrinkage. 
 
 In Fig 83 let 
 
 OA be the interior radius 
 
 of tube, 
 
 1 of jacket, 
 
 OB the exterior radius 
 OC the interior radius 
 OD the exterior radius { 
 before the cylinders are assembled. Then 
 
 2BC = 2(OB OC) 
 
 is the absolute or actual shrinkage, 
 and 
 
 2BC _ 2(OB- OC) __ 
 
 ~2~OC ~~ OC 
 
 E 
 
 FIG. 83. 
 
 is the relative shrinkage. 
 
 When the cylinders are assembled, 
 the surface of contact will take a po- 
 sition such as E E E. The jacket will 
 compress the exterior of the tube by 
 the amount BE, and the interior of 
 the jacket will be extended by the 
 amount CE, and we have 
 
 BE + C. E = BC, 
 
GUNS. 
 
 21$ 
 
 By this compression the force />/ is exerted upon the 
 exterior of the tube and the interior of the jacket. It is 
 required to find BE and C, and the shrinkage will then be 
 known. 
 
 BE 
 CALCULATION. The value - is the compression per 
 
 L/ Ls 
 
 unit of length of circumference, or of radius, of the exterior of 
 the tube, produced by the force P{. This relative compres- 
 
 BE 
 sion is strictly - , since OB is the original exterior radius, 
 
 but the error is so slight that it may be neglected. This 
 compression is-given by equation (213), since P 9 = o, hence 
 
 BE , 
 
 'oc "' 
 
 The value - is the extension of the interior of the 
 
 jacket per unit of length of circumference, or of radius, 
 duced by the force /Y- 
 
 It is given by equation (199) by making 
 
 R, = R*\ />=o; 
 #, = *,; E. = E i; 
 
 p. = /Y. 
 
 Hence 
 
 CE 
 
 _ 
 
 - ' ' -' ..... (239) 
 
 The negative sign is omitted in (238), since it simply indicates 
 compression. 
 
 Hence denoting the relative shrinkage by 0, we have 
 
 _ BE+CE _ 2R?(Rf - R^P,' 
 
 $~- oc = E O (R? - R:)(R; - R?y 
 
 Steps. The different steps in the calculation of the 
 shrinkage may be thus summarized : 
 
2l6 TEXJ^-BOOK OF ORDNANCE AND GUNNERY. 
 
 1. Calculate P l9t P e and P op by (220), (221), and (222). 
 Use smaller value of P . 
 
 2. Calculate P 1P from (230) and /, from (234), making in 
 the latter /> P , the value obtained from (221) and 
 
 (222). 
 
 3. Find /Y from (231), and compare this value with that 
 of P 1P obtained from (230). 
 
 If /Y from (231) is greater than P 1P from (230), steps 4, 5, 
 and 6 will be as follows : 
 
 4. Calculate P o9 and P op from A and B. Take smaller 
 value. 
 
 5. Recalculate/, from (234), making /> = P , the value 
 found from A and B. 
 
 6. Find P 1 from (237), using P IP from (230). 
 
 7. Calculate the relative shrinkage by (240). The value 
 of P{ to be used in (240) must correspond to the adopted 
 value of P , being either (P l + A) from (231) or P IP from (230) 
 according as P 9 is retained as originally found in step i or 
 is changed as indicated in steps 3 and 4. 
 
 8. The absolute shrinkage is obtained by multiplying 
 the relative shrinkage by the interior diameter of the jacket. 
 Hence if 5 denote the absolute shrinkage, 
 
 S = X 2R r 
 
 9. The exterior diameter of the tube should then be 
 
 2^/ = 2^ + 5. (241) 
 
 121. Measurements in Gun-construction Thickness of Wall 
 Length of Bore. 
 
 MEASUREMENTS. The value of the shrinkage having 
 been calculated by (240), the exterior diameter of the tube is 
 given by (241). The exterior of the tube is then turned to 
 this diameter, an error of 0.003 i ncn only being allowed. 
 
 After turning, the exterior diameters are measured at 
 every inch of length of tube ; if too large, they are reduced ; 
 if too small, they cannot be corrected, except by using a 
 smaller jacket. Hence it is important not to turn below 
 size. 
 
GUNS. 
 
 217 
 
 The interior diameters of the tube are also measured at 
 each inch of length. 
 
 The tube and jacket are now assembled, and, when cool, 
 the interior diameters of the tube under the jacket are 
 again measured. 
 
 The pressure of the jacket upon the tube will produce 
 a contraction of the bore of the latter, and this contraction 
 is given by equation (207), making P 1 = P/, since this latter 
 is the pressure at rest. The measured contraction should 
 agree with the calculated value ; and if it does, we have a 
 proof of the accuracy of the measurements, and of the cor- 
 rectness of the formulas. 
 
 The agreement is generally very close. 
 
 THICKNESS OF WALLS. From previous calculations it 
 has been shown that there is very little gain in tangential 
 resistance by increasing the thickness of the cylinder beyond 
 one calibre. This rule is generally followed in modern guns 
 for the thickness of wall over the powder-chamber. 
 
 The thickness at other points along the chase is obtained 
 by a consideration of the powder-pressures at the different 
 points, and these are given by the pressure-curve, w r hose 
 construction has been explained. It is also necessary to so 
 adjust the thickness of the different parts, that the weight of 
 the gun shall not exceed the limit generally allowed for the 
 different calibres, and that the axis of the trunnions or the 
 centre of gravity of the gun shall be at a distance from the 
 breech, equal to about f the total length of the gun. 
 
 The weights of guns are as follows, nearly : 
 
 8-inch 14 tons 
 
 lO-inch 28 " 
 
 12-inch 52 " 
 
 12-inch mortar , 13 " 
 
 In general, the shape of the chase conforms to that of 
 the pressure curve, and the resistance at different sections 
 along the gun is calculated so that at any section it shall 
 always be greater than the powder-pressure by a certain 
 coefficient or factor of safety. For the 1 2-inch gun the 
 elastic resistance is about 24 tons per square inch, and the 
 
2l8 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 powder-pressure 16 tons, at the chamber, so that the factor 
 of safety is f = 1.5. 
 
 LENGTH OF GUN. For a given calibre, charge of pow- 
 der, weight of projectile, etc., we can calculate by Sarrau's 
 formulas the value of u for a required initial velocity V, and 
 may so adjust the elements of loading that the maximum 
 pressure shall be constant and equal to, say, 15 tons for this 
 velocity. Generally modern guns are from 35 to 45 calibres 
 long. 
 
 122. Wire Guns. 
 
 In the built-up gun it has been shown that when in ac- 
 tion, the inner layers of the tube and jacket are strained to 
 their elastic limits respectively. None of the other fibres 
 are strained up to that limit, and hence the total strength of 
 the metal is not utilized. If instead of two cylinders we have 
 four, assembled with proper shrinkage, the total thickness 
 of the gun being constant, it is evident that the inner layers 
 of each of the four cylinders would be strained to their 
 elastic limits and hence more of the total strength of the 
 metal would be utilized. As the number of cylinders in- 
 creases, the strength utilized will be greater, till we finally 
 approach the limit where the cylinders are infinitely thin, and 
 the whole thickness of metal in each is strained to its limit. 
 
 Practical reasons, however, prevent the carrying out of 
 this method, because the longitudinal strength of the cylin- 
 ders decreases with the thickness; the expense of boring 
 and turning the cylinders is great, and it would be impos- 
 sible to bore and turn very thin cylinders accurately. 
 
 For these reasons, it has been proposed to substitute wire, 
 for the rings or hoops of the built-up gun. This wire is 
 wrapped round an inner tube with a certain tension, so that 
 the tube is compressed initially as in the case of the built-up 
 gun, and the wire extended. 
 
 The advantages claimed for the wire gun are : 
 
 i. The tension of the layers of wire can be so regulated 
 that each wire will be strained to its elastic limit when the 
 system is in action, and we approach the condition of in- 
 finitely thin cylinders. 
 
GUNS. 219 
 
 2. The wire being very small in section, any physical 
 defects can be detected, and hence all the metal in the gun 
 will be sound. 
 
 3. A high elastic limit can be given to the wire, and 
 hence it will have a greater tangential strength than a forged 
 steel hoop. 
 
 4. In order to utilize the high elastic limit of the wire,, 
 the tube may be compressed at rest beyond its elastic limit. 
 
 The objections are : 
 
 1. Compressing the inner layer of the tube beyond its 
 elastic limit violates the fundamental principle of modern 
 gun-construction ; and if this is not done, the wire gun can- 
 not in general be stronger tangentially than the built-up 
 gun, since the strength of the tube marks the limit of the 
 strength of the system. 
 
 2. The coils of wire have no longitudinal strength, and 
 hence the longitudinal strain must be supported, as in the 
 built-up gun, by a jacket, and the attachment of this jacket 
 to the tube presents difficulties. 
 
 3. The wire gun is not as stiff longitudinally as the built- 
 up gun, since the wire does not support the tube so firmly 
 as the hoops. This is a question of importance with modern 
 long guns. 
 
 123. Description of Wire Guns Woodbridge Crozier Brown 
 Segmental. 
 
 WOODBRIDGE (Fig. 84). This gun consists of an inner 
 tube, /, wrapped with wire as shown. Over the rear part 
 of the tube is a jacket, j, made of longitudinal steel bars of 
 wedge-shaped cross-section. 
 
 This jacket is wrapped with the wire w, under such 
 tension as to strongly compress the inner tube at rest. 
 The longitudinal thrust is transmitted to the jacket as fol- 
 lows : The jacket is screwed to the tube in rear ; the trun- 
 nion-hoop t' bears against a thin hoop h, and this against a 
 collar c screwed to the jacket in front. Hence the pull 
 of the breech block in rear is transmitted to the rear 
 of the jacket, and the thrust of the trunnions to the front 
 of it. 
 
22O 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 The calibre of the gun is 10 inches. 
 
 CROZIER (Fig. 85). In 
 this gun the tube is com- 
 pressed initially beyond its 
 elastic limit by the wire. 
 
 The principal features are : 
 
 1. The wire on the chase 
 is covered on the exterior by 
 thin hoops, put on with very 
 slight shrinkage, so as to give 
 stiffness, and protect the wire. 
 
 2. A jacket of cast iron or 
 cast steel is used for cheap- 
 ness, to carry the breech- 
 block and support the longi- 
 tudinal strain. It is put on 
 with very little shrinkage, the 
 tangential strength of the 
 gun depending on the tube 
 and wire alone. 
 
 3. The jacket and tube 
 are connected, and the mo- 
 tion of either prevented, by 
 a series of rings or steps, a, 
 abutting against each other. 
 
 BROWN SEGMENTAL (Fig. 
 86). In this gun there is first, 
 a small lining tube, a, which 
 extends beyond the trun- 
 nions. The metal of this 
 tube has a high elastic limit, 
 1 12,000 Ibs. The main tube, 
 b, is made of wedge-shaped 
 steel bars, of about the 
 same elastic limit. This 
 outer tube is wrapped with 
 wire, and compressed to such 
 an extent that its interior 
 
 FIG. 84. 
 
 FIG. 85. 
 
 is under compression even in action. This prevents the 
 
GUNS. 221 
 
 joints betwsen the bars from opening. The jacket is light, 
 and is not in contact with the wire except at the trunnions 
 and breech. The figure shows the method of attachment of 
 
 A 
 
 A FIG. 86. 
 
 the breech-block. The pull of the block at the breech and 
 the thrust of the trunnions in front are borne by the jacket. 
 
 Relative motion of tube and jacket is prevented by the 
 connection in rear. 
 
 These guns have been made and tried in this country. 
 In Europe the systems of Schultz, Longridge, Armstrong, 
 and others have been tried. 
 
 MEASUREMENTS. 
 
 124. Necessity for Measurements Required Standard Comparator. 
 
 NECESSITY FOR. In a modern gun it has been shown 
 that the stresses and shrinkages are functions of each other. 
 Hence, if the correct shrinkage be not given to the gun, it 
 will not properly support the stress to which it is subjected, 
 and may be either strained beyond its elastic limit, or not 
 strained up to that limit according to the actual value of the 
 shrinkage as given in construction. After these shrinkages 
 are calculated theoretically, their application to a particular 
 gun, depends on the accuracy of the measurements made by 
 the inspector during construction. Hence the necessity for 
 accurate measuring instruments, and skill in their use. 
 
 MEASUREMENTS REQUIRED. In general the following 
 measurements are required in gun-manufacture : 
 
 1. Interior diameters ; 
 
 2. Exterior diameters ; 
 
 3. Lengths; 
 
 4. Measurements by templets and gauges. 
 STANDARD COMPARATOR. In this case, as in all others 
 
 where accuracy is required, all measurements must be re- 
 ferred to a common standard. This standard is called a 
 
222 
 
 TEXT-BOOK OF ORDNAA^CE AND GUNNERY. 
 
 " comparator," and its general principles may be explained 
 as follows : 
 
 A stiff bed or body, a, of cast iron, Fig. 87, rests upon 
 three le veiling-screws with rounded points of support. 
 
 FIG. 87. 
 
 In this bed is a groove or recess, c, in which rests a 
 standard bar or rod, *', accurately graduated in inches and 
 decimal parts of an inch. On top of the bed is the rib d, 
 which forms the guide for the heads e,f, and g, which slide 
 along it. These heads can be fixed by clamp-screws in any 
 position along the bed. e is called the fixed head, /the 
 sliding head, and g the auxiliary head, hh are two sockets 
 which carry steel points, and these points can be adjusted 
 lengthwise in the sockets, and clamped by the clamp-screws ; 
 i is a microscope reading o.oooi inch ; /, a tangent screw con- 
 necting/and^. 
 
 Use.- The primary object of this instrument is to lay off 
 exact lengths. To do this, the graduated bar being in its 
 recess c, bring the ends of the steel points h h in contact. 
 Then adjust the graduated bar and microscope, till the zero- 
 line of the eyepiece of the microscope coincides with the 
 zero of the graduated bar. Clamp the fixed head, e, and 
 slide the sliding and auxiliary heads, till the microscope is 
 over the nearest division of the graduated bar correspond- 
 ing to the length to be measured. 
 
 The auxiliary head g is then clamped, and the sliding 
 head f moved by the tangent-screw k till the microscope 
 reads the required part of the inch. The distance between 
 the points h h will then be the length required. 
 
 125. Measurement of Interior Diameters of Short Hoops Meas- 
 uring-points Use. 
 The interior diameters to be measured may be 
 
G UNS. 
 
 223 
 
 1. Those of a comparatively short hoop ; 
 
 2. Those of a long hoop or tube. 
 
 In the first case, when the length of the hoop is such that 
 all parts of it can be reached by hand, measuring points or 
 rods are used. 
 
 MEASURING-POINTS. For diameters from two to ten 
 inches, the points are made of steel, and consist of a fixed 
 point, a (Fig. 88), and a micrometer-point, b. The fixed point 
 
 .,* 
 
 FIG. 88. 
 
 varies in length according to the diameter to be measured, 
 there being a number of them. Each one is threaded at the 
 end, c, and the micrometer-point screws on this thread by 
 the corresponding thread, c' . The screw d of the microme- 
 ter is accurately cut, so that one turn of the head e cor- 
 responds to a certain decimal part of one inch, generally 
 0.025. The circle /is then graduated to read o.ooi inch. 
 
 For diameters beyond 10 inches, the heat of the hand is 
 found to affect the measurements, as it causes considerable 
 expansion in a long steel rod. The rod, also, if made suffi- 
 ciently light to be readily handled, would lack stiffness. 
 For these reasons the measuring-points for larger diameters 
 are made as follows : a (Fig. 89) is a holder of wood, bored 
 
 FIG. 89. 
 
 out in the middle, b, for the reception of the fixed and mi- 
 crometer points c and d. Metal ferrules, e and/, of the shape 
 shown, are fitted to the ends of the holders, and are pro- 
 vided with clamp-screws, g, to clamp the points c and d. 
 
224 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 These points are essentially the same as before, the only 
 difference being that the lengths of the holders vary, and 
 the same points c and d are fitted to different holders. 
 
 USE. Suppose a given diameter, say 12.50 inches, is to 
 be measured. The standard comparator is first set to 12.50 
 inches, as just explained. A holder of proper length is then 
 selected, and the points c and d fixed in it. The end of the 
 fixed point c has an adjustment by which, having set the 
 micrometer-point at zero, the length of the whole rod can 
 be altered till it is exactly 12.50 inches. The interior diam- 
 eter of the hoop can now be measured, and the differences, 
 if any, in thousandths of an inch, read off on the micrometer- 
 scale on the point d. There are also other methods of ad- 
 justing the rod. 
 
 126. Measurement of Interior Diameters of Long Tubes The Star 
 
 Gauge Setting the Star Gauge. 
 
 THE STAR GAUGE. In the case of long tubes, all parts 
 of which are not readily accessible, some means must be 
 adopted of making the measurements at a distance from 
 the operator. The instrument used for this purpose is called 
 a " star gauge." Its principal parts (Fig. 90) are a long hol- 
 
 FIG. 90. 
 
 low brass rod, a, called the staff, to which are attached the 
 head, , and the handle, c. 
 
 The figure and description are intended to give only 
 a general idea of the instrument, and are not accurate in 
 details, as the instrument is too complicated to be fully 
 described here. 
 
 The head b has three or more sockets, d, which are 
 pressed inward upon the cone g by spiral springs, not 
 shown in the figure. Into these sockets are screwed the 
 
GUNS. 225 
 
 star-gauge points e. There are generally three of these, 
 120 apart, varying in length, for the different calibres to be 
 measured, so that by screwing the proper points into the 
 sockets d, any diameter can be measured. The handle c is 
 at the other extremity of the staff a. In the older forms of 
 star gauge it had a sliding motion along the staff. With 
 the new instruments motion is given by a micrometer- 
 screw. Extending through the staff is a square steel rod,/, 
 united at one end to the handle c, and terminating at the 
 other end in a cone, g. This cone has a known taper, and a 
 forward movement of one inch corresponds to a certain 
 definite increase in its diameter. This increase is marked 
 on a scale upon the handle. 
 
 Use. When the handle c is pushed forward, the cone g 
 also moves the same amount, since it is connected with the 
 handle by the steel rod/. When the cone moves forward, 
 it pushes out the sockets d, resting upon its surface, and 
 this forward motion of the handle and cone continues, till 
 the points e come in contact with the walls of the bore to 
 be measured. The amount of this outward movement of 
 the points can then be read on the scale on the handle, and 
 by comparing this with the original position of the points 
 the size of the bore becomes known. 
 
 SETTING THE STAR GAUGE. As with the measuring- 
 points previously described, it is necessary to " set " the star 
 gauge before use ; that is, to establish an origin or datum to 
 which all measurements are referred. Suppose the bore to 
 be measured is 10.00 inches in diameter. Accompanying the 
 instrument is a series of rings very accurately bored to the 
 different sizes likely to be required in practice. The 10.00- 
 inch ring is selected, and the standard comparator set to 
 that length, a measuring-point adjusted to it, and the ring 
 then tested by this point to see if it is exactly 10.00 inches. 
 If not, the error is noted and corrected for. The lo.oo-inch 
 points having been screwed into the sockets of the star 
 gauge, the ring is held so that when the handle is moved 
 forward, the points will all touch the ring. While the 
 points are in this position, the handle is adjusted so that the 
 reading- is zero. 
 
220 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 The ring is then removed, the instrument inserted in the 
 bore, and the readings of the scale taken for every inch of 
 length of bore. These readings are added to, or subtracted 
 from, the original diameter of the ring, according as they 
 are greater or less than zero, and the results give the true 
 diameter of the bore. 
 
 127. Exterior Diameters Calipers Arm Support Action. 
 
 The instruments used for measuring exterior diameters 
 are called calipers. One form consists, Fig. 91, of the arm 
 a, the measuring-points b, c, and the support d. 
 
 e 
 
 FIG. 91. 
 
 ARM. The arm a is made of steel in a semicircular 
 form, and as light as possible consistent with stiffness. The 
 arm terminates in sockets, e, at each end, which are provided 
 with clamp-screws e' . 
 
 To increase the stiffness of the arm and protect it from 
 variations of temperature in use, it is covered with wood, /. 
 
 The measuring-points b, c pass through the sockets e in 
 the arm, and are clamped in position by the clamp-screws e\ 
 The point b is called the fixed point, as it does not change 
 its position relatively to the arm when once clamped ; the 
 point c is the measuring or micrometer point, and having been 
 
GUNS. 227 
 
 clamped in the socket e, its extremity, c' , is capable of a 
 small motion by means of a micrometer-screw, whose con- 
 struction has been previously explained. This point carries 
 a scale, s, reading to thousandths. The points when in posi- 
 tion are always in a straight line. 
 
 The arm with its points is suspended from its support, d, 
 by the hook g and spiral spring k. 
 
 SUPPORT. The support of the calipers consists of a 
 standard, k, fixed to a bar, /. This bar slides longitudinally 
 upon a base, m. The standard k carries a rod, n, to which 
 the spiral spring h is attached, and to this spring the hook^-. 
 The whole support rests on the exterior of the tube to be 
 measured, being brought parallel to the axis by the feet oo, 
 and held in this position by the leather strap /, which is 
 buckled tightly around the tube. 
 
 ACTION. Suppose a diameter of 15.00 inches is to be 
 measured. Set the standard comparator to this length, and 
 having determined from it the length of a measuring-point 
 of exactly 15.00 inches, set the micrometer-point c at zero, 
 and adjust the points b and c in the sockets till the distance 
 between them is exactly 15.00 inches. Raise or lower the 
 caliper-arm till the points b and c are slightly above a hori- 
 zontal plane through the axis of the tube. The bar / may 
 then be moved along the tube parallel to its axis, sliding on 
 the bed m, and measurements made for every inch of length. 
 The bar / will slide for a length of 12 inches. The leather 
 strap p must then be loosened, the whole support moved 
 forward this distance, and the strap again tightened, when 
 measurements may be made as before, till the whole is com- 
 pleted. 
 
 128. Measurement of Lengths Step Gauge Surface Lengths. 
 
 The accurate measurement of lengths is very difficult to 
 make, and as each particular case requires a special arrange- 
 ment, only general ideas can be given. 
 
 STEP GAUGE. One of the most frequent measurements 
 required is the length of the recess or step, ab, in a hoop. If 
 this be too short, the hoop will not come in contact with the 
 preceding one when shrunk on ; and if too long, an opening 
 
228 
 
 TEXT- BOOK OF ORDNANCE AND GUNNERY. 
 
 3 
 
 C l s ..J f \ 
 
 ,,,,",, "'"' l''\' ; r - '-] JL 
 
 s 
 
 _J 
 
 D 1 
 
 7^ 
 
 f a- -i ^ 
 
 -^ HOOP. 
 
 
 will be left at the shoulder, which leaves the tube unsup- 
 ported. To measure this length, an instrument called a step 
 
 gauge is used. This con- 
 sists, Fig. 92, of a steel blade, 
 c, sliding through a socket 
 in a body, d. These blades 
 are of different lengths, cor- 
 responding to the different 
 hoops to be measured. On 
 the end of the blade is fixed 
 a steel templet, /, which ex- 
 FlG 2 actly fits the shoulder in the 
 
 hoop. The templet being 
 
 held against the shoulder b, while the body is pressed against 
 the face of the hoop at e t the length can be read off on the 
 scale. 
 
 SURFACE LENGTHS. In each shrinkage operation, the 
 changes in diameter and length due to that operation are 
 measured. The changes in diameter are measured with the 
 points, star gauge, or calipers. 
 
 For measuring the changes in length, the following plan 
 is adopted : 
 
 Two holes are made with a punch in the exterior surface 
 of the tube or hoop, and their exact distance apart before 
 shrinkage measured as follows : 
 
 An instrument, Fig. 93, consisting of a main body,#, car- 
 
 iitil i Ifl I 
 
 O O 
 
 FIG. 93. 
 
 ries a fixed head, b, and two movable points, c and d. The 
 pofnt c is attached to a sliding head, c f , which carries a 
 micrometer-screw, e. 
 
 g is an extension-bar, having holes at intervals of 0.25 
 inch. 
 
GUNS. 229 
 
 Accompanying the instrument are reference-bars,/, which 
 have holes in them exactly one inch apart, and at the left 
 end one inch is graduated into J, -J, { inch. 
 
 When the holes are punched in the surface of the hoop 
 as before explained, their distance apart is measured 
 approximately with a scale. Suppose this distance to be 
 18.40 inches. 
 
 Move the point d along the extension-bar g till it will 
 enter the 1 8-inch hole, and clamp it, the screw d' passing 
 into one of the holes in the bar g. Place the instrument on 
 the reference-bar/, the point c entering the J-inch hole in it, 
 and the point d resting in the 1 8-inch hole. The distance 
 between the points c and d\s now 18.50 inches. 
 
 Fix the micrometer e at zero, and move the points b and 
 e till they are in contact. Now place the instrument on the 
 hoop to be measured, the point c in one punch-mark and d 
 in the other, make contact again with e, and subtract the 
 reading of the micrometer-scale from 18.50 for the distance 
 apart of the holes. 
 
 After shrinkage the same process gives the distance 
 apart of the punch-marks; and the difference before and 
 after, the change due to shrinkage. 
 
 129. General Principles of Measurements Touch Interior Diam- 
 eters of Short Hoops. 
 
 In the above descriptions all the complicated details of 
 the instruments have been omitted, and only the general 
 method of their operation and use given. The templet 
 measurements require no special notice. A few general 
 principles relating to the method of using these instruments 
 must be understood. 
 
 TOUCH. The accuracy of all measurements with these 
 instruments depends upon the skill of the operator, and 
 hence practice is necessary to obtain satisfactory results. 
 In most cases the sense of touch is relied upon to determine 
 when proper contact of the measuring-points with the sur- 
 face to be measured, is obtained. 
 
 Various mechanical devices, such as electrical indicators, 
 etc., have been tried to determine when proper contact has 
 
230 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY 
 
 been obtained, and can be used to advantage when a large 
 amount of measuring is to be done. 
 
 INTERIOR DIAMETERS. In measuring these (Figs. 94 
 
 S? 
 
 FIG. 95. 
 
 and 95), the hoop is placed horizontally, and the lower fixed 
 point of the measuring-rod a is held by the operator at the 
 point whose diameter is to be measured. It is evident from 
 Fig. 95 that the diameter is the shortest line from a to b, and 
 hence if the upper point of the measuring-rod be moved 
 from b in the direction of the arrows, it will cease to touch 
 the surface of the hoop. 
 
 From Fig. 94, the diameter ab is the longest line in the 
 cross-section; and if the point be moved to either side of b, 
 it will jam against the surface of the hoop. Hence in 
 determining an interior diameter at any point with the 
 measuring-rods, hold the fixed point of the rod firmly against 
 the lower surface of the hoop at the point where the diam- 
 eter is required. Move the micrometer-point in two direc- 
 tions at right angles to each other, one along the axis of the 
 hoop, the other across the axis, till a point is found where 
 contact occurs due to both these motions. 
 
 The reading of the rod will give the diameter. 
 
 130. Interior Diameters of Long Hoops Exterior Diameters 
 Vernier Scale. 
 
 INTERIOR DIAMETERS OF LONG HOOPS. These are meas- 
 ured with the star gauge, and in order that they may be 
 correct the points must move at right angles to the axis of 
 the bore. 
 
 By the construction of the instrument these points must 
 move at right angles to the staff of the star gauge, and hence 
 
GUNS. 
 
 231 
 
 it becomes necessary that the staff be placed accurately in 
 the axis of the bore. For this purpose the gun or tube is 
 carefully levelled, and various supports are used in the bore, 
 which insure centering of the star-gauge staff. Exterior 
 rests are also provided to support that part of the staff out- 
 side the bore. 
 
 EXTERIOR DIAMETERS. In the measurement of exterior 
 diameters, the same principles apply as to interior diameters. 
 In Fig. 96 the diameter c is the longest line in the cross- 
 
 
 
 FIG. 96. 
 
 FIG. 97. 
 
 section, and the shortest line in the longitudinal section, 
 Fig. 97. Hence the fixed point of the calipers is held at a, 
 and the measuring-point b moved in two directions at right 
 angles, as in case of the interior diameters, till proper con- 
 tact is made. 
 
 VERNIER SCALE. A very useful instrument in these 
 
 FIG. 98. 
 
 measurements is a "vernier scale," Fig. 98, which consists of 
 a steel blade, a, graduated in inches and decimal divisions, a 
 
232 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 fixed jaw, b, a mo\ 7 able jaw, c, and an auxiliary jaw, d, with 
 its tangent screw, e. The principle is the same as that of the 
 standard comparator, lengths being measured between b 
 and c. The advantage of this instrument is that it can be 
 carried to any part of the shops, and when its error is 
 determined by the standard comparator, it can be used in 
 place of the latter with great convenience. Its disadvantage 
 is that it is affected by changes of temperature when carried 
 to different places in the shop, and when handled. 
 
 DESCRIPTION OF CANNON. 
 1. In U. 5. Service. 
 
 131. Classification Hotchkiss Mountain Kifle. 
 
 CLASSIFICATION. Cannon may be classified according 
 to the service for which they are intended, into mountain, 
 field, siege, or sea-coast guns ; according to the kind of fire 
 they deliver, into guns, howitzers, and mortars ; according to 
 the kinds of projectiles used, into smooth-bore and rifled ; 
 and according to the methods of loading, into muzzle- and 
 breech-loaders. As all modern guns are breech-loading 
 rifles, it is most convenient for discussion to consider them 
 according to the service for which they are intended. 
 
 Machine and rapid-fire guns will be considered later. 
 
 MOUNTAIN GUNS. 
 
 HOTCHKISS MOUNTAIN RIFLE. This is the only gun of 
 this class in service. It is made as light as practicable, so 
 that it can be carried on the back of a mule, its weight being 
 1 1 6 Ibs. Its carriage weighs 220 Ibs., and two men can pack, 
 unpack, and mount it. 
 
 The gun, Fig. 99, is made of steel in a single forging, the 
 
 FIG. 99. 
 
 trunnion-hoop being screwed on. The calibre is 1.65 
 inches; weight of shell loaded 2 Ibs. 10 ozs.; of powder- 
 charge, 5 1 ozs. The initial velocity is 1275 ft.-secs. 
 
GUNS. 
 
 233 
 
 Breech Mechanism. The mechanism is a simple form of 
 the Krupp. It consists of a rectangular steel block, b, Fig. 
 
 FIG. 100. 
 
 ioo, with rounded corners ; its front face being at right 
 angles to the axis of the bore, and its rear face slightly in- 
 clined to that axis. 
 
 This block slides transversely in a recess in the breech, 
 and when withdrawn leaves the breech open for loading. 
 It is locked in the firing position by a cam, c, entering a 
 corresponding recess in the breech, and this cam is operated, 
 and the block withdrawn and pushed home, by the lever- 
 handle, /. e is the extractor for withdrawing the empty 
 cartridge-case. It is a prismatic bolt, sliding in a groove in 
 the upper part of the breech, parallel to the axis of the bore, 
 and terminating in front in a hook, h. A tenon, /, on the 
 under side of the extractor, fits in the extractor-groove, k, 
 cut in the top of the breech-block. This groove is straight 
 for some distance, and then curves quickly to the rear. 
 When the block is withdrawn it moves in guides which are 
 parallel to its rear face, and which consequently give it a 
 motion such that the extractor is at first gradually with- 
 drawn, thus removing the empty case from its seat in the 
 chamber. 
 
 The tenon of the extractor then enters the inclined part, 
 a, of the groove in the block, and the extractor, with the 
 
234 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 IOI 
 
 cartridge-case, is drawn quickly backwards, thus ejecting 
 the case to the rear. The motion of the breech-block is ar- 
 rested by a stop-bolt, s, which is screwed through the upper 
 part of the breech, and enters the groove r on the top of 
 the block. 
 
 Ammunition. The ammunition is contained in a metallic 
 cartridge-case, and as this forms a gas-check, no accurate fit 
 of the parts of the mechanism is required, 
 and the breech-block works freely in its 
 slot. 
 
 The charge is fired with an ordinary 
 friction primer. The head of the case 
 is formed by a cup, c, inside, Fig. 101, 
 having five holes, a, in it. The exterior 
 is strengthened by a cup, b, having five 
 holes corresponding to a and a sheet- 
 iron disk, d, riveted to the cups and case, 
 and having a central hole, v. The flame 
 from the primer passes through the hole 
 v, and thence through a to the charge. 
 The gas-pressure from the charge forces the cups b and c 
 backwards, closing the hole v in d, and preventing the escape 
 of gas. The projectiles are shell and canister. In order to 
 use shrapnel, a heavier gun of 3-inch calibre has lately been 
 adopted, weight 218 Ibs. 
 
 FIELD GUNS. 
 
 132. U. S. Field Artillery 3.6-inch B. L. Mortar 3.2-inch B. L. 
 
 Field Gun, Light 3.6-inch B. L. Field Gun, Heavy. 
 The field artillery in the U. S. service consists of the 3.6- 
 inch mortar, 3.2-inch light field gun, and 3.6-inch heavy field 
 gun. 
 
 Common Features. See Figs. 102, 103, and 104. These 
 pieces are all built of gun-steel ; are breech-loaders, and have 
 rifled bores. They have conical gas-check seats, c, and cyl- 
 indrical powder-chambers, d, of larger diameter than the 
 bore, and these chambers are connected with the bore by a 
 conical slope, *, forming the seat for the rotating band of 
 the projectile, and by which it is centered in the bore. 
 
GUNS. 235 
 
 In front of this powder-chamber slope is a second conica, 
 slope, /, which is formed by cutting away the tops of the 
 lands of the rifling to a certain depth at the origin or begin- 
 ning of the rifling, and gradually decreasing the depth of 
 this cut to zero, at a certain distance from the origin, this 
 distance varying with the size of the piece. As a rule one 
 half of the lands are cut away at the origin. Thus for the 
 3.6-inch gun the depth of the rifling groove is 0.04 inch, 
 and the lands are cut away 0.02 inch at the origin. The ob- 
 ject of this rifling slope is to allow the band of the project- 
 ile to enter gradually to its full depth into the groove, and 
 thus diminish the strain due to forcing. It also facilitates 
 the loading of the projectiles, and tends to prevent the 
 escape of gas over the band, as the latter is forced readily 
 and quickly to the bottom of the groove. 
 
 3.6-INCH MORTAR. This is a short piece intended for 
 vertical fire against troops pro- _-, 
 
 tected by intrenchments or irreg- f 1^ 
 
 ularities of ground from the direct 
 fire of the field guns. 
 
 It is made of a single piece of 
 
 steel (Fig. 102), and is designed to FlG - I02 - 
 
 use the same kind of powder and the same projectile as the 
 
 3.6-inch field gun. 
 
 It is mounted upon a cast-steel carriage, and the weight 
 of piece and carriage are so adjusted that they can be read- 
 ily moved by hand. 
 
 3.2 AND 3.6-iNCH FIELD GUNS. The 3.2-inch gun (Fig. 
 103) is intended for use as a horse-artillery gun for rapid 
 movements, and the 3.6-inch (Fig. 104) for the light or field 
 battery. 
 
 Common Features. The two guns are exactly similar in 
 construction, and each consists of an interior tube, and a 
 jacket, assembled by shrinkage. 
 
 The tube is inserted in the jacket from the front ; a 
 shoulder, a, on the tube resting against a corresponding one 
 on the jacket. 
 
 Forward movement of the tube in the jacket is prevented 
 by the shoulder b, as shown in Figs. 103 and 104. The 
 
236 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 threads for the breech-block are cut in the rear end of the 
 
 jacket, which thus supports the 
 longitudinal stress. 
 
 The principal dimensions, 
 etc., are given in the table page 
 253, with those of the siege 
 guns, and of these, the weight 
 of piece, charge, and projectile 
 should be remembered. 
 
 133. Breech Mechanism of Field 
 Artillery Principal Parts 
 The Breech-block. 
 
 PRINCIPAL PARTS. The 
 breech mechanism comprises 
 those parts which are neces- 
 sary to open, close, and lock 
 the breech, to prevent the 
 escape of gas in firing, and 
 through which ihe charge is 
 ignited. 
 
 The principal parts are : 
 
 1. The breech-block, which 
 closes the breech and, by its 
 bearing on the fixed parts of 
 the gun, supports the gas-pres- 
 sure when the charge is fired. 
 
 2. The obturator, which 
 prevents the escape of gas. 
 
 3. The carrier-ring, which 
 guides the block as it is with- 
 drawn from the breech, sup- 
 ports its weight when with- 
 drawn, and by which it is 
 swung round, out of the way, 
 for loading. 
 
 4. The lever-handle or other 
 device by which the block is 
 
 r 
 
 FIG. 103. 
 
 FIG, 104. 
 
 rotated after firing, and its threads or bearings disengaged 
 from those in the breech of the gun. 
 
GUNS. 
 
 237 
 
 5. The vent, by which fire is communicated to the charge; 
 and the vent-closer, by which premature discharge is pre- 
 vented. 
 
 THE BREECH-BLOCK. In all guns in the U. S. service, 
 except the Hotchkiss mountain-gun already described, the 
 breech-block belongs to the French or interrupted-screw 
 system. That is, screw-threads are cut around the exterior 
 cylindrical surface of the block, and around the correspond- 
 ing interior cylindrical surface of the breech-recess. To 
 avoid the delay in unscrewing the block and screwing it 
 home after and before each discharge, the circumferences of 
 the block and breech-recess are divided in the field-guns into 
 six equal sectors, and the screw-threads on every alternate 
 
 FIG. 105. 
 
 sector removed, thus leaving on the block, and in the breech- 
 recess, three threaded and three slotted sectors of equal 
 width. By this arrangement the block can be pushed in or 
 pulled out of its recess, the threaded sectors on the block 
 sliding in the slotted sectors of the breech-recess. After it 
 is pushed home to within one sixth of a turn of the thread, 
 or one sixth of the pitch, a rotation through an angle of 
 60 will cause the threads on the block to engage in those 
 in the jacket, and the threads thus engaged are found to 
 have ample strength to resist the pressure of the powder- 
 gas. The threaded and slotted sectors of the block are 
 partly shown in Fig. 105. The exterior diameter of the 
 block at the threaded portion, is greater than that of the 
 
238 TEXT- BOOK OF ORDNANCE AND GUNNERY. 
 
 powder-chamber, in order to give as large a surface as possi- 
 ble for the screw-threads and thus increase their relative 
 strength, and also to leave a large opening in the breech to 
 facilitate the insertion of the projectile and charge. The 
 length of the block is greater than its exterior diameter, to 
 give a greater number of threads, and thus distribute the 
 pressure of the powder-gas over a greater number of them, 
 and reduce the stress on each, and consequently the ten- 
 dency to strip. The front face of the block is plane, and the 
 rear face has certain projections whose uses will be explained. 
 The diameter of the unthreaded portion in front is less than 
 that of the threaded portion, in order that it may enter for 
 a short distance into the gas-check seat in the rear end of 
 the tube. The rear end is not threaded, and has a shoulder, 
 a, upon it, which fits tightly against the rear face of the car- 
 rier-ring when the breech is closed, and thus prevents the 
 entrance of dust in transportation. The interior is bored 
 out for the reception of the parts of the obturator, and cer- 
 tain grooves are made on the exterior whose object will be 
 explained. 
 
 134. The De Bange Obturator Action Remarks. 
 
 The obturator prevents the escape of gas around the 
 threads of the breech-block and through the mechanism. 
 Two obturators are used in the field service : the De Bange, 
 with the 3.2 and 3.6 rifles, and the Freyre, with the 3.6 
 mortar. 
 
 THE DE BANGE OBTURATOR. This consists (Fig. 106) of 
 a central spindle or stem, a, terminating in front in a large 
 head, b, called, from its shape, the " mushroom-head "; the 
 vent, , with a copper bushing, d, in front, and the primer- 
 seat, e, in rear ; two steel cups, //', called gas-check cups, 
 and between them a plastic pad, g, made of asbestos and 
 tallow, strongly compressed by hydraulic pressure before 
 its insertion, and covered with canvas, the outer edges of 
 the pad being protected- by two thin strips of copper, m\ an 
 obturator-nut, h, held in place by a spline-screw, k, which is 
 halved into the nut and spindle ; and a spiral spring,/, bear- 
 
GUNS. 
 
 239 
 
 ing against a shoulder in the breech-block, and against the 
 front of the obturator-nut, h. 
 
 When in place in the gun, the spindle a passes through 
 the axis of the breech-block, the outer surface of the pad g 
 
 FIG. 1 06. 
 
 rests against the gas-check seat in the gun, and is held be- 
 tween the elastic gas-check cups//'. The mushroom-head 
 b is in the powder-chamber. 
 
 ACTION OF THE DE BANGE OBTURATOR. When the 
 charge is fired, the gas-pressure acts normal to the surface 
 of the mushroom-head, and the latter, with its spindle a, is 
 forced to the rear. The pressure is thus transmitted to the 
 gas-check cups //', and the elastic pad g, being held by 
 the front of the block and pressed between the cups //', is 
 forced to expand radially and pressed firmly against the 
 walls of the gas-check seat, preventing the escape of gas. 
 An elastic packing-ring, n, also expands under the pressure, 
 and, fitting tightly against the spindle a, prevents the flow 
 of the tallow of the pad, and thus avoids the sticking of the 
 pad to the spindle. When the pressure is removed, the 
 action of the spring j keeps all the parts, cups and pad, in 
 place. 
 
 The pad has the shape shown in order to have as small 
 a surface as possible in contact with the spindle and the 
 wails of the gas-check seat, to avoid sticking, and to furnish 
 
240 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 in the middle a reservoir of material that may be pressed 
 outward and inward and thus secure perfect contact. 
 
 REMARKS. The canvas cover of the pad prevents its 
 breaking in use. The shape of the gas-check cups is such 
 as to avoid all sharp angles which would cut the pad, and 
 to retain the edges of the cups for preventing the flow of 
 the tallow. The elastic packing-ring n also assists to pre- 
 vent this flow. The spline-screw k prevents the unscrewing 
 of the obturator-nut h, which is liable to occur when the 
 breech-block is rotated for withdrawing, owing to the stick- 
 ing of the pad to the walls of the gas-check seat. 
 
 135. The Freyre Obturator Action Remarks. 
 
 THE FREYRE OBTURATOR. This obturator (Fig. 107) is 
 used with the 3.6-inch mortar, and consists of a central spin- 
 
 XI 
 
 -c 
 
 FIG. 107. 
 
 die, a, terminating in front in a large flat disk ; the vent b and 
 its copper bushing, c, in front, and the primer-seat in rear ; 
 the threads and nuts, dd' , the rear nut, d ', being a locking- 
 nut with a left-hand thread, while the obturator-nut, d, has a 
 right-hand one, and hence d f prevents d from unscrewing 
 during the rotation of the block ; the spiral spring e t bear- 
 ing on a shoulder on the spindle a and a corresponding 
 shoulder in the block, and tending to push the spindle con- 
 stantly forward ; and the gas-check ring /. The exterior 
 surface,^, of the head of the spindle is conical, and ground 
 
GUNS. 241 
 
 to an exact fit with the interior surface of the conical gas- 
 check ring, /. This ring / is made of steel of high elastic 
 limit, and when in place, rests against the front face of the 
 breech-block as shown, and its length parallel to the axis of 
 the bore is such that when in this position there is a space, 
 h, between the head of the spindle and the front face of the 
 breech-block. When in place, the spindle a passes through 
 the axis of the breech-block, the outer surface of the elastic 
 gas-check ring / rests against the walls of the gas-check 
 seat, and the front surface of the spindle-head is in the 
 powder-chamber. 
 
 ACTION OF THE FREYRE OBTURATOR. When the charge 
 is fired, the gas, acting normal to the spindle-head, presses it 
 backward into the conical ring f, the space h allowing this 
 movement. The ring, /, being held against the face of the 
 breech-block, is thus forced to expand radially by the wedg- 
 ing action of the spindle-head, and is pressed firmly against 
 the walls of the gas-check seat, preventing the escape of gas 
 around the exterior of the ring. The tight fit of the two 
 conical surfaces prevents any escape between the ring and 
 head. When the pressure of the gas is removed, the elas- 
 ticity of the ring /and the action of the spring e return the 
 spindle-head and ring to their former positions. 
 
 REMARKS. This obturator has the following advan- 
 tages: 
 
 1. Being of metal, it is very slightly affected by changes 
 of temperature, weather, etc. 
 
 2. It occupies very little space in the powder-chamber; 
 and hence when space and consequently weight are impor- 
 tant, as with this mortar, it is used. 
 
 Its disadvantage is that it is liable to get out of order. 
 A blow struck on the thin edge of the ring f in loading, or 
 closing the breech, would allow the gas to escape; and 
 after a channel is once formed for the gas, the obturator 
 is useless. This accident is liable to occur in field service, 
 and to guard against it to some extent the spindle-head is 
 made to project well beyond the front edge of the ring. 
 This projecting portion would ordinarily receive any blow 
 which might injure the edge of the ring/. 
 
242 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 It will be observed that the spiral spring j in the De 
 Bange obturator, Fig. 106, acts in the opposite direction to 
 that of the Freyre, Fig. 107. The reason is as follows: The 
 gas-check ring in the Freyre being elastic, when proper 
 compression of this ring is once secured by the nuts dd r , it 
 will be retained unchanged. With the De Bange the pad is 
 not elastic, and hence il properly compressed before firing 
 this compression will change after firing, due to the great 
 pressure upon it. Hence a constant tension is always re- 
 quired with the De Bange to keep the cups and pad in 
 place, while with the Freyre the spring is used to push the 
 spindle forward, and assist in restoring the ring to its for- 
 mer position. 
 
 136. Carrier-ring Object of Latch. 
 
 CARRIER-RING. This ring guides the block, supports 
 its weight when it is withdrawn from the breech, and en- 
 .ables it to be swung round to one side of the gun, out of the 
 way of loading. It consists (Fig. 108) of a ring of steel, h, 
 
 \e 
 
 
 
 
 
 @ 
 
 / 
 
 i 
 \e 
 
 d' 
 
 
 
 i 
 
 
 
 
 108. 
 
 which surrounds the breech-block, and through which the 
 breech-block slides parallel to the axis of the piece. The 
 breech-block occupies the space a. On the interior there 
 are three lugs, b, the exact width of the slotted sectors of 
 
GUNS. 243 
 
 the block. These lugs bear in the slotted sectors, and fur- 
 nish guides for the block when it is drawn to the rear, so 
 that it is compelled to move parallel to the axis of the gun. 
 
 On the left-hand side is a stop, c, which travels in a 
 groove in the breech-block, and limits the motion of transla- 
 tion of the latter when it is withdrawn from the breech, and 
 also its motion of rotation, when turned to lock into the 
 threads of the breech of the gun, or unlocked for withdrawal. 
 This stop passes through the carrier-ring and is secured by 
 a screw, d. The stop may occupy any other convenient po- 
 sition, and may be a simple stud, as in the case of the mor- 
 tar, where the stop is at the top of the carrier-ring. 
 
 Two lugs, ee, are for the purpose of attaching the carrier- 
 ring to the jacket, by a pin which passes through holes in 
 the lugs, and corresponding holes in the jacket. This pin 
 forms the axis around which the carrier-ring, with the block, 
 swings, when the breech is open for loading. The exterior 
 surface, g, of the carrier-ring is conical, to secure a good fit 
 in the breech. 
 
 OBJECT OF LATCH. When the threads of the breech- 
 block are disengaged from the corresponding threads in the 
 breech, the block is pulled to the rear through the carrier- 
 ring. It is evident, however, that this pull upon the block 
 will cause the carrier-ring to swing around the pin passing 
 through the lugs e, and this will tend to jam the block, and 
 prevent its movement to the rear. To avoid this, the car- 
 rier-ring must be locked to the gun while the block is mov- 
 ing to the rear. When the travel of the block is finished, 
 the carrier-ring must be unlocked from the gun, in order 
 that it may be swung round with the block to the loading 
 position. These objects are accomplished by the latch /, 
 shown in Fig. 108 and in detail in Fig. 109. 
 
 137. Description of Latch and its Working. 
 
 The latch consists of a piece of metal shaped as shown in 
 Fig. 109. The lower inner end, 0, fits against one of the 
 slotted sectors of the breech-block, and is constantly pressed 
 down upon it by the action of the flat spiral spring b, acting 
 on a shoulder, c, of the latch and a corresponding shoulder, 
 
244 
 
 TEXT-BOOK Of ORDNANCE AND GUNNERY. 
 
 d, of the latch-recess. 
 
 a 
 
 b' 
 
 All the working parts are covered 
 by the latch-plate i (see Fig. 108), 
 secured to the exterior of the 
 carrier-ring by two screws, /, so 
 that in case any part breaks it may 
 be readily removed and repaired. 
 The front of the carrier-ring next 
 the breech has a hole, g, cut through 
 it, and opposite this is a recess, k, 
 in the corresponding face of the 
 latch. 
 
 Action of the Latch. Suppose 
 the breech closed and the gun 
 end of the breech-block is a trans- 
 
 FIG. 109. 
 
 fired. At the rear 
 
 verse groove, a, Fig. no, which is on a level with the slotted 
 
 sector of the block at c, and gradually increases in depth to 
 
 .--6 
 
 I 
 
 /JV1VJVTY 
 
 6J 
 
 a 
 
 
 
 
 [e 
 
 d (e) 
 
 
 
 
 
 ^- 
 
 
 
 <*^l 
 
 
 FIG. no. 
 
 its end, b. The depth of this groove at b is such that when 
 the inner end of the latch rests in it, the action of the flat 
 spiral spring, b, Fig. 109, will force the latch down sufficiently 
 far to release it from the jacket. The inner end of the latch 
 rests at b during firing, and hence at this time the carrier- 
 ring is unlocked from the jacket, and there is no strain on 
 the latch. After firing, the first operation in opening the 
 breech, is to rotate the block in the direction of the arrow. 
 As the latch is in the carrier-ring, it does not rotate with the 
 block, and hence the action of the groove a is to push up 
 the latch into its recess in the breech, and thus lock the car- 
 rier-ring to the jacket. The inner end of the latch now 
 stands at c. The block is now withdrawn, the inner end of 
 
GUNS. 
 
 245 
 
 the latch sliding along the slotted sector, and keeping the 
 carrier-ring locked to the jacket. This continues up to the 
 point d. 
 
 At this point, the path of the inner end of the latch be- 
 gins to descend along a gradual slope from d to e. Hence 
 by the action of the flat spiral spring, the latch begins to 
 move out of the jacket, being forced inward into the groove 
 de. At the end of the travel of the block, corresponding to 
 the point e, the depth of the groove de becomes sufficient 
 to allow the entire withdrawal of the latch from its recess 
 in the jacket, and hence at this instant the carrier-ring 
 becomes unlocked, and the block and ring can be swung 
 round for loading. 
 
 After Loading. After loading, when the block and car- 
 rier-ring are swung round to close the breech, the pressure 
 of the hand is applied to the rear end of the block. This 
 pressure would tend to move the block forward through 
 the carrier-ring, and hence jam the ga^-check against the 
 breech. The block must therefore be locked positively to 
 the carrier-ring in the loading position, and this is done as 
 follows : 
 
 The extremity e of the groove a in the block, termi- 
 nates in a cylindrical hole, into which the inner end of the 
 latch drops at the end of its motion. The block therefore 
 cannot move with reference to the carrier-ring, till the latch 
 is lifted from this hole e. This is accomplished as fol- 
 lows : 
 
 There is a conical stud, s (see Fig. 109), projecting from 
 the rear face of the base ring, which, as the carrier-ring is 
 closed, passes through the hole g, Fig. 109, in the front face 
 of the carrier-ring, and enters the recess // in the front of 
 the latch. This stud, bearing against the inclined end of the 
 recess /*, owing to the shape of the two surfaces, raises the 
 latch slightly till it clears the cylindrical hole e, Fig. no, 
 and stands at such a height that when the block is pushed 
 forward, the lowest part of the inclined surface de will pass 
 under the inner end of the latch, and thus cause it to move 
 up the inclined surface and push the latch home. 
 
246 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 138. The Lever-handle. 
 
 This is a device for rotating the breech-block. In the 
 mortar there are two of these handles fixed to 
 the block at opposite extremities of a diameter 
 (Fig. in). 
 
 In the 3.2 and 3.6-inch guns there is one 
 handle, h, pivoted to the upper part of the 
 block by a pin, e, Fig. 112. This handle is 
 raised vertically for rotation ; and when low- 
 ered for firing, its lower end fits into a recess, 
 c, in the end of the jacket, for additional secur- 
 ity against accidental opening. To limit the 
 vertical motion of the handle when it is raised, 
 a stop, a, is placed upon the pin e, which abuts 
 against a corresponding stop, b y on the lug /. 
 The head d of the lever-handle, is eccentric, 
 and forms a cam, with the following objects: 
 When the block is in the firing position, this 
 cam d enters a corresponding recess, r, in the 
 rear face of the carrier-ring, and thus locks the 
 FIG. i ii^ block to the ring, and with the end of the lever- 
 handle, as before explained, prevents any rota- 
 tion of the block in firing. When, after firing, the lever- 
 handle is raised and the block rotated, if an attempt be made 
 
 FIG. 112. 
 
GUNS. 
 
 247 
 
 to withdraw the latter, it sometimes fails on account of the 
 sticking of the pad in its seat. If the lever-handle be now 
 lowered, the surface of the cam d bears against the rear face 
 of the carrier-ring, since no recess is cut for it in this posi- 
 tion, and thus exerts a powerful leverage, sufficient to start 
 the pad from its seat. 
 
 The lever-handle is made to work tight between its lugs 
 in the block, in order that it may not fly up from its recess 
 in the carrier-ring, by the shock of discharge. 
 
 In the 3.2 and 3.6 guns there is a fixed bronze handle, g, 
 attached to the breech-block for the purpose of withdraw- 
 ing it. 
 
 139. The Vent-cover. 
 
 This is a device to prevent the insertion of a primer, and 
 the premature discharge of the piece, before the breech- 
 block is locked. It must be so arranged that the vent will 
 be closed at all times, except when the threads of the block 
 are engaged in those of the breech. 
 
 3.6 Mortar. For the 3.6 mortar the device is as follows: 
 A handle, a, Fig. 113, is attached to a shaft, b, which fits 
 
 FIG. 113. 
 
 into a recess on the left side of the breech-block. The 
 shaft is shown in cross-section at c. When turned into the 
 
248 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 position shown in the figure, so that the vent is open, the 
 corner d projects through the block, and binds against the 
 edge of one of the lugs / in the carrier-ring, so that when 
 in this position, with the vent uncovered, the breech-block 
 cannot be rotated to open the breech. The piece e is 
 attached to the shaft b, and closes the vent. When open or 
 closed, its ends rest on two pins, /, which retain it in posi- 
 tion, and its motion in opening or closing is limited by two 
 studs, g. In order to rotate the breech-block, the vent must 
 first be closed by turning the shaft b upwards by the handle 
 a. The corner d of the shaft then no longer bears on the 
 edge of the lug in the carrier-ring, and the surface // forms 
 part of the exterior curved surface of the block. 
 
 3.2 and 3.6 Guns. For these guns a radial slot, a, Fig. 1 14, 
 
 FIG. 114. 
 
 is made in the rear part of the breech-block which projects 
 outside the carrier-ring. In this slot slides a piece of metal, 
 b, having a pin, c, projecting from its forward face next the 
 breech of the gun. A groove, d, is cut in the rear face of 
 the carrier-ring, which is eccentric at its lower end, and the 
 pin c bears in this groove. 
 
 When the block is pushed home, the pin enters the 
 groove at e, and its weight keeps it over the vent, as it 
 stands in a vertical position during the time the block is 
 withdrawn. As the block is rotated to the right in closing, 
 the vent is still covered, due to the bearing of the pin c in 
 the concentric part of the groove d. At the last instant of 
 rotation, however, the pin c enters the eccentric part of the 
 groove d, the vent-closer is lifted, and the vent uncovered. 
 
GUNS. 
 
 249 
 
 140. Action of Mechanism of 3.6-inch Mortar. 
 
 i. Suppose the breech closed and ready for firing. In 
 this position, the threads of the block are engaged in those 
 of the gun, the gas-check is in its seat, the vent-cover has 
 been moved to the right, or downward, by hand, thus uncov- 
 ering the vent. By this motion of the vent-closer, the corner 
 of the shaft, as before explained, has been caused to project 
 beyond the surface of the block, and to bind against the 
 edge of one of the lugs of the carrier-ring, so that the block 
 cannot be rotated while the vent is open. The inner end of 
 
 the carrier- ring latch is in the extremity d of the transverse 
 groove e, Fig. 115, the outer end has left its recess, g, in the 
 gun, and the carrier-ring is unlocked from the jacket. 
 
 2. After firing, the elasticity of the spiral spring and of 
 the gas-check ring acts to move the ring from its seat in the 
 gun, and restore it to its former position before firing. 
 
 The vent-closer/is now turned upward, closing the vent, 
 and at the same time unlocking the block from the carrier- 
 ring, so that it may be turned to the left by the handles a a. 
 The block is then turned to the left 60. By this operation, 
 the threaded sectors on the block come into the slotted 
 sectors in the breech, so that the block can be pulled to the 
 
TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 rear through the carrier- ring. While the rotation of the 
 block is taking place, the inner end of the carrier-ring latch 
 is moving up the inclined groove <?, and the outer end of the 
 latch has been pushed into the recess g in the jacket, thus 
 locking the carrier-ring to the jacket. The block is now 
 pulled to the rear through the carrier-ring till its motion is 
 stopped by the stop b in the carrier-ring striking against the 
 front shoulder, b', of the longitudinal groove k. During this 
 motion of the block the inner end of the carrier-ring latch 
 is bearing on the surface of one of the slotted sectors, and 
 the carrier-ring remains locked to the gun. Near the end of 
 the motion of the block, however, the inner end of the latch 
 begins to descend along an inclined groove, /i, in the surface 
 of the block, and the outer end, due to the action of the flat 
 spiral spring before described, is withdrawn from its recess, 
 g, in the gun. At the end of the travel of the block, this with- 
 drawal of the latch is complete, and the inner end of the 
 latch drops into a cylindrical hole, i, at the end of the inclined 
 groove, thus locking the block to the carrier-ring. The 
 block and carrier-ring are now swung round by hand out of 
 the way for loading. 
 
 3. To close the breech the block and carrier-ring are 
 swung round into place. As the carrier-ring closes against 
 the breech, a conical stud, s, Fig. 109, on the rear face of the 
 latter enters a recess in the front of the latch, and lifts the 
 inner end of the latter out of the cylindrical hole i in the block. 
 The block is now pushed forward by hand, sliding through 
 the carrier-ring, the latch is pushed up into its recess in the 
 jacket by the action of the inclined surface h on the block, 
 and the forward motion of the block is continued till the 
 rear end of the groove k strikes against the stop b. The 
 block is then rotated to the right 60, engaging its threads 
 in those of the breech. At the same time the inner end of 
 the latch moves down the inclined transverse groove *, and 
 the upper end of the latch is withdrawn from its recess g in 
 the gun, thus unlocking the carrier-ring from the gun. The 
 rotation of the block to the right is limited by the stop b 
 striking against the shoulder b" at the end of the transverse 
 groove j. The vent-closer is then turned down by hand, 
 
GUNS. 
 
 251 
 
 thus opening the vent and locking the block to the carrier- 
 ring, and the mechanism is in its firing posi- 
 tion. 
 
 The action of the mechanism of the 3.2 and 
 3.6 field-guns is exactly similar, except that the 
 vent-closer is automatic. 
 
 SIEGE-GUNS. 
 
 141. 5-inch Gun 7-inch Howitzer 7-inch Mortar. 
 Siege-guns are intended for attacking and 
 defending permanent inland works, and the 
 land fronts of sea-coast fortifications. 
 In the U. S. service the pieces are : 
 
 The 5-inch siege-gun ; 
 
 The 7-inch howitzer; 
 
 The 7-inch mortar. 
 
 Common Features. These guns, like the 
 field-guns, are built of gun-steel, and are breech- 
 loading with rifled bores. They have conical 
 gas-check seats, and cylindrical powder-cham- 
 bers of larger diameter than the bore, with 
 which they are connected by a conical slope 
 for centering the projectile. They have also 
 the conical rifling slope or forcing-cone, formed 
 as explained in the field-guns, and for the same 
 purpose. 
 
 5-iNCH SIEGE-GUN. This gun is intended ^ 
 for direct fire in siege operations. It is built 
 up (Fig. 116) of a tube, jacket, trunnion-hoop, 
 a, sleeve, b, locking-ring, c, key-ring, d, and 
 base-ring, f. The tube is inserted into the 
 jacket from the rear. The peculiarity of this 
 gun is the manner of assembling the trunnion- 
 hoop. It would be preferable to have the 
 jacket and trunnion-hoop in one piece, as in 
 the field-guns, but difficulties in making such 
 a forging of the required physical qualities 
 prevent this, and hence the jacket is extended 
 
 ll'.'025 
 
 FIG. 
 
 116. 
 under the trunnion-hoop to give better support to the tube, 
 
2 5 2 
 
 TEXT-BOOK OF ORDNANCE, AND GUNNERY. 
 
 and the trunnion-hoop assembled over the front of jacket 
 
 as shown. 
 
 The surface of contact of jacket and trunnion-hoop is a 
 
 cone, with the larger base to the front,and this tends to lock 
 
 the trunnion-hoop in place, and prevent any forward motion. 
 Relative motion of tube and jacket is prevented by the 
 shoulder e and base-ring f. The locking-ring 
 c prevents forward movement of the sleeve 
 b, which is important, as the trunnion-hoop 
 abuts against b, and hence brings a thrust 
 upon it when the piece is fired. 
 
 /-INCH HOWITZER. This is a compara- 
 tively short, light piece, of large calibre, in- 
 tended to carry a shell, with a large bursting 
 charge, and to give a high-angle or curved 
 fire, and reach troops sheltered by a parapet, 
 and also to breach masonry protected by 
 an earthen cover, to destroy earthworks, etc. 
 It is built up of a tube, a jacket, a trun- 
 nion-hoop, a sleeve, a locking-ring, a key-ring, 
 and a base-ring, assembled by shrinkage (Fig. 
 117). The construction is shown in the fig- 
 ure. The tube is inserted into the jacket 
 from the rear, and has a shoulder at e which 
 prevents forward motion. The longitudinal 
 stress is transmitted from the trunnions to 
 the jacket through the locking-lip a, and for- 
 ward motion of the sleeve b is prevented by 
 the locking-ring c. The key-ring d is shrunk 
 over the locking-ring. 
 
 7-iNCH MORTAR. This is a short rifled 
 piece intended to carry the same shell as the 
 7-inch howitzer, and give a vertical fire. It 
 
 FIG. 117. 
 
 is built of a single piece of forged gun-steel (Fig. 118), and 
 resembles the 3.6-inch field-mortar. 
 
 Breech Mechanism. The breech mechanism of the 5-inch 
 siege-gun and 7-inch howitzer, are similar to that of the 3*2- 
 inch gun already described. The breech mechanism of the 
 7-inch mortar differs from that of the 3.6 mortar in the fol- 
 lowing particulars : 
 
GUNS. 
 
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254 
 
 TEXT- BOOK OF ORDNANCE AND GUNNERY. 
 
 FIG. 118. 
 
 1. It has the De Bange gas-check. 
 
 2. The vent-closer is a sliding piece which is moved over 
 the vent by turning a handle similar to that in the 3.60 
 
 mortar. This turning of the handle to open 
 the vent locks the breech-block to the carrier- 
 ring. 
 
 The principal data relating to the field and 
 siege artillery are given in the table on page 
 253- 
 
 SEACOAST GUNS. 
 
 142. Calibres Common Features 8-inch Rifle. 
 
 CALIBRES. The guns at present adopted 
 for the U. S. seacoast service are : 
 
 8-inch \ 
 
 lo-inch v steel B. L. rifles; 
 
 12-inch ) 
 
 12-inch steel B. L. mortar; 
 
 12-inch rifled mortar, with cast-iron body and 
 
 steel hoops. 
 
 COMMON FEATURES. The guns are intended for direct 
 fire against armored ships; the mortars, for vertical fire 
 against the decks of war ships. The seacoast guns, with the 
 exception of the 1 2-inch mortar with cast-iron body, are 
 built up of gun-steel, and are breech-loading \vith rifled 
 bores. They have conical gas-check seats, cylindrical pow- 
 der-chambers, which are connected with the bore proper by 
 a conical slope, and they have also the rifling slope, called 
 the forcing-cone, already described in the field and siege 
 services. 
 
 THE 8-INCH GUN, Fig. 119, is composed of a tube, T, in- 
 serted into the jacket from the rear, a jacket, J, two C or 
 chase hoops, one D hoop, four reinforce or A hoops (A^ 
 being the trunnion-hoop), and a base-ring, R. 
 
 Relative motion of tube and jacket is prevented by the 
 shoulder a and the base-ring. The other shoulders on the 
 tube reduce its thickness by successive steps from rear to 
 muzzle. C^ and C^ hoops are locked together by a locking- 
 lip, g, as shown, Fig. 120, the smaller diameter of the lip, 
 T 2 being expanded sufficiently by heat to pass over the 
 
G UNS. 
 
 255 
 
 larger diameter of C\. This prevents relative motion of C l 
 and C z hoops. The C hoops in all guns have a tendency 
 to move forward, probably due to the vibration 
 T of the chase and other causes, and to prevent this, 
 four pins, /, Fig. 121, pass through the C^ hoop 
 radially into the tube. The D hoop overlaps the 
 joint between jacket and C l and by means of the 
 shoulders at c and c', locks the 6\ hoop to the 
 jacket, and hence the jacket and \ are not locked 
 together by a lip. The small ring e is called a 
 filling-ring. It is necessary, because in assembling 
 the D hoop it is desirable to make a tight contact 
 at the shoulders c and c' . The rear end of D is 
 therefore made of such length as when hot to fill 
 the space from c to jacket-shoulder. Hence when 
 cold there will be an opening at b, which is filled 
 
 FIG. 120. 
 
 FIG. 121. 
 
 by turning out a groove, and driving into it a split 
 ring of metal, e. This gives stiffness to the chase. 
 The trunnion or A t hoop abuts against a shoulder 
 on the jacket at d. The longitudinal strain due to 
 firing is then distributed along the jacket from 
 the base-ring to the shoulder d. 
 
 The reinforce or A hoops are not locked, be- 
 cause there is no tendency to slide in these hoops, 
 and the reinforce does not require stiffening. 
 
 As a rule, it may be observed that the locking 
 of hoops together is for two purposes : 
 
 1. To obtain longitudinal stiffness. 
 
 2. To prevent sliding. 
 
 Hence reinforce-hoops need no locking, and 
 chase-hoops are not locked when the joint be- 
 
 FIG. 119. 
 tween them is overlapped by an exterior hoop. 
 
2 5 6 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 143. The 10 and 12-inch Rifles. 
 
 In these guns (Fig. 122) the tube is inserted into the 
 jacket from the front, as in the field-guns, and the breech- 
 _ screw threads are cut in the jacket. 
 
 The parts of the 10 and 1 2-inch guns are : 
 
 One tube ; 
 One jacket ; 
 Two C hoops ; 
 One D hoop ; 
 Three A hoops ; 
 Three B hoops ; 
 Four securing-pins, f\ 
 One filling-ring, e. 
 
 The following features of construction may 
 be noted : There are relatively few pieces, and 
 consequently the hoops are very long. This 
 gives great longitudinal stiffness. The chase- 
 hoops are locked together by a locking-lip, g, 
 and the sliding of these hoops prevented by the 
 four pins/. 
 
 In the 10 and 12-inch guns there is no shoul- 
 der in the jacket to prevent forward motion of 
 the tube. This motion is therefore prevented 
 by the bearing of the C^ hoop against the shoul- 
 der a on the tube, and the C l hoop is held in 
 place by the D hoop locking over two shoul- 
 ders, one on the jacket at c', and the other on 
 the C l hoop at c. 
 
 The D hoop is shrunk on over these shoul- 
 ders as shown in the figure, locking the jacket 
 and (7, hoop together ; and as tight joints must 
 be made at c and c', the length of the D hoop 
 must be such as to exactly fill the space between 
 b and the shoulder on the jacket at c' when hot. 
 Hence when cold it will leave an open joint at 
 '7, and this is filled by turning out a groove and 
 putting in the filling-ring e. It will be observed 
 FIG. 122. that this same construction is used in the 8-inch 
 
GUNS. 
 
 257 
 
 FIG. 126. 
 
 FIG. 123. FIG. 124. FIG. 125. FIG. 127. 
 
2 5 8 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 gun; but it is of greater importance here, as the C l hoop is 
 depended on to hold the tube in place, while in the 8-inch 
 
 gun a shoulder on the jacket does 
 this. The A 3 hoop has a shoulder, 
 m, near its rear end which fits over 
 a corresponding shoulder on the 
 jacket. By the shrinkage of the A 3 
 hoop on the jacket it has a firm hold 
 on the latter, and hence this shoul- 
 der on the jacket, bearing against 
 the shoulder on A 3 , strengthens the 
 jacket longitudinally, since it dis- 
 tributes a portion of the pull of the 
 breech-block to the A a hoop. The 
 forward thrust of the trunnion-hoop 
 B l is transmitted to the shoulder n 
 on the A l hoop, and from the A l 
 hoop to the jacket by the shoulder d. 
 Thus the jacket takes the longitudi- 
 nal strain in all cases. Figs. 123 to 
 127 show the 8, 10, and 1 2-inch guns 
 drawn to the same scale and giving 
 their relative sizes, and also the 12- 
 inch mortars, which are to be de- 
 scribed. 
 
 144. 12-inch Steel Mortar 12-inch Cast- 
 iron Mortar, Steel-cooped. 
 12-iNCH STEEL MORTAR. This 
 mortar, Fig. 128, is composed of 
 
 One tube ; 
 One jacket; 
 Two C hoops ; 
 One D hoop ; 
 Three A hoops ; 
 One base-ring. 
 
 The tube is inserted into the 
 jacket from the rear, as in the 8-inch 
 
 As the 
 
 FIG. 128. 
 
 FIG. 129. 
 gun, and the shoulder a prevents motion of tube. 
 
GUNS. 259 
 
 piece is short, and therefore stiff, the C hoops are not locked, 
 but four radial securing-pins are inserted in the muzzle-hoop 
 to prevent sliding. 
 
 12-iNCH MORTAR WITH CAST-IRON BODY, STEEL-HOOPED. 
 This mortar, Fig. 129, was designed before the 1 2-inch 
 steel mortar, with the object of procuring a high-power 
 B. L. mortar which would be cheap and could be made in 
 large quantities. The value of mortar-fire depends on group- 
 ing a large number of mortars in one place and under the 
 control of one person, who can thus drop a number of pro- 
 jectiles in a given area, and compensate by the number of 
 shots for the lack of accuracy. Hence the necessity for 
 cheapness. It is found, however, that the steel mortar has 
 greater power and endurance, and it is possible that the 
 manufacture of cast-iron mortars will be abandoned. 
 
 The mortar consists of 
 
 The cast-iron body ; 
 Five A hoops ; 
 Six B hoops. 
 
 The only point in the construction that requires notice 
 is that the A b hoop is shrunk on the cast-iron body over two 
 shoulders, ad. This is for the purpose of strengthening the 
 cast iron longitudinally against the pull of the breech-block, 
 and is similar to the method adopted in the 10 and 12-inch 
 
 145. Breech Mechanism Block Obturator Anti-friction Washers 
 and Spring. 
 
 The breech mechanisms of the 8, 10, and 12-inch guns 
 are essentially the same. That for the mortar differs in 
 some respects from the guns. 
 
 The essential parts of the mechanism are : 
 
 The breech-block ; 
 The obturator ; 
 The console or tray ; 
 
 The device for rotating and withdrawing the breech- 
 block ; 
 The vent and vent-closer. 
 
26o 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 BREECH-BLOCK. This resembles the blocks already de- 
 scribed for the field and siege artillery. In the 8-inch gun 
 there are three threaded and three slotted sectors ; in the 
 10 and 12-inch, four. 
 
 The rear end of the block is left unthreaded for some 
 
 TUBE. 
 
 i 
 
 *> FULL SIZE.- 
 
 FIG. 130. 
 
 distance, ab, Fig. 130. The cylinder of metal thus formed, 
 
 fits accurately into the breech-recess, when the block is 
 
 home, and prevents the entrance of sand or dust, which 
 
 might cause jamming of the threads. 
 
 OBTURATOR. This is the De Bange system modified, 
 
 and differs from that used in the field and siege services as 
 
 follows (Fig. 130) : 
 
 The front cup is replaced by a split steel ring,*:, shown in 
 
 detail in Fig. 131, fitted against 
 the outer portion of the mush- 
 room-head. The rear gas-check 
 cup is replaced by a flat disk of 
 steel, d, fitting tightly against 
 the front of the block. A split 
 steel ring, ^, similar to <:, takes 
 the place of part of the outer 
 edge of the gas-check cup for- 
 merly used, and another split 
 ring,/, fits against the spindle. 
 
 When the gas-pressure acts, these rings expand, and pre- 
 
 FIG. 131. 
 
GUNS. 26l 
 
 vent the flame and gas from reaching the covering of the 
 gas-check pad, and also from penetrating in the direction of 
 the spindle. When the pressure is relieved the rings resume 
 their normal size, and tend to cause the pad to leave its seat 
 in the gun, and thus prevent sticking. 
 
 ANTI- FRICTION WASHERS AND SPRING. In all guns 
 using the De Bange fermeture, the pad is liable to stick in 
 its seat after firing, and render the breech difficult to open. 
 This is provided for in the field and siege guns by the cam 
 -action of the head oi the lever-handle, as has been ex- 
 plained. 
 
 In the sea-coast service, the lever-handle is not used for 
 rotating the block, as it is not sufficiently powerful, and the 
 following arrangement is adopted to overcome the sticking 
 of the pad : 
 
 By referring to the field-gun mechanism, it will be seen 
 that there is a spring,/, between the obturator-nut h, Fig. 106, 
 and the shoulder in the block. Hence when the block is 
 rotated, it moves back ^ of the pitch of its thread, compress- 
 ing this spring and allowing the pad to remain fast in its seat. 
 At the end of the rotation the cam action of the lever-handle 
 draws out the pad from its seat. 
 
 In the large guns, the spring is replaced by two anti- 
 friction washers of steel, g, and two of brass, h, of the shape 
 shown in Fig. 130. Each alternate washer is of brass, so that 
 two metals of the same kind shall not rub against each other. 
 A cup-shaped spring i jests against a shoulder on the front 
 nd of the obturator-nut /, and bears on the shoulder of the 
 block. This spring acts as a cover to keep out dust. The 
 action is as follows : 
 
 When the block is rotated, it moves back \ or -J of the 
 pitch of its thread. This brings a pressure upon the 
 washers, which is thence transmitted to the obturator-nut, 
 and by this pressure the pad is loosened in its seat. The 
 object of the anti-friction washers is to allow this rotation 
 of the block to occur independently of the spindle, and this 
 is done by diminishing the lever-arm of the friction. 
 
 r s - r' 3 
 The value of this arm is, from mechanics, 7^-, in 
 
262 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 which r and r' are the exterior and interior radii of a ring. 
 By giving a double-convex section to the washers, r is de- 
 creased and r' increased ; and hence the moment of the fric- 
 tion with reference to the axis of the spindle is sufficiently 
 decreased to allow the spindle to stand fast while the block 
 rotates. 
 
 146. Apparatus for Rotating and Withdrawing the Breech-block 
 
 The Tray The Translating Screw. 
 
 ROTATING DEVICE. The lever-handle cannot be used 
 for rotating the breech-block in sea-coast guns owing to its 
 
 FIG. 132. 
 
 lack of power. The device adopted is called the " rotating- 
 ring," and is shown in Fig. 132. 
 
 It is a ring of steel encircling the breech-block, and hav- 
 ing a lug, a, the exact width of one of the slotted sectors, 
 projecting on the interior. This lug enters one of the 
 slotted sectors of the block, and the remainder of the in- 
 terior circle is of such diameter that the breech block will 
 slide through it. On the exterior there is a projecting 
 toothed sector, b, which gears into a pinion, p. When the 
 pinion is rotated by a crank, , motion is communicated 
 
G UNS. 
 
 26j 
 
 to the rotating-ring, and through the lug a to the block. 
 The rotating-ring is held in place against the rear face of 
 the breech, by a steel plate, called the " breech-plate," 
 which allows rotation, but prevents any other motion. The 
 rotation of the ring and block is limited to an angle of 
 60 or 45, according to the gun, by the surfaces c c' strik- 
 ing against corresponding surfaces in the breech-plate. The 
 rotation of the block having been completed, it can be 
 
 REAR END VIEW. 
 FIG. 133. 
 
 withdrawn from the breech, sliding through the rotating- 
 ring. 
 
 THE TRAY OR CONSOLE. In the field and siege guns, 
 the block, when withdrawn, is supported by a carrier-ring. 
 In the sea-coast guns, this method will not answer, as the 
 carrier-ring does not furnish sufficient bearing-surface to 
 support the block. A tray is therefore used for this pur- 
 pose, and is shown in Fig. 133. 
 
 It is made of brass, and is hinged to the rear face of the 
 breech, by a steel pin passing through the hub b. 
 
264 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 The tray swings around this pin, and with the block may 
 be rotated to the right, out of the way for loading. 
 
 TRANSLATING-SCREW. Near the middle of the tray is a 
 
 hole, c, which is threaded, and a 
 slot c r is cut in its top, parallel to 
 the axis of the hole. In this hole 
 FlG - I34> c, works a double-threaded screw 
 
 called the translating-screw, Fig. 134, the threads being 
 right and left handed, and one of them 
 narrower and more shallow than the 
 other. The shallow thread engages 
 in the corresponding thread in the 
 hole c, Fig. 133, so that the screw 
 when turned, will move in or out of 
 the tray. On the rear end of the 
 breech - block there is a projecting 
 stud, b, Fig. 135, called the translating- 
 stud. When the breech - block has 
 rotated one sixth of a turn to the left, this stud moves 
 down, and engages in the larger thread of the translating- 
 screw. Hence when this screw is rotated, it withdraws the 
 block from its recess with a motion equal to the sum of the 
 pitches of the two threads, for each revolution of the screw. 
 
 147. Remaining Parts of Breech Mechanism Guide-rails Guide- 
 grooves Side-latch Tray Latch. 
 
 On each side of the tray (Fig. 133) are two projections, 
 aa' , equidistant from the screw. They are called the 
 " guide-rails." 
 
 On the under side of the breech-block, at equal distances 
 from the translating-stud, are two grooves, aa', Fig. 135, 
 called " guide-grooves." These grooves do not extend the 
 whole length of the block, but end abruptly at shoulders. 
 When the block is withdrawn by the translating-screw, the 
 guide-grooves slide on the guide-rails, which thus furnish the 
 bearing for the block, and the block continues its movement 
 to the rear till it is suddenly stopped by the striking of the 
 shoulders of the grooves aa' on the front ends of the guide- 
 rails of the tray. 
 
GUNS. 265 
 
 During this motion of the block the translating-stud b, 
 Fig. 1 35,. travels in the slot c r , Fig. 133, being always engaged 
 in the larger thread of the translating-screw. 
 
 SIDE LATCH. When the block has reached the end of 
 its travel, the tray and block are swung by hand to the right 
 for loading. 
 
 To hold the tray and block in this position, and prevent 
 the accidental closing of the breech, by the swinging in of 
 the tray, a catch is provided on the under side of the tray, 
 and a side latch on the breech of the gun. This latch catches 
 the tray as it swings around, and retains tray and block till 
 the latch is lifted by hand. 
 
 TRAY -LATCH. When the tray and block are swung 
 around after loading, into the position for the insertion of 
 the block in the breech, the block is moved forward along 
 the tray by the translating-screw. 
 
 But in order that the block may enter its recess in the 
 breech, the tray must fit accurately against the rear face of 
 the breech, so that the guide-rails shall be parallel to the 
 axis of the bore. 
 
 Again, as soon as the block enters its recess and begins 
 to bear on it, the thrust of the translating-screw will tend to 
 move the tray back from the breech. There must be some 
 arrangement, therefore, to latch the tray against the breech, 
 and hold it in that position till the block is home, and this is 
 the object of the tray-latch. This latch fits into a recess, d, 
 Fig. 133, in the lower part of the tray, and engages in a cor- 
 responding recess in the breech of the gun. It is shown in Fig. 
 136. It is constantly acted on by the spring-lock^ which keeps 
 it engaged in the recess in the 
 breech of the gun. The upper 
 end of this lock bears against 
 the translating-screw in the 
 tray, and hence the lock can 
 
 rise and the tray be unlatched 
 
 FIG. 136. 
 only when the end of the 
 
 translating-screw is beyond the lock c. This happens When 
 the block is withdrawn. The sudden shock of the block 
 striking against the guide-rails in its outward motion, is 
 
266 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 FIG. 137. 
 
 communicated to the latch, and acting obliquely, a force 
 perpendicular to the axis of the latch is developed, of 
 sufficient intensity to disengage it automatically from the 
 breech. 
 
 148. Vent-cover Action of Breech Mechanism. 
 
 VENT-COVER. This consists of a flat piece of steel, a, 
 Fig. 137, pivoted loosely in the breech-block. 
 
 The head of this piece bears against the inner surface of 
 the breech-recess as the block rotates, 
 and hence it cannot move around the 
 pivot, but remains in the same radial 
 position covering the vent. At the 
 end of the rotation of the block, when 
 the threads are engaged in those of 
 the breech-recess, the head drops into 
 a groove cut for it in the breech 
 recess, and the vent-closer assumes 
 the position a', uncovering the vent. 
 When the block is rotated to the left for unlocking, the first 
 motion brings the head to its bearing against the breech-re- 
 cess, and thus closes the vent. 
 
 ACTION OF BREECH MECHANISM Breech Closed. In this 
 position of the block its threads are engaged in those of 
 the breech-recess, the gas-check is in its seat in the tube, 
 the vent-cover has moved to the right, uncovering the 
 vent, the tray is latched to the breech by the tray-latch, 
 and the translating-screw is in its recess as far as it will 
 enter. 
 
 To Open the Breech. Turn the crank attached to the pin- 
 ion of the rotating-ring, in the direction indicated by the 
 arrow on the breech. This motion is communicated to the 
 rotating-ring through the toothed sector, and from this 
 ring to the breech-block, by the lug which enters its slotted 
 sector. As the block begins to rotate to the left, the vent- 
 closer closes the vent as explained. When the block has 
 rotated one sixth of a turn, the translating-stud enters the 
 thread of the translating-screw in the tray. This screw is 
 then rotated by its crank, and the block withdrawn from its 
 
GUNS. 
 
 267 
 
 recess in the breech. At the end of its travel tne shoulders 
 on the block strike against the ends of the guide-rails on 
 the tray, and the shock disengages the tray-latch from the 
 
 FIG. 138. 
 
 breech. The tray and block can now be swung around for 
 loading. 
 
 To Close the Breech. Lift the side latch; swing the tray 
 and block around to the left till the tray-latch is engaged 
 
268 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 in its recess in the breech. The block is now driven home 
 by the translating-screw. 
 
 Rotate the block to the right by the rotating-crank, and 
 when the rotation is finished, the block will be in the posi- 
 tion first described and the gun ready for firing. 
 
 The mechanism for the 10 and 12 inch guns is so similar 
 to this that no special description is necessary. 
 
 149. Breech Mechanism of 12-inch Mortar. 
 
 In this piece the mechanism differs from that of the guns 
 as follows: 
 
 Rotating Device. On the rear face of the breech-block is 
 fixed a steel plate, k, Fig. 139, called a face-plate. The upper 
 
 FIG. 139. 
 
 end or stem of this face-plate is cut out, and carries two gears, 
 a, b, and on the exterior a third gear, c, on the same shaft 
 with b. Motion is communicated to these gears by the 
 crank d. On the rear face of the breech is a circular rack e, 
 with which the gear c engages, when the block is pushed 
 home. It is evident that a rotation of the crank d will cause 
 the face-plate and block to rotate to the right, or a reverse 
 motion of the crank, when the breech is closed, will cause a 
 rotation of the block to the left. The block is withdrawn 
 
GUNS. 269 
 
 by a translating-screw as before. The tray-latch is the same 
 in principle as in the guns, the only change in construction 
 being that the spring-lock acts in front of the pivot, and the 
 latch rises when it is disengaged. 
 
 Vent-closer. This resembles that used in the 3.2-inch 
 gun, and consists of a piece of metal,/, sliding in a slot in 
 the face-plate. A pin projecting from the front of this slid- 
 ing-piece, bears in a groove g in the rear face of the breech, 
 which is concentric for some distance with the axis of the 
 breech-block, and at its lower extremity becomes eccentric. 
 Its action in uncovering the vent is the same as in the case 
 of the 3. 2-inch guns. 
 
 Action of Mechanism. When the block is closed, the head 
 of the face-plate is at the right-hand end of the rack e, the 
 crank d is parallel to the axis of the face-plate, and is held 
 in place by a spring-lock h. After firing, the crank d is 
 turned, and the gear c engaging in the rack e, rotates the 
 block to the left. 
 
 The rotation of the block is limited, by the striking of the 
 sides of the face-plate against the ends of the circular recess 
 in which the rack is placed. The block is now withdrawn 
 by the translating-screw, and block and tray swung round 
 for loading. 
 
 To close the breech the operations are reversed. 
 
 150. Improved Mechanism Continuous Rotation. 
 
 Objections to Ordinary Mechanism. In the mechanism 
 already described, one crank is necessary to rotate the 
 block, and at the end of this movement, the power must be 
 transferred to another crank for withdrawing the block. 
 When the block is withdrawn, the power must be applied 
 to the handle of the tray to swing the block and tray 
 around. We have thus three separate and djstinct mo- 
 tions, involving loss of time, and complication of mechan- 
 ism. 
 
 IMPROVEMENTS. In the latest improved mechanism, the 
 object is to effect by the application of power to one crank, 
 and by its continuous movement, the rotation, translation, 
 and swing, of the block and tray. 
 
2/O 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 This mechanism, as applied in our service, is called the 
 Farcot, from its inventor, and consists (Fig. 140) of the fol- 
 lowing parts : 
 
 On the right side of the rear end of the breech-block is 
 a circular-toothed sector a. A cut is made in one of the 
 threaded sectors of the block parallel to its axis, and this 
 circular rack is extended along the block as shown in the 
 figure (plan), the width of this longitudinal rack b being 
 that of the thickness of the wheel c, while the width of 
 
 FIG. 140. 
 
 the circular sector a is one sixth of the circumference of 
 the block. On the top of the hinge-pin d, is mounted a 
 worm-gear c, whose teeth fit the corresponding teeth of the 
 sector a. 
 
 At the bottom of the hinge-pin d is a second worm- 
 gear, e. A* horizontal crank-shaft, /, has at the right end a 
 worm, g, gearing into the worm-gear e, and at the left end a 
 crank, h. 
 
 Action of Mechanism. When the crank h is turned, 
 motion is communicated to the worm-gear c through g and 
 e, and the action of c on the sector a rotates the block one 
 
GUNS. 
 
 2/1 
 
 sixth of a turn, till the shoulders kl on the block strike 
 against the guide-rails mn. 
 
 The block then being no longer able to turn, the teeth of 
 the wheel c, engaging in those of the rack b y along the block, 
 will force the block to the rear out of the breech-recess. 
 The cut in the threaded sector of the block, for the reception 
 of the rack b, is made so deep that the worm-wheel c binds 
 against the edges of this cut in travelling along the rack, 
 
 TABLE II. BREECH-LOADING ORDNANCE, U. S. LAND SERVICE. 
 
 
 Seacoast Guns, Steel. jSeacoast Mortars. 
 
 Model Model 
 1888, M. 1888, M. 
 
 Model 
 1888, M. 
 
 Model 
 1892. 
 
 Pro- 
 posed. 
 
 Cast iron 
 Steel - 
 hooped. 
 
 Steel. 
 
 Calibre inches 
 
 8 
 J 32,372 I 
 1 32-480 f 
 M-S 
 23.21 
 32 
 
 30 
 9-5 
 i. 08 
 3 
 51,980 
 
 48 
 0.3736 
 0.06 
 
 j t in 50 to 
 j i in 25 
 
 i4,!25 
 
 3,597 
 5 -75 
 25.66 
 
 GO 
 iS 
 
 0.9619 
 
 300 
 
 i to 108 
 
 37,000 
 J ,95 
 7,97 
 
 16.0 
 10.6 
 
 10 
 
 67,200 
 
 3 
 30.60 
 
 34 
 38.5 
 ii. 8 
 
 .*3 
 
 4 
 53. 9o 
 
 60 
 0.3736 
 0.06 
 0.15 
 i in 50 to 
 i in 25 
 
 28,977 
 7,064 
 65.09 
 27-51 
 
 c 
 
 250 
 0.9797 
 
 575 
 i to 117 
 
 37,000 
 1-975 
 15-548 
 
 20.4 
 14.6 
 
 12 
 
 116,480 
 
 5 2 
 36.66 
 
 34 
 46.2 
 14.2 
 1,125 
 4 
 53,000 
 
 72 
 0.3736 
 0.06 
 0.15 
 i in 50 to 
 i in 25 
 
 50,049 
 12,092 
 
 77-33 
 27.58 
 
 to 
 
 450 
 i .0285 
 
 1,000 
 
 i to 116 
 
 37,000 
 i,975 
 27,040 
 
 24.9 
 18.7 
 
 12 
 128,719 
 
 57-5 
 40.0 
 
 37-83 
 
 46.4 
 14-5 
 
 1. 10 
 
 4 
 
 52,640 
 
 72.0 
 o-3736 
 0.06 
 0.15 
 i in 50 to 
 i in 25 
 
 55,829 
 12,798 
 78.58 
 31.29 
 
 (d) 
 487 
 1-0535 
 
 1,000 
 
 16 
 280,000 
 
 **5 
 
 49.67 
 
 35 
 62 
 18.8 
 1.148 
 4 
 53,000 
 
 96 
 0.3736 
 0.07 
 0.15 
 i in 50 to 
 i in 25 
 
 121,487 
 29,34i 
 106.06 
 28.37 
 
 (d) 
 
 i, 060 
 
 i 
 
 2,370 
 
 12 
 31,920 
 14.25 
 10-75 
 
 9 
 4 I -75 
 12.4 
 1.18 
 3 
 29,490 
 
 68 
 c 379 
 0.07 
 
 0.175 
 
 i in 40 to 
 i in 25 
 
 12,554 
 1,990 
 iS-75 
 7.66 
 
 00 
 
 80 
 
 1.1128 
 
 j 800 
 
 | 1,000 
 
 12 
 29,120 
 
 11 
 II. 7 6 
 10 
 
 38 
 12.5 
 1.02 
 
 3 
 50,200 
 
 72 
 0-373 6 
 0.06 
 0.15 
 i in 40 to 
 i in 20 
 
 J 3>947 
 2,636 
 
 20.8 
 
 8.225 
 
 CO 
 
 105 
 
 I . 1026 
 
 800 
 
 1,000 
 
 I to 36 
 
 30,000 
 1,140 
 7,207 
 
 9-7 
 
 Weight: 
 Pounds 
 
 Tons 
 
 Total length, feet 
 Length of bore, calibres.. . . 
 Diameter over powder- 
 chamber, inches 
 Diameter of powder-cham- 
 ber, inches 
 Thickness over powder- 
 chamber, calibres 
 Number of cylinders com- 
 prised in the thickness. . 
 Maximum tangential resist- 
 ance, pounds per sq. in. . 
 Rifling: 
 Number of grooves 
 Width of grooves, inches 
 Depth of grooves, inches 
 Width of lands, inches... 
 
 Twist, calibres 
 
 Total capacity of bore, 
 cubic inches. . . 
 Capacity of powder-cham- 
 ber, cubic inches . . 
 Lengthof powder-chamber, 
 inches 
 
 Travel of projectile in bore, 
 calibres 
 Powder charge: 
 Kind 
 
 Weight, pounds 
 Density of loading 
 
 Projectile: 
 Weight, pounds. 
 Ratio to weight of piece. 
 Pressure in powder-cham- 
 ber, Ibs. per square inch 
 Muzzle velocity, ft. -sees. .. 
 Muzzle energy, foot- tons.. 
 Penetration in steel: 
 Muzzle, inches 
 3500 yards, inches 
 
 38.000 
 
 2,IOO 
 
 30,570 
 27.1 
 
 20.6 
 
 37,000 
 i,975 
 64,084 
 
 33-8 
 27 5 
 
 27.500 
 
 I,O2O 
 
 5,770 
 
 8.2 
 
 
 
 a U.R. brown prismatic, b W.H. brown prismatic, c V. P. brown prismatic. </ brown 
 prismatic; e V.M. brown prismatic. 
 
272 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 and hence any tendency of the block to rotate is overcome. 
 When the block reaches the end of its travel, it strikes 
 against the ends of the guide-rails and releases the tray- 
 latch from its recess in the breech by the shock, as before 
 explained. As the block is not able to move further on the 
 tray, but is free to swing with the tray around the pin d,. 
 the pressure of the teeth of c against those of the rack will 
 cause this swinging to take place, thus opening the breech 
 for loading. 
 
 A reversal of these motions closes the breech for fir- 
 ing. 
 
 The table on page 271 gives the details with reference to 
 the seacoast guns and mortars in the U. S. service. 
 
 151. Old Guns in IT. S. Service 3-inch Wrought-iron Rifle 
 4.5-inch Siege-gun 4.2-inch Parrott Siege-gun 8-inch Con- 
 verted Rifle 15-inch Rodman Smooth-bore. 
 3-iNCH WROUGHT-IRON RIFLE (Fig. 141). This gun was 
 used during the war of 1861-65, and is still found in service. 
 
 n It is made by wrapping boiler- 
 
 ~'ri^"^-""J"-"-"I-Jl"'Z"Z!] iron around a wrought- iron 
 LJ mandrel, heating the resulting 
 
 FlG - I 4 I - cylinder to a welding-heat, and 
 
 passing it through the rolls. The gun is then bored, turned, 
 and rifled. The object of the construction is to have the 
 fibres of the wrought iron in the direction of the tangential 
 
 FIG. 142. 
 
 stress. The objection to the construction is the liability to 
 false welds. 
 
 4.5-iNCH SIEGE-GUN (Fig. 142). This gun is made of cast 
 iron, cast -solid, and bored, turned, and rifled. It has given 
 very good results, but is uncertain in strength, like all guns 
 
GUNS. 
 
 cast on this plan, and several accidents have occurred which; 
 have caused it to be abandoned. 
 
 4.2-iNCH PARROTT SIEGE-GUN (Fig. 143). This gun is 
 also made of cast iron, but is reinforced at the breech by a: 
 
 FIG. 143. 
 
 heavy jacket of wrought iron. This jacket was made by 
 coiling a hot bar of wrought iron around a mandrel into a 
 spiral, and welding the coils into a cylinder by blows from a 
 hammer parallel to the axis of the cylinder. The cylinder 
 was next bored, and then shrunk upon the exterior of the 
 breech of the gun. At the time these guns were made, 
 nothing was known about the theory of shrinkage as at pres- 
 ent applied to guns, and hence the shrinkage was not prop- 
 erly regulated, and was very often a source of weakness, 
 especially at the junction of the front end of the cylinder 
 with the gun. In spite of this, however, these guns have 
 proved very serviceable. 
 
 8-iNCH CONVERTED RIFLE (Fig. 144). These guns were 
 made for the purpose of utilizing a large number of old 10- 
 
 FIG. 144- 
 
 inch Rodman cast-iron guns which were on hand, the idea 
 being to render them more accurate and powerful, by con- 
 verting them into rifled guns. This was done by boring 
 out the 10-inch gun to a larger diameter, and inserting 
 
 
 o? -no 
 
2/4 TEXT-BOOK OF ORDNANCE AND GUNNERY. ' 
 
 a tube into this bore. This tube was held in place by a col- 
 lar, a, screwed into the cast-iron body and resting against a 
 shoulder, b, on the muzzle end of the tube. The tubes were 
 made at first by coiling bars of wrought iron around a man- 
 drel, and welding them by axial blows. This method was 
 abandoned on account of the false welds in the tube, which 
 sometimes cracked and separated from this cause. The 
 tubes were finally made of steel, and numbers of these guns 
 are still in service. The rotation of the tube, due to the ac- 
 tion of the projectile, is prevented by a pin, c, which passes 
 through the cast iron body and enters the tube. 
 
 15-iNCH RODMAN SMOOTH-BORE. This gun is still re- 
 tained in service, and is intended to be used with large 
 charges of mammoth powder, as a secondary gun, for com- 
 paratively short ranges, and against light armor. It is 
 cast hollow on the Rodman plan; its projectile weighs 450 
 pounds, and the gun about 22 tons. 
 
 152. Foreign Guns Krupp Mechanism Locking-screw. 
 
 All heavy guns are built upon the same principles as 
 those already explained, and hence a description of the guns 
 of different countries is unnecessary. The only departure 
 from the system above described, is in the case of the breech 
 mechanism. 
 
 KRUPP MECHANISM. While the French or interrupted- 
 screw system has been adopted by most of the foreign na- 
 tions, Germany, and some others, use the Krupp system. 
 
 It has stood the test oi service and has been well and 
 favorably known for many years, and hence will be described 
 here. 
 
 The jacket a, Fig. 145, extends to the rear of the tube, 
 and carries the fermeture. A slot is cut transversely in the 
 jacket just in rear of the tube. This slot, in front, is perpen- 
 dicular to the axis of the bore, and is a plane surface, with 
 corners rounded to avoid sharp angles. In rear, the sur- 
 face of the slot is cylindrical, and the axis of the cylinder is 
 inclined to that of the bore. Two guides, bb' , are parallel 
 to the axis of the cylinder. In this slot slides a breech- 
 block, k, whose shape corresponds to that of the slot. It 
 
G UNS. 
 
 has two recesses for the guides bb' , and in the upper face, 
 a third recess, in which rests a long screw c, called the 
 translating-screw. This screw is held in two collars in the 
 breech-block, and works in a half-nut, d, on the gun. When 
 the screw c is turned by a wrench, such as e, the block is 
 drawn out of its recess or pushed home. 
 
 LOCKING-SCREW. In order to obtain a rapid motion in 
 opening and closing the breech, the screw c is cut with a 
 quick pitch. Consequently, 
 there is very little power to 
 press the gas-check firmly 
 home, or, in opening the 
 breech, to overcome any stick- 
 ing that may occur. It is 
 also necessary to have some 
 method of locking the breech- 
 block to the jacket in firing, 
 to prevent accident. 
 
 All these objects are ac- 
 complished by the locking 
 mechanism. This consists of 
 a nut, f, and a screw, g. The 
 nut has a series of rings, r, 
 formed on its exterior sur- 
 face. The outer ring is com- 
 plete, the others are partially 
 cut away. When the nut is 
 turned so that the cut-away 
 portions of the rings are in 
 rear, the surface of the nut 
 coincides with that of the rear 
 of the block. When turned 
 the parts of the rings 
 
 120^ 
 
 FIG. 145. 
 in the breech. 
 
 not cut away project beyond 
 
 the block and enter corresponding cuts 
 
 The nut has a small amount of travel along its screw g. 
 
 Action -The translating-screw c leaves the block not 
 quite forced home. The nut /is at the bottom of its recess 
 in the block, nearest the axis of the gun, and the cut rings 
 
276 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 of the nut are turned to the rear. The wrench e is now 
 applied to the screw g and the screw turned. This will 
 cause the nut /to move along the screw, it being unable to 
 turn because of the cut parts of the rings bearing on the 
 back of the transverse slot in the breech. As soon, how- 
 ever, as the rings come opposite the cuts in the breech, the 
 nut will turn, its rings entering the corresponding cuts in 
 the breech, and after turning 120, the pin h bears against 
 a shoulder on the block, and stops the rotation of the nut. 
 As the screw still turns, H:he effect will be to cause the rings 
 to bear against the cuts in the breech, and thus force the 
 block home. At the same time the rings bearing in the 
 cuts lock the block. A reversal of these operations opens 
 the breech. 
 
 153. The Gas-check General Features of the Mechanism Ad- 
 vantages and Disadvantages. 
 
 GAS-CHECK. With the Krupp mechanism, it is evident 
 that neither the De Bange nor the Freyre gas-checks can be 
 
 used, since both of them must be 
 drawn back from their seats in the 
 gun, being attached to the breech- 
 block. The Krupp block slides 
 across the breech, and hence it is nec- 
 essary to use a gas-check which can 
 be left in the gun. The Broadwell 
 ring is used. It consists (Fig. 146) 
 of two parts : the obturating-ring, 
 a, and the obturator-plate, b. The 
 exterior surface, cc?, of the ring is 
 spherical, so that it can be readily 
 seated in the gun, and returned to 
 its place if it should become un- 
 FlG - T 46. seated. The surface c'd is plane, 
 
 with a series of grooves to act as an air-packing, as before 
 explained, and also to collect any dirt that may be on the 
 surface of the obturator-plate. The obturator-plate b is of 
 hardened steel, and is fitted into the face of the breech- 
 block. The hollow e collects fouling, which, if the whole 
 
 BREECH BLOCK. 
 
 TUBE 
 
 
 C' 
 
 ; ( 
 
 ^^ 
 
 
 
 -C 
 
 
 d' 
 b 
 
 a 
 
 
 
 
 
 e 
 
 
 
 
 b 
 
 r 
 
 ^- 
 ~~*~* 
 
 1 
 
 
GUNS. 277 
 
 front surface were plane, would be drawn against the edge 
 of the obturating-ring when the block is withdrawn, and 
 thereby increase the liability to fouling of the surface c'd. 
 The surfaces c'c and c'd are those which must be kept sealed 
 against the escape of gas. The surface c'd is especially 
 difficult to seal, and hence the necessity for the heavy press- 
 ure given by the locking-screw, to set the obturator-plate 
 firmly against the ring. 
 
 Action. The gas acts upon this ring to force the thin 
 edge c against the walls of the bore, and also to press the 
 ring backwards against the obturator-plate, forcing down 
 especially the edge d. 
 
 GENERAL FEATURES OF MECHANISM. The locking- 
 screw just described is supported at its outer extremity 
 by a plate, k, Fig. 145, called the locking-plate. The 
 travel of the block is limited by a chain, or by a stop-bolt 
 which passes through the upper part of the breech, and 
 projects into a groove in the block. The jacket is bored 
 out in prolongation of the bore, for the insertion of the 
 projectile and charge in loading, and this hole is also 
 made through the breech-block, so that when the block 
 is withdrawn the hole through it is also in prolongation 
 of the bore. The rounded shape of the rear of the block, 
 and of the slot, gives strength by avoiding sharp corners, 
 and the inclination of the axis of the cylinder to that of 
 the bore, with that of the guides, gives a component mo- 
 tion of the block parallel to the axis and gradually seats 
 the block firmly, while by a slight motion outward, all 
 the parts become free and the block is easily with- 
 drawn. 
 
 ADVANTAGES. The Krupp mechanism is very simple 
 and not liable to get out of order. It has been thoroughly 
 tested, and found to be reliable. If it becomes stuck or 
 wedged in the gun, it may be more easily removed than the 
 screw, as it is more accessible. 
 
 DISADVANTAGES. It requires a heavier forging for its 
 jacket than the screw system, and consequently increases 
 -the weight of the gun for the same -length of bore. The 
 
2/8 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 Broadwell ring is not as good a gas-check as the De Bange 
 or Freyre. 
 
 The longitudinal stress is not uniformly distributed over 
 the cross-section of the jacket, and this is seen by a ten- 
 dency of the gas-check seat to become oval, the longer axis, 
 being parallel to that of the slot. 
 
 It is more exposed to a front fire when open. 
 
 It tends to guillotine the cartridge. 
 
CHAPTER IV. 
 
 PROJECTILES AND ARMOR. 
 
 PROJECTILES. 
 
 154. Classification Solid Shot Chilled Shot Steel Shot. 
 
 CLASSIFICATION. Projectiles may be classified according- 
 to their structure, as solid shot, shell, and case-shot ; accord- 
 ing to their use, into field, siege, and sea-coast projectiles ; 
 and according to their shape, as spherical and oblong. 
 
 Spherical projectiles are now obsolete. 
 
 SOLID SHOT. Solid shot were formerly used for armor- 
 piercing, and are still used in small arms against animate 
 objects. The advantages of solid shot are, that they have 
 greater weight for the same volume, and hence greater 
 energy for a given velocity ; and where it is necessary to 
 concentrate energy upon a given area, as in attacking an 
 armor-plate, they were generally employed. 
 
 The disadvantages are that for attacking armor, the pro- 
 jectile must possess great hardness to penetrate, and great 
 toughness to resist breaking up on impact, and if the shot 
 be made solid, it is subjected to initial strains due to casting 
 or forging, which cannot be removed ; the metal in the in- 
 terior is not sound, and hence we obtain weaker projectiles 
 when solid than when they have an interior cavity or core. 
 This cavity removes the unsound metal, if the projectile is 
 of cast iron, or if of steel, allows it to be treated, so that the 
 strains can be removed and toughness attained. Such shot 
 are generally called " cored shot." 
 
 The only solid projectiles at present in general use are for 
 small arms. 
 
 279 
 
28o 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 CHILLED SHOT. With the introduction and improve, 
 jnent of wrought-iron armor, cast-iron projectiles became 
 
 useless, as they were broken 
 on impact. This led to the 
 introduction of chilled cast- 
 iron projectiles. The Palliser 
 projectile, so called from its 
 inventor, Major Palliser of 
 the British Army, was for a 
 long time quite celebrated, 
 and very effective against 
 wrought-iron armor. 
 FIG. 147. It was made by casting 
 
 the ordinary cored shot in a chill, Fig. 147. 
 
 The body of the projectile is cast in sand to give tough- 
 ness, and the head in a cast-iron mould or chill a, so called 
 because it carries off the heat of the parts in contact with it 
 so rapidly as to cause chilling, and produce great hardness. 
 The exterior of this chill conforms generally to the shape 
 of the head, to insure uniform cooling, and it is lined with a 
 movable lining, b. 
 
 The latter soon becomes worn from contact with the 
 heated metal, and is removed and replaced by a new lining, 
 thus preserving the body of the chill a. The head of the 
 chilled shot is shown at c. 
 
 STEEL SHOT. As armor improved in its resisting quali- 
 ties, the chilled cast-iron projectile was broken on impact, and 
 steel shot were substituted. The best of these are made of 
 
 12 "INCH ARMOR PIERCING SHOT. 
 FORGED STEEL. 
 
 FIG. 148. 
 
 chrome steel, forged and tempered. Two processes, known 
 as the Holtzer and Firminy, are so far the best, but they are 
 secret, and nothing is known of them. The projectiles made 
 
PROJECTILES AND ARMOR. 28 1 
 
 by these processes give the best results when used against 
 modern steel armor, but they are very expensive, and hence 
 attempts are now being made, with some appearance of 
 success, to replace them by cast-steel projectiles, which are 
 tempered by a secret process. 
 
 Fig. 148 shows a forged-steel Holtzer armor-piercing 
 cored shot. 
 
 155. Shell Definition Shell for Sea-coast Service Deck-piercing 
 Shell. 
 
 DEFINITION. A shell is a hollow projectile, containing a 
 bursting charge of gunpowder, or some high explosive, and 
 a fuze to ignite this charge at some point of its flight, or 
 upon impact. 
 
 Shells are used in the sea-coast, siege, and field services, 
 and their construction depends on the purpose for which 
 they are intended. 
 
 SHELLS FOR SEA-COAST SERVICE. In the sea-coast ser- 
 vice, shells are used in high-powered guns for attacking 
 armor, or in mortars with high angle-fire for piercing the 
 decks of vessels. 
 
 Against Armor. If the shells can be made strong enough 
 to penetrate armor, they are preferred to shot, because they 
 burst after penetration, and acting in a confined space on a 
 ship, cause great destruction. For this purpose the walls of 
 the shell must be strong, and hence the cavity small. The 
 cavity being small, will not contain a large bursting charge 
 of powder, and the walls of the shell being strong, the gases 
 from this charge may not develop sufficient pressure to rup- 
 ture them. 
 
 On this account, and because of its greater destructive 
 effect, a high explosive as a bursting charge is necessary. 
 
 Gun-cotton has been tried as a bursting charge for these 
 shells. While it has given good results in some cases, it is 
 liable to premature explosion from shock and friction, and 
 if desensitized by moisture or by paraffine, it requires a 
 strong primer of dry gun-cotton to detonate it, and this 
 primer is liable to detonation by shock. The same principle 
 applies to nearly all the high explosives which have been 
 
282 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 tried, and hence the problem of a suitable high explosive 
 for armor-piercing shell is not yet solved. This has led to 
 the introduction of various methods of firing high explosives^ 
 as the pneumatic dynamite gun, etc. 
 
 With armor-piercing shell, it is sought by various means 
 to delay the action of the bursting charge till penetration is 
 complete, as by wrapping the charge in flannel, using de- 
 layed-action fuzes, etc. 
 
 AGAINST THE DECKS OF VESSELS. The problem of pen- 
 etrating the sides of armored vessels being so difficult, at- 
 tempts are made to perforate their decks. When the weight 
 of guns, machinery, and armor carried by ships of the pres- 
 
 .I2JNCH DECK PIERCING SHELL. 
 "FORGED STEEL. 
 
 FIG. 149. 
 
 ent day is considered, the available weight left for deck pro- 
 tection is comparatively small, and hence a thickness of about 
 4^ inches of protective deck is about all that can be carried. 
 Against these decks, the vertical fire of shell from heavy 
 
 CAST IRON SHELL TOR 12 INCH MORTAR. 
 
 FIG. 150. 
 
 rifled mortars is directed. The shells for these mortars do 
 not require great strength of wall, since the thickness to be 
 penetrated is so small, and hence they may be made of cast 
 iron, with great interior capacity. They carry heavy burst- 
 ing charges, and their effect is very destructive. The dis- 
 advantage is, the difficulty of hitting the object. As the 
 shells are fired with comparatively low charges, the dangers 
 
PROJECTILES AND ARMOR. 283 
 
 of premature explosion from shock are lessened, and recent 
 experiments at Sandy Hook have shown that high explo- 
 sives can be fired from these mortars with safety. At pres- 
 ent these shells are made of forged steel. 
 
 Figs. 149 and 150 show a steel deck-piercing shell and a 
 cast-iron shell for the 1 2-inch mortar. 
 
 156. Siege Shell Field Shell. 
 
 SIEGE SHELL. The shells for siege purposes are some- 
 what similar to those for deck piercing. They are used in 
 direct and curved fire, and against earth or masonry. Their 
 object, therefore, is to displace the earth and masonry, and 
 as no great strength is required against these obstacles, the 
 siege-shell are made of cast iron. In firing against masonry, 
 it is necessary not only to penetrate, but also to remove the 
 broken fragments, so that the next shot may fall upon a 
 fresh surface. For this purpose large bursting charges are 
 required, and hence large cavities, and comparatively thin 
 walls. Very long shell are sometimes supplied for this pur- 
 pose, and are called " torpedo shell." 
 
 Against earth, the maximum displacement is required, 
 and some experiments made with gun-cotton as a bursting 
 
 5 INCH SIEGE SHELL 
 CAST IRON. 
 
 FIG. 151. 
 
 charge show that it is very effective. The 5-inch siege shell 
 is shown in Fig. 151. 
 
 FIELD SHELL. In field artillery the objects to be at- 
 tacked have little resistance, as they are generally light field 
 entrenchments, buildings, or troops, and hence the effect 
 depends on the number of fragments into which the shell 
 bursts. 
 
 The number of these fragments will depend on the 
 brittleness of the material, and the pressure of the gases 
 
284 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 from the bursting charge, at the time when rupture 
 occurs. 
 
 The natural tendency of a shell is to burst in a meridian 
 plane, or a plane through its longer axis, since the total 
 pressure of the gases normal to this plane is greater than 
 that normal to the transverse plane. If the pressure of the 
 gases is developed slowly, as from a bursting charge of 
 large-grained powder, rupture will occur as just indicated, 
 and we will have a few large fragments, and the effect will 
 be limited. To avoid this it is necessary 
 
 1. To use as a bursting charge, fine-grained powder of 
 high gravimetric density. By this means the pressure is 
 rapidly developed, and the largest possible weight of charge 
 is contained in a given volume. 
 
 2. To prevent rupture in a longitudinal plane, the interior 
 of the shell is sometimes grooved spirally, to weaken it, and 
 give more fragments. A remaining velocity of 500 ft.-secs. 
 is generally considered sufficient to disable or kill a man, 
 and a fragment weighing about I ounce with this velocity 
 is effective. With the 13.5-lb. shell this would give 216 
 effective fragments, and with the 20 Ib. shell 320. In prac- 
 tice these results cannot be obtained. 
 
 Owing to the irregularity of their action, field-shells are 
 seldom used against animate objects, except at very long 
 distances, or when under cover. They are used, however, 
 with percussion fuzes, to obtain the range quickly. By 
 
 firing a percussion shell with a 
 certain elevation, so as to strike in 
 front of the target, and again with 
 
 3 20 INCH flCLD SHCLL , 
 
 CAST IRON ^^ an increased elevation, so as to 
 
 F IG . 152. strike beyond it, and observing 
 
 the points of burst, the target is 
 
 thus enclosed in a fork, and by working between these lim- 
 its, the true elevation is soon obtained. The 3.2-inch shell is 
 is shown in Fig. 152. 
 
 157. Case-shot Grape Canister. 
 
 DEFINITION. Case-shot may be defined to be a collec- 
 tion of particles enclosed in a case or envelope, the latter 
 
PROJECTILES AND ARMOR. 
 
 285 
 
 3 a 
 
 being intended to rupture in the gun, or at some point in 
 flight, and liberate the enclosed particles. 
 
 According to the place of rupture of the envelope, case- 
 shot may be divided into 
 
 1. Grape ; 
 
 2. Canister, 
 
 whose envelope is broken in the gun, by the shock of dis- 
 charge ; and, 
 
 3. Shrapnel, 
 
 whose envelope is broken at some point of the flight of the 
 projectile. 
 
 GRAPE. This projectile is no longer used, but is interest- 
 ing historically. It consists of three layers of balls, each 
 layer containing generally three balls (see 
 Fig. 153) held in place by top and bottom 
 plates, a and b, of iron ; a central bolt and 
 nut, c ; and two intermediate rings, dd. It 
 was used in the sea-coast service with 
 smooth-bore guns, against the masts and 
 rigging of ships, and against men ; also in 
 the siege and field services against ani- 
 mate objects in mass, at distances too 
 great for smaller projectiles. 
 
 CANISTER. This con- 
 sists (Fig. 154) of a number of spherical bullets 
 of lead hardened with antimony, or of cast 
 iron, contained in a can; hence the name. 
 The envelope is closed by a top and bottom 
 plate of iron, and is intended only for conven- 
 ience in transportation, and in loading. 
 
 It was used principally in the field service 
 with the old smooth-bore guns, against ani- 
 mate objects at close range. 
 
 In both these projectiles, the case rup- 
 tured in the bore, and the projectiles scattered at the muz- 
 zle, forming a cone of dispersion, with its apex at the latter 
 point. 
 
 For rifled guns it was necessary to prevent the case 
 taking the grooves, and thus giving it the rifled motion 
 
 mm 
 FT ) 
 
 d 
 
 d 
 
 FIG. 153. 
 
 FIG. 154. 
 
286 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 and increasing the lateral dispersion of the projectiles, 
 which r\vas already great. 
 
 For this purpose the case was made stronger, 
 since with the tin case, the projectiles were forced 
 sidewise by the shock of discharge, expanding 
 the case, and forcing it into the grooves. In our 
 service this was done by adopting the Sawyer 
 canister, the case of which is made of malleable 
 cast iron, weakened by spiral cuts, as shown in 
 Fig. 155, so as to insure its breaking up in the gun. 
 All these projectiles were used at short range, 
 and since the fighting range has been increased, 
 owing to the longer range and higher ballistic 
 FIG. 155. power of small arms, they are little used at the 
 present day. A few rounds of canister are sometimes car- 
 ried with the field gun for emergencies. 
 
 158. Shrapnel Cone of Dispersion Causes which Affect it. 
 
 SHRAPNEL. This projectile is now the most important in 
 field artillery, and is employed to the exclusion of all others. 
 It consists essentially of a case or envelope containing small 
 round projectiles, and a bursting charge, and fuze. The 
 charge is sufficient to rupture the envelope at a given point 
 of flight of the projectile, the fuze being arranged to ignite 
 the charge at that point. After the rupture of the envelope, 
 the contained projectiles move on with a velocity which is 
 the resultant of that due to discharge, and to the bursting 
 charge, and act from the point of burst to the target, as 
 canister. The object of the envelope then is to convey the 
 small projectiles to within striking distance of the target, 
 where they are liberated, and each particle acts. The pro- 
 jectile is used entirely against animate objects, and its advan- 
 tages over the shell are that the division of the particles is 
 made beforehand, and each one is of the proper size to exert 
 a disabling or killing effect. 
 
 CONE OF DISPERSION. When rupture of the case occurs, 
 each contained particle describes its own path, and the 
 paths thus described, taken together, form the elements of 
 the " cone of dispersion." The intersection of this cone with 
 
PROJECTILES AND ARMOR. 287 
 
 the ground is an irregular oval, and its area will vary 
 with 
 
 CAUSES WHICH AFFECT IT. i. The angle of elevation of 
 the piece ; 
 
 2. The velocity of translation of the shrapnel before 
 bursting ; 
 
 3. The velocity of rotation of the shrapnel before bursting; 
 
 4. The position of the bursting charge ; 
 
 5. The height above the ground at which the shrapnel 
 bursts. 
 
 Angle of Elevation. If this be large, other things being 
 equal, the angle of fall will be large, and the plane of inter- 
 section being more nearly normal to the mean axis of the 
 cone of dispersion, the area of the oval will decrease ; the 
 converse is true for small angles of elevation (see Fig. 156). 
 
 FIG. 156. 
 
 Velocity of Translation. The greater this velocity, the 
 greater will be the velocity of the particles in the plane of 
 fire, and consequently the longer the oval in this direction. 
 
 Velocity of Rotation. This causes the particles to move 
 at right angles to the plane of fire, and hence increases the 
 lateral dispersion of the particles, and the width of the oval. 
 
 Position of Bursting Charge. This may be in front, or in 
 rear of the particles. If in front, it decreases the velocity 
 of translation of the particles, and hence decreases the length 
 of the oval, and for this reason its effect is injurious. For 
 other reasons, however, the position is a good one, as will 
 be seen. 
 
 When in rear, it increases the velocity of the particles in 
 the plane of fire ; but there are objections to this position. 
 
 Height of Burst. It is evident that, for a given inclina- 
 tion, and for given velocities in the plane of fire and later- 
 
288 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 ally, the higher the point of burst, the greater the area of 
 the oval. 
 
 The constant tendency with shrapnel is to increase the 
 velocity of the particles in the plane of fire, and to decrease 
 that at right angles to this plane ; and the best possible con- 
 dition for the efficiency of this projectile is when the area 
 of the oval is such that each bullet will hit a man. The 
 best position for the point of burst is about 6 yards above 
 and 50 yards in front of the target. 
 
 159. Construction of Spherical Shrapnel Early Shrapnel U. S. 
 Spherical Case Boxer Spherical Shrapnel. 
 
 Spherical shrapnel is now obsolete, but the history of 
 its development shows clearly the directions in which im- 
 provements have been made. 
 
 EARLY SHRAPNEL, The projectile was invented by 
 Colonel Shrapnel of the British Army, about 1803. In its 
 early form it was simply a spherical shell filled with bullets, 
 and the bursting charge was contained in the interstices be- 
 tween them. The objections to this arrangement were : 
 
 1. When the projectile was fired the balls spread side- 
 wise, and tended to deform or burst the shell. Hence the 
 latter was made with thick walls to resist this force, and 
 this decreased the interior capacity, and consequently, the 
 number of bullets which it would contain. 
 
 2. The powder, being loose among the bullets, was sub- 
 jected to trituration and friction in handling, and hence 
 was liable to accident. Since the space between the bullets 
 
 was large, the density of loading of 
 the bursting charge was low, and 
 hence a large bursting charge was 
 required to rupture the envelope. 
 This scattered the fragments too 
 much, and rendered the action of the 
 fuze more irregular. 
 
 U. S. SPHERICAL CASE. These 
 defects suggested the improvements 
 which were made in the spherical, 
 the Civil War (Fig. 157): 
 
 FIG. 157. 
 shrapnel used durin: 
 
PROJECTILES AND ARMOR. 289 
 
 1. To prevent the spreading of the bullets, the shell was 
 first filled with them, and melted sulphur was then poured 
 in, filling the interstices between the bullets. They were 
 thus converted into a solid mass, and as their tendency to 
 spread siclewise was thus destroyed, the case was made 
 thinner, and consequently held more bullets. 
 
 2. To diminish the bursting charge, a cylindrical hole 
 was bored through the bullets and sulphur, and in this the 
 bursting charge was placed. Thus the density of loading 
 was increased, and a small bursting charge could be used 
 with less uncertainty in the action of the fuze. 
 
 The objections to this arrangement were that the sul- 
 phur caused the bullets to stick together, and prevented 
 their separation after the bursting of the case, and that the 
 effect of the bursting charge was to increase the lateral 
 dispersion of the particles. 
 
 BOXER SPHERICAL SHRAPNEL. Most of the defects in 
 the above shrapnel were remedied in the Boxer Spherical 
 Shrapnel (Fig. 158), invented by 
 Colonel Boxer of the English Army. 
 
 In this projectile, the bursting 
 charge was placed in a chamber, a, 
 formed by .introducing a wrought - 
 iron diaphragm, b, into the mold be- 
 fore casting, and allowing the cast 
 iron to cool around it. The bullets 
 
 were introduced through the open- 
 
 , & , . , FIG. 158. 
 
 ing c, the upper end of which carried 
 
 the fuze; the flame from which reached the charge through 
 a hole, d. The sulphur used as packing in the U. S. shrap- 
 nel, was replaced by coal dust. 
 
 This shrapnel possessed the following advantages : 
 
 1. The bullets did not adhere to the matrix after burst- 
 ing. 
 
 2. A small bursting charge could be used. 
 
 3. The diaphragm b weakened the case, so that it would 
 burst readily. 
 
 4. As soon as the shrapnel left the piece (since its for- 
 ward portion, which contained the fuze, was lighter than 
 
290 
 
 TEXT- BOOK OF ORDNANCE AND GUNNERY. 
 
 the rear portion), the lighter portion would turn to the rear, 
 leaving the centre of gravity in advance of the centre of 
 figure. This brought the bursting charge in rear, and 
 hence, on explosion, it acted to increase the forward ve- 
 locity of the bullets, and its tendency to scatter was very 
 small. 
 160. Oblong Shrapnel Boxer Modern Shrapnel Position of 
 
 Bursting Charge. 
 
 BOXER OBLONG SHRAPNEL. At this point the develop- 
 ment of spherical shrapnel ceased, owing to the introduction 
 of rifled guns and oblong projectiles. 
 The first oblong shrapnel of any import- 
 ance was that of Colonel Boxer. This 
 consists (Fig. 159) of a cast-iron body, a ; 
 and a wooden head, b, covered with 
 sheet-iron, c, riveted to the cast-iron 
 body. The bursting charge is contained 
 in the chamber d in rear, and over this 
 chamber, separating the charge from 
 the bullets, is a cast-iron disk, e. The 
 central tube /is filled with powder, and 
 conveys the flame from the fuze g, to the 
 bursting charge d. The balls are held 
 together by melted resin, and a paper 
 lining prevents the adhesion of the 
 matrix to the walls of the envelope. 
 
 This shrapnel has the following ad- 
 vantages : 
 
 i. Those common to all oblong pro- 
 jectiles of greater range and accuracy, 
 
 FIG. 159. 
 
 and, for a given cross-section, containing a larger number 
 of projectiles than the corresponding spherical shrapnel. 
 
 2. The charge, being in rear, acts, as with the Boxer 
 spherical shrapnel, to increase the forward velocity of the 
 bullets after rupture. 
 
 3. The head and its attachments, being relatively weak, 
 give way easily, and the bullets are swept out to the front 
 by the rear disk e\ the action in this respect being like the 
 discharge of canister. 
 
PROJECTILES AND ARMOR. 2QI 
 
 The disadvantages are : 
 
 1. The body being of cast iron, the walls are made com- 
 paratively thick to withstand the shock of discharge, and 
 this reduces the interior capacity, and consequently the 
 number of bullets which the shrapnel contains. 
 
 2. The wooden head takes up room which can be better 
 utilized. 
 
 3. The delay caused by the communication of fire from 
 the fuze to the bursting charge may interfere with the 
 action of the shrapnel, and cause it to pass beyond its 
 proper point of burst before exploding. 
 
 4. The effect of the pressure of the gases from the 
 central tube, is to cause an increase in the lateral spread of 
 the bullets, which is objectionable. 
 
 MODERN SHRAPNEL. These disadvantages suggest the 
 improvements which have been made in modern shrapnel. 
 Several of these are now under trial in this country. The 
 following changes have been made in them, in comparison 
 with the Boxer oblong shrapnel : 
 
 1. To give sufficient strength of wall to withstand the 
 shock of discharge, the body is made of drawn-steel tubing, 
 and the head and base are welded on by electricity. As this 
 is an expensive construction, wrought-iron tubing has been 
 substituted for the steel, and the head and base are made of 
 cast iron screwed into the wrought-iron body. 
 
 2. In case the bursting charge is in front, as in one of the 
 shrapnel undergoing trial, a cast-iron chamber takes the 
 place of the wooden head of the Boxer, and contains the 
 bursting charge and fuze. 
 
 3. To lessen the delay caused by communication of fire 
 through the central tube to the rear bursting charge, this 
 tube is enlarged, on the interior, and made of brass tubing 
 so as to give a larger channel for the passage of the flame, 
 and it does not occupy more space in the shrapnel, as the 
 exterior diameter of the tube is not changed. 
 
 4. To prevent adherence of the balls after rupture, the 
 matrix is made of cast iron, indented so as to hold the balls 
 in place and form a solid mass with the projectile, and yet 
 
292 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 so arranged as to break up into fragments when the shrap- 
 nel bursts, which add their effect to that of the balls. 
 
 POSITION OF BURSTING CHARGE. When the bursting 
 charge is in front, we have the following advantages : 
 
 1. It occupies less space in the shrapnel, since no central 
 tube is required ; 
 
 2. It acts promptly to burst the case, and hence the point 
 of burst can be more accurately fixed ; 
 
 3. It occupies space in the shrapnel which it is difficult 
 to fill with bullets. 
 
 Its disadvantage is: 
 
 i. It decreases the velocity of the fragments in the plane 
 of fire, instead of increasing it. 
 
 When the bursting charge is in rear, it has the advan- 
 tage : 
 
 i. It increases the velocity of the fragments in the plane 
 of fire. 
 
 Its disadvantages are : 
 
 1. It occupies increased space in the shrapnel ; 
 
 2. It causes delay in bursting ; 
 
 3. It increases the lateral spread of the fragments ; 
 
 4. It is more expensive in construction. 
 
 For these reasons it is probable that the front charge 
 will be adopted, but it is not yet settled. 
 
 161. Description of Modern Shrapnel Steel- welded Frankford 
 Arsenal. 
 
 STEEL-WELDED. The steel-welded shrapnel (Fig. 160) 
 consists of a steel tube, a, to which the base b and head c 
 are welded by electricity. The charge is in rear, and is 
 separated from the bullets by a disk, d. The central tube 
 communicates fire to the charge from the fuze. The bul- 
 lets are held in place by a matrix of resin, melted and poured 
 in after the former are in place. 
 
 THE FRANKFORD ARSENAL. This shrapnel (Fig. 161) 
 consists of a wrought-iron tube, a, to which the base b of 
 cast iron is screwed. The rotating band c fits in a groove 
 cut on the rear end of the tube a. The head d is also of 
 cast iron, carries the bursting charge and fuze, and is 
 
PROJECTILES AND ARMOR. 
 
 2 93 
 
 screwed to the body. The bullets are held in place by a 
 skeleton matrix of cast iron, consisting of a top and bottom 
 plate, and a series of intermediate plates. 
 
 These intermediate plates are made in segments, so that 
 
 the whole can be built up layer 
 by layer, and inserted in the 
 body of the case. The head 
 and base are then screwed on, 
 the band being inserted in its 
 groove before the latter is 
 screwed home. This shrapnel 
 
 -d 
 
 
 FIG. 160. 
 
 FIG. 161. 
 
 is much cheaper than the steel one, and has given good 
 results at the Proving Ground. 
 
 The Hotchkiss shrapnel is similar to this. 
 
 162. Necessity for Rotation of an Oblong Projectile Energy of 
 Rotation Required. 
 
 NECESSITY. It has been shown that an oblong projec- 
 tile when rotating about its longer axis, will move through 
 the air in the general direction of that axis. 
 
 Without this motion of rotation about the longer axis, the 
 resultant resistance of the air, acting with a certain lever 
 
2Q4 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 arm, will cause the projectile to rotate about a short axis 
 through the centre of mass. 
 
 The effect of this would be to cause great irregularity of 
 motion, owing to the varying surface presented to the air 
 by the projectile, during this rotation. 
 
 The rotary motion about the longer axis is imparted 
 to the projectile by cutting spiral grooves in the surface of 
 the bore, and by placing a device upon the projectile which 
 will fit in these grooves, and thus cause the projectile to 
 take up the rifled motion. 
 
 ENERGY OF ROTATION. The question as to the amount of 
 energy of rotation about the longer axis which the projectile 
 must have, to enable it to maintain its proper position dur- 
 ing flight, requires for its determination analytical methods 
 which are too complex to be given here. A general discus- 
 sion will show upon what principles it depends. 
 
 163. General Discussion of the Rotation of a Projectile Value of R. 
 The general discussion of the motion of rotation of an ob- 
 long projectile, based upon Euler's equations, shows that for 
 a projectile rotating from left to right, as in our service, the 
 longer axis in the time t will deviate to the right of the 
 plane of fire through an angle, 0, whose value is 
 
 Rl 
 
 t = te i > (242) 
 
 in which (see Fig. 162) R is the resistance of the air acting 
 
 at the centre of pressure, / 
 its lever-arm with reference 
 to a horizontal axis through 
 the centre of gravity, / the 
 moment of inertia about the 
 longer axis of the projectile, 
 and GO the angular velocity about the same axis'. 
 
 In order that the projectile may be stable, Rl must be small 
 and IGO large. The methods of decreasing R will be explained. 
 In order that / may be small, the centre of mass and cen- 
 tre of pressure must coincide as nearly as possible. The best 
 position for the centre of mass is determined by experimen- 
 
PROJECTILES AND ARMOR. 295 
 
 tal firing, the projectile being so weighted that this centre 
 can be changed. 
 
 To increase /, the diameter of the projectile n ust be in- 
 creased, its weight remaining constant ; or its mass or weight 
 may be increased, if its dimensions are constant, by increas- 
 ing the density of the material of which it is made. 
 
 GO may be increased by giving a more rapid twist to the 
 grooves in the gun, but this is limited by the increased 
 strain brought upon the gun, and upon the projectile. 
 
 Equation (242) shows, generally : 
 
 1. As / increases, increases; and since /depends on Z, 
 the total length of the projectile, if we increase the length 
 of the projectile, we must increase /or GO, or both. 
 
 Therefore generally a long projectile must have greater 
 angular velocity about its longer axis, than a short one of 
 the same calibre. 
 
 2. If two projectiles have the same length but different 
 diameters, the value of / will be greater for the larger pro- 
 jectile, and hence GO may be less. That is, the projectile of 
 greater diameter will require less angular velocity about its 
 longer axis, than the projectile of smaller diameter and the 
 same length. 
 
 3. If we have two similar projectiles of different densi- 
 ties, the dense projectile will require less angular velocity 
 about its longer axis, since its mass, and hence its moment of 
 inertia, is greater. Also, a shell will be more stable and re- 
 quire less angular velocity than a similar shot of the' same 
 weight, since its radius of gyration is greater. 
 
 4. Since = -j^-t measures the deviation of the longer 
 
 IGO 
 axis in the time /, the reciprocal, 7, may be taken as the 
 
 measure of the capacity of this axis to resist deviation ; and 
 for a given value of R at any time t it is evident that by 
 
 increasing the value of the ratio we increase the stability 
 
 of the projectile. 
 
 VALUE OF R. The resistance of the air, R, varies with 
 the form, cross-section, and velocity of the projectile, and 
 
296 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 with the density of the air. The resistance being R, the 
 retardation produced by this resistance will be 
 
 M* 
 
 M being the mass of the projectile. 
 
 This value of the retardation has been determined by 
 experiment, as will be explained in Exterior Ballistics. 
 
 r> 
 
 In these experiments, the expression for has been as- 
 sumed to be (equations (263) and (265), Exterior Ballistics) 
 
 & 
 
 in which A, --, and c are constants, whose values are ex- 
 
 plained in Exterior Ballistics, and f (v) is some function of 
 the velocity of the projectile. Hence we may write 
 
 For a given value of v, the retardation increases with the 
 
 72 
 
 factor -=-- and hence this factor must be made as small as 
 W 
 
 possible, by increasing Wand decreasing d. The reciprocal 
 
 W 
 of this factor, , may then be taken as a measure of the 
 
 CL 
 
 capacity of the projectile to overcome the resistance of the 
 air, just as measures its stability. 
 
 164. Sectional Density How it May be Increased Effect of its 
 Increase on the Gun. 
 
 W 
 SECTIONAL DENSITY. The factor is called the " sec- 
 
 tional density" of the projectile. The area of base being 
 
 W 
 
 \7icF , - - will be the weight of the projectiie per unit area 
 
PROJECTILES AND ARMOR. 297 
 
 W 
 
 of base, and hence -^ is taken as a measure of this weight, 
 
 the constant factor \n being omitted. The sectional density 
 is very important in considering the motion of a projectile 
 in air, and also in the gun. 
 
 If two projectiles have the same initial velocity, but 
 different sectional densities, that having the greater sec- 
 tional density will be less retarded by the air, equation (244), 
 and consequently will lose less velocity. Hence for a given 
 range, its time of flight will be less, and being exposed to 
 the action of the air, and other deviating causes, for a less 
 time, its accuracy will be greater. 
 
 If the two projectiles be fired with the same angle of 
 elevation and the same initial velocity, that having the 
 greater sectional density will have the greater range, since 
 it retains more velocity at the end of each successive inter- 
 val of time. 
 
 For the same initial velocity, the trajectory or path of 
 the projectile having the greater sectional density, will be 
 flatter or less curved than that of the other, because since 
 its velocity is greater at any point of its path, its time of 
 passage over a given distance is less, and consequently the 
 time during which the force of gravity acts upon it to pro- 
 duce curvature is less. This gives greater accuracy of fire. 
 
 An increase of sectional density therefore increases 
 
 1. The accuracy ; 
 
 2. The range ; 
 
 3. The flatness of the trajectory. 
 
 How IT MAY BE INCREASED. The sectional density 
 may be increased by increasing W or by decreasing d. W 
 may be increased by keeping the calibre constant, and in- 
 creasing the length of the projectile. This has been done 
 with modern projectiles, for large guns, till the length is 3! 
 to 4 calibres. 
 
 It may also be increased by increasing the density of the 
 metal of which the projectile is made. This is done by 
 using lead for small-arm projectiles, but this material does 
 not possess sufficient hardness for projectiles for larger 
 guns. 
 
298 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 The sectional density may also be increased, by fixing- 
 the weight W, and decreasing the calibre, or d. This 
 method has been adopted for small arms, the calibre and 
 weight of projectile having both been reduced in such pro- 
 portions as to increase the sectional density. 
 
 EFFECT OF INCREASE OF SECTIONAL DENSITY ON THE 
 GUN. Let P represent the maximum pressure per square 
 
 inch on the base of the projectile ; 
 M t the mass of the projectile. 
 
 Then we have 
 
 M~ = nr*P, (245) 
 
 from which 
 
 dv nr'P _ nr*P Pg 
 
 dt ' M W W 
 
 . (246) 
 
 g 
 Replacing r by its value %d, 
 
 (247) 
 
 W dv 
 
 As the sectional density increases, decreases, and 
 
 hence to obtain an increase of acceleration, the value of P, 
 or the pressure on the projectile, and consequently that 
 upon the gun, must increase. Since the maximum pressure 
 is fixed by the strength of the gun, equation (247) limits the 
 value of the sectional density, for a given acceleration. The 
 initial velocity is 
 
 (248) 
 
 -=/: 
 
 and for a given value of P, this velocity will decrease, from 
 equation (247), as the sectional density increases. Hence 
 when rifled guns were first introduced, using the old quick 
 powders, the pressures could not be increased, and conse- 
 quently the initial velocities of the projectiles decreased. 
 When slow-burning powders were adopted, with longer 
 
PROJECTILES AND ARMOR. 299 
 
 bores, the sectional density of projectiles was increased, and 
 also the initial velocities, with less maximum strain on the 
 gun. The reason for this has been explained in Interior 
 Ballistics. 
 
 165. Rifling Kinds Uniform Increasing. 
 
 RIFLING. In order to give to the projectile the angular 
 velocity GO required in equation (242), it is necessary to cut 
 spiral grooves in the bore of the gun, and to attach a device 
 to the projectile which will fit these grooves. The spiral 
 groove in the gun is called the rifling. 
 
 Let v denote the velocity of the projectile at any point 
 
 of the bore ; 
 0, the angle made by the tangent to one of the 
 
 grooves, with an element of the bore ; 
 r, the radius of the bore. 
 
 The velocity of the projectile along the groove, is the 
 resultant of two components, v, and v tan 0, at right angles 
 to each other. 
 
 The actual velocity of rotation of a point on the surface 
 of the projectile is cor, and this is equal to the component 
 v tan 0. Hence 
 
 car = v tan ; .*. GO = tan 0. ... (249) 
 
 UNIFORM RIFLING OR TWIST. If the value of be 
 constant for the whole length of the bore, the rifling or 
 twist is said to be uniform. 
 
 In this case the angular velocity varies directly with v 
 and inversely with r. The objection to uniform rifling is as 
 follows : 
 
 When the projectile starts from its seat, and during the 
 first part of its path in the bore, the pressure of the powder- 
 gas rises to its maximum, and the gun is subjected to the 
 greatest stress at this time. 
 
 With the uniform rifling, the angular velocity OD is im- 
 pressed upon the projectile at this time also. Hence, while 
 the gun is subjected to its greatest stress, due to the start- 
 
I3OO TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 ing of the projectile, it is also subjected to its greatest stress 
 in giving rotation to the projectile. 
 
 After rotation is once acquired, the stress due to this 
 cause falls off very rapidly. Therefore, with the uniform 
 twist, both these stresses act together. 
 
 INCREASING TWIST. If, however, the angular velocity GO 
 be imparted gradually to the projectile, it moves from its 
 seat more readily, and the strain on the gun at first is thus 
 diminished. When the powder pressures fall off along the 
 bore, the twist, or value of 0, gradually increases, till it 
 reaches its final value necessary to impart the angular 
 velocity GO to the projectile. In this case the stresses are 
 more uniformly distributed along the bore, and the gun 
 strained less at the origin of motion, while the final velocity 
 of rotation is the same. 
 
 The twist in this case is called an increasing twist, as the 
 value of increases gradually from the breech. In modern 
 guns the curve ol the rifling, when developed on a plane 
 surface, is a semi-cubic parabola, whose equation is 
 
 ji = 2pX. 
 
 To give steadiness of rotation to the projectile, the twist 
 increases from the breech to a point about two calibres 
 from the muzzle, and from this point to the muzzle it is 
 uniform. 
 
 166. Twist in Terms of Calibre Kinds of Grooves. 
 
 TWIST IN CALIBRES. The twist is generally expressed in 
 terms of the calibre, as one turn in ten calibres, etc. ; mean- 
 ing that the projectile makes one complete turn in passing 
 over a length of bore equal to ten calibres, etc. Suppose 
 the groove to be developed (Fig. 163), and let a be the de- 
 velopment of one turn of the uniform groove, n the number 
 of calibres in which the projectile makes one complete turn, 
 and r the radius of the projectile, then the distance AB 
 = 2nr and BC = 2nr, and 
 
 2TCT 71 
 
 tan - - = , 
 n 
 
PROJECTILES AND ARMOR. 
 
 301 
 
 for the value of the tangent of the angle of the rifling. For 
 the increasing groove, is variable, but for any point, its 
 
 value is . In our service, the rifling of sea-coast guns is 
 
 increasing, from one turn in 50 calibres at the breech, to 
 one turn in 25 calibres at a distance of about two calibres 
 
 from the muzzle. For the field-guns, the rifling was for- 
 merly uniform, but in the later models an increasing twist 
 has been adopted. 
 
 KINDS OF GROOVES. The number, depth, and width of 
 grooves depend on the rotating device. By a groove is 
 understood the spiral cut made in the bore, and by a land, 
 the space between two adjacent grooves. 
 
 When rifling was first introduced, the grooves were few 
 in number, and as the points of contact of the projectile 
 with the bore were also few, these points required consid- 
 erable strength. The grooves were therefore made corre- 
 spondingly deep and wide. This decreased the strength of 
 the gun, as it increased the diameter of the bore subjected 
 to the action of the powder-pressure. With a change in 
 the rotating device, the grooves increased in number, and 
 decreased in depth and width. This is called polygroove 
 rifling, and adds greatly to the strength of the gun. In 
 spite of this, the grooves are sources of weakness, as the 
 action of the powder-gas tends to erode them at the junc- 
 tion of lands and grooves, and all sharp corners must be 
 avoided. 
 
 In small arms the presence of grooves adds to the diffi- 
 culty of cleaning the bore, and the grooves in these guns 
 are made as shallow as possible. 
 
3O2 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 The shape of the groove in the sea-coast guns in our ser- 
 vice is shown in Fig. 164, which gives the grooves of the 8" 
 rifle. 
 
 FIG. 164. 
 
 The number of grooves in sea-coast guns, is six times the 
 calibre of the gun in inches. Thus the 8-inch rifle has 48 
 grooves and lands ; the lo-inch, 60, etc. 
 167. Rotating Devices Studded System Flanged System. 
 
 ROTATING DEVICES. The spiral grooves having been cut 
 in the bore of the gun, it is necessary to attach some device 
 to the projectile which will fit into these grooves, and com- 
 municate the required motion of rotation to it. Although 
 muzzle-loading projectiles are practically obsolete, a few 
 such guns still remain in our service, and a description of 
 the means employed to give rotation to their projectiles 
 will show the development of such devices. 
 
 Since muzzle-loading projectiles are of less diameter 
 than the bore, the rotating device must be made either to 
 fit the grooves before firing, or to do so after firing, by the 
 action of the powder-pressure. Accordingly, the rotating 
 devices for muzzle-loading projectiles are divided into : 
 
 1. The studded or flanged system. 
 
 2. The expanding system. 
 
 STUDDED PROJECTILES. This system was generally used 
 for muzzle-loading projectiles in Europe, and especially in 
 England. The projectile (Fig. 165) was provided with studs 
 made of a soft metal, such as zinc or copper, to avoid 
 wearing the lands of the rifling. These studs were arranged 
 in two or three rows, depending on the length of the pro- 
 jectile, and at an inclination equal to the angle of the 
 grooves. They were inserted into undercut holes in the 
 projectile, and subjected to pressure, by which the soft metal 
 was forced to fill the holes. (See Fig. 165.) 
 
PROJECJ^ILES AND ARMOR. 
 
 303 
 
 The advantage of this system is that the projectiles are 
 certain to take up the rifled motion. 
 The disadvantages are : 
 
 1. The projectiles must be adjusted to 
 each particular twist ; and if two guns have 
 the same calibre, but a different twist of rifling, 
 different projectiles must be used for them. 
 
 2. They cannot be used with an increasing 
 twist. 
 
 3. Owing to the relatively small number 
 of studs, the pressure upon each is great, and 
 they are liable to shear. To avoid this they 
 must be made strong, and this necessitates 
 increased depth and width of rifling grooves, 
 and a corresponding weakening of the gun. 
 
 4. The stud-holes in the projectile weaken 
 
 FIG. 165. 
 
 the latter, and their irregular surface increases the resistance 
 of the air to its motion. 
 
 5. Unless a gas-check is provided on the base of the pro- 
 jectile, the escape of the gas between the projectile and the 
 bore erodes the latter. 
 
 THE FLANGED SYSTEM. In this system, flanges or ribs, 
 fitting the grooves, were used instead of studs, the flanges 
 being made generally of soft metal, except in case of the 
 Whitworth. The principal example of this class is the 
 Whitworth projectile, whose cross-section is a 
 hexagon, and whose plane faces are inclined at an 
 angle equal to that of the rifling (Fig. 166). The 
 bore of the gun is rifled to correspond (Fig. i66a). 
 In this case, the fit of the pro- 
 jectile in the bore was very ac- 
 curate, and any slight fouling 
 interfered with the loading. As 
 the flanges were of hard metal, 
 they could not yield, and hence 
 any obstruction was liable to 
 FIG. 166. FIG. i66. burst the gun. These projec- 
 
 tiles have given remarkable results as regards accuracy and 
 penetration, but they are no longer used. 
 
304 TEXT-BOOK OF ORDNANCE AND GUNNERY 
 
 168. Expanding System Hotchkiss. 
 
 EXPANDING SYSTEM. This system has been largely used 
 in the United States for muzzle-loading projectiles. 
 
 It consists in placing upon the rear end of the projectile, 
 or upon its cylindrical body, a band of soft metal, such as 
 lead or brass, which is expanded by the action of the pow- 
 der-gas, and forced into the grooves when the gun is fired. 
 
 The advantages of this system are : 
 
 1. It may generally be used with either a uniform or an 
 increasing twist. 
 
 2. Projectiles of the same calibre, having* different rotat- 
 ing devices of this class, will fit any gun of that calibre, and 
 are easily loaded. 
 
 3. By the expansion of the rotating device the escape of 
 gas between the projectile and bore is prevented, since the 
 band acts as a gas-check. 
 
 The disadvantages are: 
 
 1. In some of the devices the gas was uncertain in its ac- 
 tion, occasionally failing to produce expansion, and also tear- 
 ing off the rotating device, or causing it to " strip ;" thus 
 failing to give the rotary motion to the projectile, and when 
 fired over the heads of friendly troops, causing accident to 
 them from the fragments of the band. 
 
 2. It was expensive, and required careful handling to 
 prevent damage to the rotating device, and consequent ina- 
 bility to load. 
 
 3. It failed to centre the projectile in the bore. 
 The principal examples of this class are : 
 
 The Hotchkiss ; 
 
 The Parrot t ; 
 
 The Eureka ; 
 
 The Butler. 
 
 THE HOTCHKISS. This projectile consists 
 (Fig. 167) of a body, a ; a base, b ; and a jacket of 
 lead, c, of the same diameter as the body of the 
 projectile. 
 
 When fired, the pressure of the gas forces the 
 base b up on a, and thus the lead jacket c is ex- 
 panded into the grooves. 
 
PROJECTILES AND ARMOR. 
 
 305 
 
 169. Expanding System Parrott Eureka Butler. 
 
 PARROTT. In the Parrott system a brass ring or band, 
 a, is cast upon the base of the projectile 
 (Fig. 1 68), leaving a circular channel 
 or groove, b, between the ring and 
 the base. The gas acting in the chan- 
 nel, forces the ring outward into the 
 grooves. Frequently, however, the 
 ring was torn off the base of the pro- 
 jectile, as its hold was not sufficient. 
 
 EUREKA. In this system a brass 
 cup, a (Fig. 169), is placed on the base 
 of the projectile. This base is made 
 in the form of a frustum of a cone, 
 with the smaller base to the rear. It 
 has several longitudinal grooves, b, cut 
 in it, into which corresponding projec- 
 
 FIG. 168. 
 
 tions on the interior of the cup fit, and 
 these prevent the rotation of the cup 
 around the axis of the projectile, so 
 that the rotary motion communicated 
 to the cup by the rifling, is imparted 
 to the projectile. The cup is curved 
 where it rests against the rear end of 
 the projectile, and to prevent stripping, 
 it is held in place by the screw-bolt c. 
 When the piece is fired, the gas-pressure 
 forces the cup forward on the frustum 
 of the base, till its curved surface rests 
 against the rear of the projectile. 
 
 This causes the sides of the cup 
 to expand and forces them into the 
 grooves. It is a very satisfactory muzzle-loading rotating 
 device, and is still in use in our service. 
 
 BUTLER. This system was invented by Major Butler of 
 the Ordnance Department, and consists (Fig. 170) of a brass 
 ring a, having a lip or groove b in it. It is screwed to the 
 base of the projectile to prevent stripping. When the piece 
 is fired, the gas-pressure acts in the groove b, and forces the 
 
 FIG. 
 
306 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 FIG. 170. 
 
 outer portion c of the ring outward into the grooves, and 
 the inner portion d against the base of 
 the projectile, thus insuring the adher- 
 ence of the ring to the projectile. It is 
 one of the best of these devices, and is 
 still in service. 
 
 170. Breech-loading Projectiles First Ro- 
 tating Device Hotchkiss Projectile 
 Copper Bands. 
 
 ROTATING DEVICES FOR BREECH- 
 LOADING PROJECTILES. With breech- 
 loading guns the powder-chamber is 
 larger than the bore, and hence the 
 projectile may have a rotating device 
 larger than the bore, and this may be 
 compressed into the grooves by the action of the powder- 
 gas. This is called the ''compression system," to distin- 
 guish it from the studded or flanged, and the expansion 
 systems. Its advantages are : 
 
 1. The projectile is certain to take the grooves, since its 
 rotating device is compressed into them. 
 
 2. The rotating device being larger than the bore before 
 firing, it acts as a gas-check, and prevents any flow of gas 
 between the projectile and the bore. 
 
 3. It may be so shaped as to fit accurately the chamber 
 of the gun before firing, and thus perfectly centre the pro- 
 jectile, or make its axis coincide with that of the bore. 
 This gives increased accuracy of fire, and it is impossible to 
 accomplish it with any muzzle-loading system. 
 
 Its only disadvantage is perhaps a slightly greater strain 
 on the gun due to the increased pressure necessary to force 
 the band into the grooves, but with the slow-burning powder 
 used in modern guns this may be neglected. In fact it has 
 been shown in Interior Ballistics that this increased resist- 
 ance increases the muzzle velocity. 
 
 FIRST ROTATING DEVICE. When breech-loading guns 
 were first introduced, the rotating device was a jacket of 
 lead (Fig. 171) cast on the body of the projectile. 
 
PROJECTILES AND ARMOR. 
 
 307 
 
 The objections to this are that it is difficult to make the 
 lead adhere to the projectile, and it becomes 
 detached in flight. This is dangerous in firing 
 over friendly troops, and the energy commun- 
 icated to this lead jacket is lost ; also the con- 
 tact of the hot metal with the body of the pro- 
 jectile in the process of casting, is apt to injure 
 the structure of the latter. 
 
 One rotating device of this class, the Hotch- 
 kiss, is still in use for small-calibre projectiles. 
 
 HOTCHKISS B. L. PROJECTILE. The body 
 of the projectile a, Fig. 172, is grooved cir- 
 cumferentially for about one calibre in length, 
 
 as shown, and 
 
 
 1 
 
 
 
 ( 
 
 
 
 ( 
 
 
 s 
 
 ! 
 
 o 
 
 z 
 
 a 
 
 ^ 
 
 o: 
 
 l_u 
 
 C ( 
 
 -6 ^ 
 
 LJ 
 
 cr 
 
 ( 
 
 a \ 
 
 LJ 
 
 
 
 
 1- 
 
 L_ 
 
 ^ 
 
 La. 
 
 LJ 
 CD 
 
 ( 
 
 < 
 
 
 ( 
 
 | 
 
 
 J 
 
 1 
 
 ^ 
 
 l-d' 
 
 a 
 
 FIG. 172. 
 
 projections d of the band, and the metal thus 
 displaced is forced into the grooves d'. 
 
 COPPER BANDS. The lead jacket was next 
 replaced by two bands of copper, Fig. 173, 
 placed at equal distances from the centre 
 of gravity of the projectile. The front band 
 a, was used to support the forward por- 
 tion of the projectile, and its diameter was 
 slightly less than that of the bore between 
 lands. The rear band b, was of a larger 
 diameter, and was forced into the grooves, 
 giving the rotation. 
 
 FIG. 171. 
 over these 
 grooves c, is placed a band 
 of brass, b. 
 
 Longitudinal notches are 
 also made in the grooves c, 
 to prevent slipping of the 
 band around the axis of the 
 projectile. 
 
 When the gun is fired, 
 the gas compresses the band 
 into the grooves on the 
 body of the projectile, and 
 it takes a corrugated shape. 
 The lands cut through the 
 
 -a 
 
 FIG. 173. 
 
308 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 171. Rotating Device at Present Profile of Band Placing of Band 
 Position of Band. 
 
 RECENT DEVICE. It was found that the front bearing 
 or supporting band was not necessary, and in modern pro- 
 jectiles it is replaced by a slight swell, a, Fig. 174, at the 
 base of the ogival head. The surface a is turned to a 
 diameter slightly less than that of the lands, and the body 
 of the projectile left as it comes from the casting or forg- 
 ing process. 
 
 This is less expensive, and leaves the metal on the exte- 
 rior, which is stronger than any other part of the projectile. 
 
 The rotating band is made of copper, fitted in an under- 
 cut groove, as shown, Fig. 174. 
 
 a 
 
 FIG. 174. 
 
 DETAILS OF ROTATING BAND. In modern guns, the 
 powder-chamber is joined to the bore by a long conical 
 slope, cd, Fig. 174. The exterior of the rotating band has 
 a slope slightly greater than this, so that when the projec- 
 tile is in place, it will be accurately centred by the rear 
 portion of the band, and this part of the band will also act 
 as a gas-check, completely closing the interior of the bore. 
 A number of grooves or cannelures, ^, are turned on the 
 exterior of the rotating band, to diminish the amount of 
 metal to be cut through by the lands, allow space into which 
 the portion cut out may be forced, and at the same time 
 give the necessary length of bearing surface on the lands, 
 by retaining the width of the band unchanged. The ex- 
 
PROJECTILES AND ARMOR. 
 
 309 
 
 terior diameter of the band at the rear, is slightly greater 
 than that of the bore, measured from the bottom 
 of the grooves. 
 
 For the field projectiles, the band is more sim- , 
 pie, being a plain ring of copper with the front 
 and rear faces bevelled, Fig. 175. 
 
 PLACING THE ROTATING BANDS IN POSITION. 
 This is generally done in our service, by ham- 
 mering the band into place. The band may be 
 made in two semicircles, or in a single piece of i 
 copper, whose length is just sufficient to en- FlG - J 75- 
 
 circle the projectile. In either case 
 the cross-section before insertion is 
 as in Fig. 176 at a. 
 
 When inserted in the undercut 
 groove b in the projectile, it is ham- 
 mered, or subjected to pressure, till 
 it takes the position shown at e, com. 
 pletely filling the groove. 
 
 It is then turned in the lathe to 
 the proper dimensions. 
 
 POSITION OF REAR BAND. The 
 position of the rotating band has 
 
 '-d 
 
 FIG. 176. 
 
 great influence upon the range and accuracy of the pro- 
 jectile, as has been shown by numerous experiments. It 
 must be so placed that the distance cd, Fig. 176, will be 
 sufficient to resist the shearing effect of the rifling, which 
 would tend to strip the band off to the rear. This having 
 been provided for, the best position of the band is deter- 
 mined by experiment. 
 
 172. Form of Projectiles Head Spherical Density Weight. 
 
 FORM. Numerous experiments have been made to de- 
 termine the form of projectile that will best overcome the 
 resistance of the air. 
 
 The result of these experiments shows that the resist- 
 ance is affected by the shape of that portion of the head 
 where it joins the cylindrical body, and also by the rear 
 of the projectile, since the shape of these surfaces affects 
 
3io 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 (See " Exterior Bal- 
 
 \ 
 
 the flow of the air along its sides, 
 listics.") 
 
 HEAD. The heads of all 
 modern projectiles are ogival, 
 the radius of the ogive being 
 from 2 to 3 calibres. The more 
 pointed form gives less resist- 
 ance, but introduces elements of 
 weakness, and hence the above 
 radii mark the limits thus far. 
 The head is described with 
 radii as shown in Fig. 177. 
 
 SPHERICAL DENSITY. Let 
 
 W be the weight of a solid spherical projectile, whose 
 radius is r, and W the weight of the oblong projectile of 
 the same radius. 
 
 The ratio 
 
 W 
 
 FIG. 177. 
 
 is called the spherical density of the oblong projectile, and 
 it measures the number of times the weight of the sphere 
 is contained in that of the oblong projectile. We have 
 
 W = f Trr'tf, 
 
 in which d is the weight of a cubic inch of the metal of the 
 projectile, and r is in inches. Making d = lb., which is its 
 approximate value, and taking n = 3, we have 
 
 W = r* 
 
 and substituting in (250), we have 
 
 r. W 
 
 ^~ r s ' 
 
 (250 
 
 which is generally taken as the measure of spherical density. 
 
 This value has increased from 2.0, when oblong projec- 
 tiles were first introduced, to 3.0 in 1880, and 4.7 in 1894. 
 
 WEIGHT. For the weight of a spherical projectile we 
 have 
 
PROJECTILES AND ARMOR. 
 
 or the weight of a spherical projectile in pounds is equal to 
 the cube of its radius in inches. 
 
 For an oblong projectile we have, equation (251), 
 
 W = S X r\ 
 
 or the weight of an oblong projectile in pounds is equal to 
 its spherical density, multiplied by the cube of -the radius 
 in inches. Hence having the date of manufacture of a pro- 
 jectile, its spherical density is known, and from this its 
 weight. This rule gives very close approximations, and 
 avoids the necessity of remembering anything except the 
 spherical density. Since the weight is proportional to the 
 
 W 
 cube of the calibre, the quotient will be constant for all 
 
 similar projectiles. 
 
 173. Manufacture of Projectiles Pattern Flask Molding Gate 
 and Riser. 
 
 PATTERN. Cast-iron projectiles are made as follows : 
 
 A pattern is first made of the 
 shape of the projectile to be cast. 
 Its diameter is slightly greater 
 than that of the projectile, to I ' ' r~6 
 
 allow for the shrinkage or con- 
 traction of the metal in cooling. 
 It is also slightly conical, instead 
 of cylindrical, on the exterior, to 
 permit its ready withdrawal from 
 the mold. In Fig. 178 the pat- 
 tern is made in two parts, and 
 each part is conical from a to b. 
 The spindle c is used to support 
 the pattern in molding, and to 
 mark the position of the core in 
 the mold. 
 
 It terminates in a conical 
 bearing, d. FIG. 178. 
 
 Core. To form the interior cavity in a cored shot or 
 shell, a second pattern or core e, Fig. 178, is required. This 
 
 -c 
 
312 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 core is made of a mixture of sand and other substances 
 which render it adhesive, and is formed upon a hollow 
 spindle, /, which terminates in a conical bearing, g, of the 
 same size as d on the shot-pattern spindle. The spindle/ 
 being hollow, and having holes along it, allows the gases 
 formed by the contact of the melted metal with the core, to 
 escape. 
 
 FLASK. The pattern for the shot or shell is placed in a 
 box called a flask, Fig. 179. This flask is made in parts 
 
 FIG. 179. 
 
 corresponding to the pattern of the projectile, and these 
 parts are bolted together before casting. It contains a 
 cross-bar, a, at the top, with a conical hole in it, into which 
 the conical bearing of the spindle fits as shown. 
 
 MOLDING. To form the mold, the part of the pattern 
 containing the conical spindle, is seated in the cross-bar a, 
 and this part of the flask, with pattern, placed on a board, 
 
PROJECTILES AND ARMOR. 313 
 
 the plane xy down. Cylindrical sticks b and c are placed as 
 shown, and molding composition, composed of sand, clay, 
 and carbonaceous material, rammed in. This part of the 
 flask is now inverted, the remainder of the pattern, the 
 flask, and the cylindrical stick b put in place, and molding 
 composition rammed in from the opposite direction, filling 
 the flask. The parts of the flask are then separated along 
 xy, and the pattern and sticks withdrawn. 
 
 The core, having been separately molded, is then put in 
 place, its spindle occupying the position shown, and being 
 centred by the conical bearing in the cross-bar a. 
 
 The parts of the flask are next bolted together. 
 
 GATE AND RISER. The channel b is called the gate. 
 The metal is poured through it into the mold. In large 
 projectiles, it generally enters low down, and in a tangen- 
 tial direction, to give a rotary motion to the metal as it 
 enters the mold, and thus sweep the scoria and impurities 
 to the centre and top. 
 
 The channel c is called the riser. It allows the escape 
 of gas from the mold, and the collection of the scoria, and 
 also allows fresh metal to.be poured in to fill up cavities and 
 make up for shrinkage due to cooling. 
 
 174. Operation of Casting Kind of Iron Used Position of Head 
 and Base of Projectile in Mold Steel Projectiles. 
 
 OPERATION OF CASTING. The cast iron is melted either 
 in cupola or reverberatory furnaces, and run into ladles, 
 from which it is poured through the gate b, into the mold. 
 The pouring is continued till the metal fills the riser c, and 
 fresh portions of melted metal are added to the riser as the 
 latter sinks. 
 
 As soon as the iron has cooled sufficiently, or set, the 
 flask is removed, the core broken up, the spindle drawn out, 
 and the projectile covered with the molding composition, to 
 allow it to cool slowly. If a chilled projectile is to be cast, 
 the chill is inserted in the mold before casting, as previously 
 explained. 
 
 KIND OF IRON. For small projectiles, since they cool 
 rapidly, and become very hard, soft iron is employed. For 
 
314 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 large projectiles, a harder and tougher iron is used. The 
 selection of the proper kinds of iron can only be determined 
 by experience, and it is usual to prescribe a certain tensile 
 strength for each kind of projectile, and to test specimens 
 from a number of them, to see that they come up to the re- 
 quired standard. 
 
 POSITION OF HEAD AND BASE IN MOLD. In Fig. 179 
 the projectile is shown cast head down, with the core-spin- 
 dle projecting through the base. This position gives great 
 density to the head, and less to the base. For armor- 
 piercing shot, and in all cases where great strength of head 
 is required, the casting is made in this position. But for 
 shell, especially those with a base fuze, it is important to 
 have a strong and sound base, as if it is weak or spongy ? 
 the gas from the powder-charge would penetrate the base, 
 and -burst the shell in the gun. In this case, therefore, the 
 shell would be cast base down. 
 
 STEEL PROJECTILES. Forged steel projectiles are cast 
 as ingots, and are forged, and bored and turned to proper 
 dimensions. 
 
 They are then tempered by a secret process, and are now 
 made of such hardness and toughness, that they will pene- 
 trate the best armor-plates whose thickness does not exceed 
 \\ times their diameter, without cracking or deforming the 
 projectile. 
 
 Cast-steel projectiles are also tempered by a secret pro- 
 cess. 
 
 175. Inspection and Proof of Projectiles Quality of Metal Shape 
 
 and Dimensions Eccentricity Ballistic Test. 
 The objects of inspection are : 
 
 1. To test the quality of the metal ; 
 
 2. To see that the shape and dimensions agree with those 
 specified ; 
 
 3. To see that the centre of gravity is on or near the 
 longer axis of the projectile. 
 
 QUALITY OF METAL. This is determined by testing spec- 
 imens taken from different lots. For cast-iron projectiles, 
 the soundness is tested by striking the projectile with a ham- 
 
PROJECTILES AND ARMOR. 315 
 
 mer, and a punch is used to determine the depth of any holes 
 that may be discovered. Finally the shot or shell is sub- 
 jected to water or steam pressure, applied to its interior. 
 Any cracks or cavities will be detected by the escape of 
 the water or steam. Chilled shot are struck with a hammer, 
 at the junction of head and body. 
 
 For Steel S/wt and Shell chemical analyses are made, to 
 determine the composition. After the final treatment, the 
 shot are cooled to about 40 F., and then suddenly heated by 
 plunging them into a water-bath, at a temperature of 212 F. 
 When they become uniformly heated to this temperature, 
 they are suddenly plunged, with their axes horizontal, half 
 way into a bath of water, at a temperature of 40 F. Any 
 great initial strain to which they may have been subjected in 
 tempering, will be detected by this treatment. The shell 
 are subjected to an interior hydraulic pressure of 1000 Ibs. 
 per square inch. 
 
 SHAPE AND DIMENSIONS. These are determined by tem- 
 plets and gauges. For example, the profile of the projec- 
 tile is determined by using a templet of sheet iron or steel, 
 correctly made, and applying it to the exterior of the pro- 
 jectile as in Fig. 180, a being the templet. 
 
 FIG. 1 80. FIG. 181. 
 
 The diameters are determined by two rings, called ring 
 gauges, Fig. 181. One of these has a diameter equal to 
 the maximum that is allowed, and the other the mini- 
 mum. 
 
 The maximum ring must pass overall the projectiles, and 
 'the minimum over none. 
 
 ECCENTRICITY. When the centre of gravity of the pro- 
 
TEXT-BOCK OF ORDNANCE AND GUNNERY. 
 
 a 
 
 a 
 
 jectile does not lie on the longer axis, the projectile is ec- 
 centric. 
 
 This eccentricity, if large, affects the 
 flight of the projectile, causing irregu- 
 larity, and hence its limits must not ex- 
 ceed a certain amount. To detect it, 
 the projectiles are first placed on a roll- 
 ing-table, which is an iron table having 
 two parallel ribs, a a, Figs. 182 and 183, 
 at a distance apart slightly less than the 
 length of the cylindrical body of the pro- 
 jectile. 
 
 This table being leveled, if the centre 
 of gravity of the projectile, does not CO- 
 FIG. 182. incide with the longer axis, the projec- 
 tile when rolled on the ribs, as shown, will come to rest 
 with its centre of gravity below that axis. If no eccen- 
 tricity exists, the projectile will remain indifferently 
 
 D 
 
 FIG. 183. 
 
 in any position. When eccentricity is detected by this 
 means, its amount can be measured with the eccentric cali- 
 pers. These consist of a curved steel arm, d, Fig. 183, car- 
 
PROJECTILES AND ARMOR. 317 
 
 rymg a sliding point, b, and a scale, c. The point is gradu- 
 ated in inches, and c is a vernier scale. The thickness of 
 wall is read off on the scale, and that of the opposite wall 
 also. One half the difference of the readings, gives the 
 eccentricity. 
 
 BALLISTIC TEST. Steel shot and shell are subjected to 
 actual firing tests against armor-plates. For this purpose a 
 certain number are taken from each lot manufactured. The 
 shot are fired with a striking velocity of 1625 feet-seconds 
 against a steel plate i-J times the calibre of the gun in thick- 
 ness, and the 12" mortar shell against a 4^-inch steel plate, 
 at an angle of 60. The shot and shell must penetrate com- 
 pletely in each case, without breaking up. 
 
 ARMOR. 
 
 176. Kinds of Armor. 
 
 Armor may be divided into 
 
 1. Chilled cast iron ; 
 
 2. Compound ; 
 
 3. Steel. 
 
 Wrought-iron armor is now obsolete. 
 
 Chilled Cast-iron Armor. This armor, on account of its 
 great weight, is used only on land, in the form of turrets. 
 
 It is manufactured by Gruson, of Germany, and is cast 
 in large blocks of the proper shape, the outer face of the 
 blocks being chilled, and thus acquiring great hardness. 
 These blocks are built into turrets, whose form is shown in 
 the text-book of the Engineering course. It depends for its 
 great resistance upon the following : 
 
 1. Its intense surface hardness prevents the entrance of 
 the projectile ; 
 
 2. Its great mass distributes the effect of the blow ; 
 
 3. Its curved form deflects the projectile. 
 
 Its resistance to penetration is greater than that of any 
 other armor. 
 
 Compound Armor. Wrought-iron armor was the first kind 
 adopted, and it had sufficient resistance to keep out the or- 
 dinary cast-iron projectiles, but was readily penetrated by 
 those of chilled cast iron. 
 
3l8 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 It became necessary, therefore, to harden the face ol the 
 armor in order to break up these projectiles. This led to 
 the introduction of the compound armor, which has been 
 extensively used in England, and is still employed there. 
 
 It is formed by welding a hard steel face to a wrought- 
 iron back, and the armor is distinguished into two makes, 
 according to the method of welding adopted. 
 
 The two methods of manufacture are : 
 
 1. Cammell & Co. Wilson s Patent. The firm of Cammell 
 & Co. manufacture compound armor by the Wilson patent, 
 which consists in forming a back of wrought iron, by forg- 
 ing or rolling. This back is placed in a furnace, raised to a 
 welding heat, and while at this temperature a layer of 
 melted steel is run on one of its faces. After partially cool- 
 ing, the compound plate is removed from the furnace and 
 passed between heavy rolls, to reduce it to the proper thick- 
 ness, and improve its quality. The steel face is then treated 
 to remove strains. 
 
 2. Brown & Co. Ellis Patent. This method consists in 
 forming the wrought-iron back and hard steel face sepa- 
 rately. These are then placed in a furnace parallel to each 
 other, and a short distance apart, and raised to a welding 
 heat. Melted steel is then run between the plates, welding 
 them together. 
 
 177. Steel Armor History Improvements Latest Steel Plates- 
 Harvey and Tresidder Processes of Surface Hardening. 
 HISTORY. Steel armor, when first introduced, was hard 
 and brittle, and broke up under the action of projectiles. 
 The percentage of carbon was then reduced, and the plates 
 no longer broke up, but allowed the projectiles to penetrate. 
 It was shown, however, by the Italian experiments at Spez- 
 zia in 1876, that the low steel plate was superior to those 
 made of wrought iron. To prevent the penetration of pro- 
 jectiles, the face of the plate was tempered in oil, or oil- 
 hardened, and the plate then annealed, to remove internal 
 strains. As projectiles improved, however, this hardness 
 was not great enough to resist penetration, and hence new 
 improvements were made. 
 
PROJECTILES AND ARMOR. 319 
 
 IMPROVEMENTS. These consist generally 
 
 1. In having better facilities for the mechanical treat- 
 ment of steel in large masses, such as heavy hammers, 
 forging-presses, etc. 
 
 2. Combination of the steel with other ingredients, such 
 as nickel, which increases its toughness and tenacity, and 
 consequently decreases its tendency to break up. 
 
 3. Special treatment of the steel, as the Harvey process, 
 by which the face is made hard, while the back retains its 
 toughness. 
 
 LATEST STEEL PLATES. From the time of the Italian 
 experiments in 1876, up to those at Annapolis in 1890, com- 
 petitive trials have been going on between the steel and the 
 compound armor. 
 
 The tests at the latter place, showed the superiority of 
 the all-steel plate, and it has been adopted in our Navy. 
 
 The steel plates which have given the best results up to 
 the present time, are known as high-carbon nickeled steel 
 and low-carbon nickeled steel, referring to the relative quan- 
 tity of carbon in the alloy, although it is small in each case. 
 The high-carbon nickeled-steel plate has so far given the best 
 results. All the plates are hardened on the surface by the 
 Harvey process. 
 
 HARVEY PROCESS. This consists in carbonizing to a 
 higher degree the outer surface of the plate, for a certain 
 depth, depending on the dimensions of the plate, and then 
 hardening this surface. 
 
 The process is as follows : The plate is embedded in 
 sand and clay in a furnace, leaving a certain thickness ex- 
 posed. The furnace is then filled with carbonaceous material, 
 well packed over the exposed portion of the plate, and the 
 whole raised to a high temperature, which is maintained for 
 some time. The material is then removed, and when the 
 plate has cooled sufficiently, its surface is hardened by the 
 application of cold water. 
 
 TRESIDDER PROCESS. This process is used in England, 
 and consists in heating the plate to a certain temperature, 
 and applying cold water to the surface under heavy press- 
 ure, and through a number of small holes, thus producing 
 
320 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 numerous small streams of water acting together. The idea 
 is that the force with which the water is applied, brings it 
 directly into contact with the hot metal, thus cooling it 
 rapidly, and preventing the formation of the envelope of 
 steam (spheroidal state) around the particles of water, and 
 the consequent slow rate of cooling, which would be the 
 case if the water were applied without pressure. 
 
 178. Effect of Projectiles on Armor Early Armor Compound 
 
 Armor Steel Armor. 
 Armor yields in two ways : 
 
 1. By racking, or breaking up ; 
 
 2. By punching. 
 
 EARLY ARMOR Punching. Wrought-iron armor was at 
 first generally attacked by heavy projectiles, moving with 
 low velocities, as with the old 1 5-inch smooth-bore. Al- 
 though the armor itself was soft, and yielded naturally by 
 punching, the effect of these projectiles was to break its 
 fastenings, and cause it to rack. As guns and projectiles in- 
 creased in power, however, this armor yielded entirely by 
 punching. That is, the effect of the blow was to punch a 
 hole through the armor, and if the bolts held, no part of 
 the plate beyond that struck, was affected. 
 
 Racking. The object of armor, however, being to keep 
 out projectiles, this defect led to the introduction of the 
 harder kinds, as shown. This hard armor, instead of yield- 
 ing locally to the blow of the projectile, distributed the 
 energy of that blow over a greater mass of the plate, and 
 when the energy was sufficient, the plate broke up, or was 
 racked. 
 
 COMPOUND ARMOR. The effect of projectiles upon this 
 armor, is to break up the hard steel face, and to punch the 
 wrought-iron back. The punching effect is, however, very 
 much diminished by the energy lost in breaking up the 
 steel face. The difficulty with this armor seems to be that 
 the welding of the steel face to the wrought-iron back is 
 uncertain, and hence after a few blows, the steel face breaks 
 up, and separates from the wrought-iron back. Also the 
 face being elastic, and the back having no elasticity, the 
 
PROJECTILES AND ARMOR. 321 
 
 former, after being struck, tends to recover its first position, 
 while the latter does not. This increases the tendency of 
 the front and back to separate. It follows that a compound 
 plate must have a rigid support in rear for the best results. 
 
 STEEL ARMOR. This armor at first yielded by rack- 
 ing, owing to its hardness and brittleness. Oil-hardening, 
 however, decreased its brittleness and increased its tough- 
 ness, so that the effect of the improved projectile was to 
 punch it. 
 
 The modern processes of surface-hardening, however, 
 have combined hardness with toughness, so that, at the pres- 
 ent day, the armor resists both racking and punching to a 
 remarkable degree. The history of the improvement is ob- 
 vious : decrease of hardness and brittleness to decrease 
 racking, and afterwards a combination of hardness and 
 toughness to prevent both punching and racking. 
 
 179. Backing Fastenings for Old Armor. 
 
 BACKING. That portion of an armored structure di- 
 rectly in rear of the plate, is called the backing, and the 
 character of this backing depends upon that of the armor. 
 
 Chilled Cast Iron. This armor has no backing, or rather 
 the cast iron itself may be regarded as forming the backing 
 for the hard chilled face, since the thickness and mass are 
 great. 
 
 Compound Armor. For this armor, a rigid backing is re- 
 quired, to give the best results. For land structures, a rigid 
 backing may be used, since weight is no objection, but for 
 ships, such a backing is impossible, and it would therefore 
 seem that this armor cannot give the best results when used 
 under such circumstances. It is, however, the standard 
 armor of the British Navy. An objection to the rigid back- 
 ing is that it tends to cause racking of the armor-bolts. 
 When an elastic backing is used with this armor, it allows 
 the plate as a whole to yield to the blow of the projectile. 
 But, as before stated, the steel face, being elastic, returns to 
 its former position after the blow, while the wrought-iron 
 back does not, and hence there is a tendency for the face 
 and back to separate. The rigid backing, on the other hand, 
 has the opposite effect. 
 
322 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 Steel Armor. This armor, being elastic, requires an elastic 
 backing, and not a rigid one, since the elastic backing allows 
 the plate to yield to the force of the blow, and the elasticity 
 of the plate causes it to return to its former position. 
 
 Fig. 184 shows the arrange- 
 ment of backing as generally 
 used, and may consist of one or 
 two thicknesses of timber, b y 
 placed against the steel sides, 
 a a, of the vessel. 
 
 FASTENINGS FOR OLD AR- 
 MOR. The original armor-bolt 
 
 FIG. 185. 
 
 FIG. 184. 
 
 FIG. 186. 
 
 for wrought-iron armor, was shaped as shown in Fig. 185. 
 
 The objections to this bolt were : 
 
 I. If under water, it leaked. 
 
 * 2. When the plate was struck, the bolt would snap at 
 the bottom screw-thread a, and the nut would fly off, acting 
 as a projectile. 
 
 The French made the first attempt to remedy this, by 
 using an ordinary wood-screw, Fig. 186, which screwed into 
 the backing, but did not pass completely through it. This 
 prevented leakage, and the flying of the bolt-heads about 
 the deck. 
 
 The English changed the arrangement of the armor-bolt 
 
PROJECTILES AND ARMOR. 
 
 323 
 
 by placing a rubber washer, k, under the nut, and cutting a 
 plus thread on the bolt, as in Fig. 187. In this case the bolt 
 
 FIG. 187. 
 
 has the same strength throughout, the thread is not a source 
 of weakness, and the rubber washer allows a certain play in 
 the direction of the length, and thus prevents snapping from 
 the sudden strain, and it also prevents leaking. 
 
 180. Improved Fastenings for Iron Armor For Steel Armor 
 
 Tests of Armor-plates. 
 
 IRON ARMOR. In addition to the strains brought to bear 
 upon the bolt in the direction of its length, causing elonga- 
 tion and snapping in the older 
 forms, there is a cross-strain due to 
 the displacement of the armor side- 
 ways. To obviate this, the English 
 spherical-headed bolt was devised, 
 as shown in Fig. 188. This shape of 
 FIG. 188. head and nut, causes the strain to be 
 
 always along the axis of the bolt ; and to allow the bolt to 
 take its normal position when the plate is displaced laterally, 
 a clearance is made around it. 
 
 STEEL ARMOR. With this armor, or with the compound 
 armor, where it is necessary to preserve the steel or hard- 
 ened face intact, the bolt must not pass through the plate. 
 It is therefore screwed for a short distance into the back of 
 the plate. In naval vessels, the backing is comparatively 
 thin, and hence the bolt must be lengthened by some 
 means, so that the stretch per unit of length may not be 
 sufficient to break the bolt. The following arrangement is 
 adopted in the Navy (Fig. 189). 
 
324 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 a is the armor-plate; b, the backing; c, the armor- 
 bolt, reduced in diameter as shown, to give lateral play 
 in the iron pipe d, which passes through the backing 
 and furnishes a seat for the bolt ; e and /, rubber wash- 
 ers which are set up by the pressure of the nut g, and 
 prevent leaking ; h, a sleeve, whose object is to increase the 
 length of the bolt, so that the elongation per unit length 
 
 FIG. 189. 
 
 when the plate is struck, may prevent fracture ; /, a cup- 
 shaped washer, containing the rubber washer k, and the 
 iron washer /. The washer k gives elasticity to the whole 
 system. The sleeve h distributes the pressure of the nut g 
 over a large area of the sides of the ship, and also, as stated, 
 increases the length of the bolt. The number of bolts is 
 greater for the steel and compound armor, than for the old 
 wrought-iron armor. 
 
 TESTS OF ARMOR-PLATES. The test of armor-plate pre- 
 scribed by the Ordnance Department is as follows : One 
 plate is selected from a lot, and is bolted to an oak backing 
 36 inches thick, properly supported, with rubber washers 
 placed between the steel washers of the bolts in rear. The 
 calibre of the gun is to that of the plate as i : i-J; .that is, 
 for a Q-inch plate an 8-inch gun, etc. One armor-piercing 
 shot is fired from this gun, so that the centre of the shot-hole 
 shall not be nearer any edge of the plate than 2\ calibres. 
 
 The projectile must have the following striking-energy : 
 
 For an 8-inch gun 3000 foot-tons 
 
 For a lo-inch gun 5000 " 
 
 For a 1 2-inch gun 7643 " 
 
PROJECTILES AND ARMOR. $2$ 
 
 Under these conditions, the whole of the projectile must 
 not get through the plate, nor must the plate break up, or 
 pieces be detached, or cracks produced which expose the 
 backing to view. 
 
 181. Penetration of Armor Wrought Iron Steel. 
 
 WROUGHT IRON. Most of the formulas for penetration 
 have been deduced for wrought-iron armor, on account of 
 the length of time it has been in use, and the numerous ex- 
 periments that have been made upon it. 
 
 In deducing these formulas two different hypotheses 
 have been adopted : 
 
 1. That the projectile acted as a punch, separating a 
 disk of metal from the plate. In this case, the resistance to 
 be overcome, was the resistance of the metal to shearing 
 along the circumference of this disk, and hence the energy 
 of the projectile to overcome this resistance was estimated 
 per inch of shot's circumference, and was obtained by di- 
 
 E 
 
 viding the total energy by the circumference, or . 
 
 Ttd 
 
 2. That the projectile acted as a wedge, forcing the par- 
 ticles of the metal apart. In this case the penetration is 
 proportional to the energy per unit of area of cross-section, 
 
 E 
 
 or - 
 nr* 
 
 The principal formulas deduced under the first hypothe- 
 
 esis are : 
 
 / 3 = JL ; (Fairbairn's) . . . (252) 
 
 Ttdk 
 
 /2.035 = . (English Admiralty) (253) 
 
 (Muggiano) . . . (254) 
 
 And under the second hypothesis : 
 
 5575 
 
 (deMarre's) . . . (255) 
 
326 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 ' 14 *' 1 (Maitland>s) 
 
 (Krupp>s) (257) 
 
 (G * vre) ..... < 258) 
 
 In these formulas 
 
 / is the thickness of wrought iron, in inches, which 
 
 the projectile will penetrate ; 
 E, the energy of the projectile in foot-tons ; 
 d, its diameter in inches ; 
 /, its weight in pounds ; 
 v, its striking velocity in feet-seconds ; 
 , a constant. 
 
 STEEL ARMOR. For steel armor, it was customary to 
 calculate the penetration in a wrought-iron plate of the 
 same thickness, and add a certain percentage of increase of 
 resistance, varying from 10 to 30 per cent. This method is 
 not satisfactory, as steel armor varies greatly in resistance 
 according to treatment ; and for the modern Harveyized 
 plates, penetration seldom occurs, owing to the hard face, 
 unless the gun greatly overmatches the plate. 
 
 The formulas generally used are those of de Marre, as, 
 follows : 
 
 For soft plates of Creusot steel, backed, 
 
 r- 7 = 0.0009787^ ...... (259) 
 
 For the steel plates used as protection against steel shell 
 from rapid-fire guns, unbacked, 
 
 f>-> = 0.000734^. . ..... (260) 
 
 For the wood backing, with plate in front of it, 
 
 / = 0.006168^- ....... (261), 
 
PROJECTILES AND ARMOR. $2? 
 
 Captain Orde Browne gives a rule which enables some 
 idea to be formed of the relative powers of guns against 
 armor, as follows : The penetration of a projectile in wrought- 
 iron armor is one calibre for every thousand feet striking vel- 
 ocity. 
 
 For example, a lo-inch projectile, striking with a velocity 
 of 1200 feet-seconds, will penetrate 1.2 calibres, or 12 inches. 
 
CHAPTER V. 
 FUZES AND PRIMERS. 
 
 FUZES. 
 
 182. Definition Classification Time Fuzes Requisites Dif&cul- 
 ties. 
 
 DEFINITION. Fuzes are the means used to ignite the 
 bursting charge of a projectile at any point of its flight, or 
 upon impact. 
 
 CLASSIFICATION. They are classified according to their 
 mode of action, into 
 
 1. Time; 
 
 2. Percussion ; 
 
 3. Combination ; 
 
 4. Delayed action fuzes. 
 
 TIME FUZES. A time fuze is one which ignites the burst- 
 ing charge at some fixed time after the projectile has left 
 the muzzle, and it consists generally of a column of compo- 
 sition, whose rate of burning is known, which is set on fire 
 by the discharge of the piece, and whose time of burning is 
 regulated by the length of the column. 
 
 REQUISITES. The requisites of a good time fuze are : 
 
 1. Its rate of burning should be uniform, and not affected 
 by storage or changes of climate. 
 
 2. It must be safe in handling, and certain in its operation. 
 These conditions are very difficult to fulfil, and hence a 
 
 good time fuze is perhaps the most difficult one to obtain. 
 
 Recent improvements have, however, done much to 
 obviate the difficulties formerly experienced. 
 
 DIFFICULTIES. The difficulties in making a reliable 
 time fuze are : 
 
 328 
 
FUZES AND PRIMERS. 329 
 
 1. To obtain a column of composition whose rate of burn- 
 ing is uniform. 
 
 The rate of burning of a composition depends upon its 
 density, trituration, composition, and degree of moisture, as 
 explained in Interior Ballistics. For the same composition, 
 it is very difficult to obtain a uniform density throughout a 
 long column. The old method of preparing a time-fuze was 
 to place a small quantity of the composition in the fuze-case, 
 and strike it a certain number of blows with a mallet and 
 drift, and repeat this operation till the fuze was completed. 
 This did not give uniform density. 
 
 A second method was to subject it to hydraulic pressure, 
 but this also failed. The method now in use gives better 
 results, and will be explained. 
 
 2. For long times of burning, a long column of composi- 
 tion is required, and the results obtained by the old method 
 were so unsatisfactory, that the ingredients of the composi- 
 tion were varied, in order to give a decreased rate of burn- 
 ing and thus shorten the column. This changed irregularly 
 the rate of burning,- increased the difficulty of preservation, 
 and also increased the residue. 
 
 3. It was found impossible to guard against the changes 
 due to storage, climate, etc., as they affected both the 
 composition, and the fuze-case. 
 
 4. After a uniform rate of burning is obtained, the press- 
 ure of the air on the composition, during flight, changes 
 this rate. 
 
 5. With modern breech-loading guns, and high veloci. 
 ties, a small error in burning, increases the error in burst- 
 ing of the projectile. 
 
 6. The flame from the powder-charge will no longer 
 ignite the fuze. 
 
 183. Time Fuzes Difficulties, How Overcome. 
 
 To overcome these difficulties, the following changes in 
 manufacture have been made : 
 
 Uniform Rate of Burning. To obtain a uniform rate of 
 burning, and a column of composition of sufficient length to 
 answer for the greatly increased ranges, a lead tube 0.62 
 
330 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 inch in diameter is filled with mealed powder. The ends 
 are then closed, and the tube, with the enclosed powder, 
 drawn out by a process similar to that of wire-drawing-, till 
 the diameter is decreased to 0.152 inch. The rate of 
 burning is tested by burning inch lengths of this compressed 
 powder, and its rate is found to be very uniform. In this 
 case, the pressure is applied in the direction of the shortest 
 dimension of the column, so that it is more uniform in its 
 effect ; and if there be any difference in density, this differ- 
 ence, is neutralized by the burning of the column at right 
 angles to the direction of the pressure, so that the same 
 variation of density exists throughout each cross-section. 
 
 Changes of Climate, etc. These have less effect upon the 
 composition, because it is contained in a metallic case which 
 is less subject to change. 
 
 Variation due to Pressure of Air in Flight. This is cor- 
 rected for, as far as possible, by graduating the fuze tempo- 
 rarily with the rate of burning as determined at rest, and 
 then correcting this graduation, by actual test, on the firing- 
 ground. 
 
 Ignition of Fuze. With the old fuzes, and muzzle-loading 
 projectiles, there was always a space between the surface of 
 the bore and that of the projectile, through which the flame 
 from the powder-charge could pass to ignite the fuze. This 
 was called the " windage." With modern breech-loading 
 projectiles, this space is closed by the band of the projectile, 
 and hence the flame cannot pass through to ignite the fuze. 
 The arrangement for accomplishing this with the modern 
 time fuze, will be explained. 
 
 184. Older Forms of Time Fuze in Use Mortar Fuze Sea-coast 
 
 Fuze Bormann Fuze. 
 
 The older forms of time fuze still in use in the U. S. 
 service are : 
 
 The mortar-fuze ; 
 The sea-coast fuze ; 
 The Bormann fuze. 
 
 MORTAR FUZE. This is used in the old siep-e and sea- 
 
FUZES AND PRIMERS. 
 
 33* 
 
 coast smooth-bore mortars. It consists (Fig. 190) of a coni- 
 cal case or plug, a, of wood graduated on 
 the exterior into inches and tenths. On the c '{ 
 interior there is a cylindrical cavity, b, bored 
 out nearly to the bottom, and filled with the 
 fuze-composition, driven as explained. The 
 top of this cavity is enlarged at c, and filled 
 with mealed powder moistened with alcohol, 
 to insure ignition from the flame of the 
 powder-charge. This is covered with a 
 paper cap, c f j on which is marked the rate 
 of burning in seconds per inch. The gradu- 
 ations begin at d, and stop at e. To prepare 
 this fuze for use, the paper cap is removed, 
 the fuze cut at the proper division, counting 
 from the top, by sawing off the lower end, or 
 better by boring a hole into the composition 
 with a gimlet, as at/, as this prevents the composition from 
 being dislodged by the shock of discharge, and finally by 
 driving with a drift the fuze into the fuze-hole of the shell. 
 
 THE SEA-COAST FUZE. This was used in the old smooth- 
 bore guns, and at present in the 1 5-inch Rodman gun. 
 
 For ordinary firing, this fuze (Fig. 191) is composed of a 
 
 FIG. 191. 
 
 conical wood plug, a, with a conical hole, b. In this hole is 
 placed the fuze, c, which is contained in a conical paper case. 
 
332 
 
 TEXT- BOOK OF ORDNANCE AND GUNNERY. 
 
 The fuzes are of variable composition, and are marked on 
 the exterior according to their time of burning. For ricochet 
 firing over water, and for heavy charges, a brass fuze-plug, 
 d, of the same shape is used, the distinctive feature being 
 the water-cap, e, which is a brass cap, having a zigzag chan- 
 nel, filled with mealed powder. The shape of this channel 
 renders the access of water difficult, and hence prevents the 
 extinction of the composition. 
 
 THE BORMANN FUZE. This was used with spherical 
 shell and shrapnel, in the field service. 
 
 It consists (Fig. 192) of a pewter fuze-case, a, containing 
 a ring of composition, b. Over this ring, b, lies an arc, c, 
 graduated in seconds. At the zero end of the arc, this ring, 
 
 FIG. 192. 
 
 b y communicates with a channel, d, filled with fine powder, 
 leading into a chamber, e, filled with the same powder, 
 which is supported by a tin disk, /. The composition, b, is 
 pressed into its recess in the direction of its shortest dimen- 
 sion, and burns around the ring at right angles to this direc- 
 tion. Hence the fuze possesses one of the good qualities of 
 the modern time-fuze. The other end of the ring of com- 
 position, has no communication with the chamber e. Owing 
 to its shape, and the material of which the case is made, this 
 fuze is liable to be driven into the shell by the shock of dis- 
 charge ; and to prevent this, and increase the effect of the 
 bursting-charge in the projectile, a wrought-iron disk, g, is 
 screwed into the fuze-hole, below the fuze. 
 
 The action of the fuze is as follows : If required to burn 
 any given time, say four seconds, the case is cut at the mark 
 4, exposing the ring of composition. 
 
FUZES AND PRIMERS. 333 
 
 This composition then burns in both directions ; but hav- 
 ing no communication with the chamber e, in the direction 
 toward 5, it will burn for four seconds, and then fire the 
 charge. 
 
 The objections to the fuze are : 
 
 1. Its time of burning is too short for modern ranges ; 
 
 2. It is difficult to ignite by the flame from the charge ; 
 
 3. If once cut, it cannot be used for a greater time of flight. 
 The modern time fuze is not used, except in combination 
 
 with the percussion fuze. 
 
 185. Percussion Fuzes Requisites Essential Parts. 
 
 A percussion fuze is one which is prepared for action by 
 the shock of discharge, and which acts by the impact of the 
 projectile. 
 
 REQUISITES. The requisites of a good percussion fuze 
 are, that it shall be safe in handling, and certain in its opera- 
 tion. 
 
 Safety in Handling. This requires : 
 
 1. A safety device which will prevent accidental dis- 
 charge in store, transportation and handling, or from acci- 
 dental shock, such as dropping the projectile. 
 
 2. A safety device which will prevent accidental dis- 
 charge in loading, and which will be released only on firing 
 the piece. 
 
 These may be combined in one, as will be seen later. 
 Certainty of Action. This requires : 
 
 1. That all the parts of the fuze be protected from clog- 
 ging, by the action of the bursting-charge in transportation, 
 and by other causes, such as dust, etc. 
 
 2. A safety device which will prevent relative motion of 
 the parts of the fuze during flight. 
 
 ESSENTIAL PARTS. The essential parts of every percus- 
 sion fuze are : 
 
 A case, to contain all the moving parts and protect them ; 
 
 A plunger, which is moved backward or forward on im- 
 pact, and which fires the fulminating composition ; 
 
 A fulminating composition, which is fired by the impact 
 of the plunger; 
 
334 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 The priming, which is a charge of powder ignited by the 
 fulminate, and which ignites the bursting-charge; 
 A safety device in transportation ; 
 A safety device in loading ; 
 A safety device in flight. 
 
 186. Percussion Fuzes in IT. S. Service Classification Hotchkiss 
 
 Front Percussion Fuze Action of Fuze Safety Devices. 
 CLASSIFICATION. Percussion fuzes are classed accord- 
 ing to the position they occupy in the projectile, as : 
 
 1. Front fuzes, which are inserted in the head of the pro- 
 jectile, at the point of the ogive; 
 
 2. Base fuzes, which are inserted in the centre of the base. 
 The front-fuze is sometimes used with field projectiles, 
 
 and generally when penetration is not required. 
 
 The base fuzes are used with armor-piercing projectiles, 
 and generally where penetration is required, and where the 
 head of the projectile must have great resistance. 
 
 The front fuze has the advantage of having the bursting 
 charge of the projectile thrown toward it on impact, and 
 there is no danger of the flame from the charge in the gun 
 entering the cavity of the projectile, and causing premature 
 explosion. 
 
 The percussion fuzes used in the U. S. service are the 
 Hotchkiss Front an'd Hotchkiss Base Fuzes, or modifica- 
 tions of them. 
 
 HOTCHKISS FRONT PERCUSSION FUZE. This fuze con- 
 sists of a brass case, a, Fig. 193, threaded on the exterior for 
 screwing into the projectile. The upper end is closed by a 
 screw cap, b, carrying a projecting point, c. In the case a, is 
 a plunger, d, composed of a brass case, e, and a lead body,/, 
 in which is a brass wire, g. The central part of the lead 
 body carries the priming charge of powder, h, and on the 
 top of this priming is the fulminate, i. The brass case e, 
 encloses the lead body/, to prevent the upsetting laterally 
 of the plunger, by the shock of discharge, and its conse- 
 quent wedging in the fuze-case. 
 
 When the plunger is inserted in the case a, the brass 
 wires g, occupy the position shown, and the rear end of a is 
 
FUZES AND PRIMERS. 
 
 335 
 
 closed by a conical lead plug, /, bearing against the 
 wires. 
 
 ACTION OF FUZE. When the piece is fired, the shock of 
 discharge causes the lead plug/ to be dislodged from its 
 seat in the fuze, and to fall into the cavity of the projectile. 
 The plunger d then moves to the rear, and rests, during 
 flight, upon the shoulder k, at the bottom of the fuze cavity. 
 Upon impact, the plunger d is thrown forward, the fulmi- 
 nate *, striking the pointy and thus firing the priming 
 charge k, which fires the bursting charge. 
 
 SAFETY DEVICES IN TRANSPORTATION AND LOADING. 
 These are combined in this fuze, and are formed by the 
 conical lead plug, bearing on the brass wire g. 
 
 SAFETY DEVICE IN FLIGHT. In all percussion-fuzes, the 
 plunger has a tendency to move forward in the fuze cavity 
 during flight. This is due to the fact that the projectile is 
 retarded by the resistance of the air, while the plunger, not 
 being subjected to this action, is not affected by it, and its 
 only retarding force is friction, which is very small. If the 
 plunger moves forward, it will either explode the fulminate 
 during flight, or else if the sensitiveness of the fulminate be 
 diminished to prevent this, it will be so close to the point c, on 
 impact, that it may not acquire energy sufficient to cause 
 the explosion at that time. In this fuze, the safety device 
 in flight, is provided by the wires g, which spread out- 
 
336 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 ward when the lead plug j is dislodged, and thus prevent 
 the forward motion of the plunger till impact. 
 
 187. Hotchkiss Base Percussion Fuze Action of Fuze Safety 
 
 Devices. 
 
 HOTCHKISS BASE PERCUSSION FUSE. The Hotchkiss 
 base percussion fuze consists of a brass case, a, Fig. 194,, 
 
 of the shape shown. It is threaded on the exterior at b, 
 for screwing into the projectile, and on the interior at c, 
 for the cap, which carries the fulminate. The flanges at d 
 are made thin, to act as a gas-check, and prevent the en- 
 trance of the gas from the charge of the gun into the fuze- 
 cavity, thus prematurely exploding the projectile. 
 
 In the case a is a plunger, e, composed of a brass jacket, 
 fj a lead body, *, and a firing-pin, h. The combination of 
 lead and brass is for the purpose previously described. The 
 firing-pin, h, is made of steel, roughened on the outside, and 
 the lead body is cast around it, so that before firing its point 
 is slightly below the upper surface of the plunger. 
 
 The upper part of the fuze-case carries the screw cap z, 
 which is composed of the party, which screws into the fuze- 
 case, the fulminate k, the screw cap / closing j, and the 
 safety disk of copper m. 
 
 ACTION OF THE FUZE. When the piece is fired, the 
 shock of discharge causes the heavy plunger e to slide to the 
 rear along the pin h, taking the position shown in Fig. 195. 
 
FUZES AND PRIMERS. 
 
 337 
 
 The action of the brass casing of the plunger is to 
 prevent the spreading of the lead body, and consequently 
 cause the latter to take a firm hold on the 
 firing- pin. 
 
 When the projectile strikes, the plun- 
 ger is thrown forward, the point of the 
 firing-pin passing through the hole n in 
 the screw cap, strikes and explodes the 
 fulminate, the flame from which passes 
 through the hole o into the interior of the 
 projectile, and ignites the bursting-charge. 
 
 SAFETY DEVICES IN TRANSPORTATION 
 AND LOADING. These are combined in 
 this fuze and consist of : FlG - r 95. 
 
 1. The projecting pin h being held firmly in the lead ; 
 body of the plunger, with its point below the upper surface 
 of the latter, so that it requires the shock of discharge to 
 force the plunger down over the pin, and allow its point 
 to project. 
 
 2. Making the lengths of the plunger and projecting 
 portion of the pin h such, that before firing they are held 
 tightly in position in the case, and hence the plunger cannot 
 acquire any motion which might force it along the pin. 
 
 SAFETY DEVICE IN FLIGHT. This is provided by the 
 copper disk m on the bottom of the fulminate cap, so that 
 if the point of the pin should touch the cap in flight, it will 
 not cause an explosion. 
 
 188. Combination Fuzes Requisites Frankford Arsenal Com- 
 bination Fuze Action of Fuze. 
 
 A combination fuze is one which contains both a time* 
 and a percussion fuze in the same case, and is intended to- 
 increase the chances of bursting the projectile, and of readily 
 and quickly varying the kind of fire. 
 
 REQUISITES. A good combination fuze must combine 
 the requisites of both time and percussion fuzes, without 
 being too bulky or too expensive. 
 
 THE FRANKFORD ARSENAL COMBINATION FUZE. This 
 fuze is used in the U. S. service for field shrapnel, and con- 
 sists (Fig. 196) of a case, a, of bronze, the front portion of 
 
338 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 which carries the time fuze, and the rear portion the pen 
 cussion fuze. 
 
 The time fuze is composed of the plunger b, the firing. 
 
 r-v 
 
 FIG. 196. 
 
 pin c, the cone d, the time-train e, the cover /, cap g, and 
 clamping-nut h. 
 
 The plunger b is cylindrical in shape, and contains the 
 j-^-] fulminate i, in a recess at its base. Its upper 
 
 extremity is pierced to receive a safety-pin,/, 
 and there are five radial lugs, k, Fig. 197, which 
 support the plunger on the top of the fuze 
 body, and prevent it from falling against the 
 firing-pin c, when the safety - pin at j is re- 
 moved, before loading. 
 
 The firing-pin c is of steel, inserted into the 
 body of the fuze at the bottom of the plunger 
 channel. 
 
 The cone d is an alloy of soft metal, held in 
 place on the fuze-body by the clamping-nut h, and a groove 
 
 FIG. 197. 
 
FUZES AND PRIMERS. 339 
 
 m at the bottom, and is prevented from turning by a steel 
 pin, /. 
 
 The lip m on the bottom of the cone, entering the 
 groove in the body, acts as a gas-check to prevent ignition 
 of the powder in the tube n. On the exterior of the cone d, 
 is a left-handed groove which carries the time-train <?, and 
 this time-train communicates at its lower end with the 
 priming-charge in the tube/z, and thence with the chambers. 
 
 The time-train e is formed, as previously described, of a 
 lead tube, filled with mealed powder, and wire-drawn. 
 
 The cover /is of brass, arid is held in place by the cap g, 
 and prevented from turning by a small pin projecting from 
 the body a, and fitting in a slot in its lower edge. On the 
 exterior of the cover is a left-handed groove, corresponding 
 to that on the time-cone d, and this groove is pierced with 
 holes numbered from I to 15, corresponding to the number 
 of seconds, the spaces between the holes being divided into 
 five equal parts. 
 
 The percussion fuze is a modification of the Hotchkiss 
 base fuze previously described, and consists of the primer 
 in front ; a plunger-spindle, u, carrying a firing-pin, #'; a 
 plunger-sleeve, v\ a safety-ring of brass, w\ and a safety- 
 disk of copper, / ; the fuze being closed in rear by the screw- 
 plug s, and this screw-plug, and the exterior of the plunger 
 sleeve v, being grooved longitudinally, for the passage of 
 the flame from the chamber o to the bursting-charge. 
 
 ACTION OF FUSE. i. As Time Fuse. Suppose the fuze 
 is to burn 12 seconds. A hole is punched through the 
 cover, time-train, and cone, into the interior of the fuze, at 
 the i2-seconds mark. Just before loading, the safety pin is 
 removed from the hole/. This allows the time plunger b to 
 rest on the top of the fuze-body, where it is held by the five 
 radial lugs, k. The projectile is now inserted in the gun. 
 By the shock of discharge these five lugs are broken, and the 
 time-plunger b is thrown to the rear, its primer striking the 
 firing-pin c, which explodes the fulminate. The flame from 
 the fulminate passes through the four radial holes /, at the 
 base of the fuze body, and ignites the ring of compressed 
 powder q. The flame from this powder, ignites the fuze 
 
34 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 composition at the hole marked 12, which has been punched 
 through the time-cone d, and after burning for twelve sec- 
 onds, this ignites the priming charge in the tube n and 
 chamber o. The flame from this charge passes down along 
 grooves r in the percussion fuze body and screw s, and 
 ignites the charge. 
 
 2. As a Percussion Fuze. When the piece is fired, the 
 plunger sleeve v slides relatively to the rear, against the 
 resistance of the safety ring w, and this ring is pushed from 
 its groove, and along the spindle u. When the plunger 
 sleeve v reaches its extreme rear position, the safety ring w 
 slips into the groove w f , and, as its diameter has been in- 
 creased by passing over the plunger spindle, it now fits into 
 the groove in the plunger sleeve, and locks the spindle and 
 sleeve together. ' The point of the firing-pin u' now pro- 
 jects beyond the plunger sleeve, and on impact, the sleeve 
 and spindle are thrown forward, exploding the primer. 
 
 Safety Device in Transportation. The safety pin/, for the 
 time-fuze, and the plunger sleeve v, and safety ring w, for 
 the percussion fuze. 
 
 Safety Device in Loading. The radial lugs k for the time 
 fuze, and the sleeve and ring, as before, for the percussion 
 fuze. 
 
 Safety Device in Flight: Percussion Fuze. The copper 
 disk /. 
 
 189. Delayed-action Fuzes The Merriam Delayed-action Fuze- 
 Action of Fuze. 
 
 A delayed-action fuze is one which is prepared for action 
 by the shock of discharge, and whose final action is retarded 
 till the projectile has passed through the object or reached 
 a certain position where its explosion will be most effective. 
 
 THE MERRIAM DELAYED-ACTION FUZE. The principles 
 of this class of fuzes will be best explained by the descrip- 
 tion of one of them which has been tried the Merriam Fuze. 
 
 This fuze consists of a case r body, a, Fig. 198, 
 threaded on the exterior for screwing into the base of 
 the projectile. In the interior of the case are a ham- 
 mer, b, in the form of a sphere, held in place by 
 
FUZES AND PRIMERS. 
 
 341 
 
 clips, c, which abut against a shoulder in the case and a 
 circular recess in the ball b ; 
 two pistons, d, which are 
 forced forward by the press- 
 ure of the gas of the powder- 
 charge in the gun ; a flat 
 spring, e, which keeps the ball 
 in place during flight; three 
 small balls,/, which are held 
 firmly in their seats below 
 three percussion-caps, g\ a 
 valve, h, in front, which 
 moves parallel to the axis of 
 the fuze, and carries on its 
 forward face a ring, z, of com- 
 pressed powder ; four radial 
 
 chambers, / carrying priming-charges of powder, and a 
 screw, k, whose use will be explained. 
 
 ACTION OF FUZE. When the piece is fired, the pressure 
 of the gas pushes forward the two pistons d, and these, 
 striking the clips c, push them off the shoulders in the case. 
 The ball b, is thus left free to move forward, but is pre- 
 vented from doing so in flight, by the flat spring e. When 
 the projectile strikes the object, such as an armor-plate, the 
 ball b is thrown forward, and, striking one of the small balls 
 / drives it against its percussion-cap, exploding it. The 
 flame from this cap passes into the chamber /. 
 
 When the ball b is thrown forward by the striking of the 
 projectile, the valve h also moves forward at the same time, 
 and bears against the front of the fuze-case, thus closing the 
 openings oo which communicate with the priming-charges 
 in the chambers/ The valve h reaches its seat against the 
 front of the case before the ball b explodes the caps g, be- 
 cause it has a shorter distance to travel. The flame from 
 the percussion-caps, entering the chamber /, ignites the com- 
 pressed powder ring t, but, as this ring of powder is held 
 between two closely-fitting surfaces, it can burn only on 
 the edge. As long as the projectile is passing through the 
 plate, or until it stops in the plate, it is being retarded, and 
 
34 2 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 the acquired energy of the valve will keep it in contact witb 
 the front face of the fuse. As soon, however, as the projec- 
 tile passes through the plate, or stops in it, the valve h will 
 move back and open the holes o o, and the charge will be 
 tired. The screw k, holds back the valve h, when screwed 
 down, and there is no delayed action in this case. 
 
 PRIMERS. 
 
 190. Definition Classification Requisites Common Friction- 
 Primer Action. 
 
 DEFINITION. Primers are the means employed to ignite 
 the powder-charge in a gun. 
 
 CLASSIFICATION. Primers are classified according to the 
 method by which they are fired, into 
 
 1. Friction ; 
 
 2. Electric ; 
 
 and each of these may be either common or obturating. 
 
 A common primer is one which ignites the charge, and 
 is blown out of the vent, allowing the gas of the charge to 
 escape through the latter. - 
 
 An obturating primer is one which remains seated in the 
 vent at discharge, and prevents the escape of gas through 
 the vent. 
 
 The primers used with small-arm ammunition will be 
 explained later. Those used with cannon are described 
 here. 
 
 REQUISITES. Primers should be safe in handling, not 
 liable to damage or accident in store, and certain in action. 
 
 The requisite of safety in handling prevents the use of 
 mercuric fulminate, except in the small-arm primers. As a 
 general rule mercuric fulminate cannot be used where it is 
 exposed to friction of any kind. Hence in fuzes it may be 
 safely used, since all the parts are relatively fixed, and well 
 protected ; but this is not the case with primers. 
 
 COMMON FRICTION PRIMER. This primer, (Fig. 199), is 
 composed of two copper tubes, a and b, at right angles to 
 each other ; a copper wire, c, flattened and roughened at one 
 end ; a charge of powder filling the tube a ; and a friction 
 
FUZES AND PRIMERS. 
 
 343 
 
 composition of antimony sulphide and potassium chlorate, 
 filling the tube b. 
 
 The tubes a and b are each made from copper disks, a' 
 and ', by the successive action of punches and dies, by 
 which the diameter and thickness of the tubes are decreased, 
 and their length increased, as shown in the figure. After 
 the proper length and diameter of each have been obtained, 
 a hole is drilled in the side of the tube a, near its head, the 
 
 a 
 
 FIG. 199. 
 
 tube b soldered to #, the wire c inserted through the hole 
 in a, its rough end resting in the tube b, which is then filled 
 with the friction composition in a moist state, and the end 
 of b closed on the wire, to hold the latter in place. The tube 
 a is filled with small-arms powder, and its lower end closed 
 with a wad of wax. The outer end of the wire c is formed 
 into a loop, for the attachment of the hook of the lanyard. 
 
 ACTION. When the wire is pulled by the lanyard, the 
 roughened edges fire the friction composition in the tube b> 
 and this ignites the powder in a. 
 
 191. Common Electric Primer Action. 
 
 It is often necessary to fire at a distance from the gun, 
 as in experiments ; or from a central station where the ob- 
 
344 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 ject can be plainly seen ; or where all the guns of a battery 
 are to be fired simultaneously. 
 
 For this purpose the electric primer is used. 
 
 FIG. 200. 
 
 COMMON ELECTRIC PRIMER. The common electric 
 primer (Fig. 200), consists of two copper tubes, a and b, 
 and two insulated copper wires, c, joined at one end by a 
 small platinum wire, f. 
 
 These wires are inserted in a plug of wood, d, and are 
 surrounded by a small quantity of dry gun-cotton, e. This 
 plug of wood, with its wires and gun-cotton, is inserted into 
 the tube a, and the outer end is closed down to hold it in 
 place, and the opening filled with wax. The tube b is in- 
 serted in a beforehand, and soldered to it, as shown in the 
 figure, and is then filled with small-arms powder, and the 
 open end closed with wax. 
 
 ACTION. When the circuit is closed, the current heats 
 the fine platinum wire, f t and this fires the gun-cotton, 
 which fires the powder in the tube b. 
 
 192. Obturating Friction Primer Action. 
 
 With large guns, the long-continued action of the gases 
 under high pressure, erodes the vent rapidly, if allowed to 
 issue freely through it, and hence an obturating primer is 
 necessary for these guns. 
 
 OBTURATING FRICTION PRIMER. The obturating fric- 
 tion primer (Fig. 201), consists of a case, a, threaded on the 
 
FUZES AND PRIMERS. 
 
 345 
 
 exterior at b, to screw into the vent. A shoulder, c, limits 
 the extent to which the case can be inserted. At the rear 
 end, d, the case is square, to give a purchase for screwing it 
 in and removing it. On the interior, the case is pierced 
 with the hole e for the passage of the wire/. This passage 
 is enlarged in front and has a cone-shaped surface at g. 
 The front of the case is made thin at h, for a reason to be 
 given later. The other parts of the primer are a brass wire, 
 
 V *' x '" f 
 
 FIG. 201. 
 
 y, roughened at its forward end, and having a conical sleeve, 
 /, loose upon it, and a conical enlargement, i' ' . 
 
 Upon this wire is secured pellet of friction-composition, 
 /, and these parts, when inserted into the primer-case, occupy 
 the positions shown ; the rear end of the wire being twisted 
 into a loop, for the attachment of the hook of the lanyard. 
 
 The front part of the case is filled with small-arms pow- 
 der. 
 
 ACTION. The primer is inserted into the vent and 
 screwed home, till stopped by the shoulder c. When the 
 wire is pulled to the rear by the lanyard, the roughened 
 end fires the pellet of friction-composition /, and this fires 
 the priming charge. 
 
 The gas may escape in two ways : first along the outside 
 of the case and around the screw-thread ; second, through 
 the hole e in which the wire rests. 
 
 To prevent escape along the outside, the thin part of the 
 case h, in front, expands under pressure, and fits tightly 
 against the walls of the vent, thus forming a perfect gas- 
 check. To prevent escape through the hole e, the drawing 
 back of the wire f, in firing, brings the conical enlargement 
 
346 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 i' firmly against the front of the sleeve 2, and the latter 
 against its conical seat, g, in the case, and the gas-pressure 
 keeps it in place, thus closing the hole e. 
 
 193. Obturating Electric Primer Action. 
 
 OBTURATING ELECTRIC PRIMER. This primer is used 
 for the same reasons as the common electric primer, and con- 
 
 FIG. 202. 
 
 sists, (Fig. 202), of a case, a, exactly similar on the exterior to 
 that of the obturating friction primer just described. On 
 the interior, the forward part of the case b is made thin to 
 serve as a gas-check, as before explained. A seat, of the 
 shape shown at c, is made near the middle of the case, and a 
 hole, d, allows the wires e to pass through. The other parts 
 of the primer are, the two insulated wires, e, passing through 
 a hard rubber plug, /, and connected at their forward ends 
 by a piece of platinum wire, g. A small piece of gun-cotton, 
 h, is wound round the platinum wire, and the whole inserted 
 in the primer case, occupying the position shown. 
 
 The front of the primer case is filled with small-arms 
 powder. 
 
 ACTION. When the circuit is closed, the current heats 
 the platinum wire g, and this fires the gun-cotton h, which 
 in turn ignites the powder in the front of the primer case. 
 
 The escape of gas around the outside of the primer is 
 prevented by the expansion of the thin portion of the case 
 in front, as before. The escape through the hole d is pre- 
 vented by the hard rubber plug f y which is forced into its 
 seat by the pressure. 
 
CHAPTER VI. 
 
 EXTERIOR BALLISTICS. 
 
 194. Definitions. 
 
 Exterior Ballistics treats of the motion of a projectile in 
 air, after it has left the piece. 
 
 The Trajectory, a, Fig. 203, is the curve described by 
 the centre of gravity of the projectile during its passage 
 through the air. 
 
 FIG. 203. 
 
 , 
 
 The Line of Fire, be, is the prolongation of the axis of the 
 piece. 
 
 The Plane of Fire is the vertical plane containing the line 
 of fire. 
 
 The Line of Sight, def, is the straight line passing through 
 the sights and the point aimed at. 
 
 The Plane of Sight is the vertical plane containing the line 
 of sight. 
 
 The Angle of Sight, s, is the angle made by the line of 
 sight with the horizontal. 
 
 347 
 
34** TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 The Angle of Departure, g ! , is the angle made by the line 
 of departure with the horizontal. 
 
 The Angle of Elevation, 0, is the angle made by the axis 
 of the piece with the horizontal. 
 
 The angle of elevation generally differs slightly from the 
 angle of departure, owing to the movement of the gun at 
 discharge. This movement is due to the elasticity of the 
 parts of the carriage, and the lack of accurate fitting of the 
 trunnions in their beds, the play of the elevating device, etc. 
 The Jump, j, is the difference between the angle of de- 
 parture and of elevation, and must be determined by exper- 
 iment. 
 
 The Angle of Fall, GO, is the angle made by the tangent to 
 the trajectory with the horizontal at the end of the range. 
 
 The Range, bh, is the horizontal distance from the muzzle 
 to the point where the projectile strikes. 
 
 Initial Velocity is the velocity of the projectile at the 
 muzzle. 
 
 Remaining Velocity is the velocity of the projectile at any 
 point of the trajectory. 
 
 Final Velocity is the velocity of the projectile at the end 
 of the range. 
 
 Drift, kf, is the departure of the projectile from the 
 plane of fire, due to the resistance of the air, and the rotation 
 of the projectile. 
 
 Direct Fire is from guns, with service charges, at all 
 angles of elevation not exceeding 15. 
 
 Indirect or Curved Fire is from guns, with less than service 
 charges, and from howitzers and mortars, at all angles of 
 elevation not exceeding 15. 
 
 High-angle Fire is from guns, howitzers, and mortars at 
 all angles of elevation exceeding 15. 
 
 195. Forces Acting on a Projectile Circumstances of Motion 
 
 Drift. 
 
 FORCES ACTING. In the case of an oblong projectile, 
 which is the only one considered, a motion of rotation about 
 its longer axis is given to it, by the rifling of the gun, as it 
 passes through the bore. When it leaves the bore, it is sub- 
 
EXTERIOR BALLISTICS. 349 
 
 jected to the action of gravity, and the resistance of the air. 
 It is therefore a free body, having a motion of translation 
 and of rotation impressed upon it, and acted on by the two 
 forces above mentioned. 
 
 CIRCUMSTANCES OF MOTION. The exact motion of the 
 projectile under these circumstances is very complex, and 
 is discussed in mechanics under the subject of " Rotation." 
 
 The general result of the action of the forces may be 
 stated as follows : 
 
 When the projectile first issues from the piece, its longer 
 axis is tangent to the trajectory. The resistance of the air 
 acts along this tangent, and is at first directly opposed to 
 the motion of translation of the projectile, and hence its 
 resultant coincides with the longer axis, and it exerts no 
 effort to overturn the projectile about its shorter axis. 
 
 The longer axis of the projectile, being a stable axis of 
 rotation, tends to remain parallel to itself during the passage 
 of the projectile through the air, but the tangent to the 
 trajectory changes its inclination, owing to the action of 
 gravity. The resistance of the air acting always in the 
 direction of the tangent, thus becomes inclined to the longer 
 axis of the projectile, and for projectiles in our service, and 
 modern projectiles generally, its resultant intersects the 
 longer axis, at a point in front of the centre of mass. 
 
 In Fig. 204, G being the centre of mass, and R the re- 
 
 FIG. 204. 
 
 sultant resistance of the air, this resultant acts with a lever- 
 arm /, to rotate the projectile about a shorter axis through 
 G, perpendicular to the plane of fire. 
 
 If the projectile possesses sufficient energy of rotation 
 about its longer axis under these circumstances, the rotation 
 about the shorter axis will not occur, but the practical re- 
 sult will be, that for projectiles rotating from left to right, as 
 
35 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 in our service, the point of the projectile will move slowly 
 to the right of the plane of fire. As soon as this motion of 
 the point to the right occurs, it causes a relative change in 
 the direction of the resistance of the air, and an oblique 
 pressure is produced on the left side of the projectile, by 
 which it is forced sidewise to the right, out of the plane of 
 fire. At the same time, the resultant of this new oblique 
 pressure, and of the rotation, causes the point of the pro- 
 jectile to move downward. 
 
 The result of the continued action of these forces is 
 practically 
 
 1. To cause the axis of the projectile to describe a cone 
 about the tangent to the trajectory. 
 
 2. To force the projectile bodily to the right, and out of 
 the plane of fire. 
 
 DRIFT. This departure of the projectile from the plane 
 of fire, due to the causes above mentioned, is called drift, 
 and may be computed by Mayevski's formula, which will 
 be given later. The actual motion of the projectile is more 
 complex than that above given, and its full investigation 
 requires analytical methods. 
 
 196. Form of Trajectory Causes Affecting Resistance Form 
 Cross-section Density of the Air. 
 
 FORM OF TRAJECTORY. From the above it appears, that 
 the trajectory is not a plane curve, but one of double curva- 
 ture. It is also shown by analytical methods, that the drift 
 increases more rapidly than the range, and hence the pro- 
 jection of the trajectory on the horizontal plane, is convex 
 to the horizontal projection of the line of fire, Fig. 203. 
 
 The trajectory ordinarily considered, is the projection of 
 the actual curve upon the vertical plane of fire. This pro- 
 jection so nearly agrees with the actual curve that the re- 
 sults thus obtained are practically correct, and the advan- 
 tage of considering it, instead of the actual curve, is, that we 
 need consider only that component of the resistance of the 
 air which acts directly along the longer axis of the projec- 
 tile, and which is directly opposed to the motion of transla- 
 tion. 
 
EXTERIOR BALLISTICS. 35 I 
 
 CAUSES AFFECTING RESISTANCE. The resistance of the 
 air to the motion of a projectile varies with 
 
 1. Its form ; 
 
 2. Its cross-section ; 
 
 3. The density of the air; 
 
 4. The velocity of the projectile. 
 
 FORM. Experiment shows that the ogival form of head 
 offers less resistance than any other, and the radius of the 
 ogive has been increased up to 2 and 3 calibres. Beyond 
 this latter radius other considerations, such as strength to 
 resist deformation, etc., enter. The resistance depends 
 principally upon the form of the head near its junction with 
 the cylindrical body of the projectile, as this affects the flow 
 of the air over the projectile. The shape of the rear portion 
 of the body also affects the resistance, and a projectile which 
 is barrel-shaped in rear, such as the Whitworth, offers less 
 resistance than one cylindrical in form, for the same reason 
 as above. Practical considerations of ease of manufacture, 
 facility of packing, etc., have, however, prevented the adop- 
 tion of the Whitworth shape. 
 
 CROSS-SECTION. Numerous experiments show that the 
 resistance of the air varies directly with the area of cross- 
 section of the projectile. 
 
 DENSITY OF THE AIR. Experiment also shows that the 
 resistance varies directly with the density of the air, and as 
 this density varies with the temperature and pressure, read- 
 ings of the thermometer and barometer must be taken, when 
 accurate results are to be obtained. These readings are 
 used to calculate the densities, as will be explained. 
 
 197. Relation between Velocity and Resistance Experiments. 
 
 EXPERIMENTS. The relation between the velocity of a 
 projectile, and the resistance opposed to its motion by the 
 air, has been the subject of experiment from the earliest 
 times to the present day. The most notable experiments 
 upon this subject are : 
 
 i. Robins in 1742 made the first experiments by means 
 of the ballistic pendulum which he invented. His conclu- 
 sions were, that up to iioo ft.-secs. the resistance is propor- 
 
35 2 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 tional to the square of the velocity ; at iioo ft.-secs. the law 
 of the resistance changes; beyond 1 100 ft.-secs. the resist- 
 ance is nearly three times as great as if calculated by the 
 law of the lower velocities. 
 
 2. Hutton in 1790 improved the ballistic pendulum, and 
 made numerous experiments with large projectiles. His 
 conclusions were, that the resistance increases more rapidly 
 than the square of the velocity for low velocities, and for 
 higher velocities that it varies nearly as the square. 
 
 3. General Didion made a series of experiments at Metz 
 in 1839 an d 1840 with the ballistic pendulum, and spheri- 
 cal projectiles of varying weights. His conclusions were, 
 that the law of resistance is expressed by a formula of the 
 general form 
 
 R oc 
 
 a and b being constants. This formula held for sh'ort ranges, 
 but not for heavy charges and high angles of elevation. 
 
 4. Experiments were therefore made again at Metz in 
 1857, and with electro-ballistic instruments. The conclu- 
 sions from these experiments were, that the resistance varies 
 as the cube of the velocity. Experiments by Prof. Helie at 
 Gavre, in 1860 and 1861, gave practically the same result. 
 
 5. The most accurate experiments upon this subject were 
 made by the Rev. Francis Bashforth in England, in 1865, and 
 again in 1880. The advantage of these experiments is that 
 they were made with a very accurate instrument, and with 
 comparatively modern projectiles. The conclusions in 
 general were, that the resistance varies with some power of 
 the velocity, and that this power varies with the velocity, 
 being generally as follows : 
 
 For velocities between 900 and 1 100 ft.-secs ...... v* 
 
 11 " between iioo and 1350 ft.-secs... ... v* 
 
 " " above 1350 ft.-secs .............. v* 
 
 6. The most recent experiments on the subject, and those 
 now adopted for use, were made by Krupp in 1881 with 
 modern guns, projectiles, and velocities. General Mayevski 
 discussed the results of these experiments, and deduced ex- 
 pressions for the resistance as follows : 
 
EXTERIOR BALLISTICS. 353 
 
 198. Method of Determining Resistance. 
 
 The resistance of the air is a force expressed in pounds 
 per square inch, and it opposes the motion of the projectile 
 in its passage. 
 
 The effect of this force is to retard the projectile. There 
 are therefore two quantities to be determined : 
 
 1. The resistance, or pressure of the air, in pounds per 
 square inch ; 
 
 2. The retardation, or loss of velocity in feet per second, 
 produced by this resistance. 
 
 METHOD EMPLOYED TO DETERMINE RESISTANCE. The 
 method generally employed to determine the resistance of 
 the air, consists in measuring the velocities v l and v^ of the 
 projectile, at two points M l and M 9 , situated at such a dis- 
 tance apart, that the path of the projectile, over this distance, 
 may be regarded as a right line ; and also so that the resist- 
 ance may be considered constant over this distance. The 
 energy of the projectile at the point M l is \mv*, and at 
 M^ , \mv*. Their difference, fyn(v? v^], is the loss of 
 energy over this distance due to the resistance of the air ; 
 and supposing this resistance constant, and calling the re- 
 sistance p, and the path /, we have 
 
 pl = bn(v? - V?) (262) 
 
 This, being the mean resistance, corresponds to the mean 
 
 ^+^Q 
 
 velocity, or - 
 
 By properly selecting the points, and varying the veloc- 
 ity so as to include all service velocities, we obtain a series 
 of values for the velocity and resistance, from which a curve 
 can be constructed, giving the law of resistance for different 
 velocities. 
 
 The distance between M, and M^ must be chosen accord- 
 ing to the velocities and projectiles used. Thus for low 
 velocities, and large projectiles, the distance between the 
 points must be greater, since the loss of velocity over a 
 given path is less in this case, than for small projectiles 
 moving with high velocities. 
 
354 TEXT-BOOK Of ORDNANCE AND GUNNERY. 
 
 199. Modifications of General Method Results Resistance. 
 
 MODIFICATIONS. When the curve of resistance obtained 
 by the above general method is plotted, it is found that 
 sudden changes occur in it for different velocities. 
 
 Also the above expression does not take account of vari- 
 ation in the form and cross-section of the projectile, or in 
 the density of the air. 
 
 To have a general expression into which all these quan- 
 tities enter, General Mayevski proceeded as follows : 
 
 Denoting the resistance as before by p, the retarda- 
 tion is 
 
 A JL 
 
 M " W p ' 
 
 in which M is the mass of the projectile ; 
 W, its weight in pounds ; 
 g, the acceleration of gravity, 32.2 ft.-secs. 
 
 A 
 This expression was placed equal to --f(v\ in which A 
 
 is a constant to be determined by experiment, C a factor 
 called the " ballistic coefficient," and f(v) some function of 
 the velocity. Hence we have 
 
 The Ballistic Coefficient C. The value of this coefficient is 
 
 in which 
 
 , is the standard density of the air ; 
 
 <S, the density at the time of the experiment ; 
 
 c, the coefficient of reduction ; 
 
 d, the diameter of the projectile in inches ; 
 W, its weight in pounds as before. 
 
 Substituting the value of C from (264) in (263), we have 
 
 p = Af W (26s) 
 
EXTERIOR BALLISTICS. 355 
 
 For a given projectile, all the quantities which enter the 
 ballistic coefficient C are known, and they take into account 
 the cross-section and weight of the projectile, and the den- 
 sity of the air. 
 
 The form of the projectile enters in the coefficient of 
 reduction c as follows : For projectiles of a standard form, 
 or for those with which the experiments are made, the coef- 
 ficient of reduction is taken as unity. For those differing 
 from the standard, the retardation will be greater or less, as 
 the form is less or more suited to overcome the resistance. 
 Hence this coefficient will have values greater than unity 
 for projectiles whose resistance is greater than the standard, 
 and values less than unity for those whose resistance is less 
 than the standard. For the older forms of projectiles in our 
 service c = i, for the new form c = 0.9 nearly. 
 $ 
 
 The values of for all pressures and temperatures in 
 
 practice are calculated and tabulated for use in Table III 
 (Ballistic Tables). 
 
 The only remaining quantities in formula (265) are A and 
 f(v\ and the object of the experiments is to determine the 
 values of A and the exponent of v. 
 
 RESULTS. As a result of the experiments, the general 
 value (265) for the retardation assumes the following forms 
 for different velocities : 
 
 For all velocities greater than I33oft.-seconds, 
 
 Jlp = -,'; log A =4, 1525284; 
 1330 ft.-secs. > v> 1 120 ft.-secs. 
 
 W P = ~C V * ' log A = 7' 36435 1 ; 
 1 1 20 ft.-secs. > v > 990 ft.-secs. 
 
 -j^rP^^ 6 ; log ,4 =^8865079; 
 990 ft.-secs. > v > 790 ft.-secs. 
 
356 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 -^p = ~v z ; log A = 8.8754872 ; 
 790 ft.-secs. > v > 100 ft.-secs. 
 -j-p = ^v* ; log A = 5.7703827. 
 
 RESISTANCE. The corresponding resistance in pounds 
 
 W 
 
 is obtained for each velocity by multiplying by since 
 
 o 
 
 6 cd * ' " \ . . . (266) 
 
 200. Trajectory in Air Nomenclature Equations of Motion. 
 
 NOMENCLATURE. Considering the motion of translation 
 only, and that the resistance of the air is directly opposed 
 to this motion, let (Fig. 205). 
 
 X -* y 
 
 2\ "T 
 
 FIG. 205. 
 
 R be the retardation due to the resistance of the air, its 
 value being given by equation (265) ; 
 
 V, the initial velocity ; 
 
 v, the velocity of any point of the trajectory whose co-ordi- 
 nates are x and y ; 
 
 z/j, the velocity in the direction of x\ 
 
 0, the angle made by the tangent to the trajectory with the 
 horizontal, at the origin ; or the angle of elevation ; 
 
 0, the value of for any other point of the trajectory ; 
 
 x and y, the co-ordinates of any point of the trajectory, in 
 feet; 
 
 X, the whole range in feet. 
 
 EQUATIONS OF MOTION. The only forces acting on the 
 
 projectile after it leaves the piece, are the resistance of the 
 
 air and gravity. 
 
EXTERIOR BALLISTICS. 357 
 
 The resistance of the air is directly opposed to the mo- 
 tion of the projectile, and continually retards it. Gravity 
 is supposed to act vertically, and retards the projectile in 
 the ascending portion of the trajectory, while it accelerates 
 it in the descending- portion. 
 
 Considering the ascending portion, we have for the ac- 
 celeration along x, since gravity has no component in that 
 direction, 
 
 ', ...... (267) 
 
 from this 
 
 dv, 
 
 The velocity along x is 
 and along y, 
 
 dx 
 
 v i = j7 = v cos 6 ; (269) 
 
 dy 
 
 -^ = v sin 8 v l tan ..... (270) 
 
 Substituting the value of dt from (268) in (269) and (270), 
 we have 
 
 (27I) 
 
 v l tan dv. 
 
 Zcosd 
 The acceleration along the radius of curvature is 
 
 v* 
 
 
 Substitute in this for r its value -^ from calculus, 
 
 (273) 
 au 
 
 and we have 
 
 v* ds i dsdB dB 
 
 > - (274) 
 
358 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 hence 
 
 gcosBdt 
 
 (275) 
 
 Substitute in (275) for cos & its value from (267) and for 
 v its value from (269), and we have 
 
 g cos 6 dv. 
 
 (276) 
 
 Collecting these equations, we have 
 
 dt = - 
 
 dx - 
 
 dv, 
 
 1 
 
 R cos B ' 
 
 R cos B ' 
 
 v. tan dv 
 dy=-- 
 
 dO = 
 
 R cos B ' 
 g cos 
 
 (A) 
 
 If these equations could be integrated directly, they would 
 give the values of x, y, t, and for any point of the trajectory. 
 But as they are expressed in terms of R, v l9 and B, three in- 
 dependent variables, the direct integration is impossible. 
 
 201. Method of Integrating Equations A. 1st Step. 
 
 IST STEP. The first step in the process of integration is 
 to replace R by its value from equation (263), 
 
 and to make 
 
 /(*>) = *r, (277) 
 
 in which n represents the, exponent of the power of v which 
 is proportional to the retardation, for any particular velocity, 
 and, according to Mayevski's experiments as shown, varies 
 from 2 to 6. 
 
 From equation (269) we have 
 
 v l = v cos 6 ; 
 
EXTERIOR BALLISTICS. 
 
 359 
 
 hence 
 
 Making these substitutions in the value of R above, we 
 have 
 
 A 
 
 W~ C cos ff 
 
 (279) 
 
 Substituting this value of R in the first, second, and 
 fourth of equations (A), we have 
 
 C 
 dt =~ A 
 
 <**=- 
 
 dv 
 
 \\ (280) 
 
 (281) 
 
 (282) 
 
 Dividing both terms of (282) by cos' 0, we have 
 
 ' ' ' ' <** 
 
 or, since cos 6 = 
 
 sec ff 
 
 m 
 
 gC dv, 
 
 cos 2 e A sec"" 1 0v 
 Collecting these equations, we have 
 
 (284) 
 
 dV 
 
 A 
 
 J_C_ dv, . 
 
 3?^ec M ~ x 6 v? ' 
 C dv, 
 
 (285) 
 
360 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 202. Method of Integration of Equations (A) 2d Step. 
 
 2D STEP. In equations (285), deduced by the ist step, 
 the first members are exact integrals. The second members 
 are not, however, because they contain the two independent 
 variables see"" 1 and v r For all cases of direct fire the 
 value of sec differs but little from unity, since for angles 
 of 15, sec 6 1.035, an d for angles less than this, its value is 
 still more nearly unity. Hence sec 6 can be replaced by 
 unity without great error. 
 
 Siacci shows, however, by analysis, that a more correct 
 value for direct fire is 
 
 sec* - ' = sec" - 2 0, (286) 
 
 and this value has been universally adopted. 
 
 Substituting this value of sec" ~ I in equations (285), we 
 have 
 
 dB gC dv, 
 
 cos 2 A sec* ~ 2 v? + * ' 
 C dv, 
 
 dt= - 
 
 A sec* ~ 2 I'/ : 
 
 . C dv, 
 
 dx = 
 
 A sec* ~ 2 vf ~ x " 
 
 . . . (287) 
 
 Taking the first of equations (287), multiply the numer- 
 ator and denominator of the second member by sec 3 = 
 sec 2 sec 0, and we have 
 
 cos 3 6 ~ A 
 
 Butsec 2 = 5-z and since is constant, sec dv l = 
 
 d(y^ sec 0); hence 
 
 dti gCd(i\ sec 0) 
 
 cos 2 6 ~~ A cos" (v, sec 0)* + r ' 
 
 and by the same process the other two equations may be 
 placed in a form in which the second members can readily 
 be integrated. Hence we have 
 
EXTERIOR BALLISTICS. 
 
 dO gC d(v^ sec 0) 
 
 cos 2 A cos 2 (^ sec 0) w 
 
 ^4 cos (v l sec 0) 
 
 C d(y^ sec 0) 
 ~ 
 
 , sec 
 
 361 
 
 (288) 
 
 Making 
 
 v, sec = 
 
 ^ cos 6 
 cos 
 
 F cos 
 
 F, sec = T- = F, 
 cos 
 
 (289) 
 
 (290) 
 
 from equation (269), and integrating equations (288) between 
 the limits and 6 to which correspond Fand u, we have 
 
 tan - tan 6 = n /^ [j, - ^]; . (291) 
 
 7-WT-x ; ( 2 92) 
 
 / = 
 
 # = 
 
 C 
 
 (n i)^4 cos 0L&' 
 
 (Jt^t^^wrrrl (293) 
 
 203. Simplification of Equations (291), (292), and (293) Method 
 
 of Calculating the Functions which Enter them. 
 SIMPLIFICATION. To simplify equations (291), (292), and 
 (293), make 
 
 /() = 
 
 (294) 
 
 T-() = 
 
 . . . (295) 
 . . . (296) 
 
 s(0 = 
 
 >-2)^ 
 
 -+Q' 
 
 . (297) 
 
362 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 Making these substitutions, equations (291), (292), and 
 (293) can be written, 
 
 . (B) 
 
 ' See (289) ...... ' ' ' (F) 
 
 In equations (294), (295), etc., the expression /(), is 
 called the inclination function, T (u) the time function, and 
 S(u) the space function; Q, Q\ Q" ; , etc., are arbitrary con- 
 stants. The values of these iunctions may be calculated 
 and tabulated for convenience, and the resulting tables are 
 called " Ballistic Tables." Those used in the present course 
 were calculated by Capt. James M. Ingalls, ist Artillery, 
 U. S. Army. By their use the calculation of these functions 
 is avoided for any particular case, and the use of the formu- 
 las facilitated. 
 
 CALCULATION OF FUNCTIONS. As an illustration of the 
 method of calculation, take the T(u) function, equation (296): 
 
 In this equation, n is the exponent of the power of v to 
 which the resistance of the air is proportional ; A, a constant 
 determined by Mayevski's experiments, as explained ; and 
 Q" an arbitrary constant. 
 
 For values of v greater than 1330 ft.-secs., we have n 2 
 and log A 4.1525284. Hence for these velocities we have 
 
 T(u) = -^-^ - + Q". 
 [4.1525284] 
 
 The ballistic tables are so constructed that all the func- 
 
EXTERIOR BALLISTICS. 363 
 
 tions S(u), T(u), etc., reduce to zero for u = 2800 ft.-secs. 
 Hence we have 
 
 and solving 
 
 <2"=:- 2.5137. 
 
 When the velocity is 1330 ft.-secs., n 3 ; log A = 
 7.0364351 ; hence 
 
 T(u} = 
 
 2 x [7.036435 
 
 But to avoid abrupt changes in the table, the value of 
 T(u) for 1330 ft.-secs. must be placed equal to that which 
 would be obtained if n = 2, or from the first equation in 
 which Q" enters. This may be done, since Q" is arbitrary, 
 by placing 
 
 -2.5137= 
 
 [4.1525284] x 1330 2 x [7-0364351] x 1330 
 
 Solving with reference to g/', we have 
 " = +0.1791. 
 
 Therefore, for all values of u or v greater than 1330 ft.- 
 secs. the value of T(u) is calculated by the equation 
 
 [4,525284] x 
 
 and for all values of u or v between 1330 and 1120 ft.-secs. 
 by the equation 
 
 T(u) = - = - + 0.1701. 
 2 X [7.036435 i]X' 
 
 Below 1 1 20 ft.-secs. we make a similar change, equating 
 the known value for 1120 with the new values for A and , 
 and determine the new arbitrary constant as before, and so 
 on for all the functions. 
 
364 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 204. Relation between x and y. 
 
 We have from equation (B), since tan 6 = -~ t 
 
 dy C 
 
 /- = tan - 
 
 2 COS* 
 
 also, 
 
 fc/j = v COS 
 
 z> cos B 
 Vl Sec * = cos = * ( See 9 ^' 
 
 d (z/j sec 0) = d#. 
 
 Whence, substituting in the third ol equations (288), we 
 have 
 
 C du 
 ~ A u~* 
 or 
 
 dx du 
 
 ....... (299) 
 
 Multiplying (299) and (298) together member by member, 
 we have 
 
 2 COS' . , . 
 
 tan 
 
 6T 2 
 
 Integrating and making x and y both zero at the origin, 
 where u '= F, we have 
 
 C AJu w 
 
 Making 
 
 we have 
 2 cos 2 
 
EXTERIOR BALLISTICS, 365 
 
 From equation (D) we have 
 
 ?L = S(u) S(V) (301) 
 
 Dividing (300) by (301), member by member, we have 
 
 AuA 
 
 (302) 
 
 or finally, 
 
 y C \A(u)-A(V) 
 
 x --. tan - 2 cog2 ^ | s ^ 'S(r) ' 
 
 In this equation A (21} is called the altitude function. 
 Collecting these equations, we write 
 
 . . . (B) 
 
 (C) 
 cos 
 
 (D) 
 
 cos 6 /T _ 
 
 u v-- (F) 
 
 COS0 
 
 These are the fundamental equations of Exterior Ballis- 
 tics, and the object now is to explain their modifications and 
 methods of use. 
 
 205. Modifications of General Formulas for the Whole Range X 
 
 For the Summit of the Trajectory. 
 
 MODIFICATIONS FOR RANGE X. The range being the 
 distance from the muzzle, to the point where the projectile 
 in the descending branch of the trajectory, pierces the hori- 
 zontal plane through the muzzle, we have for this point 
 
 8 = &) 
 
 t = T: 
 
 u = u < 
 
366 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 and making these changes in (B), (C), (D), (E), and (F), we 
 have 
 
 Combining (B') and (E x ) and eliminating /(F), we have 
 
 Au-A 
 
 SUMMIT OF TRAJECTORY. For this point we have 6 = o, 
 and since 
 
 sin 20 = 2 sin cos 0, 
 we have from equation (B) 
 
 ... (303) 
 
 \^ 
 and from (F) 
 
 U ' = ^' (34) 
 
 in which u and V Q are the values of u and v for the summit 
 of the trajectory. 
 
 Substituting in (E r ) for 
 
 its value from (303), we have 
 
EXTERIOR BALLISTICS. 367 
 
 and this value in (E') and (G) gives 
 
 sin 20- cj/(*.)-/(F)]-;. (306) 
 
 tan = 7 (") - 7 > (307) 
 
 When and GO are both small, as in direct fire, we may 
 without material error suppose 
 
 GO, 
 hence 
 
 2 cos a tan GO = 2 cos 2 GO tan GO = sin 2co ; 
 
 and substituting in (307), we have 
 
 sin 2Go ~ "! /(#) /( ) [ ... (308) 
 
 206. Auxiliary Formulas. 
 
 Equations (E), (E 7 ), and (G) can be more readily used for 
 calculation, if the quantities 
 
 A(u)-A(V] 
 
 and 
 
 (*) 
 
 are calculated and tabulated for use. 
 
 jf 
 
 These quantities are functions of -^ and V, as may be 
 
 o 
 
 shown in the following manner: 
 
 Suppose it is required to compute the height of trajec- 
 tory y, by (E), angle by (E'), and angle K> by (G), having 
 given the ballistic coefficient C, the initial velocity F, and 
 the whole range X, or part of the range x. 
 
 In equation (E), and u are unknown. can be com- 
 puted from (E x ) when (# w ) is known, and GO in (G) can be 
 computed also when (u u ) is known. 
 
 Hence (u u ) is the only unknown quantity required to 
 complete the solution. u u can be found from (D r ), since 
 
368 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 and u can be found from (D) since 
 ? 
 
 It follows from this that the quantities (a) and (b) are func^ 
 
 tions of -^, or ^ and F, and therefore the values of these 
 C- o 
 
 J 
 
 expressions when tabulated should have -= and V as argu- 
 
 o 
 
 ments. 
 
 We therefore place 
 
 A(u.)-A(V) I(V , 
 ~ J ^> 
 
 - 
 
 *'' (3IO) 
 
 a + & =m, . . . (313) 
 
 and making the corresponding changes in equation (B), we 
 have 
 
 tan 6 = tan --- r - 
 2 cos' * 
 
 reducing 
 
 tan0 = tan0{i- i ^ r (. . . . (314) 
 In (E), 
 
 ^r 2 COS 
 
 reducing 
 
 (315) 
 
 in (E'), 
 
 sin 20 = AC, ......... (31-6) 
 
EXTERIOR BALLISTICS. 3691 
 
 in (G), 
 
 and for small angles of elevation, since 
 
 = , 
 we have, from (317), 
 
 sin 200 = BC. . . . . . . (318) 
 
 Substituting in (314) and (315) for sin 20 its value from 
 (316), we have 
 
 tan = tan | I - ^ j ; . . . . (319) 
 
 . . . (320) 
 
 The auxiliary quantities #, , A, B, m, are generally 
 written a f(zV\ b =f(zV), m =f(zV\ etc. 
 
 207. Explanation of Ballistic Tables. 
 
 The values of the quantities A (u), S(u), T(u), etc., have 
 been calculated and tabulated as before explained, and their 
 values are found in Ballistic Table I, for all velocities from 
 2800 to 400 ft.-seconds, for ogfval projectiles. Table II 
 gives the value of the corresponding quantities for spherical 
 projectiles. 
 
 In these tables u is a general expression for velocity, 
 so that if v or V be given, its value will be found in the 
 column headed u in the tables. 
 
 To illustrate their use, find the values of the different 
 functions from Table I, for a velocity of 1137.6 ft.-secs. 
 
 We have from the table 
 
 S(u) = 5(1137.6); 5(1137) =6413-2; 
 
 5(o.6) = 4-26 = 7.1 X .6 = 4.26. 
 (1137.6) = 6408.9 
 
 A(u) = A (1137-6); A (i 137) = 341-73 ; 
 
 A (0.6) = .636 = i. 06 X .6 = .636. 
 
 A (1.37.6) = 341-09 
 
37 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 /() = /(! 137.6); 7(i 137) = 0.14942 
 
 7(o.6) = .000216 = 00036 X .6 =.0002 1 6 
 7(1137^)) = 0.14920 
 
 T(u)= ^(1137.6); T(i 137) = 3-736; 
 
 r(o.6) = .0036 = .006 X .6 = .0036 
 = 3-732 
 
 Conversely, having the values of the quantities 5 (u) y 
 A(u), etc., to find the corresponding values of , we proceed 
 as follows : 
 
 Find the value of u for 
 
 S(u) =6430.7; 
 A(u)= 360.9 ; 
 f(u) = 0.1580; 
 7 = 3-720. 
 
 From Table I we have 
 
 5 () = 6427.4, = 1135, 
 6430.7 - 6427.4 = 3.3. 
 
 Tabular difference for i ft.-sec. = 7.2. 
 
 7.2:3.3:11:* 
 x 0.46 ft.-secs., 
 hence 
 
 u for S(#) = 6430.7 = 1135 0.46 = 1134.54 ft.-secs.; 
 A (u) = 360.45, u 1120 ft.-secs.; 
 
 360.9 - 360.45 = 0.45- 
 Tabular difference for i ft-sec. = 1.15. 
 1.15 :o.45:: I :*; 
 
 x 0.39 ft. -sees.; 
 hence 
 
 u for A (u) = 360.9 = 1 1 20 0.39 = 1119.61 ft.-secs. 
 
EXTERIOR BALLISTICS. 371 
 
 The same method applies to all other cases, and it is 
 evident that the table is used like a table of logarithms. 
 
 208. Auxiliary Tables Values of/(zF), z, and V. 
 
 These tables are found in Ballistic Table I, and give the 
 values of the quantities A, B,a, b, and m ; and the tables are 
 headed " auxiliary A," "auxiliary B" and "auxiliary m." 
 The values of a and b are taken from the table for A and B, 
 since a and b are general cases of A and B. The expressions 
 for these quantities are given by equations (309) to (313), and 
 their values were calculated and tabulated by Capt. Ingalls. 
 
 By referring to the tables it will be seen that the argu- 
 
 x X 
 
 ments are z and v. z is used for brevity in place of ~^ or , 
 
 C C 
 
 and hence the value of z is 
 
 x X 
 
 *=c or ~c (32I) 
 
 In this table there are two columns of differences, A z and 
 
 4* 
 
 A z corresponds to differences in the argument z, and A v to 
 those of the argument V. 
 
 USE OF TABLES. We may have the following cases : 
 
 1. A given value of z and one of F, neither of which is 
 found in the table ; to find the corresponding value of A, B, 
 or m. 
 
 2. A given value of A, B, or m and one of V, neither of 
 which is found in the table ; to find the corresponding value 
 of*. 
 
 3. A given value of A, B, or m, and one of z, neither of 
 which is found in the table ; to find the corresponding value 
 of F. 
 
 Suppose we have a value of z and one of F given, and 
 the corresponding value of A, B, or m is required. 
 Let/^F) denote the value sought ; 
 
 z t and F the next smaller values of z and F found in 
 
 the tables ; 
 / G&o F ) the value from table corresponding to z and 
 
37 2 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 For an increase of 100 in z, we find that/(# e F ) increases 
 by 4, ; hence, for an increase of z z , the increase in 
 
 f(*.V.) will be 
 
 loo : z z 9 : : A x : x ; 
 
 x 
 
 100 
 
 Again, for an increase of 50 ft.-secs. in F, /(#, F ) decreases 
 by d v ; hence, following the same rule, the decrease for 
 F- F will be 
 
 F F 
 
 The true value of /(sF) then will be 
 
 A =/(,F) =/(..F.) + A- ^ A. (322) 
 
 Suppose now we have given f(zV) and F, and wish to 
 find z. 
 
 Solving equation (322) for z, we have 
 
 inn ( F F 
 
 Or, having f(zV) and ^, required F. Solving equation 
 (322) for F, we have 
 
 -- (324) 
 
 209. Examples of Use of Auxiliary Tables Ballistic Coefficient -^. 
 
 EXAMPLE i. Find the value of A =zf(zV) for z = 1446.7 
 and V 1224.4. 
 
 In formula (322) we have 
 
 z. = 1400 ; 
 
 F = 1200; 
 
 A z = .0028 ; 
 4, = .0025 ; 
 
 * z. = 46.7 ; 
 
EXTERIOR BALLISTICS. 373 
 
 Hence 
 
 4.6.7 . 
 
 A = f(*V) = .0352 + X .0028 - - X .0025, 
 
 f(zV) = .0352 + .0000876 = .0353. 
 
 In a similar manner B = f(zV), and m=f(zV) may be 
 found by using the proper tables. 
 
 EXAMPLE 2. Find z for B =f(zV) = 0.1430, and V 1740. 
 In formula (323) we have 
 
 z for F(i70o) and B (.1409) = 5100. 
 
 4, = .0046 ; 
 
 4, = .0054 ; 
 F- F = 4o; 
 f(*r) = 0.1430; 
 /(*.Fi) = 0.1409; 
 
 F = 1700. 
 
 Hence 
 
 In a similar manner, having f(zV) = A or m, z may be 
 found, using the proper tables. 
 
 EXAMPLE 3. Find V for m f(zV) 0.2400 and z = 5250. 
 In formula (324) we have 
 
 V. for m (.2331) and z (5200) = 1750, 
 
 A v .0101 ; 
 4, = .0072 ; 
 
 * ^o = 5o ; 
 
 jar. = 5200 ; 
 
 /(^r) = .2 4 oo. 
 
 Hence 
 V = '75 + ^i { X .0072 + -2331 - -2400 
 
 v= 1733-67- 
 
374 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 In a similar manner, having f(zV) = A or B, V may be 
 found, using the proper tables. 
 
 BALLISTIC COEFFICIENT. The value of this coefficient 
 is given by equation (264), and its calculation involves that 
 
 ft ft 
 
 CALCULATION OF -p The values of ^ are given in Table 
 
 III, for degrees Fahrenheit from o to 100, and for heights 
 
 ft 
 
 of barometer from 28 to 31 inches. To find the value of ~ 
 
 for any intermediate values of F and H not in the tables, we 
 
 proceed exactly as in the case of the auxiliary tables. 
 
 ft 
 
 EXAMPLE. Find the value of -r 1 for F = 49. 6 and H =.- 
 
 29.30 inches. From Table III we have 
 
 s^ 
 For F = 49 and H = 29 inches ; ^ = 1.0,12 ; 
 
 t\ 
 Difference for i F= + .002 ; 
 
 Difference for o.6 = + .0012; 
 
 p. 
 Difference ~ for i inch H .034 ; 
 
 Difference for 0.30 inch .0102. 
 Hence 
 
 -^ for F= 49 .6 and H 29. 30 inches =: 1.012 -}- .0012 .0102 
 
 = 1-003. 
 
 PRACTICAL PROBLEMS. 
 
 210. Kind of Fire to which Formulas Apply Problem I Use of 
 
 Equation B. 
 
 KIND OF FIRE. The formulas above deduced apply 
 strictly to direct fire only, where the values of and 6 are 
 so small that Siacci's value of sec may be used without 
 appreciable error. 
 
EXTERIOR BALLISTICS. 
 
 375 
 
 The formulas give, however, sufficiently accurate results 
 for indirect or curved fire, and hence they are used for both 
 direct and curved fire ; but for mortar fire they must be 
 modified, as will be explained. 
 
 PROBLEM I USE OF EQUATION (D). Assume equa- 
 tion (D), 
 
 * = C\S(u)-S(V)-\. 
 
 Since C is generally known, we have in this equation 
 three quantities, x y u, and V, any two of which being given, 
 the third can be found. Solving equation (D) for each of 
 the three quantities, we can write 
 
 or, since 
 
 the two latter can be written 
 
 For the whole range X we have similar equations, 
 changing u into U M and x into X. Collecting these equa- 
 tions, we have 
 
 x=C[S(u)-S(V)-\; 
 
 (325) 
 
 S(r)=S(u)-*; 
 
 X=C\_S(u)-S(V}}; 
 
 x X 
 
376 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 These equations enable us to solve the following prob- 
 lems, which may be grouped under Problem i. 
 
 Given. 
 
 Required. 
 
 C,u, V 
 
 X 
 
 C, V,x 
 
 U 
 
 C, x, u 
 
 V 
 
 C, u., V 
 
 X 
 
 C, V,X 
 
 u*> 
 
 C, X, u u 
 
 V 
 
 In this problem, if the angle of elevation does not exceed 
 10, the values of u and v will be practically the same, but 
 for angles greater than 10 the value of t/must be calculated 
 from that of u by equation (F), 
 
 cos 
 *cos7' 
 
 and tor this purpose the value of 6 must be known. 
 Its calculation will be explained later. 
 
 Problem 2. Use of Equations (316) and (321). 
 Assuming the above equations, we have 
 
 sin 20 = A C: . 
 
 (316) 
 (321) 
 
 i. Having C, 0, and V, find the whole range X. 
 From (321) we have 
 
 X=Cs. 
 
 In this equation X and z are unknown. 
 But A =f(zV\ and from (316) 
 
 Hence in the equation A = f(zV\ we have/(^F) and V 
 given to find z, which is obtained from equation (323), using 
 auxiliary table A. 
 
 This value in equation (321) will give X. 
 
EXTERIOR BALLISTICS. 
 
 377 
 
 2. Having C, 0, and X, find the initial velocity F. We 
 have 
 
 A=f(zV\ 
 
 in which A, z, and Fare unknown. But from (316) 
 
 sin 20 
 
 and from (321) 
 
 X 
 *=> 
 
 Hence we have f(zV) and z given to find F, which is 
 obtained from formula (324), using auxiliary table A. 
 
 3. Having C, F, and X, find the angle of elevation 0. 
 
 From (316) we have 
 
 sin 20 = AC, 
 in which A and are unknown. But 
 
 in which 
 
 X 
 2 =^ 
 
 and F is given. Hence we can find A by formula (322), 
 using auxiliary table A. This value of A in (316) gives 0. 
 We have, therefore, for Problem 2, 
 
 Given. 
 
 Required. 
 
 C, 4>, V 
 
 X 
 
 c,<t>,x 
 c, v,x 
 
 V 
 
 
 
 212. Problem 3 Time of Flight. 
 
 i. Having C, 0, F, and x, find the time of flight for the 
 range x. 
 
 From equation (C) we have 
 
 C [T(u-(T(V)l 
 
 
 COS 
 
 in which , the velocity at the point x, and t, the time to 
 that point, are unknown. 
 
37$ TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 But we have, equation (D), 
 
 in which z = -~ and F are known. Hence u can be deter- 
 mined, and this value of u in equation (C) will give t. 
 If = or < 10, u v ; if > 10, 
 
 COS0 
 
 cos 0' 
 
 2. Having C, 0, F, and X, find the time of flight for the 
 whole range X. 
 
 From equation (C') we have 
 
 cos 
 
 in which w , the remaining velocity at the end of the range, 
 and T, the time to that point, are unknown. 
 But we have, equation (D'), 
 
 in which z =-^ and Fare known. Hence u u can be deter- 
 o 
 
 mined, and this value of U M in equation (C ; ) will give T. 
 The same remarks apply to u and Fas in i. 
 If = or < 5, cos 0=i, practically, and we have 
 
 For Problem 3 we have, then, 
 
 Given. 
 
 Required. 
 
 C, </>, V, x 
 C, <1>, V, X 
 
 t 
 
 T 
 
 213. Problem 4 Angle of Inclination. 
 
 i. Having C, 0, F, and ^r, find the value of 0, the inclina- 
 tion of the tangent at the point x. 
 
EXTERIOR BALLISTICS. 379 
 
 We have, irom (314), 
 
 in which and m are unknown. We have 
 
 m=f(*V\ 
 in which m and 2 are unknown. But from (321) 
 
 from which z can be found, and hence m by formula (322),. 
 using auxiliary table m. 
 
 This value of m in (314) will give 9. The value of 6 thus 
 found, when substituted in equation (F), will give v when- 
 ever > 10. 
 
 The value of 6 may also be calculated from equation 
 
 (319), 
 
 r ~i 
 
 tan 6 = tan I i -jj, 
 in which m is found as above, and 
 
 A = ^*- (equation (316)). 
 
 2. Having , 0, F, and ^T, find the value of <, the angle 
 of fall. 
 
 We have from (317) 
 
 BC 
 
 tan GO = - 5 - , 
 2 cos 2 0* 
 
 in which /? and GO are unknown. But we have 
 
 in which B and # are unknown. From (321) 
 
 X 
 
 * = T' 
 
 from which can be found. We have then z and F given, 
 
380 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 from which B =f(zV) can be found, using auxiliary table B 
 and formula (322), and this value of B in (317) will give GO. 
 If = or < 5, we have, equation (318), 
 
 sin 2ao = B C. 
 
 214. Problem 5 Height of Trajectory Maximum Height. 
 
 HEIGHT OF TRAJECTORY. Having C y 0, V, and x, find 
 the height of the trajectory at the range x. 
 
 We have from (320) 
 
 r i 
 
 y = x tan i - - , 
 
 l_ *L I 
 
 in which y, a, and A are unknown. From (316) we have 
 
 _ sin 20 
 A ~^> , 
 
 from which A can be determined. We have also 
 
 in which a and z are unknown. But 
 
 x 
 
 '=?> 
 
 from which z can be determined, and we have then z and V 
 given, from which we can find af(zV) by the use of aux- 
 iliary table A y and formula (322). These values of A and a 
 in (320) will give y. Equation (315) may also be used. 
 
 MAXIMUM HEIGHT. Having C, 0, and V, find the 
 maximum height of the trajectory. 
 
 This will be at the summit of the trajectory, and for this 
 point 6 o. 
 
 We have from (320) 
 
 in which y, x, a, and A are unknown. 
 
 For the summit of the trajectory make y = y and x = 
 
 To find # , we have, (321), 
 
 x, = Cz, 
 in which # and z are unknown. Assume equation (319), 
 
 tan 6 = tan [i Sfl 
 
EXTERIOR BALLISTICS. 381 
 
 Since Q = o at the summit, we have 
 
 m A, 
 and from (316) 
 
 sin 20 
 m = A = gr , ..... (326) 
 
 from which m can be determined. Then m-=.f(zV\ in 
 which m and V are known and z can be found by auxiliary 
 table m and formula (322). This value of z in (321) above 
 will give x , the range corresponding to the summit. 
 In equation (320), since m = A by (326), we have 
 
 but 
 
 m = a + b. 
 Hence 
 
 ra + 6-a] 
 ,. = *.. tan *L J> 
 
 or 
 
 
 ^ = * tan ...... (327) 
 
 In this equation y^ and b are unknown. But we have 
 b=f(zV\ in which z and Fare known, and hence b can be 
 calculated by auxiliary table B and formula (322). This 
 value in (327) will give _^ . 
 
 215. Problem 6 To Determine the Dangerous Space Rule of 
 
 Double Position. 
 
 DANGEROUS SPACE. The dangerous space is the hori- 
 zontal distance over which an object of a given height will 
 be struck. Suppose the height of the object is. 6 feet. If 
 we find first the whole range f<gr a given elevation, initial 
 velocity, etc., and then find the range at which the height 
 of the trajectory is 6 feet, it is evident that for every point 
 beyond this latter range, in the descending branch of the 
 trajectory, the height will be less than 6 feet, and the object 
 will be struck. The dangerous space, then, is the difference 
 between the whole range, and the range corresponding to the 
 given height. It is also evident that in general there will 
 be two points of the trajectory whose heights are the same 
 
$82 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 one point in the ascending branch, and one in the descend- 
 ing branch. The point in the descending branch is alone 
 considered. 
 
 The problem then resolves itself into computing first the 
 whole range, and then the range whose ordinate is y, and 
 taking their difference. 
 
 DATA. The data are C, 0, and V. 
 
 METHOD. To find the whole range X, use the method 
 of Problem 2. 
 
 To find the abscissa of the point whose ordinate is y. 
 This problem is apparently the inverse of Problem 5, for 
 which equation (320) is used ; but on examining that equa- 
 tion it will be found that a is a function of ;r, and hence we 
 have two unknown quantities, and the equation cannot be 
 solved. The same is true of all the equations into which y 
 and x enter ; there is no direct and simple relation between 
 them. Hence the problem must be solved by approxima- 
 tion. 
 
 For this purpose combine equations (D), (E), and (303), 
 and we have 
 
 /(*.) S(u)-A (u) = ~y + I(u.)S(r) - A (V). (328) 
 
 In this equation we can compute /() by (303), and hence 
 all the quantities which enter the second member are 
 known. 
 
 Represent this known quantity by k. Then we have 
 
 k = I(u }S(u)-A(u), 
 
 in which u is known, and we have to determine the value 
 of u by approximation. 
 
 RULE OF " DOUBLE POSITION." For this purpose we 
 make use ot a method called the rule of " double position." 
 Suppose we have an unknown quantity u whose value is 
 sought. Let #! represent a quantity slightly greater than u, 
 and &, a quantity slightly smaller. 
 
 Suppose u^ substituted for u in the given equation, and 
 the latter solved. A certain value will be obtained which 
 will be erroneous. Denote the difference between this 
 erroneous value and the true value by e t . Similarly, sub- 
 
EXTERIOR BALLISTICS. 383 
 
 stitute u^ for u, and denote the difference between the 
 erroneous value and the true value by e a . 
 
 Then the hypothesis upon which the rule of double posi- 
 tion is based is, that the errors e l and e a in the results are 
 proportional to the errors made in assuming the values of , 
 and 2 . 
 
 The errors in assuming u l and # a are 
 
 and 
 
 u u,\ 
 
 and from the above hypothesis we have 
 
 e, : e a :: u - , : u a , 
 and by division 
 
 fc i e a : e a :: # 2 ^ : # a ; 
 
 , e, : e, :: a t : * t , 
 
 which expresses the rule of " Double Position." 
 
 216. Example. 
 
 The above is best illustrated by a numerical example. 
 Suppose k = 17666.1, and /(#) = 1.55658. 
 Then we have 
 
 17666.1 = 1.55658 S(u) A (u). 
 Suppose 
 
 u, = 430 ft.-secs.; 
 
 5(^ = 21579.4; 
 A(u)= 15797.3; 
 
 17666.1 = 1.55658 x 21579.4 - 15797-3; 
 
 1 = + 126.6. 
 
 Again, suppose 
 
 u^ = 420 ft.-secs. ; 
 
 5 () = 21978.7; 
 A (*)= 16861.3; 
 
 17666.1 = 1.55658 X 21978.7 16861.3; 
 e , = - 315.9; 
 
TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 , - , = 126.6 -f 315.9 = 442.5 ; 
 
 *,= - SIS-?; 
 U 9 U t = - 10 ; 
 
 u # a = u 420. 
 Then 
 
 442.5 : 315.9 :: 10 : u 420. 
 
 u 427.139 ft.-secs. 
 
 This value of u in the equation containing S(u) and A (u) 
 gives 
 
 e, = +6.6. 
 
 It is necessary therefore to make a second trial. Assum- 
 ing u 9 = 426.8 ft.-secs., and proceeding as before, we find 
 
 e, = - 8.2 ; 
 and forming the same proportion as before, we find 
 
 u = 426.9878 ft.-secs., 
 
 and this value of u will satisfy the original equation. There 
 is also another value of u which will satisfy the equation, 
 but it will readily be seen that it belongs to the ascending 
 branch of the trajectory, and is not used. 
 
 Having the value of u for the point whose ordinate is y 
 we find x by equation (D), 
 
 and the dangerous space is 
 
 S = X- x. 
 
 As an approximate value for u in making these supposi- 
 tions, the value u<* for the end of the range may be calcu- 
 
 lated and used. 
 
 \ 
 
 217. Eigidity of Trajectory Drift. 
 
 RIGIDITY OF TRAJECTORY. In the previous problems it 
 has been assumed that the point of fall of the projectile is 
 in the horizontal plane passing through the centre of the 
 muzzle, or that the right line drawn from the centre of 
 the muzzle to the end of the range, or the chord of the 
 trajectory, is horizontal. 
 
EXTERIOR BALLISTICS. 385 
 
 Suppose, however, as is generally the case in practice, 
 that the object aimed at is above or below the level of the 
 gun, the angle of elevation or depression being a. 
 
 Then it has been proved analytically that the relations 
 existing between the elements of the trajectory, and the 
 chord which represents the extreme range, are the same 
 within certain limits, whether the chord is horizontal or in- 
 clined. In other words, the whole trajectory, with its chord, 
 may be revolved a certain distance about a horizontal axis 
 passing through the centre of the muzzle, without changing 
 the relations between the trajectory and its chord. 
 
 This principle is called the" Rigidity of the Trajectory," 
 and its practical use is as follows : 
 
 Suppose we fire at an object whose elevation is OL. Cal- 
 culate the angle of elevation for the given range, as usual, 
 and aim directly at the target with the rear sight set at the 
 elevation 0. The act of aiming at the target gives the 
 actual elevation (0 -|- a). , If a is depression, it is affected 
 with a minus sign. This subject is discussed later. 
 
 DRIFT. Mayevski's formula for drift is (see IngahV 
 Hand-book) 
 
 __ 
 n t cos 1 S () - 5 (V) ~ * ( K) ) 10,000 ' (329) 
 
 in which 
 
 D is the drift in feet ; 
 
 u = 0.53 for cored shot ; 
 
 u = 0.64 for shell ; 
 
 n = the twist of the rifling in calibres, at the muzzle 
 
 - = 0.41 for projectiles 2.5 calibres long ; 
 = 0.37 for projectiles 2.8 calibres long ; 
 
 - 0.32 for projectiles 3.4 calibres long ; 
 
 TT= 3.1416; 
 
 g = 32.2 feet ; 
 
 C, 0, and Fas in other ballistic problems ; 
 
TEXT- BOOK OF ORDNANCE AND GUNNERY. 
 
 B(u), B(V], M(V) are drift functions whose values are 
 found from Table I, like those of S(u), A (), etc.; 
 X, the range in feet. 
 
 The drift will be more or less affected by the wind, ac- 
 cording to its direction and velocity, and its effects will be 
 further explained under the subject of Pointing. 
 
 218. Problem 7 Mortar Fire Modified Equations Calculation. 
 
 MODIFIED EQUATIONS. The formulas for direct fire 
 were obtained from the differential equations (A) by assum- 
 ing that the inclination 6, of the tangent, at every point of 
 the trajectory, is relatively small, and hence its cosine or 
 secant constant, and approximately unity. For high angle 
 or mortar fire, however, such an assumption is manifestly 
 incorrect, since the angle 6 varies greatly throughout the 
 trajectory. 
 
 For mortar fire, therefore, Siacci assumes that there 
 is a mean value of coo 0, which will satisfy the differential 
 equations, and make their second members exact inte- 
 grals. This mean value is denoted by a, and its value is 
 
 shown analytically to be a = - \ ' , (0) representing 
 
 tan tan u 
 
 , and 0, I r^r, and their numerical values 
 
 COS-+ 1 J COS-+ 1 6* 
 
 being given in Table IV, together with the values of tan 
 4> and tan 0. 
 
 This is applied as follows : In the integration of equa- 
 tions (A) in the case of direct fire, the second step consisted 
 {see page 360) in substituting for sec*- 1 0, the constant value 
 sec w ~ 2 0. But for mortar fire, a must be substituted for 
 sec"" 1 0, wherever the latter occurs, instead of sec"~ 2 0. 
 
 To show the effect of this substitution, take the second 
 
 of equations (285), dt -j jn Writing for sec 
 
 *cl SeC ' t\n 
 
 its mean value a, we have dt = - \ Multiplying- 
 
 Aa n ~ l vf 
 
 numerator and denominator by a, dt = ~ - L . Repre- 
 
 A frf* 
 
EXTERIOR BALLISTICS. 387 
 
 senting av^ by u, we have u = av 1 = av cos 0. Making the 
 same substitutions in the remaining equations (285), and 
 integrating, we have the following formulas for mortar fire : 
 
 .... (330) 
 . . . . (331) 
 
 .... (332) 
 
 (333, 
 
 in which 5 is the length of any arc of the trajectory, meas- 
 ured from the origin ; U Va cos ; u = av cos B ; v = 
 velocity at the point S; 6 = the inclination of the tangent 
 at the same point. 
 
 The values of the functions A(u), S(u), etc., can be taken 
 from Table I, u and U being first calculated as explained in 
 the nomenclature. 
 
 CALCULATION. The most important problems in mortar 
 fire are to find the whole range X, and the time of flight, T, 
 for that range. For this purpose the given data are gen- 
 erally C, 0, and V. It is evident, however, that with the 
 given data, equations (331) and (332) cannot be solved, and 
 the solution is obtained as follows : 
 
 For the end of the range y = o, and from equation (333) 
 we have , 
 
 2 tan >4K) . . 
 
 ~~ - - (334) 
 
 For mortar fire the angle of fall is very nearly equal to the 
 angle of elevation, and under this supposition we have, 
 since 8 = GO, 
 
 (0) - (O) (0) + (a?) (0) 
 
 tan tan tan + tan GO tan 0' 
 
 from which a is known. The first member of equation (334) 
 is therefore known, and also A(U) and S(U) in the second 
 member. u<* is therefore found by " Double Position," as 
 previously explained. This value of u m in (330), (331), and 
 (332) will give the remaining values sought. 
 
388 TEXT-BOOK Of ORDNANCE AND GUNNERY. 
 
 SUMMARY TABLE. 
 
 Given. 
 
 Required. 
 
 Problem. 
 
 C,u, V 
 
 X 
 
 I 
 
 C, V,x 
 
 U 
 
 I 
 
 C, x, u 
 
 V 
 
 I 
 
 C, M , F 
 
 X 
 
 I 
 
 C, F, X 
 
 
 
 I 
 
 X" 1 \7~ 
 
 C, A, HU 
 
 V 
 
 I 
 
 C, 0, F 
 
 X 
 
 2 
 
 0, ^ 
 
 V 
 
 2 
 
 c, v,x 
 
 
 
 2 
 
 C, 0, F, x 
 
 t 
 
 3 
 
 C, 0, F, ^ 
 
 T 
 
 3 
 
 C, 0, F, * 
 
 e 
 
 4 
 
 C, 0, F, ^ 
 
 &) 
 
 4 
 
 0, F, * 
 
 y 
 
 5 
 
 6", 0, F 
 
 y 
 
 5 
 
 C, 0, F 
 
 * 
 
 5 
 
 0, V 
 
 Dangerous space 
 
 6 
 
 C, 0, F 
 
 X 
 
 7 
 
 (7, 0, F 
 
 X 
 
 7 
 
 C, 0, F 
 
 s 
 
 7 
 
 C, 0, F 
 
 t 
 
 7 
 
 0, F 
 
 T 
 
 7 
 
 C, 0, F 
 
 y 
 
 7 
 
 NOTE, Ingalls' Ballistic Tables are to be used in these problems, and the 
 methods of Capt. Ingalls have been followed in deducing the equations. 
 
CHAPTER VII. 
 
 ARTILLERY CARRIAGES THEORY OF RECOIL. 
 
 ARTILLERY CARRIAGES. 
 
 219. Classification Principal Parts of Field and Siege Gun Car- 
 riages The Axle. 
 
 CLASSIFICATION. Artillery carriages may be classified 
 according to the service for which they are intended, into 
 field, siege, and sea-coast carriages. 
 
 Field and siege carriages are generally wheeled, and are 
 intended to support the guns in firing, and to transport them 
 from place to place, with their ammunition and necessary 
 supplies. 
 
 Sea-coast carriages are intended only to support the 
 guns in firing, and hence their construction differs materi- 
 ally from that of field and siege carriages. 
 
 PRINCIPAL PARTS OF FIELD AND SIEGE GUN CAR- 
 RIAGES. In the field and siege services, the carriage which 
 supports the piece, and from which it is fired, is called the 
 gun-carriage. 
 
 Its principal parts are : 
 
 1. The axle ; 
 
 2. The wheels; 
 
 3. The stock or flasks ; 
 
 4. The brakes ; 
 
 5. The elevating device. 
 
 THE AXLE. The principal parts are the body, the rein- 
 force, and the arms. 
 
 The body is the middle part of the axle, between the 
 arms, upon which the heads of the cheeks rest, and which 
 bears the weight of the piece and the force of recoil. It is 
 
 389 
 
39 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 generally made of steel, and is solid, as this construction is 
 necessary to resist the force of recoil in these carriages. 
 Its length is governed by the requirement that the track of 
 the wheels shall be the same as that of ordinary vehicles, so 
 that it can be used on the same roads. 
 
 Reinforce. To increase the strength of the axle and 
 its resistance to bending under the force of recoil, and also 
 to furnish a support for the cheeks of the carriage, the axle 
 is generally reinforced. In the old carriages the axle-body 
 was enclosed in wood ; in the new field-carriages it is en- 
 closed between two steel plates riveted together and fitting 
 the exterior of the body accurately. For larger carriages, 
 or for those in which the recoil is taken up by hydraulic 
 buffers, this is not necessary. 
 
 The Axle-arms. These form the supports for the 
 wheels, and are the axes about which they revolve. The 
 arms are made solid, terminating the axle-body. They 
 are conical in shape, as this gives stiffness with small 
 weight, enables the wheel to be put on easily, insures a 
 good fit between wheel and axle-arm, and enables any wear 
 to be taken up by means of washers. 
 
 The axis of each arm is inclined slightly downward so as 
 to make the lower element nearly horizontal. This causes 
 the lower spoke of the wheel to stand Vertical, and relieves 
 it from cross-strain, and also prevents a thrust upon the 
 linchpin. The axis of the arm is also inclined slightly to 
 the front, so that when the wheel meets any obstacle in that 
 direction it will be free from cross-strain. These two in- 
 clinations of the axle-arm are called the " set." The wheel 
 is secured on the arm by a linchpin which passes in a 
 vertical direction through a hole in the end of the arm, and 
 is held in place by a semicircular catch passing under the 
 latter. 
 
 A shoulder on the inside, next the body, holds the wheel 
 in place. 
 
 220. The Wheels Parts. 
 
 The principal parts are, Fig. 203, the central part or 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 39 1 
 
 nave N, the spokes S, the rim R, and the tire T. The nave 
 receives the pressure of the axle arm and transmits it to the 
 spokes. Formerly naves were made of wood, and lined 
 
 FIG. 203. 
 
 with a metal box, called the nave-box, which diminished the 
 wear. Now they are made of malleable cast iron or bronze, 
 in two parts, one (a) forming the nave-box and the other 
 (b) forming a support for the spokes in front, which are 
 inserted between these parts, pressed into place by a strong 
 radial pressure, and bolted as shown at d, so as not to 
 weaken them. 
 
 By this arrangement a spoke can be readily removed 
 and replaced. This construction is used in the Archibald 
 wheel, which is adopted in the U. S. service. 
 
 An enlargement c is sometimes made in the middle of 
 the nave-box to contain the lubricant. 
 
 The spokes s, receive the pressure from the nave and 
 transmit it to the rim. In our service they are made of 
 hickory, as this gives great stiffness and elasticity for a 
 given weight. 
 
 The stiffness is required to resist the thrust in firing, and 
 strength is also required to enable the wheel to be used on 
 rough ground, where the spokes are liable to be broken by 
 contact with obstacles. The spokes are set at a slight angle 
 with the axis of the nave, thus forming a conical surface. 
 This is called the dish, and its object is as follows : 
 
 When the ground is inclined, the weight of gun and car- 
 
39 2 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 riage produces a thrust on the lower wheel in the direction 
 of the arrow. If the spokes were per- 
 pendicular to the axis of the nave, this 
 thrust would cause a cross-strain on 
 them, and its effect would be to loosen 
 them in the nave, or cause them to 
 FIG. 204. work. The dish enables the spokes to 
 
 resist this lateral thrust, and it is converted into a strain of 
 compression. The whole structure thus acts as a circular 
 truss, the rim being the tie. 
 
 The Rim. This distributes the weight which it receives 
 from the spokes, to the ground. It is generally made of 
 wood for the same reasons as in case of the spokes, and in sev- 
 eral segments, called felloes. The object of this is to avoid 
 cutting across the grain of the wood, and consequent weak- 
 ness. 
 
 The Tire. The segments of the rim and the spokes are 
 held in place by the steel tire T, Fig. 203, which is shrunk 
 on, and binds all the parts together. It also protects the 
 rim from wear, and when any of the parts become loose, it 
 can be removed, shortened, rewelded, and reset. For this 
 purpose it is made of low steel. It is held in place on the 
 rim by countersunk bolts passing through both. 
 
 221. Object of Wheel-The Stock. 
 
 OBJECT OF WHEEL. The object of the wheel is to trans- 
 fer the resistance to motion from the ground, where it is 
 great and irregular, to the surface of the axle arm, which 
 is lubricated, and the resistance of which is consequently 
 small and regular. 
 
 The power being applied with a lever-arm, whose length 
 is the radius of the wheel, while that of the resistance or 
 friction is the radius of the axle-arm, the advantage of the 
 wheel as a mechanical power increases with the radius of 
 the wheel, and decreases with that of the axle-arm. On this 
 account the radius of the wheel should be as great as pos- 
 sible and that of the axle as small as possible. 
 
 The radius of the axle-arm is fixed by the requirement 
 oi strength to support the shock of recoil; and that of the 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 393 
 
 wheel by considerations of weight, draught, and facility of 
 turning. A high wheel also is unstable. These considera- 
 tions have fixed the diameters of wheels in the field and 
 siege services as follows: field service, 5/j- inches; siege ser- 
 vice, 60 inches. The siege wheel is much stronger and 
 heavier than that for the field service. 
 
 An increase in width of rim also distributes the weight 
 over a greater area and enables the wheel to better over- 
 come the resistance offered by soft ground to traction ; but 
 it increases the weight of the wheel and decreases the 
 facility of turning. 
 
 THE STOCK. This consists of two pieces, called the 
 flasks, which are separated at the upper ends, forming the 
 cheeks, and which gradually converge at the lower ends, 
 and are united there by a solid piece called the trail-plate 
 or lunette. The cheeks rest upon the axle body or rein- 
 forcing plates, and have on their upper surfaces two trun- 
 nion-beds, in which the trunnions of the gun rest. The 
 trunnions are held in place by two caps, called cap squares, 
 which fit over bolts projecting from the cheeks at the 
 extremities of the trunnion-beds, and are fastened by keys 
 or bolts. The flasks are also united by various transoms, to 
 give stiffness to the structure. The supports for the elevat- 
 ing screw or other device are generally attached to the 
 stock. 
 
 The distance between the flasks varies with the size of 
 the gun, and should be sufficient to allow the breech to be 
 depressed to the maximum extent required in service. By 
 this separation, also, the strain due to recoil is distrib- 
 uted over a greater length of axle body, and thus the 
 resistance to bending is increased. The stock is subjected 
 to a strong transverse stress in firing, and hence must be 
 designed to resist this. It also acts to couple the gun-car- 
 riage to the limber when the gun is to be transported, and 
 it gives the necessary third point of support in firing, and 
 enables the piece to be pointed. To it are attached the 
 supports for the sponges and rammers, and in general, if 
 possible, no parts are allowed to project below the 
 plane of its lower edges, to avoid striking obstacles. When 
 
394 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 not required to resist the shock of firing, its use is simply 
 to connect the carriage and limber, and its construction 
 then differs materially from that described, being much 
 simpler and lighter. 
 
 222. The Brakes Friction-brakes Shoe Hotchkiss Lemoine 
 Nordenfelt. 
 
 BRAKES. The object of a brake in the field and siege 
 service is to limit the recoil, so that the piece may be kept 
 approximately in its firing position, and thus avoid the 
 fatigue to the cannoneers of running the piece back over a 
 considerable distance to that position after discharge, and 
 the consequent delay in loading. 
 
 The principles of brakes will be explained under the 
 subject of recoil. 
 
 For the field and siege services they may be divided 
 into 
 
 1. Friction-brakes. 
 
 2. Elastic brakes. 
 
 3. Hydraulic brakes. 
 
 FRICTION-BRAKES. These, as will be seen later, do not 
 give the best results, but are sometimes preferred on 
 account of their simplicity, and as being less liable to get 
 out of order. 
 
 SHOE. The simplest friction-brake is the shoe, which 
 consists (Fig.'2O5) of a strong piece of iron, a, fitting the 
 
 FIG. 205. 
 
 wheel, and attached by a chain, b, to the stock. It is 
 often used in travelling, and transforms the rolling into 
 sliding friction. 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 
 
 395 
 
 THE HOTCHKISS BRAKE (Fig. 206) consists of a conical 
 box, a, working in screw-threads on the axle-body b. The 
 nave of the wheel is also made conical at c. 
 
 a 
 
 FIG. 206. 
 
 By turning the handle d attached to the brake, it is 
 screwed up till the conical surfaces are in close contact. 
 The friction between these surfaces, when the wheel rotates, 
 tends to tighten the brake, and thus increase the resistance to 
 rotation, while if the moment of rotation becomes too great, 
 the surfaces will slip, and thus prevent destruction of the 
 parts. 
 
 THE LEMOINE BRAKE is used in the French service. It 
 consists (Fig. 207) of a rope, a, attached to the brake-beam 
 at b, and wound loosely around the nave of the wheel. 
 
 This rope is tapering, being larger at #, and gradually 
 decreasing in size. It is attached in front to a cross-bar, c, 
 and this is connected to the rod d, which moves freely in 
 the direction of its length, and carries a heavy mass, e. The 
 action of the brake is as follows : When the piece is fired, 
 the carriage recoils in the direction of the arrow, while the 
 rod d, on account of the mass e, moves relatively forward. 
 It is held in this position by the notches on d bearing against 
 the edges of the plate through which it slides. This tight- 
 ens the cord around the nave of the wheel, and causes it to 
 be wound up as the wheel turns. Owing to the increase 
 
39 6 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 in diameter of the rope, it is wound more rapidly as the 
 length of recoil increases and its velocity decreases, so that 
 
 FIG. 207. 
 
 the brake is applied gradually. It may also be applied 
 by hand, in travelling, by pulling out the rod d by the 
 handle d' '. 
 
 NORDENFELT BRAKE. This is found on the carnage of 
 the Nordenfelt rapid-fire gun, and 
 also on the Hotchkiss carriage. It 
 consists of a frame, one side of which 
 is shown in Fig. 208, attached to the 
 axle above its centre at the points 
 aa ; bb are the brakes, c the rod con- 
 necting them, dd rubber washers 
 through which the brake-rods ee pass. 
 As the points of support a are eccen- 
 tric with reference to the axle, when 
 the brakes are lowered, they come 
 in contact with the wheels, and any 
 rotation in recoil binds them still 
 more tightly. When not in use, 
 they are hooked up to the cheeks of 
 the carriage. This brake is elastic 
 also. 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 397 
 
 223. Elastic Brakes Buffington Englehardt Belleville Springs. 
 
 ELASTIC BRAKES. These check and moderate recoil by 
 transmitting the first shock to some elastic body, which 
 is thereby deformed, and when this body resumes its 
 original form, clue to its elasticity, the shock is gradually 
 transmitted to the parts of the carriage. This relieves the 
 carriage from the sudden shock, and thereby enables it 
 better to sustain recoil. 
 
 THE BUFFINGTON BRAKE. This was designed by Colo- 
 nel Buffington of the Ordnance Department, and is used 
 with the field carriages. 
 
 ,C 
 
 FIG. 209. FIG. 210. 
 
 The older form consists of a rod, a, Fig. 209, surrounded 
 by a spiral spring in a casing. The outer end of this rod is 
 formed into a hook, which fits over the tire of the wheel. 
 The casing which carried the rod and spring is attached to 
 a hook, b, above the centre of the axle. When the rod and 
 casing are lowered, the hook rests against the tire, being 
 eccentric to the wheel. Any rotation of the wheel in the 
 direction of recoil draws the rod out of the casing, and com- 
 presses the spiral spring. The brake is thus gradually ap- 
 plied. Various defects in this brake have caused the adop- 
 tion of the later form shown in Fig. 210. 
 
 Later form shown in Fig. 210. Instead of the casing 
 and spiral spring, the rod is attached to a bow-spring, <:, 
 which is elongated when the wheel recoils. It is held ver- 
 tically when not in use. 
 
 THE ENGLEHARDT BUFFER. This is used on some of the 
 English carriages. It consists (Fig. 211) of an elastic buffer, 
 
 a, of cork, rubber, or springs, which rests against a transom, 
 
 b, attached to the cheeks of the carriage. 
 
 These cheeks have a bracket, c, in front, in which the 
 axle d rests, and which allows them to move backward 
 
398 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 independently of the axle, and they are notched in rear at 
 e, to allow a motion independent of the cross-bar /. The 
 axle is attached to the cross-bar / by the brace g, and this 
 attachment is made as near the axle-arm as possible, to 
 
 a' 
 
 y 
 
 n--/ 
 
 c*' N 
 
 h 
 
 FIG. 211. 
 
 avoid bending. A bolt, h, passes through the buffer , and 
 through a hole in the transom b, and is attached rigidly to 
 the cross-bar/. The action is as follows: When the piece 
 is fired, the cheeks and transom b recoil together, the axle 
 and cross bar sliding in their notches c and e. This motion 
 compresses the buffer #, and as it recovers its shape, the 
 force of recoil is gradually transferred to the wheels and 
 axle, through the cross-bar /and brace g. 
 
 BELLEVILLE SPRINGS. These are saucer-shaped disks 
 of steel, s, Fig. 212, fitted edge to edge; and kept in place 
 
 FIG. 212. 
 
 by an axial rod, r, for which purpose a hole is pierced in the 
 centre of each disk. Since they occupy a relatively small 
 space, a large number of them may be employed, and the 
 compression of each is small. They are, however, expen- 
 sive, and spiral springs are often used in place of them. 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 
 
 399 
 
 224. Hydraulic Brakes Elevating Devices The Elevating Screw. 
 
 HYDRAULIC BRAKES. These are not used in the field 
 service, owing- to their weight, and liability to get out of 
 order when subjected to rough usage, but they are used in 
 the siege carriages, and in general wherever the recoil is 
 great, and it is necessary to regulate it very exactly. They 
 will be considered under Sea-coast Carriages, where they 
 are always used. 
 
 ELEVATING DEVICES. These are used to give the proper 
 elevation to the piece, and may consist of 
 A screw ; 
 A toothed sector ; 
 A combination of levers. 
 
 THE ELEVATING SCREW is generally double, and consists 
 (Fig. 213) of an exterior hollow screw, 
 #, working in a fixed nut, b. 
 
 The exterior of the screw a has a 
 left-hand thread, its interior a right-hand 
 one. A second screw, c, works in the 
 interior thread of a. d is a hand-wheel, 
 which is free to rotate, but is fixed to 
 the nut b, so that it has no motion of 
 translation. A longitudinal channel or 
 spline, e, is cut on the exterior of a, and 
 a key on d fits this. The action is as 
 follows : When d is turned it causes a to 
 turn with it, on account of the spline 
 and key, and at the same time a working 
 in the fixed nut b moves parallel to its 
 
 a 
 
 FIG. 213. 
 
 The head of 
 
 being fixed 
 
 own axis. 
 
 by a strap, s, to be described, cannot turn, and c is forced 
 to move parallel to its own axis by the rotation of <z, and 
 the action of its interior screw-thread. The resultant 
 motion is, for each turn of d, equal to the sum of the pitches 
 of the two screws. 
 
 The advantage gained is that we are enabled to use an 
 elevating screw, which is short ordinarily, but which can be 
 lengthened to give any elevation or depression desired. 
 
 Strap. To cause the blow on the head of the elevating 
 
400 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 screw, upon firing, to be normal to its axis, and thus avoid 
 bending, the nut b, in which the screw works, is arranged 
 on trunnions between the cheeks of the carriage, and a 
 strap, s, Fig. 214, is attached at one end to the head of the 
 
 FIG. 214. 
 
 screw c, and at the other to an axis, /, parallel and near 
 to the axis of the trunnions of the gun. In this way the 
 axis of the screw, c, is kept nearly normal to the axis of the 
 gun for all elevations. 
 
 225. Elevating Devices The Toothed Sector The Levers. 
 
 THE TOOTHED SECTOR. -- This is used generally in 
 combination with gearing, on the larger guns. It consists 
 (Fig. 215) of a toothed arc, a, bolted to the gun, and acted 
 
 a -1 
 
 FIG. 215. 
 
 FIG. 216. 
 
 on by a gear, b. This gear may be worked directly by a 
 hand-wheel, or more frequently .by intermediate gearing. 
 To gain power, and secure small motions, a worm-gear is 
 frequently used. 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 401 
 
 THE LEVERS. A combination of levers, called a 
 "4azy-tongs," is used as an elevating device on the light 
 3.20 carriage. It consists (Fig. 216) of the arms a, 
 jointed as shown and attached at b by a fixed axis to 
 the carriage. Two side levers, c, are attached to a fixed 
 axis at d on the carriage, and to the arms a at e. A 
 screw, /, passes through the other extremity of the side 
 levers c, and works in two collars, hh, attached to the car- 
 riage. When the screw f is rotated by the handle g, the 
 side levers c are raised or lowered, and acting on the arms a 
 through its connection e, it causes the structure to elongate 
 or contract, and thus to elevate or depress the gun. The 
 device is connected with the breech of the gun by a leather 
 strap, k, passing over the breech. 
 
 226. Draught Modes of Work of Horse Pack-horse Draught- 
 horse Angle of Traces. 
 
 DRAUGHT. Field and siege carriages are intended not 
 only to support their pieces during firing, but also to trans- 
 sport them from place to place. For this purpose the 
 two-wheeled gun-carriage must be converted into a four- 
 wheeled one, by the attachment of a limber. This leads 
 to a consideration of the load which can be carried by the 
 horse, and the best method of attaching him to the carriage. 
 
 MODES OF WORK OF HORSE. A horse may carry his 
 load on his back, in which case he acts as a pack animal ; or 
 he may draw this load by being attached to a carriage, as a 
 draught animal; or these two methods may be combined. 
 
 PACK-HORSE. This method is only used in the moun- 
 tain service, when the roads are impassable for wheeled 
 vehicles. Under such circumstances the load for a horse is 
 from 200 to 250 Ibs., and, if moving at a walk, he can carry 
 this load 25 miles in a day. If at a trot, the load or the dis- 
 tance, or both, must be reduced. In this case he can carry 
 the same load about 17 miles in a day. 
 
 The daily work of a pack-horse is considered equal to 
 that of five men. The mule is a better pack animal than 
 the horse, as he can carry more, is more sure-footed, and 
 eats less*. He is therefore generally used for this purpose. 
 
402 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 DRAUGHT-HORSE. A horse can, by the aid of the wheel, 
 draw much more than he can carry, and hence it is always 
 advantageous to use him as a draught animal. 
 
 In considering the draught of a horse, his effort may be 
 divided into two parts: first, that necessary to start the 
 carriage, and second, that necessary to keep it in motion. , 
 
 The first being only temporary, may approximate the 
 maximum strength of the horse, but it is important to know 
 it, as upon it is based the strength of the harness. 
 
 Experiment shows that this effort varies with different 
 horses from 600 to 1000 Ibs., as measured with a spring 
 dynamometer. 
 
 The second part of the effort varies with circumstances, 
 such as the load, nature of the roads, etc., from -^ to ^ of 
 the load. When horses are used together in a team they 
 will do less work than the same number singly, owing to 
 their interference with each other. 
 
 ANGLE OF TRACES. The angle made by the traces with 
 the ground also influences the amount of work done by a 
 draught-horse. 
 
 If the traces be attached to the carriage at a point higher 
 than that at which they are attached to his shoulders, it is evi- 
 dent that a component of the pull acts upward and decreases 
 the hold of the horse on the ground, and, consequently, his 
 power to pull. On the other hand, if this point is below the 
 point of attachment at the shoulder, the vertical component 
 acts in the opposite direction, and increases his hold on the 
 ground. Experiment has shown that when the horse car- 
 ries no load, the best result is obtained when the traces 
 make an angle of from 10 to 12 with the ground. The 
 tangent of 12 being about |-, this shows that the horse pulls 
 best when \ of his load is transferred to his shoulders. On 
 the other hand, if a horse carry a load of 150 to 200 Ibs., and 
 pull at the same time, experiment shows that this angle 
 should be 6 or 7. 
 
 Making allowance for bad roads and rough usage, ar- 
 tillery horses draw less than those of commerce, and the 
 loads allowed per horse are about as follows : 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 403 
 
 Horse artillery, 650 Ibs. ; 
 Field artillery, 700 to 850 Ibs. ; 
 Siege artillery, 1000 Ibs. 
 
 227. Modes of Attachment of Horses Attachment of Traces. 
 
 MODES OF ATTACHMENT. Horses may be attached to a 
 carriage in three ways : 
 
 1. In single file, with the wheel-horse in shafts; 
 
 2. In double file, with one of the wheel-horses in shafts; 
 
 3. In double file, with the two wheel-horses on oppo- 
 site sides of a pole. 
 
 The team is ordinarily composed of six horses, arranged 
 in pairs. The horses nearest the carriage are called the 
 wheel-horses, those next in front the swing-horses, or swing- 
 team, and those in front the lead-horses or leaders. 
 
 In each team the left horse is the near, and the right 
 horse the off horse. The near horse carries the driver. 
 
 Single File. The objections to this method of attach- 
 ment are that much of the tractile force is lost, owing to the 
 curving and turning of ordinary roads ; it is difficult to 
 make all the horses pull together ; and the shaft-horse, being 
 subjected to the irregular action of the other horses of the 
 team, is soon worn out. For heavy loads over good straight 
 roads at a slow pace, it has the advantage of a direct pull. 
 
 Double File, Wheel-horse in SJiafts. This method obviates 
 the defects of the long line of traction on ordinary roads, 
 and it controls the movements of the carnage well ; but it 
 subjects the shaft-horse to excessive fatigue, and hence is 
 not generally used. 
 
 Double File, with Pole. This method is generally adopted, 
 as it gives the advantages of a short line of traction, with 
 comparatively little fatigue to the wheel-horses, the con- 
 trol of the carriage being effected by two horses instead 
 of one. 
 
 ATTACHMENT OF TRACES. The traces may be attached 
 to the carriage by a single fixed bar, a, called the splinter- 
 bar, as in the old carriages, or by a double tree, b, which is 
 pivoted at its middle point to the pole, and the traces 
 
404 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 attached to each end by a movable single tree, c. Fig. 217 
 shows the old and the new methods. 
 
 ^y 
 
 
 FIG. 217. 
 
 The advantage of the old method is that it is simple and 
 strong. The disadvantages are that it throws an unequal 
 amount of work upon the two horses, so that a willing 
 horse will do most of the work, and there is no method by 
 which the driver can detect this. Consequently, the re- 
 sultant of the traction in this case will not coincide with the 
 pole or middle of the axle. 
 
 The advantage of the new method is that it obviates the 
 above difficulty, and forces an unwilling horse to do his 
 share of the work. The single trees also prevent chafing, 
 by yielding to the motion of the horse as he advances his 
 shoulders in pulling. 
 
 228. Support of Pole Line of Draught of Traces. 
 
 SUPPORT OF POLE. The weight of the pole may be 
 supported 
 
 1. By counterbalancing it in rear of the axle ; 
 
 2. By suspending it from the necks of the horses ; 
 
 3. By a combination of these methods. 
 Counterbalancing Weight of Pole. The advantage of this 
 
 method is, that it frees the necks of the horses from the 
 weight of the pole, and they are consequently not fatigued 
 by it. 
 
 The disadvantages are, that if it is done by placing the 
 trunnions of the gun well to the rear on the gun-carriage, it 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 
 
 405 
 
 causes difficulty in limbering, because of the extra weight 
 lifted. If it is done by allowing the trail to project over 
 the pintle hook and rest upon a circular sweep-bar, a, Fig. 
 218, it is difficult to limber, as the trail must be raised suffi- 
 
 l 
 
 FIG. 218. 
 
 ciently to pass over the pintle b. As quickness of limbering 
 is of importance with field artillery, this method is not used. 
 
 In the siege service, where quickness is not required, 
 -and where the weights are relatively great, it is used, espec- 
 ially th'e method shown in Fig. 218. 
 
 Suspending Weight from Necks of Horses. The advantage 
 of this method is that the attachment of the trail to 
 the limber can be made at the most convenient place for 
 limbering, and the weight of the gun can be thrown so 
 far forward as to render the operation of limbering very 
 easy. The great objection, however, is that it fatigues the 
 horses too greatly, and cannot be used. 
 
 Hence a combination of these two methods has been 
 adopted in the field service. To diminish the weight rest- 
 ing on the necks of the horses, the ammunition-chest of the 
 limber has been placed, so that its centre of gravity when 
 loaded is directly over the axis of the axle, and the weight 
 upon the trail when the gun is limbered is regulated to 
 partly counterbalance that of the pole. 
 
 LINE OF DRAUGHT OF TRACES. This is so arranged 
 that the line of traction shall be continuous from the lead- 
 
406 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 horses to the carriage, and is accomplished by attaching the- 
 traces of the swing-team directly to those of the wheelers,, 
 and those of the lead-team directly to the traces of the 
 swing-team. By this means each horse pulls independently 
 of all the others, and there is no interference. 
 
 229. Turning Angle Direction of Carriage Backing. 
 
 TURNING ANGLE. The angle required to turn the car- 
 riage in, is called the turning angle, and is measured by one 
 half the horizontal angle through which the pole sweeps. 
 In practice an angle of 60 is sufficient. It varies with the 
 arrangement of the horses, the height of the front wheels, 
 the length of stock, the position of the pintle, and the thick- 
 ness of the stock at the point where the front wheels strike 
 it. Other considerations determine that the height of the 
 front wheels shall be the same as those of the rear ones for 
 interchangeability, that the length of stock shall be gov- 
 erned by considerations relating to recoil, and that the 
 position of the pintle shall be considered with reference to 
 ease of limbering and weight of pole on the horses' necks, 
 as before explained. For carriages that do not withstand 
 the shock of recoil, the length of stock is adjusted with 
 reference to the turning angle. 
 
 DIRECTION OF CARRIAGE. This is given by means of 
 the pole. The latter being attached to the necks of the 
 wheel-horses, the direction may readily be changed by 
 directing the wheel-team to the right or left. 
 
 BACKING. The pole is also used to stop and back the 
 carriage. The wheel-horses are attached to the front of the 
 pole, as will be explained when the harness is described. 
 
 In stopping or backing the backward thrust of the horses 
 is applied at the end of the pole, and this thrust transmitted 
 to the rear along the pole to the carriage. 
 
 230. The Harness. 
 
 The harness at present in use for the field artillery was 
 designed by Major Williston of the artillery. That for the 
 wheel-team differs slightly from the swing and lead harness.. 
 For the wheel-team it consists of 
 
ARTILLERY CARRIAGES THEORY OF RECOIL.' 407 
 
 1. The head gear to guide and hold the horses; 
 
 2. The saddle to transport the driver; 
 
 3. The draught harness, by which the carriage is moved 
 forward ; 
 
 4. The breeching, by which the carriage is stopped, or 
 moved to the rear ; 
 
 5. The breast straps, by which direction is given to the 
 carriage, and the weight of the pole supported. 
 
 For the swing and lead teams the breeching and breast 
 straps are omitted, and the traces are supported by a single 
 hip strap. 
 
 FIG. 219. 
 
 Head Gear. The head gear consists (Fig. 219) of the 
 bridle a, by which the horse is guided, and the halter for 
 holding him when not in the carriage. 
 
 The bridle and halter are the same as those used in the 
 cavalry service. The bridle rein of the off horse passes 
 through a pulley on the front of his saddle, so that there is 
 a direct instead of an oblique pull, in stopping and backing. 
 
 Saddle. The saddle x is the same as that used in the 
 cavalry service. Each horse is saddled, the saddle being- 
 held in place and motion to the front prevented by the 
 back strap t and crupper t' , while the collar is secured to 
 
408 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 the saddle in front by the strap v. The girth strap or 
 cincha w prevents motion of the saddle around the horse. 
 The near horse carries the driver, and the off horse may 
 carry an extra cannoneer. Saddle-bags, b, are used, as in 
 the cavalry service, to carry the clothing, etc., of the drivers. 
 
 Draught Harness. This consists of a collar, c, made 
 of U-shaped steel. It is hinged at the top, and closes at the 
 bottom with a spring catch. It rests against the shoulders 
 of the horse, and is intended to distribute the force of trac- 
 tion over a greater area, and thus prevent chafing. 
 
 A strong leather tug, d, is attached to each branch of 
 the collar, and at the outer end of the tug is an iron ring, e, 
 through which the front trace-chain f passes. 
 
 The trace g is a stout leather strap, terminated at the 
 front end by a chain and toggle, / and at the rear end by a 
 ring, through which passes the rear trace-chain //, having at 
 one end a hook and at the other end the spring /. The rear 
 ends of the trace-chains y, of the swing horses, are attached 
 directly to the front trace-chains /of the wheel-horses, thus 
 giving a continuous line of traction throughout the teams. 
 The loin strap u supports the traces at their middle point. 
 The trace-chains of the wheel-horses are attached to the 
 single trees z, and in unharnessing, these are detached from 
 the double tree, and hooked to the rear of the saddle, for 
 which purpose a hook, k, is provided. The spring / is used 
 to attach the traces of the wheel-horses to the single trees i. 
 This allows a gradual starting of the carriage, and thus 
 diminishes the fatigue of the horses, and the strain on the 
 harness. 
 
 Breeching. This consists of a breech strap m, hip straps 
 ss', two side straps s", and a broad flat strap or martingale, n. 
 The breech strap m passes around the hind-quarters of the 
 horse, and is supported by the hip straps ss', two on each side. 
 The breech strap is joined to the martingale n by the two 
 side straps s". The martingale n passes along under the 
 horse, and between his forelegs to the front, where it is con- 
 nected to a transverse bar, o, on the front end of the pole, 
 called the neck yoke. This yoke, o, is of wood, and has a 
 ring, p, attached at its middle point, which slips over the 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 409 
 
 -end of the pole, and rests against a stop, q, on the under 
 side. The collars of the wheel-horses are attached to the 
 ends of the neck yoke o by the breast straps r. 
 
 In backing, the pressure is exerted by the horse against 
 the breech strap m, and this pressure is transmitted through 
 the side straps s" and the martingale n, to the neck yoke <?, 
 and thence to the pole. 
 
 The action of the harness may be understood from 
 Figs. 220 and 221. For draught and direction t represents 
 
 ,-t ,-t b ,-t 
 
 
 .SU 
 
 ' *> ff*fh* 
 
 r -d 
 
 L 
 
 FIG. 220. 
 
 the traces, s the single trees, d the double tree, b the breast 
 straps, c the collar. For breeching b' is the breech strap, 
 
 ' m .XT^N J ^6 s ^ e stra P s > ;; * tne martingale, 
 -''" n the neck yoke. 
 
 The great advantage of the pres- 
 ent harness over the old is the 
 change in the breeching, by which 
 FIG. 221. the horse has a direct instead of an 
 
 oblique thrust to the rear. Many other improvements are 
 embodied in it. 
 
 CARRIAGES FOR flOUNTAIN AND FIELD ARTILLERY. 
 
 231. Carriage for Hotchkiss Mountain Gun For 3.6 Field Mortar. 
 
 HOTCHKISS MOUNTAIN CARRIAGE (Fig. 222). -The flasks 
 a are made of steel strengthened with angle-irons, b, and with 
 three transoms, c, d, e, and a trail-plate, g. The axle is solid, 
 and the wheels have bronze naves. Recoil is checked when 
 necessary, by a rope tied around the spokes of the wheels, 
 and passing over the stock. 
 
 The elevating screw passes through the transom e. For 
 
4io 
 
 TEXT- BOOK OF ORDNANCE AND GUNNERY. 
 
 draught, a pair of shafts is attached to the trail by the hook 
 h and a pin, and the gun and carriage drawn by one mule. 
 The gun and carriage are generally packed on two mules, 
 
 Jh 
 
 FIG. 222. 
 
 and the ammunition carried in boxes on mules also. Weight 
 of carriage, 220 Ibs. The carriage for the 3-inch gun is 
 similar to this. 
 
 
 FIG. 223. 
 
 3.6 MORTAR CARRIAGE (Fig. 223). This carriage is 
 made of cast steel, in a single piece, provided with a clamp- 
 ing device in front, which bears against a steel arc attached 
 to the mortar. 
 
 Elevation is given by the quadrant, and the mortar 
 clamped in position by the clamping device. When in use 
 the carriage rests on a wooden platform, and recoil is 
 checked by a heavy rope attached to stakes in front. 
 
AR TILLER Y CARRIA GES THEOR Y OF RECOIL. 4 * l 
 
 232. 3.2-inch Field-gun Carriage. 
 
 This carriage was designed by Colonel Buffington of the 
 Ordnance Department. Its principal features are 
 
 1. The method of reinforcing the axle; 
 
 2. The formation of the flasks ; 
 
 3. The elevating device ; 
 
 4. The brake. 
 
 Reinforcing Axle. -- To stiffen the axle against recoil, 
 the body is enclosed (Fig. 224) between two plates of steel, 
 
 FIG. 224. 
 
 which are riveted together temporarily, bored out to a 
 diameter slightly less than that of the exterior of the axle 
 body, and the plates then riveted tightly together. The 
 width of these plates is in the plane of the lower edges of 
 the flasks, and hence they resist the force of recoil. They also 
 serve as supports for the flasks which are bolted to them. 
 
 Formation of Flasks. Each flask (Fig. 225) is formed 
 of two pieces of sheet steel, stamped while hot between 
 dies into the shape shown, and riveted 
 together through the flanges. The 
 lower edge a of the outer piece of 
 each flask projects inward, forming 
 
 N ^ a a/ a'' a flange, to which the transoms are 
 
 FIG. 225. riveted, and by which the flasks are 
 
 bolted to the axle plates. The flasks are connected by 
 transoms, three of which form a tool-box, with a hinged lid, 
 for carrying tools, oil-can, and loose primers. 
 
 The above construction gives great lateral and vertical 
 stiffness. The lower ends of the flasks converge to a trail- 
 plate, at the extremity of which is the lunette ring, by which 
 the carriage is hooked to the limber. 
 
 Elevating Device. This is an assemblage of jointed 
 levers, previously described, called a " lazy tongs." 
 
412 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 Brake. The bowspring brake is used. 
 
 Minor Parts. The wheels are of the Archibald pat- 
 tern. The trail handspike is made of two pieces of wood 
 split axially, arid having a sheet of steel between them, the 
 whole bound together by a series of rings. The handspike 
 is hinged to the trail-plate, and when not in use is folded 
 against the trail, and held in place by a spring catch. 
 
 There are two seats for cannoneers on the axle. The 
 flasks also carry the supports for the sponge and rammer, 
 etc. 
 
 The complete gun-carriage is shown in Fig. 226. 
 
 FIG. 226. 
 233. The Limber. 
 
 The principal parts of the limber are 
 
 1. The wheels and axle ; 
 
 2. The pole ; 
 
 3. The supports for the ammunition-chest ; 
 
 4. The ammunition-chest. 
 
 Wheels and Axle. The wheels are the same as those 
 of the gun-carriage. The axle is of steel, but as it does not 
 withstand the shock of recoil, it is not reinforced. 
 
 The Pole. This consists of two parts, one of which is 
 permanently attached to the limber, and is called the fork, 
 a (Fig. 227), and the other the pole proper, b. 
 
 The fork is of steel, of this section, ["" "1 , and is attached 
 to the axle-body. It is prolonged to the rear, and carries 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 413 
 
 upon its rear end the pintle-hook c and key d. The pole b 
 is made of light elastic wood, and as it may be broken, is 
 held in the fork by a bolt, e, and can be readily removed 
 and replaced. Its outer end carries a pad, f, to prevent 
 injury to the swing-horses, and a stop, g, against which the 
 neck yoke rests ; h is the double tree held by a bolt, t. 
 
 FIG. 227. 
 
 Supports for Ammunition-chests. The ammunition-chest 
 / (Fig. 229) is supported by the fork, and by the two 
 hounds . These hounds are braced to the fork in rear, and 
 are connected together in front, and also to the fork, by a 
 cross-bar/. 
 
 The hounds not only support the chest, but they 
 strengthen all the parts, and assist in transmitting the force 
 of traction to the axle. The chest is bolted to the hounds 
 front and rear. The hounds and fork also support the foot- 
 boards m (Fig. 229), upon which the feet of the cannoneers 
 rest. 
 
 Ammunition-chest. This is made of wood for lightness. 
 It carries the ammunition for the immediate supply of 
 the gun, and is of the same size as the chests of the caisson 
 for interchangeability. It also furnishes seats for the can- 
 noneers. 
 
414 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 The lid opens on top. The advantage of this is that the 
 chest can be made waterproof until the water reaches the 
 lid. Its disadvantage is that the ammunition is less accessi- 
 ble than if the lid opened on the rear side. The advantage 
 in case of field artillery outweighs the disadvantage, since 
 the cartridges for this service are carried in bags, and hence 
 the ammunition would be spoiled by access of water. For 
 metallic ammunition, as with machine guns and the revolv- 
 ing cannon, as they are not liable to damage by water, the 
 lid opens on the side for accessibility. 
 
 The interior of the chest is divided into three parts by 
 two partitions (Fig. 228). The projectiles are placed up- 
 right in the end divisions a, and th'e 
 cartridges in the middle division b. 
 The cartridges are thus in a measure 
 protected from fire by the pro- 
 jectile. The chest is low, so that a 
 man of ordinary height can easily 
 
 a 
 
 a 
 
 To avoid accident, no 
 
 FIG. 228. 
 get at the ammunition. 
 
 Each chest carries 42 rounds, 
 primers are carried in the chest. 
 
 Packages of primers are carried in the cylindrical boxes, 
 with screw tops (n, Figs. 227 and 229), and loose primers in 
 the tool-box of the gun-carriage. 
 
 FIG. 229. 
 
 The limber complete is shown in Fig. 229. The descrip- 
 tions of the caisson, forge and battery wagon, and artillery 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 
 
 415 
 
 store- wagon, are omitted. The carriage and limber for the 
 3.6-inch field-gun resemble those for the 3.2-inch gun. 
 
 CARRIAGES FOR SIEGE ARTILLERY. 
 
 234. 5-inch Siege-gun Carriage. 
 
 FIG. 230. 
 
 This carriage (Fig. 230) is made of steel plate -J inch 
 thick, the cross-section of the flasks being as shown at A. 
 
 The cheeks are united by two transoms, b, c, in front, and 
 connected in rear of c, as shown in figure A. The axle r is 
 of steel and hollow. The elevating device is a double 
 screw e, connected by a strap d with an axis d' , parallel to 
 and under the trunnions. The object of the strap has been 
 explained. 
 
 Recoil is checked by a hydraulic buffer, s, which, when 
 the gun is in the firing position, is connected by straps /to 
 a bolt, g, on the platform. The piston-rod of this buffer is 
 attached to the carriage by a lug, h. Figure B shows the 
 arrangement of buffer and straps for attachment to bolt on 
 platform ; k is the travelling trunnion-bed, only one being 
 shown ; / is the lunette plate and lunette. When arranged 
 for travelling, the pintle of the limber passes through /, the 
 gun is moved back into the travelling trunnion-beds k, the 
 hydraulic buffer occupies the position /, and the elevating 
 
TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 screw the position n. The principal characteristic of the 
 carriage is the height of the trunnion-beds, which are 72.25 
 inches, or 6 ft. i in. from the ground. This is to enable the 
 gun to be fired over a parapet of sufficient height to shelter 
 the gunners. 
 
 235. 7-inch Siege-howitzer Carriage. 
 
 This carriage (Fig. 231) is made of steel plate f inch 
 thick, the cross-section of the flasks being similar to that of 
 the siege carnage. The cheeks are held together by tran- 
 soms, and the axle is solid. The carriage differs from the. 
 5-inch in the following points: 
 
 FIG. 231. 
 
 The cheeks are cut out at ab to decrease the weight. 
 The piece is supported on sliding trunnion-pieces, e. In 
 front are two hydraulic buffers, d, which limit the recoil of 
 the trunnion-pieces c to about six inches. In rear of the 
 sliding trunnion-pieces c are two sets of Belleville or spiral 
 springs ^, which return the piece to its firing position upon 
 the carriage. The rod upon which the springs are strung 
 passes through a hole, /, in the travelling trunnion beds n. 
 
 The recoil of the carriage is checked by the buffer g, 
 attached as in the 5-inch siege-carriage. The elevating 
 device consists of a rack, h, bolted to the howitzer, in which 
 works a worm, t, mounted between two lugs,/, on the slid- 
 ing trunnion-piece c. 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 417 
 
 A splined or square shaft, k, passes through this worm 
 and its lugs,/, and fits loosely, so that the worm may slide 
 along the shaft. When recoil occurs, the trunnion-car- 
 riages slide to the rear along the upper surface, m, of the 
 cheeks, carrying with them the piece and the elevating- 
 gears // and i. The springs e then act to force the gun 
 and elevating gear back into position. With this carriage 
 the first shock of recoil is taken up by the upper buffers, d, 
 and the strain gradually transmitted to g. The carriage 
 can thus be made lighter and stronger. 
 
 236. 7-inch Siege-mortar Carriage. 
 
 FIG. 232. 
 
 This carriage (Fig. 232) is made of steel plate as in the 
 case of the 5 and 7-inch wheeled carriages, and in its method 
 of checking recoil and restoring the piece to the firing posi- 
 tion it resembles the 7-inch howitzer carriage. It differs, 
 however, in many particulars. 
 
 It is not a wheeled carriage, but is intended to rest upon 
 a platform when the piece is fired, like the old smooth-bore 
 mortar carriages. Two hydraulic buffers, a, in front, check 
 the recoil, while the coiled springs b in rear of the sliding 
 trunnion-pieces c, return the piece to the firing position. 
 These coiled springs are enclosed in a telescopic or sliding 
 case, de, the part d sliding over e in recoil. 
 
TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 The platform has three traverse-circles,/, bolted to it, 
 and also two clamping-circles g. Flanges, //, on the mortar 
 carriage fit under these clamping-circles, and retain the car- 
 riage in place, preventing its recoil. Lugs, i, are attached to 
 the carriage, against which handspikes, /, rest. The lower 
 ends of these handspikes are shod, and fit into teeth, k, on 
 the clamping-circles. By moving the handspikes, the mor- 
 tar carriage may be traversed in azimuth for pointing. 
 Elevation is given by a bar, /, which is inserted in radial 
 grooves formed in a piece of wrought iron, m, bolted to the 
 trunnion. The cheeks are connected by transoms to 
 strengthen them, and are cut out at o for lightness. 
 
 CARRIAGES FOR SEACOAST ARTILLERY. 
 
 237. Classification Barbette Carriages Barbette Carriage for 
 8-inch Rifle Principal Parts Base-plate Rollers and 
 Distance-rings. 
 
 CLASSIFICATION. Seacoast carriages are classed into 
 
 1. Barbette; 
 
 2. Casemate or turret ; 
 
 3. Disappearing; 
 
 according as the piece is fired over the parapet; through 
 a port or embrasure ; or over the parapet, the gun recoiling 
 below it on discharge. 
 
 BARBETTE CARRIAGES. The barbette carriages for 8, 10 
 and 12-inch guns resemble each other in general, differing 
 only in certain details of construction on account of the 
 varying weight of the guns. The 8 and lo-inch carriages 
 are made principally of cast iron, the 12-inch of cast steel. 
 The 8-inch carriage may be taken as a type of the others, 
 and will be described. 
 
 CARRIAGE FOR S-INCH RIFLE PRINCIPAL PARTS. The 
 principal parts of the carriage (Figs. 233 and 234) are: 
 
 1. The base-plate or lower roller path, A ; 
 
 2. The rollers and distance-rings, B ; 
 
 3. The chassis, C; 
 
 4. The top carriage, D. 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 419 
 
 FIG. 233. 
 
 DlC" IfTlfl PfT~lir III! Ill 11 
 
 FIG. 234. 
 
420 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 BASE-PLATE. This consists of a heavy casting, A, shown 
 in plan, section, and elevation, Fig. 235. It rests upon a 
 bed of concrete, to which it is bolted by the anchor-bolts a \ 
 b is the roller-path upon which rests a series of conical 
 forged steel rollers, E. The central portion, c, corresponds 
 to the pintle in the old carriages, and around it fits a collar, 
 d, Fig. 236, upon the chassis, so that rotation in azimuth 
 occurs about this central projection. 
 
 ROLLERS AND DISTANCE-RINGS. A ring of conical 
 forged steel rollers, E, Fig. 235, rests upon the roller-path 
 
 FIG. 235. 
 
 b of the base-plate, and upon these rests the corresponding 
 upper roller-path, c, Fig. 236, of the chassis. These rollers 
 are shaped as shown at E, the object of the flange d being 
 to keep the rollers in place by its bearing on the inner 
 edge of the roller-path. For the 8-inch carriage there 
 are twenty of these rollers. They are held in place by 
 two distance-rings, B, which are slotted for the axis of the 
 rollers as shown at e. The distance-rings are kept in place 
 and braced by the braces/ 
 
 338. 8-inch Barbette Carriage The Chassis. 
 
 This consists (Figs. 234 and 236) of the circular horizon- 
 tal part a and the two vertical cheeks b. The circular part, 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 
 
 421 
 
 a, supports the cheeks, and carries on its lower side the 
 upper roller path c, and the central collar d, which fits over 
 the corresponding central projection, Fig. 235, in the base- 
 plate. The upper surfaces e of the cheeks b are inclined to 
 the front, and carry at their forward ends the lugs /which 
 hold the piston-rods of the hydraulic buffers. 
 
 In modern carnages, the irregularities due to sliding 
 friction are avoided by placing the top carriage on rollers, 
 and throwing all the work of checking the recoil upon the 
 buffers, which can be very accurately regulated. 
 
 These rollers are shown at inserted in recesses in the 
 
 FIG. 236. 
 
 chassis-rail, and rotating on journals, so that the exterior of 
 the roller is just above the chassis-rail. 
 
 The device for traversing in azimuth is shown in front 
 and in plan in Fig. 234. It consists of a cross-shaft, /z, with 
 cranks. This shaft carries a worm, z, gearing into a worm- 
 wheel, /, which works upon an axis, k, attached to the 
 chassis. 
 
 In rear of the worm-wheel is a sprocket-wheel, /, on the 
 same shaft withy and attached to it, so that one cannot turn 
 independently of the other. A chain, m, is attached at one 
 end to the bed-plate at n, and the other end of the chain at a 
 corresponding point near the first, not shown in drawing. 
 
 This chain passes under a small wheel in a fork at o and 
 
422 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 thence over the sprocket-wheel /. When motion is given 
 to / by the shaft, worm, and cranks, the chain will pass over 
 the sprocket-wheel and the chassis turn on its rollers, E. 
 Vertical motion of the chassis is prevented by clips, #, bolted 
 to it and embracing a flange, y, on the bed-plate. 
 
 The device for hoisting the ammunition is shown in rear 
 of the chassis. The projectile is run up on a truck (see Fig. 
 233), and is then lifted together with the loading-tray by the 
 lever/. This lever is on a horizontal shaft, q, which carries 
 a worm-gear,^-, acted on by the worm s on the shaft t. Its 
 action is evident. 
 
 239. 8-inch Barbette Carriage The Top Carriage and Buffers 
 Elevating Device. 
 
 ,e 
 
 FIG. 237. 
 
 THE TOP CARRIAGE AND BUFFERS. These are shown 
 in Fig. 237 in section and elevation. The top carriage 
 carries the gun, and consists of a single casting, comprising 
 the buffers b, and their connecting transom, a. On the top 
 of .each buffer is cast the bracket c, carrying the trunnions of 
 the gun. 
 
 This top carriage rests on the rollers of the chassis-rail, 
 as shown in section, and is held in place, and prevented from 
 lifting at discharge, by the flanges d. In the section are also 
 shown the ribs or throttling-bars, e, which regulate the flow 
 of liquid in the buffers, there being two in each cylinder, 
 held in place by bolts passing through the walls of the 
 cylinders. The action of these buffers will be explained 
 under the subject of Recoil. 
 
 A cross pipe, /, called ah equalizing pipe, connects the 
 liquid in the two cylinders, and insures their uniform resist- 
 ance. 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 
 
 423 
 
 The pistons and rods are removed, by unscrewing the 
 nuts, g, which close the rear ends of the cylinders, and then 
 by removing the locking and piston nuts h, t, the piston and 
 rod can be pushed out to the rear. 
 
 The recoil is limited to 40 inches. 
 
 ELEVATING DEVICE. This is shown in Fig. 238. It 
 consists of a square shaft, a, attached to the right side of the 
 chassis, and working in fixed bearings at b and c\ d\s a 
 sliding bearing attached to the top carriage. In this bear- 
 ing works a bevel-gear, e, gearing into a second bevel-wheel, 
 f, on the vertical shaft, g, attached to the top carriage. A 
 worm, h, on this shaft gears into the worm-wheel i, on the 
 horizontal shaft/, and on this same shaft/ is a second gear- 
 
 m 
 
 FIG. 238. 
 
 wheel, k, engaging with the rack /, on the gun. When recoil 
 occurs, the sliding bearing d, moves along the square shaft a, 
 carrying with it the bevel-gear e, so that the gears are con- 
 stantly engaged, and the gun can be elevated in any posi- 
 tion. The return to battery carries the gear e along the 
 shaft a. By means of the hand-wheels m and , the gun may 
 be elevated from front or rear. The return of the piece to 
 the firing position is due to gravity. Carriages of this kind 
 are called gravity return carriages. 
 
 240. The 12-inch Mortar Carriage General Features Springs. 
 GENERAL FEATURES. This carriage consists of 
 
 1. The bed-plate or lower roller-path A ; 
 
 2. The rollers and distance-rings^; 
 
 3. The upper roller path or racer C\ 
 
424 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 4. The cheeks D\ 
 
 5. The spiral springs^, and the hydraulic cylinders H. 
 The upper roller-path is circular, and supports the cheeks, 
 
 which are vertical, the two together forming the top car- 
 riage. The lower roller-path is also circular. 
 
 SPRINGS. On the side of each cheek is cast a cylindrical 
 recess, E (Figs. 239 and 240), which contains a column of 
 spiral springs, F. 
 
 These springs are in ten separate lengths, and each 
 length is composed of two coils, an inner one, F' , and an 
 
 FIG. 239. 
 
 outer one, F. A pile of Belleville springs, F", forms the 
 upper end of the column, and upon these the mortar is 
 supported as follows : The trunnion-carriage G, of cast steel, 
 has a projecting lug, g' , through which passes the adjusting 
 screw K. 
 
 The lower end of this screw bears on the Belleville 
 springs, and by means of it the trunnion carnages may be 
 adjusted till the mortar is in the proper position for loading, 
 and it is then secured in that position by the jam-nuts k' . 
 
 The trunnion-carriages G, are two heavy blocks of cast 
 steel, in which the trunnions rest, and which slide, under the 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 
 
 425 
 
 force of recoil, along ways planed on the inner side of the 
 cylindrical recess E; a slot, m, Fig. 241, being left in the 
 
 recess for the projecting lug g'\ 
 K a sec tion of the trunnion-carriage 
 ~Z\ -, and recess is shown in Fig. 241. 
 
 t The object of the spiral springs 
 is to return the mortar to the fir- 
 ing position. They are set at an 
 angle of 50 with the horizontal, 
 the mortar being fired between 
 the limits 35 and 65, so that this 
 is a mean between them. To ob- 
 tain a column of springs of suf- 
 ficient length to return the piece 
 E to its proper position, the cylin. 
 drical recesses in the cheeks are 
 lengthened by bolting a cylinder 
 E f , Figs. 239 and 240, to the bot- 
 __ TT> torn of E. 
 
 F' 
 
 -G 
 
 241. The 12-inch Mortar Carriage 
 Hydraulic Buffers. 
 
 Recoil is checked by two 
 hydraulic buffers, H, Figs. 239 and 
 240, one on each side of the car- 
 riage, bolted to the flanges of the 
 cylindrical recesses E. The pis- 
 ton-rods //, Figs. 240 and 242, of 
 E* these cylinders are attached to 
 the lower ends of the trunnion- 
 carriages G. When the piece is 
 
 FIG. 240. 
 
 FIG. 241, 
 
426 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 fired, the spiral springs return it to the firing position, and 
 
 hence this is a spring-return carriage. 
 
 The arrangement of the hydraulic buffer for checking 
 recoil and maintaining a constant resist- 
 ance in the cylinder, differs from that 
 for the 8, 10, and 1 2-inch guns as fol- 
 lows : 
 
 A channel, A, Fig. 242, is bored 
 parallel to the axis of the cylinder H. 
 Holes, a, are bored at different intervals 
 along this channel, and are partially or 
 entirely closed by screw-plugs, b, fitting 
 into the holes c. These plugs, b, are of 
 different shapes, so that they will either 
 completely close the openings a, when 
 screwed home, or will leave them par- 
 tially or entirely open. They are never 
 entirely removed. When the gun re- 
 coils, the piston moves in the direction 
 of the arrow, Fig. 242. At the first 
 instant of recoil, if all the holes a are 
 open, it is evident that the liquid will be 
 forced freely through these holes, and 
 will flow along the channel A, and return 
 above the piston, into the cylinder. As 
 the motion of the piston continues, each 
 of these holes will, in succession, be cut 
 off, and the flow of the liquid being thus 
 limited, its resistance will increase. By 
 
 partially or entirely closing the holes a, it is evident that 
 
 any resistance to flow, within limits, may be obtained. An 
 
 equalizing-pipe,/, connects the two cylinders, to keep the 
 
 pressure the same in both. 
 
 The piston-rod h! , passes through the cylinder at both 
 
 ends, to equalize the volumes, and the piston-head, s, is 
 
 solid. 
 
 Its upper side is of the shape shown, and the upper 
 
 cylinder-head, s', is correspondingly shaped. When the 
 
 springs return the piece to the firing position, the head of 
 
 FIG. 242. 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 
 
 427 
 
 the cylinder,/, enters the recess in the piston-head, s, and by 
 gradually forcing out the liquid, the counter-recoil is 
 checked, and the piece comes into the firing position 
 without shock. Buffers, , Fig. 240, on the trunnion-car- 
 riage also avoid this. 
 
 242. Remaining Parts of the 12-inch Mortar Carriage Roller- 
 paths Elevating-gear Traversing-gear Loading- scoop. 
 
 ROLLER-PATHS. In the 8, 10, and 1 2-inch carriages, 
 horizontal motion of the parts is prevented by the central 
 collar or pivot, as explained. In the 1 2-inch 
 mortar carriage, as the recoil of the piece is 
 downward, the central part of the carriage 
 must be left open, and hence the central collar 
 cannot be used. Resistance to horizontal 
 motion is therefore obtained by forming the 
 upper roller-path, C, so that it overlaps the 
 lower one, A, as shown in Fig. 243, which is a FIG. 243. 
 section of the two. Vertical motion is prevented by the 
 weight of the system. 
 
 ELEVATING-GEAR. This consists of a bronze toothed 
 sector, a, bolted to the mortar, con- 
 centric with the axis of the trun- 
 nions, into which works a gear, b. 
 A large gear, c, on the same shaft is 
 driven by the gear d, and on the same 
 shaft with d is a hand-wheel, e. 
 
 The gears b, c, d, and the 
 hand-wheel, e, are all mounted on 
 the trunnion-carriage, G, and as the 
 mortar is mounted on the same 
 carriage, the whole elevating device recoils together. Each 
 trunnion-carriage carries its own elevating-gear. 
 
 TRAVERSING-GEAR. This consists of a vertical shaft, a, 
 Fig. 245, attached to the upper carriage, carrying a gear, 
 b, at its lower end, and a worm-wheel, c, at its upper 
 end. The wheel, b, gears into a toothed ring, d, on the 
 
 FIG. 244. 
 
428 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 a 
 
 FIG. 245. 
 
 inside of the lower roller-path, and the shaft is rotated by a 
 worm, e, driven by cranks, /, on a horizontal shaft, g, passing 
 through the front of the cheeks of the 
 top carriage. This device is also shown in 
 Fig. 239. 
 
 For pointing in azimuth, a cast-iron 
 circle, graduated in degrees, is fixed 
 around the upper roller-path, and a pointer 
 attached to this path, indicates the direc- 
 tion. 
 
 LOADING-SCOOP. This consists of a 
 scoop or tray, a. Fig. 239, at the end of a 
 lever, b. This lever is pivoted to the rear 
 of the chassis on a shaft, c, which carries 
 also the bent lever d. The outer end of 
 this lever carries a nut, e, in which works 
 the screw,/. This screw is supported in 
 bearings on the left side of the top carriage, and extends to 
 the front, where it ends in a hand- wheel, g. By turning this 
 hand-wheel, the scoop is raised or lowered, carrying the 
 projectile and charge to the breech of the mortar. 
 
 The loading position for the mortar is an elevation of 5. 
 
 243. Casemate or Turret Carriages General Principles Disappear- 
 ing Carriages General Principles. 
 
 GENERAL PRINCIPLES OF TURRET CARRIAGES. - - The 
 general object of these carriages, is to secure a minimum 
 height, and minimum embrasure opening. Hence the cen- 
 tre of rotation is at the centre of the embrasure, and the 
 chassis is simply a pair of rails, which support the buffers 
 carrying the gun. 
 
 Elevation is given by lowering or raising the rear ends 
 of the rails, and direction by rotating the turret. None of 
 these carriages have as yet been designed for the land 
 service. 
 
 GENERAL PRINCIPLES OF DISAPPEARING CARRIAGES. 
 Owing to the great cost of modern guns and carriages, it is 
 important to protect them as much as possible from injury 
 from fire. This may be done either by placing them in 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 429 
 
 armored casemates or turrets, or in gun-lifts, or by using 
 the ordinary barbette battery, and placing the gun upon a 
 disappearing carriage. The great cost and confined space 
 of the casemates, turrets, and gun-lifts, has caused the adop- 
 tion of the disappearing type of carnages in exposed sites. 
 
 The object of a disappearing carriage is, to enable the 
 gun to be fired over an ordinary parapet, thus giving it all 
 the advantages of an extensive field of view and of fire, 
 with room for manoeuvre, and to utilize the force of recoil 
 in returning the gun to cover for loading, and in storing up 
 sufficient energy, during recoil, to return the gun to the firing 
 position. 
 
 There are therefore two points to be especially con- 
 sidered : 
 
 1. The means of checking recoil, so that the gun will be 
 covered during loading. 
 
 2. The method of storing up energy sufficient to return 
 the piece to the firing position. 
 
 Checking Recoil. -- In all these carriages, the gun is 
 mounted at the ends of lever-arms, and these arms are 
 pivoted, in various ways, to the chassis. The recoil is 
 checked by hydraulic buffers, or in some cases by pneu- 
 matic buffers, which allow the lever-arms to rotate grad- 
 ually to the rear, bringing the gun down to the loading 
 position. 
 
 Return to Firing Position. The energy necessary to 
 return the gun to the firing position, is stored up in various 
 ways. In the English service, a hydro-pneumatic buffer 
 is used ; that is, the liquid which is forced out of the 
 hydraulic cylinder, by recoil, passes into an air-chamber, 
 and compresses the air sufficiently, to give the necessary 
 pressure for returning the gun to the firing position, as soon 
 as a valve is opened between the air-chamber and the 
 hydraulic cylinder. 
 
 Spiral or Belleville springs are also employed. The 
 recoil is checked by the hydraulic buffer, and the springs 
 restore the piece to its firing position. 
 
 Counterweights may be used, either alone, or in connec- 
 tion with air pressure. 
 
430 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 244. Buffington-Crozier Disappearing Carriage. 
 
 Two successful carriages of this type have been tried in 
 the United States, and an outline description of each will be 
 given. 
 
 BUFFINGTON-CROZIER. This carriage was designed by 
 Colonel Buffington, and modified by Captain Crozier, both 
 of the U. S. Ordnance Department. 
 
 The carriage consists of the chassis, A, Fig. 246, the sup- 
 porting levers, >, carrying the gun, the hydraulic buffers, C, 
 and the counterweight, D. The carriage is a front-pintle 
 one. The gun is mounted on the upper ends of the support- 
 
 FIG. 246. 
 
 ing levers, B. These levers have trunnions, ^, near the mid- 
 dle, which are mounted on the hydraulic buffers, C. The 
 lower ends of the levers are connected by a cross-head at /, 
 and from this cross-head, is suspended the counterweight, 
 D. This counterweight rises and falls vertically, while the 
 trunnions, e, with the buffers, move horizontally along the 
 chassis-rail, a. When the piece is fired, the force of recoil is 
 taken up by the buffers, which move back as stated, while 
 the counterweight, D, is raised vertically, sliding on guides, 
 g. The gun in the loading position is shown at G. The 
 counterweight is held in its position after firing, by a pawl, 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 43! 
 
 //, and ratchet, t, which being released, allows the weight to 
 descend, and thus the gun is raised to the firing position. 
 The trunnions of the gun describe an arc of an ellipse in 
 their descent. The bars E are for giving elevation. They 
 are attached to a straight rack, b, on the inside of the chassis, 
 which is worked by the hand- wheel c. The elevation may 
 be given in either the loading or the firing position. The 
 carriage rests in front upon a ring of rollers, F, as previously 
 described, and is traversed by the chain, d, passing over a 
 sprocket-wheel, and worked by a crank. 
 
 245. The Gordon Disappearing Carriage. 
 
 FIG. 247. 
 
 FIG. 248. 
 
 This carriage was designed by Capt. Gordon of the 
 U. S. Ordnance Department, and consists (Figs. 247 and 
 248) of the chassis a, the top carriage b, the counterpoise c, 
 the lever-arms d, the hydraulic cylinders e, and the air- 
 chamber f. 
 
 The chassis, a, is a heavy casting, supporting all the parts, 
 and it rests when in the firing position upon a platform. 
 When the piece is to be moved in azimuth, the chassis is 
 supported on a hydraulic pivot, not shown in the drawings, 
 
432 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 by which arrangement the traversing is effected with very 
 little power. 
 
 On the upper side of the chassis, four levers, d, are 
 mounted, two of them being shown in the drawing. 
 
 These levers rotate about the axes, g, and carry at their 
 lower ends, a heavy counterweight, c. On the upper ends 
 of these levers is mounted the top carriage, , which sup- 
 ports the piece. A hydraulic cylinder, e, extends along the 
 chassis. 
 
 Its piston is forced in, during recoil, and the liquid, thus 
 forced into the air-chamber f, compresses the air, and 
 stores up the energy necessary to return the piece to the 
 firing position, when the proper valve in the air-chamber 
 is opened. The trunnions describe an arc of about 180 
 during recoil, thus bringing the gun close to the parapet, 
 and affording good cover. The elevating device is attached 
 to the top carriage. This is a centre-pintle carriage. 
 
 Several disappearing carriages are in use abroad, as the 
 Moncreiff, Armstrong, Canet, etc. 
 
 246. Old Seacoast Carriages in II. S. Service. 
 
 Certain old carriages are still retained in the U. S. ser- 
 vice for the 8-inch converted rifles, and the 1 5-inch Rodman 
 smooth-bore guns. They consist (Fig. 249) of a chassis, a,. 
 and a top carriage, b, made of wrought iron. 
 
 FIG. 249. 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 433 
 
 The chassis is composed of two parallel, I-shaped rails, 
 connected by transoms, and attached to it, between the rails, 
 is the hydraulic buffer, c. The piston of this buffer is at- 
 tached to the top carriage by a lug, d, on the latter. The 
 buffer itself, is one of constant orifice, and variable resistance, 
 as will be explained. Bolted to the rear end of the chassis- 
 rail, is an inclined rail, e. The retraction gear is shown at/. 
 The principle of this carriage is as follows : 
 When the piece is fired, the top carriage rests, through- 
 out its length, upon the chassis-rail, and hence the force of 
 recoil is distributed over this length, and the top carriage 
 starts to the rear on sliding friction. After a very small 
 movement in recoil, the wheel, g, of the top carriage (Fig.25o), 
 strikes the wedge-shape drail, e, and begins to rotate. This 
 causes the top carriage to tip slightly forward, and brings 
 
 FIG. 250. 
 
 the front wheel, h, into bearing on the chassis-rail. The car- 
 riage then moves on rolling friction. The result of this 
 arrangement is, that the top carriage rests, throughout the 
 recoil, on rolling friction, as shown Fig. 250. A spring pawl 
 and ratchet, retain the top carriage in the loading position, 
 after recoil, and by releasing the pawl, the top carriage 
 returns on rolling friction to its firing position, by gravity. 
 
 For drill purposes, to bring the gun from battery, for 
 loading, the rear wheel, g, is mounted on an eccentric axle, 
 and when thrown into bearing against the chassis-rail, by the 
 action of a handspike, it tips the top carriage forward, and 
 brings the front wheel, //, also into bearing. The piece, and 
 top carriage, are then drawn to the rear, by a rope attached 
 to the latter (Fig. 249), and wound round a drum on the shaft 
 of the retraction gear/. 
 
434 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 THEORY OF RECOIL. 
 
 247. Maximum Velocity of Recoil. 
 
 The velocity of recoil at the instant the projectile leaves 
 the muzzle is given by equation 65, Interior Ballistics. This 
 does not represent the maximum velocity of recoil, however, 
 for the reasons stated, and a new equation is necessary to 
 determine this velocity. 
 
 In equation 65, it is assumed, that the mean velocity of 
 the particles of the charge, is one half that of the velocity of 
 
 the projectile; that is, the equation contains the termf v\ 
 
 in which c3 is the weight of the charge, and v the velocity of 
 the projectile. 
 
 This is very nearly true while the projectile is in the 
 bore, because the layer of gas next the projectile has the 
 same velocity as the latter, and this velocity decreases to 
 zero, for the layers toward the bottom of the bore. 
 
 But when the projectile leaves the muzzle, this condition 
 no longer exists. The gases, which were before confined, 
 rush out with greatly increased velocity, and this affects 
 the recoil of the piece. 
 
 Let P denote the weight of gun, and part of the carriage 
 
 which recoils ; 
 
 p, the weight of the projectile ; 
 c3, the weight of the charge ; 
 V m ', the maximum velocity of recoil; 
 V, the initial velocity of the projectile ; 
 v m , the mean of the maximum velocities of the powder- 
 gas upon issuing from the piece. 
 Then the equation 
 
 Pr*!=pV+&v m (335) 
 
 expresses the equality of momenta of the piece, projectile, 
 and charge at this instant. 
 
 General Sebert of the French Artillery, has determined 
 with his velocimeter, previously described, that in order that 
 the above equation be true, the value v m must be about 3000 
 ft -sees. 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 435 
 
 Hence the maximum velocity of recoil is given by 
 
 Vml= tV*** t ..... (336) 
 
 while the velocity of recoil during the time the projectile is 
 in the bore is (equation 65) 
 
 , & 
 
 pv + -v 
 
 248. Periods of Recoil Relation between Time, Velocity, and 
 Length of Recoil in First Period. 
 
 PERIODS. The recoil of a gun is divided into two 
 periods : 
 
 1. From the time the gas begins to act, until the maximum 
 velocity of recoil is attained. 
 
 2. From the end of the first period, till the piece is 
 brought to rest. 
 
 RELATIONS BETWEEN TIME, VELOCITY, AND LENGTH OF 
 RECOIL IN FIRST PERIOD. In order to determine the cir- 
 cumstances of recoil in the first period, it is necessary to 
 know the relations between the time, velocity, and length of 
 recoil, and these are determined in the following manner: 
 
 If the distance recoiled by the piece, at the end of any 
 time /, be denoted by x, the velocity at that time is 
 
 dx 
 "-*> 
 
 and the distance x passed over is 
 
 'v'dt. 
 
 =/< 
 
 Hence, considering the expression / v'dt, if we con- 
 struct a curve whose abscissas are the values of /, and whose 
 ordinates are the corresponding values of v' , this curve 
 will be of the form Fig. 251, and from it we deduce the fol- 
 lowing laws : 
 
 i. The velocities of recoil increase very rapidly at first, 
 till the point of inflection i is reached, and then more slowly, 
 
43^ 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 till they cease to increase at the time corresponding to the 
 maximum velocity F,/, which time is denoted by r. 
 
 2. The area included between the curve, the axis T, and 
 any ordinate v', is the distance x passed over in recoil, at 
 
 the time t corresponding- to that ordinate, since x / v 'dt ; 
 
 and the total length of recoil during the first period is the 
 area corresponding to the ordinate r. 
 
 This curve was constructed by experiment, by obtaining 
 with the Sebert velocimeter, the values of v f corresponding 
 to different values of t. 
 
 249. Ordinary Case Steps in the Solution of the Problem. 
 
 In the case just considered, the relations between the 
 velocities of recoil v ', and the corresponding times /, were 
 determined by experiment. 
 
 ORDINARY CASE. Ordinarily, this relation between v ' 
 and t is not known. It may, however, be determined by a 
 series of steps as follows : 
 
 STEPS. We have the relation between the velocity of 
 the projectile v and the length of its travel u in the bore, 
 by Sarrau's monomial or binomial formulas; hence we have 
 a relation v =/(u). 
 
 i. We next determine the time t required for the projec- 
 tile to pass over any length of bore u. This gives a relation 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 
 
 437 
 
 2. Combining the curves v = f(u) and t =/(), we de- 
 termine the relation v =.f(f). 
 
 This is done by using the ordinates of the time curve 
 / =f(u) as abscissas, and those of the velocity curve v =f(u) 
 as ordinates, and constructing a curve whose equation is 
 /=/(/). This equation gives the relation between the 
 velocity of the projectile, and the corresponding time /. 
 
 3. To pass from this curve to that of the velocity of re- 
 coil as a function of the time t, we have equations (65) and 
 (336), giving the relation at any time t between the velocity 
 of the projectile and that of the piece; and knowing that of the 
 projectile we may at once find that of the piece as a function 
 of the time, or v' =f(i), which is the curve required. 
 
 V 
 
 
 
 FIG. 252. 
 
 Having the curve v ' = /(/), we can determine, as pre- 
 viously shown, the time, and length of recoil, corresponding 
 to any given velocity. 
 
 250. First Step Time of Passage of Projectile over a Given Length 
 of Bore Difficulty Remedy. 
 
 Assuming the binomial and monomial formulas (91) and 
 (121), Interior Ballistics, we apply the one which is suitable 
 to the particular case under consideration, and construct 
 the curve whose abscissas are the values of u, and its ordi- 
 nates the corresponding values of v. This curve will be of 
 the form Fig. 252. 
 
 The value for the velocity at any point u is, from calculus, 
 
 du 
 
 
 dt' 
 
43 8 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 from which we have 
 
 1- *L 
 
 v ~~ du 
 
 Multiplying by du and integrating, we have 
 
 or 
 
 FIG. 253. 
 
 Hence if we construct a curve whose abscissas are the 
 values of u, and its ordinates the corresponding values of , 
 the area included between this curve, the axis of u, and any 
 ordinate will give for any value of u the time t required 
 
 for the projectile to pass over this distance u in the bore. 
 The form of this curve is shown in Fig. 253. 
 DIFFICULTY. The only difficulty in this case is that for 
 
 very small values of v the ordinates will be large, and will 
 
 not fall within the limits of an ordinary drawing, and hence 
 the area under the curve cannot be accurately measured, 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 
 
 439 
 
 and therefore the time corresponding to a given travel u 
 cannot be exactly ascertained. 
 
 REMEDY. To obviate this difficulty, we assume (as is 
 nearly correct) that the velocity of the projectile, as a 
 function of the time varies nearly as the abscissas and 
 ordinates of a common parabola, whence we have 
 
 V = 2pt 
 
 Multiplying by dt and integrating, we have 
 I vdt = I -jjrdt = u = I J~2ptdt = 
 
 (337) 
 
 (338) 
 
 FIG. 254. 
 
 At the instant the shot leaves the bore, v in equation 
 (337) becomes the initial velocity V. Denoting the cor- 
 responding time by t ' , we have, equation (337), 
 
 V 
 
 and this value of -\/2p in equation (338) gives 
 
 '.= !' (339) 
 
 u being the total length of travel of the projectile. Com- 
 
440 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 paring this total time of passage of the projectile through the 
 bore, with that obtained from that part of the area under the 
 curve of reciprocals which can be measured, the value of 
 the unmeasured portion can be ascertained very nearly. 
 Thus the relation t = f(u) is determined and the curve is 
 given in Fig. 254. 
 
 251. Second and Third Steps in Determining the Curve of Velocity 
 of Recoil as a Function of the Time. 
 
 SECOND STEP. Taking the ordinates of the curve 
 t f(u] as abscissas, and those of the velocity-curve 
 v =f(u) as ordinates, we construct a curve v =f(t), showing 
 the relations between the velocity of the projectile and the 
 corresponding time, and this curve will be of the form 
 shown in Fig. 255. 
 
 FIG. 255. 
 
 THIRD STEP RELATION BETWEEN VELOCITY OF PRO- 
 JECTILE AND THAT OF RECOIL. We have for the velocity 
 of recoil of the piece and carriage while the projectile is in 
 the bore, equation (65), 
 
 and for the maximum velocity of recoil, equation (336) 
 
 V ' 
 
 v m 
 
 pV + 3QOO&? 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 44! 
 
 Since v is determined as a function of t by the second 
 step, v' may be found for the corresponding times by 
 ^equation (65), by multiplying the ordinates of the curve just 
 
 determined, Fig. 255, by the ratio - f . A curve can 
 
 then be constructed, similar to that in Fig. 255, giving the 
 velocities of recoil of the piece, for each instant of the 
 passage of the projectile through the bore, and the area 
 under this curve, bounded by the axis of T and any 
 ordinate v' will give the corresponding space passed over, 
 
 since Cv'dt x. 
 
 After the projectile quits the bore, equation (65) no 
 longer applies; but it is known that the curve becomes 
 tangent to a line parallel to the axis of T, at a point given 
 
 FIG. 256. 
 
 by equation (336), and it is reasonable to infer, that the rate 
 of curvature of the curve of recoil, will continue uniform up 
 to this point of tangency. 
 
 Hence, drawing a line parallel to the axis of T, at the 
 distance given by equation (336), 
 
 77 / _- 
 
 * m 
 
 and continuing the curve already drawn, preserving its gen- 
 eral rate of curvature up to this line, we have the curve 
 
442 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 v' = /(/), giving- the time and space passed over in recoil, 
 and this curve will be of the form Fig. 256. 
 
 252. Example 8-inch Steel B. L. Rifle First Step Curve t f(u}. 
 
 For example take the case of the 8-inch Steel B. L. Rifle. 
 The velocity curve for this gun, with 125 pounds brown 
 powder, is given in Fig. 257. 
 
 v 
 
 .u 
 
 FIG. 257 
 
 From it we obtain the following abscissas and ordinates 
 
 u (Feet). 
 
 0.46 . . 
 
 1.70.. 
 2.40 . . 
 3.20.. 
 3.70.. 
 7.30.. 
 9.50.. 
 
 11.50. . 
 13.00. . 
 
 14.30.. 
 15.75,. 
 
 z/ (Foot-seconds). 
 
 387 
 
 935 
 1080 
 1197 
 1259 
 
 1545 
 1655 
 1727 
 
 1787 
 1827 
 1859 
 
 1743 - 1884 I. V. 
 
 From which we have the following values of , and the 
 curve of reciprocals, Fig. 258. 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 
 
 u (Feet). I. 
 
 v 
 
 0.46 002584 
 
 I./O OOI069 
 
 2.4O , 0009259 
 
 3-20 0008354 
 
 370 0007943 
 
 7.30 0006472 
 
 9.50 0006042 
 
 11.50 0005790 
 
 1 3.00 0005 596 
 
 14-30 0005473 
 
 15-75 0005379 
 
 1743 - 0005308 
 
 443 
 
 FIG. 258. 
 
 For the total time of passage of the projectile through 
 the bore we have, using the area of the parabola (eq. 339), 
 
 Hence the total area under the curve of reciprocals 
 should be nearly .01387 second. 
 
 In the absence of a more accurate method, the area under 
 the curve, which can be measured, may be obtained by con- 
 sidering each portion of the area bounded by the curve, the 
 
444 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 axis of u, and the two adjacent ordinates, as a trapezoid, and 
 finding its area. 
 
 Thus for the first trapezoid we have 
 
 ( .002584 
 ordinates \ 
 
 { .001069 
 
 Value of u = 1.24 1.70 0.46. 
 
 . /.oo2 5 84 + .00 1 069^ 
 Area ( ! j X 1.24 = .00227 sec. 
 
 Following this method, we have the table: 
 
 /P , Successive Successive times, Total times, 
 
 differences. seconds. seconds. 
 
 0.46 o 
 
 1.70...--... 1.24 OO227 .OO227 
 
 2.40 0.70 0006979 0029679 
 
 3.20. 0.80 000704 0036719 
 
 370 0.50 0004075 0040794 
 
 7.30 3-60 002592 0066714 
 
 9.50 2.20 001386 0080574 
 
 II.5O 2.OO ,.. .OOIl8o 0092374 
 
 13.00 1.50 000854 OI009I4 
 
 14.30 1.30 000715 0108064 
 
 15.75 i-45 000787 0115934 
 
 17.43 1-68 000897 0124904 
 
 From this table we can obtain the time of travel of the 
 projectile over any distance u. 
 
 The sum of the times is .01249 second, while the total 
 time is, as above shown, .01387 second. 
 
 Hence the difference, .00138 second, is the area that can- 
 not be measured. 
 
 253. Examples Second and Third Steps. 
 
 The table on page 442 gives the curve v f(u), that on 
 this page the curve t =/(). Taking the ordinates of the 
 latter curve as abscissas, and those of the former as ordi- 
 nates, we can form the following table, whose abscissas and 
 ordinates are those of the curve v =f(t): 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 445 
 
 Total Successive times, Ordinates. 
 
 times, t. seconds. Velocities foot-seconds, v. 
 
 O O 
 .00138.... 00138 387 
 
 .00365 00227 935 
 
 .00435 000698 1080 
 
 .00505 .000704 1197 
 
 .00546 0004075 1259 
 
 .00805 002592 1545 
 
 .00944 OOI386 1655 
 
 .01062 OOIlSO 1727 
 
 .OII47 OOO854 1787 
 
 .01219 000715 1827 
 
 .01297 000787 1859 
 
 .01387 000897 1884 1. v.; 
 
 and from this we construct the curve of velocities of the 
 projectile as a function of the times. Passing to the consid- 
 eration of the recoil of the piece and carriage, we have, 
 equation (65), 
 
 p = 300 Ibs. ; 
 & - 125 Ibs. ; 
 P = 1 8 tons = 40320 Ibs. 
 Hence 
 
 v' = .00899^ = .009^. 
 
 From this formula, having the values of v and the corre- 
 sponding times /, we can form the following table and con- 
 struct the curve of recoil of the piece and carriage as a 
 function of the time. 
 
 Velocity of recoil of 
 
 Total times, Piece and Carriage, 
 
 seconds. foot-seconds. 
 
 0.0000 
 .00138 3-483 
 
 .00365 , 8.41 5 
 
 00435 9720 
 
 .00505 10.773 
 
44-6 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 .00546 H.33I 
 
 .00805 1 3-95 
 
 00944 14-895 
 
 .01062 I5.56I 
 
 .OI 147 16.083 
 
 .OI2I9 16.453 
 
 .01297 16.73 I 
 
 .01387 16.956 
 
 From equation (336) the maximum velocity of recoil is 
 
 ' = 23.32 ft.-seconds. 
 
 H- .01387 
 
 FIG. 259. 
 
 From the above data the curve of recoil, Fig. 259, may 
 be constructed. 
 
 Drawing a line parallel to the axis of T, at the distance 
 V m f = 23.32 ft.-secs., this line will mark the limit of accelera- 
 tion. 
 
 From this curve, the time corresponding to any velocity 
 of recoil can be obtained, and the area under the curve will 
 give the corresponding space passed over. 
 
 254. Problems. 
 
 i. Required the time at which the velocity of recoil is 
 13.905 ft.-sec. 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 447 
 
 The table page 446 shows it to be .00805 second. 
 
 2. Required the space passed over in recoil at the end of 
 this time. 
 
 It will be the area under the curve, from the origin, up 
 to the ordinate whose value is 13.905 ft.-secs., or, approxi- 
 mately, the sums obtained by adding the separate areas 
 regarded as trapezoids, up to this point. As an approxima- 
 tion to the true result, regard the curve as a parabola. The 
 result thus obtained will be slightly too great. The area 
 under the curve will be two thirds the rectangle of the ab- 
 scissa and ordinate of any point. 
 
 Hence for the area in question we have 
 
 s = - X .00805 X I3-9 5 = -0746 ft. = .895 inches. 
 j 
 
 3. Required the space passed over by the gun and car- 
 riage at the time the projectile leaves the bore. 
 
 By the same method of approximation we have 
 
 s = - X -01387 X 16.956 = .1567 ft. = 1.88 inches, 
 o 
 
 4. Required the time at which the velocity of recoil is a 
 maximum, and the space passed over at this time. 
 
 The curve v' = f(t) gives, by measurement, for the value 
 of t = .0395 seconds. 
 
 The space passed over will be approximately 
 
 s = - X .0359 X 23.32 = .558 ft. = 6.70 inches. 
 
 In the same way all the circumstances of the recoil of a 
 gun during the first period, may be obtained, having the 
 curve v = f(u), which can be obtained from Sarrau's 
 formulas. 
 
 255. Time and Length of Recoil in Second Period. 
 
 TIME OF RECOIL. At the beginning of the second 
 period, the acceleration is zero, and the gun and carriage 
 have acquired the maximum velocity of recoil V m r . For 
 simplicity of discussion, suppose the chassis horizontal. 
 
TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 The only force acting during the second period is friction,, 
 and this being practically constant, will uniformly retard 
 the carriage and piece, till they are brought to rest. 
 Let/ be the coefficient of friction = 0.2 about; 
 y the retardation due to friction ; 
 P the weight of the gun and carriage which is mov- 
 ing in recoil ; 
 
 M the mass of the moving parts; 
 V" the velocity of recoil at any time t during the 
 
 second period. 
 Then from mechanics 
 
 dV" fP 
 r = -*- = M (340) 
 
 The velocity at any time t during the second period will 
 be, from (340), 
 
 
 When t = o, or at the beginning of the second period, 
 V" = V m ' \ hence in (341) we have 
 
 V "=^-W f - ...... (342) 
 
 At the end of the second period, when recoil ceases, 
 V" = o, and the corresponding time is, from (342), 
 
 n VJ 
 
 ~ r= ~ ....... (343) 
 
 LENGTH OF RECOIL. Assuming equation (342), we have 
 for the length of recoil, at the end of any time, /, in the second 
 period 
 
 __ 
 
 dt~ " M' 
 
 v"dt=v m dt-tdt. . ( 344 ) 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 449 
 
 s = 
 
 (345) 
 
 At the end of.recoil we have for the value of t, from (343), 
 
 V 
 
 rr> 111 
 
 ~'~~' 
 
 Substituting this value of / in (345) gives 
 
 but 
 
 V ' 2 i fP V ' ' 
 
 -i:f^= (346) 
 
 hence in (346) 
 
 (347) 
 
 FIG. 260. 
 
 256. Curve Representing Total Recoil Application to 8-inch Rifle. 
 Second Period. 
 
 CURVE OF TOTAL RECOIL. The curve representing all 
 the circumstances of recoil of the piece and carriage, will be 
 obtained, by combining that for the first period, with the 
 right line representing the second period, and will be of the 
 form Fig. 260. 
 
 APPLICATION TO S-INCH RIFLE. 
 
 i. Required the time, from the beginning of the second 
 period, at which the velocity of recoil will be 10 ft.-secs., 
 and the space passed over at that time . 
 
 From (342), 
 
 10 = 23.32 .2 X 32.2 X/; 
 
45 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 t = 2.068 seconds ; 
 from (345), 
 
 s = 23.32 X 2.068 i X .2 X 32.2 X (2.o68) 2 ; 
 s = 34.46 feet. 
 
 2. Required the time from the beginning of the second 
 period to the end of recoil, and the total space passed over 
 in recoil : 
 
 From (343), 
 
 23.32 
 
 - = 3.621 seconds. 
 
 32.2 X .2 
 
 From (347), 
 
 s = - ^ 42.22 feet. 
 
 2 X 32.2 X -2 
 
 In a similar manner, all the circumstances of the recoil 
 during the second period can be obtained, having the value 
 of V m ' from formula (336). i 
 
 257. Wheeled Carriages Cases. 
 
 The preceding discussions relate to carriages which slide 
 in recoil, such as those for seacoast guns. 
 
 For wheeled carriages two cases may arise : 
 
 1. The carriage may recoil, the wheels rotating, and not 
 leaving the ground or platform upon which they rest. 
 
 2. The wheels may leave the ground or platform, depend- 
 ing upon the relative values of the components of the force 
 of recoil which act to produce translation and rotation. 
 
 In the second case, the phenomenon of recoil is composed 
 of alternate periods, during which the wheels rise, and return 
 again to the platform. 
 
 If the carriage slides in recoil, with the wheels always in 
 contact with the ground, the preceding discussions apply, 
 the only change necessary being a decrease in the value of 
 the coefficient of friction, due to the lubrication of the bear- 
 ing surfaces of the nave and axle-arm. The coefficient, /, in 
 this case is decreased to about two thirds its ordinary value. 
 
 If the wheels rise, increased pressure is produced on the 
 trail. This increased pressure, decreases the extent of recoil 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 
 
 451 
 
 as compared with that which obtains in the first case, and hence 
 the values for time, velocity, and length of recoil deduced for 
 the first case, will be greater than those for the second. As the 
 calculations in the second case are somewhat complicated, 
 those for the first case may be used instead of them, as being 
 safe in practice. 
 
 258. To Calculate the Angle of Elevation of the Piece for which the 
 Wheels will Rise. 
 
 The rotation of the carriage about the trail, depends on 
 the angle of elevation at which the piece is fired. There is 
 a limiting angle for which this rotation will occur. For all 
 
 7 
 
 D I 
 
 FIG. 261. 
 
 angles greater than this, rotation will not occur, and for all 
 angles less than this, it will always occur. It is required to 
 determine this limiting angle. 
 
 Let OM, Fig. 261, be the axis of the piece, and the line 
 of action of the force P . Resolving this force into its com- 
 ponents parallel and perpendicular to the ground, we have 
 
 OE = P Q cos ot ; 
 ON = P sin a. 
 
 With reference to the point C, the component OE acts 
 with a lever-arm OD to raise the wheels, while ON acts 
 with a lever-arm DC to keep them in contact with the 
 
45 2 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 ground. Let G be the centre of gravity of the system,, 
 composed of gun and carriage. 
 
 Then the weight P acts at G, with a lever-arm CI, to 
 keep the wheels down. In addition to these, the system 
 moves under the action of the force OE with an accelera- 
 tion y, and hence its force is My, and this force diminishes 
 the rotative effect of the force OE, since the action of 
 this force OE, is to produce both rotation around C, and 
 translation along CD. 
 
 This latter force, My, has a lever-arm GL We have 
 therefore, calling those forces which tend to cause a lifting 
 of the wheels positive, and those which oppose it negative, 
 
 + OE, lever-arm OD ; 
 
 - ON, " DC; 
 
 - P, " CI; 
 
 - My, " GL 
 
 When the sum of the moments of these forces with 
 respect to C is zero, the wheels will be on the point of 
 leaving the ground. 
 
 Hence this gives the condition required. 
 
 Making 
 
 we have 
 
 + P. cos a . a P sin a . d P . b Myh = o. (348) 
 
 The value of y is obtained as follows : Denoting the 
 total pressure of the powder-gas by P , the component of 
 this pressure causing recoil is P 9 cos a. This force is opposed 
 by the friction due to the component P sin a and the weight 
 of the gun and carriage P. Hence the force opposing 
 motion isf(P sin a -f- P). 
 
 From mechanics we have therefore for the acceleration 
 
 X = -i[/> cos a-f(P, sin + />)]. . . (349) 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 453 
 
 Substituting this value for y in (348), which can be done, 
 since the wheels are just about to leave the ground, and 
 therefore the case is one of horizontal sliding, we have 
 
 P. cos a(a - k) - P Q sin a(d - fh) - P(b - fh) = o. (350) 
 
 Now making P o in comparison with P , and calling 
 <x the value of a for this limit, where the wheels are just 
 quitting the ground, we have 
 
 a-h 
 = _, ...... (351) 
 
 in which a and d can be found by direct measurement of 
 the gun and carriage, and the centre of gravity by suspend- 
 ing the system in two different positions, and noting the 
 point of intersection of the lines of suspension when pro- 
 duced. 
 
 BRAKES AND BUFFERS. 
 
 259. Necessity for Means of Checking Recoil Conditions which a 
 Good Brake should Fulfil Classes. 
 
 NECESSITY FOR MEANS OF CHECKING RECOIL. The 
 above discussion, and its application in the case of the 8-inch 
 gun, show, that unless some artificial means be employed 
 to check recoil, its extent will be so great as to cause 
 inconvenience. 
 
 This is especially true with modern field, siege, and 
 seacoast guns, where the weights and initial velocities of 
 the projectiles have greatly increased, without a correspond- 
 ing increase in the weight of gun and carriage, and hence 
 the length of recoil has been greatly increased. 
 
 In the field and siege services, this entails great fatigue 
 upon the cannoneers in running the gun and carriage back 
 to battery, with a consequent delay in firing, and exposure 
 to the enemy's fire. 
 
 In the seacoast service, the length of recoil must be 
 limited to three or four calibres, on account of cover, as the 
 guns, if mounted in turrets, or similar places, have very lim- 
 ited space for working; and if mounted in barbette, a long 
 
454 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 recoil exposes the gun to hostile fire, and increases the time 
 between shots. For these reasons, brakes or buffers are 
 employed with modern guns. 
 
 CONDITIONS WHICH A GOOD BRAKE SHOULD FULFIL. 
 A good brake or buffer should fulfil the following conditions : 
 
 1. Its resistance should be constant at all times. 
 
 2. For the same piece, charge, and projectile, the length 
 of recoil should always be the same, which is a proof of the 
 regularity of its action. 
 
 3. It should be entirely automatic. 
 
 4. Its line of resistance should be as nearly as possible in 
 the line of action of the force producing recoil, so as to avoid 
 an overturning moment; and it must not interfere with the 
 movement of the gun to and from battery, and its manoeu- 
 vring. 
 
 CLASSES. Brakes are divided into two general classes: 
 
 1. Friction brakes. 
 
 2. Hydraulic brakes. 
 
 260. Friction Brakes for Seacoast Carriages Objections. 
 
 The various friction-brakes for field and siege carriages, 
 have already been explained. Those for seacoast carriages 
 consist generally of a series of plates, fixed to the chassis, 
 between each pair of which, slides a plate attached to the 
 top carriage. The plates are so arranged, that by means of 
 a screw or other device they may be pressed together, and 
 the friction due to this pressure limits the recoil. 
 
 Let P 9 represent the pressure at each surface in contact ; 
 n y the number of surfaces ; 
 S, the length of recoil in second period ; 
 f, the coefficient of friction ; 
 P, the weight of gun and carriage recoiling ; 
 V m ', the maximum velocity of recoil with brake acting. 
 Suppose the chassis horizontal ; then the work of fric- 
 tion of the plates, plus that of the piece and carriage, over 
 the path S, will be equal to the total energy of recoil. 
 Hence 
 
 PV '* 
 P )xS=-- (352) 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 455 
 
 In this equation, for a given value of S, everything is 
 known except P , and its value can be determined so as to 
 limit the recoil to a given length 5. 
 
 OBJECTIONS. The objections to friction-brakes are : 
 
 1. They oppose to the initial motion of the system, the 
 maximum resistance, when the velocity of recoil is greatest, 
 and hence the resistance is not uniform during the recoil. 
 
 2. The resistance is not constant for any two consecutive 
 shots, since it varies with the condition of the surfaces in 
 contact. For the first shot, if the surfaces are slightly rusty, 
 the resistance will be great; for succeeding shots, as the 
 surfaces become polished, the resistance decreases, and if 
 the surfaces be wet or lubricated, the resistance decreases. 
 All these causes necessitate a regulation of the pressure for 
 each shot. 
 
 3. The friction-brake is not automatic, as it has to be 
 undamped after each shot, to allow the gun to run in battery, 
 and has then to be clamped again before firing. Accidents 
 are liable to ocdur from this cause. 
 
 For these reasons the friction-brake has been abandoned 
 for seacoast guns, and is only retained in different forms in 
 field guns, where the weight of the hydraulic buffer, and its 
 liability to get out of order, would be objectionable. 
 
 261. Hydraulic Brakes General Description Classification Object 
 of Discussion. 
 
 GENERAL DESCRIPTION. This brake consists of one or 
 more cylinders filled with non-freezing liquid, and attached 
 either to the chassis, or to the top carriage. In modern 
 carriages the cylinders are generally two in number, and 
 are attached to the top carriage as near the axis of the gun 
 as possible, to increase the mass of the system recoiling, and 
 thus diminish its velocity; and also to bring the line of re- 
 sistance of the brakes as nearly as possible coincident with 
 the axis of the bore, and thus diminish the overturning 
 moment. 
 
 In each cylinder moves a piston, pierced with holes 
 parallel to the axis of the cylinder, and having a piston-rod 
 attached to the chassis. 
 
456 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 When the piece and top carriage recoil, the cylinders 
 move to the rear, and the liquid is forced through the holes 
 in the pistons. The resistance which the liquid opposes to 
 the motion of the pistons, limits the recoil. 
 
 CLASSIFICATION. There are two kinds of hydraulic 
 brakes in use : 
 
 1. Those with constant orifices and variable resistance. 
 
 2. Those with variable orifices and constant resistance. 
 OBJECT OF DISCUSSION. The principal points to be de- 
 termined in discussing a hydraulic brake are : 
 
 1. The length of recoil ; 
 
 2. The area of orifice ; 
 
 3. The pressure in the hydraulic cylinder; 
 
 4. For the hydraulic brake of constant resistance, the 
 law of variation of the areas of orifice, in order that the re- 
 sistance shall be constant. 
 
 In the discussion, the friction of the liquid is neglected, 
 as this is found in practice to be small. The flow, also, is 
 supposed to take place through a thin partition, so that the 
 contraction of the liquid vein may be neglected. 
 
 The velocity at the beginning of motion, is supposed to 
 be the maximum velocity of recoil. 
 
 262. Hydraulic Brakes with Constant Orifice and Variable Resist- 
 ance Nomenclature Value of Total Resistance Opposing 
 Recoil. 
 
 NOMENCLATURE. Let A be the effective area of cross- 
 section of the piston ; that is, the area of the piston minus 
 that of the piston-rod and orifices ; 
 
 a, the area of the orifices of flow ; 
 *V m ', the maximum velocity of recoil of the system ; 
 v f , the velocity of recoil at any time /; 
 v, the velocity of flow of the liquid through the 
 
 orifices at that time r 
 P, the weight of the system recoiling ; 
 a, the angle of inclination of the chassis to the 
 
 horizontal ; 
 
 #, the density of the liquid filling the cylinder 
 (weight of unit volume) : 
 
 * With the brake acting. 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 457 
 
 /, the coefficient of friction ; 
 F, the total resistance which opposes the recoil. 
 VALUE OF F. The total resistance, F, is composed of 
 two parts : 
 
 1. The resistance of the brake, F'. 
 
 2. The resistance due to the friction of the moving parts, 
 and the inclination of the chassis, F". 
 
 We have then 
 
 f=F';+-F" ....... (353) 
 
 The value of F" is 
 
 F" =P(sma+fcos<x) ..... (354) 
 
 The value of F', the resistance of the brake, is equal to 
 the total pressure exerted by the piston upon the liquid. 
 
 To determine this, we know from the law of continuity 
 of the fluid, that the volume of liquid displaced by the pis- 
 ton, must be equal to that which passes through the orifices 
 in it ; hence we have 
 
 va t ..... ... (355) 
 
 or 
 
 ....... (356) 
 
 This velocity v is that due to a height of fall 
 
 v = tf2gH\ , ...... (357) 
 
 and if we suppose a column of liquid whose constant height 
 is H and density #, it will produce a pressure per unit of 
 surface at its base, sufficient to cause the velocity of flow v. 
 Hence this is the pressure exerted per unit of surface by 
 the piston, upon the liquid, or it is the weight of a column 
 of liquid whose height is H, density tf, and area of base 
 unity. This pressure is 
 
 P=8Xff y ....... (358) 
 
 and the total pressure on the surface A of the piston is 
 
 pA = F' = <* X H X A, ..... (359) 
 
45 8 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 whence 
 
 "=- (360) 
 
 Substituting for v and If in (357) their values from (356) 
 and (360), we have 
 
 $A 
 
 from which 
 
 Substituting the values of F' and F" from (361) and (354) 
 in (353), we have for the value of the total resistance to 
 recoil 
 
 ). - (362) 
 
 263. Length of Recoil with Constant Orifice. 
 
 Dividing both members of equation (362) by M, we have 
 for the acceleration of recoil 
 
 Placing 
 
 2/V 
 and 
 
 ^(sin a +/cos ) = K, 
 we have 
 
 (364) 
 
 M*9 
 
 But 
 
 dx 
 
 ^/ 
 
 and 
 
 ' (365) 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 459 
 
 Whence 
 
 v'dv' 
 d *=~ ..... ' (366) 
 
 Integrating between the limits V m ' and v', 
 A-' v'dv' i (BV m " + 
 
 ./, - BV- + K =* = 1^6 log \^wr+ - (367) 
 
 Replacing B and K by their values, we obtain an 
 equation giving the relation between v' and x which is too 
 complex for general use. To simplify it, make 
 
 / = o, a = o, 
 
 which is equivalent to supposing that the brake acts alone, 
 without friction, and that the chassis is horizontal. 
 In this case we have 
 
 K=o; 
 and substituting this value of K in (367), we have 
 
 x ,, , ioff-T- (^68) 
 
 <L4 3 log e v' 
 
 When v' o, at the end of recoil, x = oo from equation 
 (368), which shows that the recoil will continue indefinitely 
 if the brake with constant orifices act without the aid of 
 friction. 
 
 264. Area of Orifice for a Given Length of Recoil with Constant 
 Orifices Pressure in Cylinder. 
 
 Since for v' = o, x = oo , we cannot find directly from 
 equation (368) the area of orifice which will limit the recoil 
 to a fixed length /. This area can, however, for all prac- 
 tical purposes be determined as follows: 
 
 Suppose that when 
 
 the remaining energy of the system becomes very small, and 
 the carriage is about to come to rest, and let / denote the 
 length of recoil for which v' = z//. Then, from (368), 
 
460 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 (MYloge 
 
 * = - -TF7 ..... (369) 
 
 2/> log -=- 
 
 ' ?'/ 
 
 for the area which will give the length of recoil /. 
 
 PRESSURE IN CYLINDER. The total pressure in the 
 cylinder at the beginning of recoil is, from (361), 
 
 (370) 
 
 and at any time at which velocity is z/ it is 
 
 and the pressure per unit of area will be 
 F* $A*VJ 
 
 2ga* 
 
 and 
 
 (372) 
 
 respectively. 
 
 265. Hydraulic Brake with Variable Orifices and Constant Resist- 
 ance Reason for Using it Objects of Discussion Value of 
 Total Resistance opposing Recoil. 
 
 REASON FOR USING BRAKE WITH CONSTANT RESIST- 
 ANCE. For the brake with variable resistance, equations 
 (372) show that the resistance is greatest when the velocity 
 of recoil is greatest. This is contrary to the first condition 
 imposed upon a good brake, and it evidently throws a great 
 strain upon the carriage. 
 
 For this reason these brakes are no longer used with 
 modern carriages, but are replaced by those whose orifice of 
 flow is large at first, so as to allow a free flow of liquid 
 when the velocity of recoil is greatest. As the velocity of 
 recoil decreases, and its length increases, the orifices of flow 
 are gradually closed automatically, and the resistance thus 
 made constant throughout the recoil. 
 
ARTILLERY CARRIAG ES THEORY OF RECOIL. 461 
 
 OBJECTS OF DISCUSSION. The objects of the discussion 
 are to determine 
 
 1. The length of recoil ; 
 
 2. The maximum area of the orifice of flow ; 
 
 3. The law of variation of the area of orifice in order 
 that the resistance shall be constant; 
 
 4. The constant pressure in the cylinder. 
 
 In this discussion, the first period of recoil, during which 
 the resistance is approaching its constant value, is neglected, 
 as being very short, and the resistance is supposed to be 
 constant from the beginning of recoil. 
 
 TOTAL RESISTANCE OPPOSING RECOIL. The nomen- 
 clature being the same as before, let <z be the maximum 
 area of orifice of flow, and suppose it to be also the initial 
 area. 
 
 Then we have, as in the case of the brake with constant 
 orifice, equation (354), 
 
 F" = P(sm a +/COS a) (373) 
 
 Also, equation (361), 
 
 dtfV" 
 
 F' = r~ (374) 
 
 2ga* 
 
 Since F 1 is constant by hypothesis, we must have for any 
 other values of v r and #, as V m f and a , 
 
 F' = 
 from which 
 
 F = F' + F" = f- + P(sin a + f cos a). (3/6) 
 
 266. Length of Recoil with Variable Orifice. 
 
 Dividing both members of equation (376) by M, we have 
 for the acceleration of recoil, as before (equation 363), 
 
 dv' F rdA'VJ* 
 
 (377) 
 
462 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 Integrating, 
 
 ~ /? A 3 J7 /a ~~1 
 
 iin a +/COS a) \t + C. (378) 
 
 When / = o, v' = FJ = C, hence 
 
 ,y^ ~ w sj P/y ^ lo\ '1^ / \ \O / ^// 
 
 Integrating again, 
 
 V /a ~1 
 
 , . (380) 
 
 which is of the same form as 
 
 h = vt - l -gt\ 
 
 and hence it is the equation of a uniformly retarded motion, 
 as it should be, since the resistance is constant. 
 
 When the recoil ceases v = o, and x = /, the total 
 length of recoil, and the corresponding time is, from (379), 
 
 V ' 
 T = * ~' ' ' 
 
 2 p a J + ^(sm a + f cos or) 
 
 and this value of T in (380) gives for the total length of 
 recoil 
 
 i I V '* I 
 
 * = /= 2 <M'F t " ' 
 
 2 p> + g (sm a + f cos a} 
 
 Equations (381) and (382) are similar to 
 
 v v* 
 
 t = h = 
 
 g tg 
 
 for bodies falling freely in vacuo, under the action of gravity, 
 as should be the case, since we have a constant force acting 
 in both cases. 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 463 
 
 Placing equation (382) in the form 
 
 sn a 
 
 we see that / increases as V m ' increases and as a decreases, 
 which should be the case. 
 
 267. Maximum Area of Orifice for the Brake with Variable Orifices. 
 
 To find the value of a , the maximum area of orifice in 
 this case, solve equation (382) for a*, and we have 
 
 6 /A 3 i 
 
 X 
 
 _ _ 
 2g-/(sin a+fcosa) ' 
 
 for the maximum area of orifice. 
 
 Suppose the chassis horizontal and the top carriage 
 mounted on rollers so as to avoid friction ; then 
 
 a = o, / = o, 
 and (384) becomes 
 
 6 1 A* 
 
 *:=-p- ......... (385) 
 
 The area of orifice in this case is independent of the 
 velocity of recoil, and hence we conclude that if the top 
 carriage be placed on rollers and the chassis be horizontal, 
 the length of recoil will be the same for a given area of 
 orifice, no matter what the initial velocity of the projectile, 
 charge of powder, or angle of fire may be. 
 
 268. Law of Variation of Areas of Orifice for Constant Pressure in 
 Cylinder. 
 
 The energy of the system at the beginning of recoil is 
 
 PV " 
 
 ; after passing over the length of recoil x, when the 
 
 > 
 
 /V 
 
 velocity is v' t the energy is - , and the work done over 
 
 c> 
 
 the path x is Rx, in which 
 
464 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 -- 
 
 ~ dt~g ~dT' 
 
 From mechanics, the original energy of the system is 
 equal to its remaining energy after passing over a given 
 path, plus the work done over that path ; hence 
 
 or 
 
 (387) 
 
 Since the resistance is constant and the recoil uniformly 
 retarded, we have from the laws of constant forces 
 
 (388) 
 
 Substituting this value of F w /a under the radical sign in 
 (387), we have 
 
 _7 (389) 
 
 Since F' is constant, we have, from (374) and (375), 
 
 J 2 = -^-^T- (390) 
 
 from which 
 
 Dividing through by V m f in (389) and substituting for 
 -j- its value from (391), we have 
 
 -j',- (392) 
 that is, the areas vary as the ordinates of a parabola. 
 
ARTILLERY CARRIAGES THEORY OF RECOIL. 465 
 
 These variable areas of orifice are obtained in different 
 ways, one of the methods adopted in our service being to 
 cut rectangular notches in the piston-head, and have bars 
 bolted to the sides of the hydraulic cylinders, parallel to the 
 axis, whose profile is such that at the origin the maximum 
 opening will be a . 
 
 269. Profile of Rib for Constant Pressure Maximum Pressure in 
 Cylinder. 
 
 The profile of the rib or throttling-bar will then be a 
 parabola. As the piston moves down the cylinder, the 
 areas of orifice will be gradually diminished so that the 
 pressure shall remain constant. 
 
 The equation of the parabola giving the profile of the 
 rib is determined as follows : 
 
 Suppose there are n similar notches in the piston-head. 
 
 The area of each one will be -. Let b and d be the breadth 
 
 n 
 
 and depth of each notch. The rib in the cylinder must 
 have the same breadth, b, and a variable depth, y. 
 
 Then for the area of an orifice at any time we have 
 
 = b(d- y\ .'. a = nb(d-y\ . . . (393) 
 and this value of a in (392) gives 
 
 for the equation of the curve of the profile of the rib. 
 
 PRESSURE IN CYLINDER. This is given by equation 
 (375)- 
 
 * a 
 
 <7=aconstant " ' ' (395) 
 
 and per unit of area 
 
 pi SA* V /a 
 
CHAPTER VIII. 
 POINTING; PROBABILITY OF FIRE. 
 
 POINTING. 
 270. Definitions. 
 
 POINTING. To point a piece is to give it such a direction 
 and elevation that the projectile, when fired, will hit the 
 object aimed at. 
 
 OPERATIONS. The pointing of a piece includes two dis- 
 tinct operations : 
 
 1. Giving the axis of the gun an elevation such that the 
 projectile shall strike at the proper distance, or range, from 
 the muzzle. 
 
 2. Giving the axis of the gun such a direction that the 
 projectile shall strike a given point or object at that distance. 
 
 SIGHTS. The instruments used in pointing are called 
 sights, and there are two of these for each piece : the front 
 sight and the rear sight. 
 
 Front Sight. This is fixed to the muzzle of the gun, or 
 to one of the rimbases, usually the right, and consists gen- 
 erally of a fixed point, or thin edge, or of cross-wires in a 
 tube, the point, edge, or cross-wires being at a definite dis- 
 tance above the axis of the bore, and if on the rimbase, at a 
 fixed distance to the right or left of that axis. 
 
 Rear Sight. This generally consists of a rod, bar, or 
 standard, graduated in degrees or ranges, and fixed in a 
 socket on the breech of the gun. This standard carries a 
 sliding notch or small hole, which is capable of being ad- 
 justed to any height on the rod, corresponding to a given 
 range or elevation, within service limits. The notch or hole 
 has also a motion at right angles to the axis of the bore, to 
 correct for wind, drift, and other causes of lateral deflection. 
 
 466 
 
POINTING PROBABILITY OF FIRE. 467 
 
 In Fig. 262 let A represent the front sight ; 
 OC, the rear-sight standard ; 
 EC, the sliding piece, which is supposed to 
 
 be at right angles to OC', 
 E, the rear-sight notch. 
 
 Triangle of Sight. Then the triangle OCE is called the 
 triangle of sight, and ECO is a right angle. 
 
 Zero of the Rear Sight. The point O, where the line OA, 
 drawn parallel to the axis of the piece through the top of 
 the front sight, intersects the axis of the rear sight. 
 
 Natural Line of Sight. The line OAB, parallel to the 
 axis of the piece, and passing through the zero of the rear 
 sight and the top of the front sight. 
 
 Sight Radius. The length of the line OA. 
 
 D 
 F 
 
 -O 
 
 FIG. 262. 
 
 Artificial Line of Sight. Any line, such as EAF, passing 
 through the notch of the rear sight and the top of the front 
 sight. 
 
 Natural and Artificial Planes of Sight. The vertical 
 planes containing the natural and artificial lines of sight 
 respectively. 
 
 Plane of the Rear Sight. The plane perpendicular to the 
 axis of the piece, containing the triangle ECO. 
 
 271. Cases which may occur in Pointing First Case Height of 
 Rear Sight Corrections for Drift. 
 
 CASES. The following cases may occur in pointing : 
 I. The axis of the trunnions may be horizontal, and the 
 
 target situated in the horizontal plane passing through the 
 
 centre of the muzzle. 
 
468 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 2. The axis of the trunnions may be horizontal, and the 
 target situated above or below the horizontal plane through 
 the muzzle. 
 
 3. The axis of the trunnions may be inclined, and the 
 target situated in the horizontal plane. 
 
 4. The axis of the trunnions may be inclined, and the 
 target situated above or below the horizontal plane. 
 
 The second case is the usual one for sea-coast guns, and 
 the fourth for field guns. 
 
 FIRST CASE. In Fig. 263 let 
 HB represent the line of fire projected on the vertical 
 
 plane ; 
 
 H'B' , the same line projected on the horizontal plane ; 
 D and /?', the target ; 
 
 CAD and F 'A ' D ', the projections of the artificial line of 
 sight on the vertical and horizontal planes respect- 
 ively. 
 
 Then CO is the height of the rear sight necessary to hit 
 the point D, and F'C' the correction for drift. 
 
 C A *, 
 
 t : 
 
 M 
 
 C' A' 
 
 FIG. 263. 
 
 If these distances be known for a given range MD, it is 
 evident that by fixing the rear sight with the proper eleva- 
 tion and drift, and giving the axis of the gun the direction 
 shown, the target will be struck. 
 
 To CALCULATE HEIGHT OF REAR SIGHT. In Fig. 263 
 let h be the height of the rear sight CO ; 
 
POINTING PROBABILITY OF FIRE. 469 
 
 /, the length of the sight radius OA ; 
 0, the angle of elevation >MD,the line MD being hori- 
 
 zontal ; 
 6, the angle CA O made by the natural and artificial 
 
 lines of sight ; 
 d, the angle MDG. 
 Then in the triangle MDG we have 
 
 MGD = BMD - MDG. 
 But the angle MGD = CAO = 6, hence 
 = - d. 
 
 The angle # is always very small, being the angle sub- 
 tended at the target by the vertical projection of the chase 
 of the gun from front sight to muzzle, and hence we have 
 
 or 
 
 tan = tan ; 
 but 
 
 hence 
 
 h 
 
 -y = tan0; .-. h I tan 0. . . . (397) 
 
 This value of h is laid off on the rear sight from the zero, 
 and gives the graduation corresponding to the angle 0. 
 CORRECTION FOR DRIFT. In Fig. 263 let 
 
 D denote the drift B'D'\ 
 
 d, the distance F' C' , or the correction for drift ; 
 
 #, the angle of drift, B'M'D'. 
 In the similar triangles F'A'C and N'A'D' we have 
 
 FT' N' D' N' D' 
 
 fj> = ^-F- t ; - F'C' = J = C'A'-^~ r . (398) 
 
 But 
 
 C'A' = CA, nearly, = T^TTT = zr" 
 
 cos CA cos 
 
 or, since == 0, 
 
 / 
 
 ~ COS 
 
47 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 The distance N' D' is very nearly equal to the drift B 'D 1 \ 
 and A' N' = M' B' , or the range R, very nearly. 
 Making these substitutions in (398), we have 
 
 ID 
 
 d =~R^^> (399) 
 
 272. Second Case. 
 
 In this case the axis of the trunnions is horizontal, and 
 the target above or below the horizontal plane through the 
 muzzle. 
 
 In Fig. 264 let D be the target situated above the hori- 
 zontal plane MD' r ; 
 0, the angle BMD\ 
 
 a, the angle of elevation of the target 
 above the horizontal plane. 
 
 M ^^-^=^^r- 
 
 . ' 1 * i . 
 
 D" 
 
 FIG. 264. 
 
 In the deduction of the equations of Exterior Ballistics,. 
 the horizontal plane MD" through the centre of the muzzle, 
 is alone considered, and all functions of the trajectory re- 
 ferred to this plane. 
 
 By the principle of the rigidity of the trajectory, the 
 curve may be revolved through a certain angle about a hori- 
 zontal axis passing through the point M, without changing 
 the relations between the curve, its ordinates and angles, 
 and the chord MD". 
 
 For all practical purposes the points M and A may be 
 considered as coinciding, and the revolution as taking place 
 about the latter point. 
 
 Hence if the proper elevation OC, and correction for 
 drift, be obtained from equations (397) and (399) for the range 
 MD" MD, on the supposition that the target is situated 
 on the horizontal plane, and then the gun be revolved about 
 the axis of the trunnions through the angle a, till the line 
 
POINTING PROBABILITY OF FIRE. 
 
 471 
 
 0' 
 
 of sight CA passes through the point Z>, the projectile will 
 hit the. target, since this is equivalent to revolving the 
 whole trajectory for the given range MD" through the angle 
 a. The same discussion applies to the drift, which is not 
 altered by the elevation of the target, but is the same for 
 the same range. 
 
 Hence, for this case, give the rear sight the same eleva- 
 tion and correction for drift as if the target were situated 
 on the horizontal plane through the muzzle, and then ele- 
 vate the gun till the artificial line of sight passes through 
 the target. 
 
 273. Third Case Errors Fourth Case. 
 
 THIRD CASE. In this case the axis of the trunnions is 
 inclined, and the target is in the horizontal plane through 
 centre of muzzle. 
 
 Let Fig. 265 be a section of the gun through the plane 
 of the rear sight, the axis of the bore being horizontal. The 
 zero of the rear sight, and top 
 of front sight, are projected 
 at O. 
 
 Let OC be the correct ele- 
 vation, and FC the correction 
 for drift, which will cause the 
 projectile to strike the target. 
 
 Suppose that, due to inequal- 
 ities of the ground or other 
 causes, the gun is rotated to the 
 right, about the axis of the bore, 
 through the angle (9. The zero 
 of the rear sight, and top of 
 front sight, will now be pro- 
 jected at O', and the new posi- 
 tion of the rear sight will be 
 O'C'F'. The axis of the bore 
 or line of fire has not changed 
 its position, and the gun, if 
 fired, will hit the target. But 
 if the gun be resighted before 
 firing, using the sights in their FIG. 265. 
 
47 2 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 revolved position, the artificial line of sight will no longer 
 pass through the target, and if it be made to do so, , this will 
 change the position of the line of fire, or axis of bore, and 
 the projectile will no longer strike the target. 
 
 ERRORS. By this rotation of the gun, the following 
 errors have been introduced : 
 
 i. Instead of having the proper vertical height of rear 
 sight equal to OC or O"C", it is equal to 0"C"' t or too 
 small. 
 
 This may be explained as follows : The front sight, and 
 zero of rear sight projected at <9, have been lowered verti- 
 cally by the rotation a distance O"O ; and since the height of 
 rear sight above the zero should remain unchanged, this 
 height should now be O"C" , equal to OC. But the rear- 
 sight notch is actually at a height O' f C'", and hence is too 
 low by the distance C"C'". 
 
 2. Instead of having the proper correction for drift FC, 
 we have F [V C', which is too small. 
 
 3. The artificial line of sight, before rotation occurs, 
 passes through the point F, and the top of the front sight 
 projected at O. Hence, looking from the rear, the line of 
 sight FO is oblique to the axis of the gun and diverges to 
 the right. 
 
 After rotation the artificial line of sight passes through 
 F', and the top of the front sight projected at O'. Hence, 
 looking from the rear, this new line of sight F'O' is oblique 
 to the axis of the gun and diverges to the left. If, therefore 
 the gun were correctly pointed before rotation, and be re- 
 pointed after rotation, the projectile will deviate to the 
 right. 
 
 This latter error is shown in plan, the same letters being 
 used. It is of very frequent occurrence in small-arms firing, 
 when the rear sight is not held vertically, the bullet deviat- 
 ing to the side toward which the sight is inclined. 
 
 To avoid these errors it is necessary to construct the 
 rear sight so that its standard or upright will rotate about 
 the point O. By means of a spirit-level fixed at right angles 
 to the axis OC, this axis can always be kept in a vertical 
 plane. With this arrangement, whenever the front sight 
 
POINTING PROBABILITY OF FIRE. 473 
 
 and the zero of the rear sight are lowered vertically through 
 a distance O"O, by rotation due to the inequality of the 
 ground or other causes, the notch of the rear sight will be 
 lowered the same amount, the vertical heights OC and O'C" 
 and the correction for drift remaining unchanged. This 
 arrangement is made in all field-gun sights. 
 
 With this arrangement of the sights the pieces are pointed 
 as in the first case. 
 
 FOURTH CASE. In this case the axis of the trunnions 
 is inclined, and the target above or below the horizontal 
 plane. 
 
 If the standard of the rear sight rotates about the zero, 
 as explained, the pointing is executed as in case two. 
 
 FIG. 266. 
 
 274. Permanent Angle of Drift. 
 
 Referring to Fig. 263, it is evident that the drift increases 
 more rapidly than the range, and hence each range requires 
 a special correction for drift. It is found, however, that 
 within certain limits of error, a permanent correction may 
 be made for drift, by giving the rear-sight standard an in- 
 clination to the left at a certain angle i with the vertical. 
 This applies only to small arms where the barrel can be 
 held with the front sight vertical, and to guns with fixed 
 platforms, where the axes of the trunnions are horizontal. 
 For field-guns, as before explained, the standard of the rear 
 sight is kept vertical. 
 
 To determine this permanent angle, in Fig. 266 
 
 let i = the angle FOC required ; 
 h = OC, the height of rear sight ; 
 d FC, the correction for drift , 
 1= OA, the length of the sight radius; 
 
474 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 = the angle of elevation BAD ; 
 e the angle DAD'. 
 
 Then in the triangle FOC we have 
 
 d = h tan i ; 
 but from (397), 
 
 h = /tan ; 
 
 hence 
 
 d = I tan tan i, 
 
 tan i -7 ....... (400) 
 
 / tan 
 
 From the triangle OA C we have 
 
 AC=tsec0, ...... (401) 
 
 and from FAC, 
 
 d AC tan e, 
 or from (401), 
 
 d I sec tan *;.,,. (4010) 
 but from the figure, 
 
 drift 
 
 tan e = -^-^ = 
 
 AD range 
 
 hence in (4010) 
 
 d = /sec 0-77, ..... (402) 
 
 Z> denoting the drift and ^ the range. 
 
 Substituting this value of d in (400), we have 
 
 It is known from Exterior Ballistics that sin increases 
 more rapidly than the range, and so also does D. Hence 
 these variations partly correct each other and tend to make 
 the angle i constant, and hence this constant correction for 
 drift can be applied without great error. For long ranges, 
 however, this correction is only partial, and an additional 
 one must be made with the sight. 
 
POINTING PROBABILITY OF FIRE. 4/5 
 
 From equation (403) the amount of drift corrected for by 
 
 this method is 
 
 D R sin tan i ; 
 
 if any greater drift exists, as D', the difference, 
 
 D f D = D' R sin tan i, 
 
 \ 
 must be corrected for by the sight. 
 
 275. Indirect Pointing. 
 
 When the target cannot be seen from the gun, the above 
 methods must be modified. 
 
 The simplest case is that of mortar -firing, where the tar- 
 get is invisible from the piece, but may be seen from the 
 parapet of the emplacement. In this case the plane of sight 
 is established by plummets suspended from trestles, the ele- 
 vation given approximately, and the mortar moved or trav- 
 ersed, till the planes of fire and of sight coincide. 
 
 The second case is where the target cannot be seen from 
 the battery, but is visible from some place sufficiently near 
 to communicate with the battery. In this case an observer 
 watches the point of fall, and signals to the battery its posi- 
 tion as to range and deviation. The aim is then corrected, 
 and this is continued till the target is struck. An auxiliary 
 mark, which is visible from the gun, is selected, and the sights 
 directed upon this mark before each shot. When the target 
 is struck, the piece is thereafter sighted upon this auxiliary 
 mark, without changing the sights as adjusted for that shot. 
 If a suitable mark cannot be obtained, the bearing of the 
 target may be observed by a compass. Then by placing 
 the compass in rear of the gun, the bearing of the target may 
 be laid off by stakes and the gun directed upon them, the 
 firing being corrected by an observer. 
 
 In some services sights are arranged so that they may 
 be reversed in position ; that is, the rear sight is placed in 
 the position ordinarily occupied by the front sight, and the 
 latter replaces the rear sight. (See /-inch howitzer sight, 
 page 493.) In this case the marking stake or stakes are 
 placed in rear, and the sights directed upon them. Reflect- 
 ing sights are also used when cover is of importance, and 
 
TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 for turrets, the sights are placed on the exterior, and at the 
 opposite extremity of the diameter upon which the gun is 
 situated. While the turret is revolved 180 for loading, the 
 sighting is effected, and when the gun is loaded, a traverse 
 of 1 80 brings the gun into firing position. 
 
 276. Causes of Deviations in Pointing Effect of Wind. 
 
 CAUSES OF DEVIATIONS. When a gun is correctly 
 pointed, as explained, the projectile should pass through 
 the target. This, however, does not occur unless further 
 corrections be made to eliminate other causes of error. 
 
 The principal of these are : 
 
 1. The effect of the wind. 
 
 2. Errors in estimating distance to target. 
 
 3. Effects of light on sights. 
 
 4. Personal errors of the eye. 
 
 5. Errors in height of front and rear sights. 
 
 6. Motion of target. 
 
 7. Rotation of the earth. 
 
 8. Variations in ammunition. 
 
 9. Jump. 
 
 EFFECT OF WIND. The effect of wind is to increase or 
 decrease the range, according as it is blowing from rear to 
 front, or from front to rear, and to increase or decrease the 
 drift of the projectile. 
 
 The velocity of the wind is generally expressed in miles 
 per hour, and is obtained from an anemometer. A vane or 
 other indicator gives its direction. Let W be the velocity 
 of the wind in miles per hour, and <p the angle which its 
 direction makes with the line of fire. The angle is meas- 
 ured from front to rear, being zero when the wind blows 
 directly from the front along the line of fire. 
 
 Then the component which increases or decreases the 
 range is W cos 0, and that which increases or decreases 
 the drift is W sin 0. 
 
 The effect upon the increase or decrease of range is ob- 
 tained by reducing W to feet, and regarding the projectile 
 as having a velocity equal to v + W cos or v W cos 0. 
 
POINTING PROBABILITY OF FIRE. 
 
 Using these values for v in the ballistic formulas, the effect 
 of the wind along the range can be calculated. 
 
 The component which produces deviation is W sin 0. 
 Various formulas are given for calculating its effect, but the 
 subject is very difficult. 
 
 When the wind is blowing from the left, its relative mo- 
 tion with respect to the projectile is less because the latter 
 is moving in the same direction. When it blows from the 
 opposite direction the reverse is the case. To correct for 
 lateral deviation due to wind, the drift-slide is set towards 
 the wind. That is, if the wind is from the left, the slide is 
 moved to the left. 
 
 For small-arm firing, the direction of the wind is ex- 
 pressed by a clock-face notation, the clock being supposed 
 to be held in the hand of the firer, with the Xll-o'clock 
 mark toward the target and the Ill-o'clock mark to the 
 right. A wind blowing directly from the target is called a 
 Xll-o'clock wind ; one directly from the left, a IX-o'clock 
 wind, etc. 
 
 Assuming the force of the wind as unity, a table is given 
 in the "Rifle and Carbine Firing," showing the proportions 
 of the rectangular components of the different winds, and it 
 is found practically, that the lateral deflections produced by 
 them are proportional to these components. 
 
 The amount of lateral deviation produced by a wind 
 blowing at right angles to the line of fire, with a velocity of 
 one mile per hour, is called the coefficient of deviation. 
 Calling this coefficient k, we have for any wind whose 
 velocity is W, and which makes an angle with the line of 
 fire, for any given range, 
 
 D kWsiu 0. 
 
 The relation between k and R must be determined by 
 experiment. 
 
 277. Estimating Distances By the Eye By Sound Le Boulenge" 
 Telemeter. 
 
 It is evident that unless the distance of the target be 
 known, the proper elevation and correction for drift cannot 
 
47 8 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 be given, since these depend on the range. In actual opera- 
 tions the distance of the target is seldom known. For sea- 
 coast guns, the channel or harbor is surveyed and plotted, 
 and buoys may be planted at different known distances. In 
 siege operations, the distance of the target may be obtained 
 by observations with various instruments of precision ; but 
 for field artillery, where time is lacking, the distance must 
 be obtained rapidly by estimation, by range-finders, or by 
 trial shots. 
 
 Distances may be estimated 
 
 1. By the eye ; 
 
 2. By sound. 
 
 BY THE EYE. This method requires considerable prac- 
 tice to obtain results of any accuracy. For short ranges 
 the eye may be trained by trial, by observing carefully 
 the appearance presented by known objects at different dis- 
 tances, such as the height of a man, the parts of his dress, 
 etc., which are visible at those distances. Each individual 
 must form a standard of comparison for himself; and since 
 this method is only applicable for relatively short distances, 
 it is of more importance for small-arm fire. 
 
 Objects vary in appearance according to the nature of 
 the ground, being apparently nearer for level ground ; also 
 on a clear day, or with a distinct background, they appear 
 nearer than under opposite conditions. 
 
 BY SOUND. This method is based on the fact that 
 sound travels about i TOO feet per second in air. Hence, if 
 the time in seconds be noted between the flash and the re- 
 port of a gun, or between the flash and the report of a shell 
 fired from the battery, the distance is obtained by multiply- 
 ing the time in seconds by noo feet. This time may be 
 measured by a stop-watch, or by counting the number of 
 steps taken in the interval, and knowing the number of 
 similar steps which the observer takes per second. 
 
 LE BOULENGE TELEMETER. An instrument called the 
 Le Boulenge telemeter is used for measuring distances by 
 sound. It consists of a glass tube filled with liquid, in 
 which a disk is placed, whose specific gravity is slightly 
 greater than that of the liquid. When the tube is held ver- 
 
POINTING PROBABILITY OF FIRE. 
 
 479 
 
 tical, the disk falls through the liquid with a motion which 
 is nearly uniform. To use the telemeter, the tube is held 
 horizontal, with the disk at zero. When the flash is seen, it 
 is turned quickly to a vertical position ; when the report is 
 heard, it is turned back to a horizontal position. A scale on 
 the tube gives the range directly, corresponding to the dis- 
 tance passed over by the disk. 
 
 It is evident that it would be difficult in practice to 
 observe the burst, and hear the report of any particular 
 shell. 
 
 278. Range-Finders Principle Class 1. 
 
 The estimation of distances by the eye and by sound 
 being so inaccurate, instruments called range-finders or 
 telemeters have been devised to measure the distance to the 
 target. 
 
 FIG. 267. 
 
 PRINCIPLE. In Fig. 267 let C be the target. 
 
 In the isosceles triangle ADC, if the angles at A and D, 
 and the base AD, are known, the angle ACD can be found, 
 arftl we have 
 
 BC = 
 
 tan A CD' 
 
 or in the right-angled triangle ABC or BCD, if the angle 
 .at A or D be known, we have 
 
 BC= 
 
4^0 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 or 
 
 AB 
 
 AC = 
 
 sin ACS' 
 
 The object of these instruments is to measure rapidly 
 and accurately the angles A and D. 
 
 To avoid calculations, the angles A and D are so chosen 
 that the value of the tangent or sine of C shall be some sim- 
 ple number, as j 1 -^, J^-, ^, etc. ; or the angles may vary and 
 the base have a fixed value, the corresponding multipliers 
 being inscribed on the instrument. 
 
 This divides the instruments into two general classes 
 
 1. Those having fixed angles and variable bases ; 
 
 2. Those having variable angles and fixed bases 
 
 FIG. 268. 
 
 and a third class which combines the qualities of the two 
 above, viz., 
 
 3. Those having variable angles and variable bases. 
 
 CLASS i. In this class of range-finders the base is pro- 
 portional to the range. This gives greater accuracy, as 
 with a small base, a slight error in measurement of either 
 angles or base leads to a large error in range. The general 
 idea of this class of instruments is as follows : Two mirrors 
 are fixed at an angle, say, of 44 if (Fig. 268). A ray of 
 light striking one of these mirrors is reflected twice, and 
 according to a well-known principle of optics, the ray, after 
 two reflections, makes with the original direction of the inci- 
 
POINTING PROBABILITY OF FIRE. 481 
 
 dent ray, an angle of 88 34', or twice the angle of the 
 mirrors. An observer standing at A and looking toward />, 
 sees /? directly, and by reflection in the mirrors, makes the 
 image of C coincide with B. The point A is then marked 
 by a stake. Moving to B, which must be found by moving 
 along AB and looking towards A, the reflection of C is 
 made to coincide with A. The angle at C is then 
 
 1 80 -2 X88 34' = 2 52', . 
 and measuring AB we have 
 
 _ 
 
 SSlFSff 7T 
 
 = 40 X \AB = 2oAB. 
 
 FIG. 269. 
 
 279. Range-finders Class 2 Class 3 Depression Range-finders 
 Range and Position Finder. 
 
 CLASS 2. In this class we have a fixed base and a variable 
 angle. To save time, the instruments are generally adjusted 
 so that the range can be read off at once. As the measure- 
 ments must be very accurate, telescopes are often used to 
 measure the angles, and this necessitates a very accurate 
 mounting and increases the difficulty of transportation. 
 
 CLASS 3. These instruments can be used by either 
 method, but the variable base is generally preferred. 
 
 DEPRESSION RANGE-FINDERS. Let AB, Fig. 269, repre- 
 sent the vertical height of a gun, or of a range-finder, above 
 the surface of the water, and C an object, such as a ship, 
 whose distance is to be determined. If the angle C'BC be 
 -measured, and the height AB be known, it is evident that 
 the distance BC can be determined as before. These instru- 
 
482 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 ments are called depression range-finders, the angle being 
 measured in a vertical plane. 
 
 RANGE AND POSITION FINDERS. In sea-coast batteries 
 it is often necessary to fire at objects, such as ships, which 
 cannot be seen from the guns. In this case it is necessary 
 to find not only the range but also the position of the object, 
 which is generally in motion, in order to hit it at any given 
 time. An instrument used lor this purpose is the Fiske 
 Range and Position Finder, invented by Lieut. Fiske of the 
 U. S. Navy. 
 
 FIG. 270. 
 
 FIG. 271. 
 
 280. The Fiske Range-finder. 
 
 In Fig. 270 let A represent the target, and BC a known 
 base. Then 
 
 AC: BC:: sin ABC : sin BAC. 
 
 sin BAC 
 
 The angle ABC can be readily measured. The angle 
 BAC=- DBE, the line BE being parallel to AC. The Fiske 
 Range-finder measures the angle DBE by the use of the 
 Wheatstone bridge, as follows : 
 
 Suppose the two semicircles in Fig. 270 replaced by two 
 metallic arcs (Fig. 271). At the centre of each of these arcs 
 
POINTING PROBABILITY OF FIRE. 483 
 
 is pivoted a telescope, the pivot of which is connected to a 
 battery, B. The telescopes are in electrical contact with 
 the arcs. These metallic arcs are connected at their ex- 
 tremities with a galvanometer, c, the whole forming a 
 Wheatstone bridge, whose arms are aabb. 
 
 When the two telescopes are pointed on the object A, 
 it is evident that the arms of the bridge are unequal, and 
 hence do not balance, and this fact is indicated by the de- 
 flection of the needle of the galvanometer. The arc FD is 
 noted. 
 
 By swinging the telescope at F, around, till the needle of 
 the galvanometer indicates zero, the bridge balances, the tele- 
 scope being parallel to the one at C, and the arc or angle 
 DF FE DE is equal to the angle at A. From this the 
 distance AC can be calculated, or be read off directly on a 
 properly constructed scale. 
 
 Generally, in using the instrument, the telescopes are 
 mounted at a distance from the battery where the view is 
 uninterrupted, while the galvanometer is at the gun. The 
 observers keep the telescopes constantly directed on the 
 target, and the man at the gun balances the bridge, by intro- 
 ducing a variable resistance into the circuit, till the needle 
 stands at zero. This variable resistance is graduated so as 
 to indicate the range corresponding to the resistance in- 
 troduced. 
 
 281. The Fiske Position-finder Range by Trial Shots. 
 
 To find the position of the object, the Fiske Range- 
 finder is modified as follows, Fig. 272. 
 
 Let A and B be the arcs with their telescopes as de- 
 scribed, and D a chart drawn to scale, on which are two 
 metallic arcs, A' and B' . The arc A' is connected electri- 
 cally with A and with a galvanometer, A", forming a 
 Wheatstone bridge, and in the same way the arc B' is con- 
 nected with B, and with the galvanometer, B". The arc A' 
 carries a metallic rule, AC', pivoted at the centre of the arc, 
 and B 1 a rule, B'C', similarly pivoted. 
 
 When the rule AC is parallel to the telescope at A, the 
 galvanometer A" is at zero. When B'C' is parallel to the 
 
484 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 telescope at B, the galvanometer B" is at zero. Hence their 
 intersection C' marks the position of the object on the chart. 
 Let G be the gun in battery, and G f its corresponding posi- 
 tion on the chart. The gun has a metallic arc with which a 
 pointer is in contact, and the arc G' has a metallic rule, G 'C ', 
 in contact with it. The gun G with its arc and pointer, and 
 the metallic rule G ' C ', are electrically connected with a gal- 
 vanometer, G", near the gun, forming a third Wheatstone 
 bridge. It is evident that by traversing the gun in azimuth 
 till its axis is parallel to the rule G'C, the galvanometer G" 
 
 FIG. 272. 
 
 will indicate zero, and the gun will have the proper direc- 
 tion. The elevation may be telephoned from the observing 
 station, or else the gunner, knowing the range and direction 
 of the object, may take the elevation directly from a range 
 table. Other arrangements of the same nature may be 
 made with this instrument, using the principle of the 
 Wheatstone bridge. 
 
 RANGE BY TRIAL SHOTS. Owing to various causes, 
 
POINTING PROBABILITY OF FIRE. 485 
 
 the determination of distances in the field by range- 
 finders is attended with difficulty, and the method actually 
 adopted in all services is that by trial shots. Two plans are 
 used. 
 
 In the first a percussion-shell is fired with an elevation 
 which will cause it to strike short of the target. The point 
 of fall is observed. A second shell is then fired with an 
 elevation which will cause it to strike beyond the target. 
 Its point of fall is also observed. The target is then en- 
 closed in a fork. 
 
 Taking a mean of these two elevations will give a still 
 closer approximation. If this shot falls short, a mean of 
 this elevation and of that beyond will give another approx- 
 imation, and so on. ' 
 
 By this means the range is soon found. 
 
 The second method is to fire the first shot short, and 
 then increase the elevation slightly, and so on by succes- 
 sive increments till the proper range is attained. The diffi- 
 culty is in observing accurately the point of fall for long 
 ranges. 
 
 282. Effect of Light Errors of the Eye Errors in Height of Front 
 and Rear Sights. 
 
 ERRORS DUE TO LIGHT. In clear weather shots usually 
 fall short, since, in a bright light, objects appear nearer, and 
 the distance is underestimated, and, in addition, a finer sight 
 is taken, owing to the distinctness of the front sight. The 
 converse is true on a dark day. With regard to lateral 
 deviation, if one side of the sight is brighter than the other 
 the deviation will be from the light. 
 
 ERRORS OF THE EYE. These vary with different indi- 
 viduals, and must be corrected by training. 
 
 ERRORS IN HEIGHT OF FRONT AND REAR SIGHTS. In 
 the previous discussions it has been assumed that the zero 
 of the rear sight, and the top of the front sight, are at the 
 same distance from the axis of the piece. If this be so, the 
 natural line of sight is parallel to the axis of the piece in all 
 positions, and hence the vertical plane containing this line 
 is likewise parallel to the plane of fire in all positions. 
 
486 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 A-~~ 
 
 If, however, the height of the front sight is not the same 
 as that of the zero of the rear sight, an error is introduced* 
 To show this, in Fig. 273 let A and B 
 be the vertical projections of the rear 
 and front sights, respectively, and AB 
 the horizontal projection of the natu- 
 ral line of sight when the axis of the 
 trunnions is horizontal. 
 
 Suppose that, due to inequalities of 
 the ground, the axis of the trunnion is 
 revolved through the angle 0. 
 
 Then A' and B' will be the verti- 
 cal projections of the rear and front 
 sights, and A' B' the horizontal projec- 
 tion of the natural line of sight. This 
 line is now inclined, in its revolved 
 position, to the axis of the piece, and 
 hence in the revolved position the 
 plane of sight will intersect *he plane 
 of fire. Hence, to an observer behind the gun, if the line of 
 sight be directed on the target T, the gun will shoot to the 
 left. 
 
 This error is similar to that discussed in subject 273. In 
 that case it can be removed by keeping the rear sight verti- 
 cal. The error in the present case can only be removed by 
 making the heights of front sight and of zero of rear sight 
 equal. 
 
 283. Motion of Target Rotation of the Earth Variations in 
 Ammunition. 
 
 The target may move directly toward or from the gun, 
 at right angles to the line of fire, or oblique to that line. As 
 the last case includes both the others, it will be considered. 
 
 Let AB, Fig. 274, be the line of fire, and BC the direction 
 of motion of the target, making the angle with the line of 
 fire. Suppose the range AB and the rate of motion of the 
 object known. 
 
POINTING PROBABILITY OF FIRE. 487 
 
 During the time that the projectile is moving over the 
 distance AB the object has moved over the distance BC. 
 Let v denote the velocity of the object and t the time of 
 flight of the projectile ; then 
 
 BC = vt. 
 
 Suppose the correction for drift to be such as to cause 
 the projectile to strike at B. Then to hit the object the 
 correction should be made to cover the additional distance, 
 
 D + CC = D + vt sin 0, 
 
 in a direction toward the motion of the target. If this 
 motion is not known it must be estimated. 
 
 This will still leave a small error in range BC' = vt cos 
 which must be compensated for by a slight increase in ele- 
 
 B C' 
 
 FIG. 274. 
 
 vation, or by retaining the elevation corresponding to AB 
 and aiming beyond the target the estimated distance BC'. 
 
 ROTATION OF THE EARTH. This is not generally taken 
 into account. Its effect in the northern hemisphere is to 
 cause projectiles to deviate to the right. 
 
 VARIATIONS IN AMMUNITION. The effect of increasing 
 the charge and density of loading is to increase the initial 
 velocity. That of increasing the weight of the projectile is 
 to decrease this velocity, as has already been shown in Inte- 
 rior Ballistics. With modern guns these variations in 
 ammunition are very slight, and their effects may be neg- 
 lected. Variations in moisture also affect the initial velocity, 
 
488 TEXT- BOOK OF ORDNANCE AND GUNNERY. 
 
 a damp powder giving less velocity and a dry powder 
 greater velocity, for the reasons previously explained. 
 
 Also the heating of the bore increases this initial velocity, 
 since less heat is lost by the gases. 
 
 284. Jump. 
 
 This error is caused by the motion of the gun upon 
 discharge, due to the elasticity of tke parts of the carriage, 
 the lack of accurate fitting of gun to carriage, the vibration 
 of the chase, etc. It varies with different guns and car- 
 riages, and is determined by experiment for any particular 
 gun as follows: 
 
 In Fig. 275 let AB be a vertical screen or target, placed 
 
 FIG. 275. 
 
 at such a distance from the muzzle of the gun O that it will 
 not be affected by the blast. Let OB be the axis of the bore, 
 supposed horizontal. The point B where the axis of the 
 bore prolonged pierces the target is found by inserting a 
 disk in the breech of the gun with a small peep-hole in the 
 centre, and placing in the muzzle a pair of cross-hairs whose 
 intersection is at the axis of the bore. Looking through 
 the peep-hole and at the cross-hairs, the point B is marked 
 on the target. When the gun is fired, suppose OA to be the 
 line of departure. Then AOB is the angle of jump required. 
 The projectile will strike the target at some point C. From 
 the triangle AOB we have 
 
 AB AC+CB 
 
 tan AOB = 
 
 OB~ OB 
 
POINTING PROBABILITY OF FIRE. 489 
 
 From the laws of falling bodies we have 
 
 (403*) 
 
 For the short distance OB we may regard the velocity 
 of the projectile as uniform. Denoting this velocity by v t 
 and the distance OB by a, we have 
 
 This value of / in (4030) gives 
 
 The distance BC to the centre of shot-hole C can be 
 measured ; calling this b, we have, for tan AOB, 
 
 tan AOB =, + - 
 
 2v* ' a 
 
 in which the second member is known, since v can be calcu- 
 lated by Exterior Ballistics. 
 
 If the shot does not strike vertically above B y there will 
 
 -i c 
 
 be a lateral deviation c t whose measure is tan . 
 
 a 
 
 If OB is not horizontal, the same principle applies, the 
 triangle A OB being an oblique, instead of a right-angled tri- 
 angle. 
 
 285. Description of Sights for 8, 10, and 12 Inch Seacoast Guns. 
 
 These guns have two sets of sights. The first set, AA' t 
 Fig. 276, is on the middle element of the reinforce, and 
 consists of a simple rear-sight notch, A, and a conical front 
 sight, A r . They cannot be used for elevations, and are for 
 catching the target readily, and giving the general direc- 
 tion. 
 
490 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 The second set, BB ', Fig. 276, is placed on the left 
 side of the gun, as shown, and are on this side so as to be 
 
 FIG. 276. 
 
 out of the way of loading, and so that the gun may be 
 sighted while the charge and projectile are being inserted. 
 
 The rear sight, Fig. 277, slides 
 through a bronze socket, C, bolted to 
 the breech-plate. This socket is in- 
 clined to the left at the permanent drift 
 angle, which is 2 30' for the 8-inch gun, 
 2 45' for the lo-inch, and 3 oo' for the 
 12-irich. It is prolonged upward a dis- 
 tance ab, to give increased support and 
 steadiness to the sight. 
 
 The socket carries a worm, c, which 
 engages in a corresponding thread, </, in 
 the right-hand edge of the sight. This 
 worm is worked by a hand-wheel, e, and 
 pinion, /, and the hand-wheel e is held 
 in place, and motion prevented, by a 
 clamping-wheel, e" . The functions of 
 the worm are to raise and lower the rear 
 sight, and to hold it fixed in any given 
 position, so that it will not be moved by 
 the shock of firing. 
 
 The sight consists of a hollow steel 
 bar, B, one inch square, graduated in 
 degrees, and each degree into six parts. 
 The smallest reading on the sight is 
 therefore 10 minutes. The top, a, of the 
 divided into 10 equal parts, and the 
 
 FIG. 277. 
 bronze socket, C, is 
 
POINTING PROBABILITY OF FIRE. 49! 
 
 divisions on the sight are diagonal, so that by means of the 
 scale on the socket, each of these graduations on the sight, 
 can be divided into ten equal parts, giving one minute for 
 the least reading. 
 
 The top or head of the sight, consists of a deflection-bar, 
 g, with a vertical projection, carrying a notch, i, and a peep- 
 sight, 2. The notch is used in connection with the top of 
 the front sight, to catch the target quickly, and the peep- 
 sight with the cross wires of the front sight, for final adjust- 
 ment. The deflection-bar, -, has a horizontal sliding motion 
 through the top of the rear-sight bar, to correct for wind, 
 drift, and other errors, and is clamped in any position by 
 the clamp-screw h. It is graduated as shown, each gradua- 
 tion being y^ o" f tne ran ge. 
 
 For deflection to the left, the bar is used in the position 
 shown. For deflection to the right the small pin x is pushed 
 in, the bar entirely removed from its socket, and reinserted 
 from the right, the graduations being the same on the re- 
 verse side. 
 
 The right-hand side of the sight-bar, contains a portion, 
 of a screw-thread d, into which gears the 
 worm, c, for raising and lowering, as 
 before explained. 
 
 The front sight B' , Fig. 278, consists 
 of two truncated cones, with the smaller 
 bases together at the middle, and carry- 
 ing two flat steel cross ribbons, w, halved 
 into each other. It has also a top sight FlG - 278 - 
 
 /, which is used with the open notch of the rear sight B. 
 
 286. Gunner's Quadrant for Mortars. 
 
 When the angle of elevation exceeds 15, the rear sight 
 above described, becomes so long as to be difficult to handle 
 and it may bend under its own weight, so as to cause in- 
 accuracy in aiming. 
 
 The target, also, in such cases, is not generally visible from 
 the gun or mortar, and for these reasons the rear sight is 
 not used. To give the necessary elevation in such cases, 
 and for mortar-fire generally, the gunner's quadrant is used. 
 
492 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 This consists, Fig. 279, of the body a, and a movable 
 arm, b. 
 
 The body is made of bronze, and carries an arc graduated 
 on one side from o to 44, and on the opposite side from 
 45 to 89. On the inside edge of the graduated arc are 
 
 FIG. 279. 
 
 teeth c, each of which corresponds to one degree. An arrow 
 is marked on each side of the body, and when the quadrant 
 is in use, the arrow on the side on which the reading is taken 
 must always point in the direction of the target. 
 
 The movable arm, b, is pivoted to the body at d. 
 
 This arm has a small toothed sector, e, which is acted on 
 by a spiral spring, contained in the arm, and by which the 
 sector is pressed outward, so that its teeth will remain 
 engaged with those of the graduated arc. The upper sur- 
 face of the movable arm, b, is the arc of a circle, and on this 
 arc rests a level, /. This level bears on the arm at two 
 points only, and is of such a length that when moved along 
 the arc from its zero-point, to its extreme position at the 
 other end of the arm, the angle moved over is one degree. 
 
 The arm is graduated in minutes. 
 
 Degrees are read on the graduated arc, and minutes by 
 the scale on the movable arm. 
 
POINTING PROBABILITY OF FIRE. 
 
 493 
 
 To Use the Quadrant. Suppose the elevation to be 
 20 1 8'. 
 
 Press back the toothed sector, e, and move the arm, b y 
 till its index is opposite the 20 mark on the graduated arc. 
 
 Slide the level,/, along the movable arm, b, till its index 
 is opposite the 18' mark on the arm. The quadrant is now 
 set to 20 iS'. 
 
 Place the side, ;#, on the flat surface prepared for it, near 
 the breech of the gun, or the side, m' ri , against the face of the 
 muzzle, being careful to keep the side on which the reading 
 is taken, to the left, and the arrow, 0, pointing toward the 
 target. Elevate the piece till the bubble in the level comes 
 to rest in the centre. For any elevation greater than 45, 
 as 60 33', use the graduations on the other face of the arc, 
 and the scale on the movable arm as above. 
 
 The other side of the quadrant must now be turned to 
 the left, and the arrow on it pointed toward the target. 
 Elevate the gun as before. 
 
 287. Sights for Siege Artillery For 7-inch Howitzer. 
 
 The sight for the 5-inch siege-gun, is exactly similar to 
 that for the 3.2 field-gun to be described. That for the 
 7-inch mortar is the gunner's quadrant already described. 
 
 SIGHT FOR /-INCH HOWITZER. This piece has a com- 
 paratively low initial velocity, and curved fire. Hence the 
 sight for this gun should give a large scale for correcting 
 lateral deviations, as they will be greater than for the siege- 
 gun, which has a high velocity. 
 
 FIG. 280. 
 
 Being fired from a fixed platform, the inclination of the 
 trunnions may be neglected, in comparison with the errors 
 due to low velocity, and hence the standard does not rotate 
 
494 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 about its zero-point, so as to remain always in a vertical 
 plane. 
 
 For the 5-inch siege-gun, its high velocity renders it 
 more accurate, and although it is fired from a fixed plat- 
 form, and the inclination of the trunnions is consequently 
 small, any error due to this cause is eliminated by the rota- 
 tion of the rear-sight standard. 
 
 Position. The sights for the /-inch Howitzer, (Fig. 280), 
 are placed on the right side of the piece, the rear sight, A, 
 in a hole drilled through the rear end of the jacket, and the 
 front sight, B, on the right rim-base. 
 
 The Rear Sight. A hole, (Fig. 281), is drilled in the 
 jacket, in which fits a socket, b, 
 held in place by a set-screw, c. The 
 sight is a round steel rod, a, made 
 flat on the rear side, which con- 
 tains the graduations in degrees, 
 and the usual diagonal scale. 
 
 This rod fits accurately in the 
 socket b, and carries a sliding collar, 
 .d, (Figs. 281 and 282), which may be 
 fixed at any point along the scale 
 by the clamp-screw, e. The rear 
 upper edge f of this 
 bevelled, and carries a 
 means of which the 
 diagonal divisions may 
 be read to I minute. 
 
 The bottom of this 
 collar has two projec- 
 tions, n, diametrically 
 opposite. These fit 
 into corresponding 
 notches, n' (Fig. 282), 
 in the top of the socket 
 b. 
 
 The axis of these 
 
 FlG - 28r - notches is at right an- 
 
 gles to the axis of the bore, and they are so arranged that 
 
 collar is 
 scale by 
 
POINTING PROBABILITY OF FIRE. 
 
 495 
 
 
 
 u 
 
 the sight may be inserted into the socket for a reading of 
 the deflection-bar to the right, or by lifting the sight and 
 turning it 180 about its axis, the sight may be reinserted in 
 the socket, and' the deflection-bar can be read to the left. 
 The correction for lateral deviation is 
 given by a deflection-bar, h (Fig. 281), 
 sliding in a socket, g, on the top of the 
 rear sight-bar, and clamped in any posi- 
 tion by the clamp-screw i. It is gradu- 
 ated similarly on both sides, and by 
 turning the sight 180, as previously ex- FlG - 28 3- 
 
 plained, deflections may be read to the right or to the left. 
 A vernier, v, on the right edge of the socket,^, enables the' 
 divisions on the deflection-bar to be read to 
 -jL- of the scale, the vertical divisions on this 
 bar being y^ of the range. The deflection- 
 bar is provided with two movable sight- 
 pieces, r and u (Figs. 281 and 283), fitting into 
 a socket, s, on the deflection-bar, and held in 
 place by a clamp-screw, /. For direct pointing 
 the sight piece, r, is placed in its socket in the 
 deflection-bar, and u in the front-sight socket. 
 For indirect pointing upon an object in rear, 
 when the target is not visible, the sight- 
 pieces r and u are interchanged. 
 
 Front Sight. The front sight consists 
 (Fig. 284) of a base,#, fastened to the rimbase 
 by four screws. 
 The top is provided with a socket of the same shape and 
 dimensions as that of the deflection-bar h (Fig. 281). The 
 thumb-screw */ clamps the sighting-piece firmly in position. 
 
 288. Sights for Field Artillery 3.6 Mortar 3.2 Field-gun. 
 
 SIGHTS FOR 3.6 MORTAR. The sights for this piece 
 
 FIG. 284. 
 
 FIG, 285. 
 
49<5 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 (Fig. 285) are a notch, A, in rear, and a point, B, in front, 
 
 near the muzzle. 
 
 SIGHTS FOR 3.2 FIELD-GUN. The rear sight consists of 
 
 a base, A, Fig. 286, which fits in a corresponding socket in 
 
 the gun ; a pivot, B, Fig. 287, 
 which fits into the bearing & t 
 Fig. 286, of the base, and ro- 
 tates around the bearing b, 
 Fig. 287 ; and a standard, C, 
 Fig. 288, carrying the gradua- 
 
 FIG. 286. FIG. 287. 
 
 tions. The pivot B, Fig. 287, has two cuts, c, c' , of the shape 
 shown, in which slide corresponding projections, c, c' , Fig. 
 288, of the standard. 
 
 The cylindrical part, b, of the pivot, B, is held in place 
 
 FIG. 288. 
 
 in the base A, Fig. 286, by two screws, a, a', passing through 
 
POINTING PROBABILITY OF FIRE. 
 
 497 
 
 the side of the base. These screws enter slots, a, a', 
 Fig. 287, in the pivot B, and allow 
 a certain amount of rotation to the 
 pivot. 
 
 The standard which carries the 
 graduations consists (Fig. 288) of 
 an upright bar, C ; a sliding-piece, 
 D, moved up and down along the 
 bar, C, by a screw, d, and carrying 
 the peep-sight, d' \ a cross-bar, e, 
 carrying the graduations for lateral 
 deflection ; a screw, /, working in a 
 half-nut, /, in the pivot B, Fig. 
 287, by means of which the stand- 
 ard is moved to the right or left; 
 a spirit-level,/, which indicates the 
 vertical position of the standard; 
 and two projections, c, c' , which fit 
 in the corresponding cuts, c, c', in 
 the pivot B. 
 
 The axis of rotation is at the 
 zero of the scale, and the usual 
 diagonal scale, divided into 10- 
 minute intervals, is read to one 
 minute, by a scale on the sliding- 
 piece D. 
 
 The assembled sight is shown in 
 Fig. 289, and its action is evident. FIG. 289. 
 
 Front Sight. This consists (Fig. 290) of a base, 
 c ^^~e 
 
 \r~d 
 
 __- 
 
 - 
 
 ,-, 
 
 _-*. 
 
 c 
 
 
 
 (/) 
 
 r 
 
 
 
 b 
 
 
 a 
 
 FIG. 200. 
 
 bolted to the right rim-base ; a standard, b ; and a cylinder, c. 
 
49^ 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 These are all formed in one piece. The cylinder carries 
 two thin cross ribbons of steel, d,.in an inner cone, c', and 
 a front sight-point, e. The point e and top of slide d" , 
 Fig. 289, are used for coarse sighting, while the cross- 
 ribbons and peep are for fine sighting. 
 
 The sights are on the right side of the piece. That for 
 the 3.6-gun is similar. 
 
 289. Deviations How Measured. 
 
 DEVIATIONS. Owing to the causes previously explained, 
 if a series of shots be fired at a given point of a target, they 
 will in general not hit the point aimed at, nor will they be 
 grouped symmetrically around this point. Each shot will 
 have a trajectory differing from the other shots, and all 
 these trajectories taken together will form a sheaf of 
 trajectories, whose shape in general is that of a bent 
 cone. The axis of this cone is called the mean trajectory, 
 and all the others are grouped symmetrically about it. 
 The point where this axis pierces the target is called the 
 centre of impact, and the distance of this centre of impact 
 from the point aimed at, is called the mean deviation. In 
 Fig. 291 let O be the point aimed at; AC the axis of the 
 
 a 
 
 FIG. 291. 
 
 sheaf of trajectories ; C the point where this axis or mean 
 trajectory pierces the plane of the target. Then C is the 
 centre of impact, and OC the mean deviation. 
 
 How MEASURED. It is usual to measure deviations in 
 three directions : 
 
 1. In the direction of the range; 
 
 2. Laterally, in the direction ab\ 
 
 3. Vertically, in the direction ac. 
 
 For the mean range deviation the target is usually taken 
 
POINTING PROBABILITY OF FIRE. 
 
 499 
 
 horizontal, and the measurements made from the centre of 
 the target, in the direction of the range. In case a hori- 
 zontal target cannot be used, the mean range deviation may 
 be obtained from the mean vertical deviation, by considering 
 that part of the mean trajectory, CD, in rear of the target to 
 be a straight line, making an angle GO with the horizontal 
 equal to the angle of fall. This angle can be calculated by 
 the formulas of Exterior Ballistics. 
 We have then 
 
 D'D = CD' cotang GO ; 
 
 or, if the mean range deviation is measured on a horizontal 
 target, we have for the mean vertical deviation 
 
 CD' = DD' tan GO. 
 
 The same method applies to any shot of the sheaf of 
 trajectories. The mean lateral deviation is measured parallel 
 to ab, and is OD' in the figure, and the mean vertical devia- 
 tion is measured parallel to ac, and is CD' in the figure. 
 The lateral and vertical deviations of any shot are measured 
 in the same way, from the point aimed at, to the centre of 
 the shot-hole. 
 
 290. To Find the Centre of Impact Example. 
 
 In order to measure the mean deviations, it is necessary 
 to determine the position of the centre of impact. For this 
 purpose, in Fig. 292, assume an origin of co-ordinates at the 
 
 ok- 
 
 FIG. 292. 
 
 lower left-hand corner O of the target, and axes OX in the 
 direction of the range, OY laterally, and OZ vertically. 
 
500 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 The point O is selected as an origin, for convenience, to 
 avoid the use of negative co-ordinates. 
 
 Let #', #", etc., denote the distances of the shot-marks 
 
 from O measured parallel to OX\ 
 y,y, etc., parallel to <9F; 
 z' , z" , etc., parallel .to <9Z; 
 
 X ', F ', Z' ', the co-ordinates of the point aimed at; 
 ^f, F, Z, the co-ordinates of the centre of impact ; 
 w, the number of shots. 
 Then 
 
 g/ *> x >>> etc. 
 
 n 
 
 7 *' + z" + z'" + etc. 
 n ; 
 
 and the point whose co-ordinates are (XY) in the horizontal 
 plane, and (FZ) in the vertical plane will be the centre of 
 impact. 
 
 The mean deviations in range, laterally and vertically, 
 will then be 
 
 In range X X' ; 
 Laterally F- F; 
 Vertically Z - Z '. 
 
 Similarly for any shot the deviations in range, laterally 
 and vertically, will be 
 
 In range x' X' ; 
 Laterally / F' ; 
 Vertically z' Z '. 
 
 In these calculations the positive sign indicates distances 
 beyond, to the right, and above the centre of impact ; the 
 negative sign distances short of, to the left, and. below that 
 centre. 
 
 EXAMPLE. Eight shots are fired from the 3.2o-inch steel 
 field-gun at a vertical target, range 1760 yards. 
 
POINTING PROBABILITY OF FIRE. 
 
 501 
 
 Size of target 40 by 20 feet. The co-ordinates of the 
 shots, measured from the lower left-hand corner of the target, 
 are as given in the table. 
 
 Find the mean deviation in range, laterally and verti- 
 cally, or the co-ordinates of the centre of impact. 
 
 TABLE. 
 
 No. of Shots. 
 
 Co-ordinates, feet. 
 
 Lateral. 
 
 Vertical. 
 
 I 
 
 2 
 
 3 
 
 9-00 
 21.68 
 14.25 
 
 9.50 
 5.OO 
 5.66 
 
 4 
 5 
 6 
 
 17.00 
 II.OO 
 19.00 
 
 5.00 
 
 8.66 
 9.82 
 
 7 
 8 
 
 I7.OO 
 14.83 
 
 10.32 
 9.00 
 
 8)12376 
 
 8)62.96 
 
 Y= 1547 
 
 Z= 7 .S 7 
 
 The co-ordinates of the centre of the target are 
 Y' = 20, Z' = 10. 
 
 Hence the mean lateral and mean vertical deviations 
 are: 
 
 Mean lateral Y Y' 4.53 feet left; 
 Mean vertical Z Z' = 2.13 feet below. 
 
 'The mean deviation in range must be calculated. 
 
 In Fig. 293 OA is the vertical height of the point aimed 
 at, 10 feet. Assume the angle of fall for this range and 
 elevation GJ = 3.oo, which is very nearly correct. 
 
 The centre of impact C is below the point O, 2.13 feet. 
 Find first the point B, which is the position of the centre of 
 
502 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 the target O on the horizontal plane ; then C ', that of the 
 centre of impact; and the difference C'B is the mean error 
 in range. 
 We have 
 
 AB 10 X cotan 3 = 190.8 feet = 63.6 yards X' \ 
 
 AC' (10 2.13) X cotan 3 =150.1 feet = 50.03 yards = X. 
 
 Mean deviation in range X X' 40.7 feet 
 
 1 3' 5^ yards short. 
 Mean range 1760 - 13.56 = 1746.44 yards. 
 
 C' 
 
 FIG. 293. 
 
 291. Errors. 
 
 The centre of impact, as its name indicates, is the centre 
 of the group of shots fired, and all the shot are grouped 
 symmetrically about it. Hence, if this point be taken as a 
 new origin of co-ordinates, for every positive abscissa or 
 ordinate, there must be a corresponding negative one, and 
 the algebraic sums of the abscissas or ordinates measured 
 from this point, are equal to zero. 
 
 The abscissa or ordinate of any shot measured from the 
 centre of impact is called the error. Corresponding to the 
 case of deviations, errors are measured in three directions : 
 along the range, laterally, and vertically. The distinctions 
 between deviations and errors are : 
 
 1. Deviations are measured from the point aimed at ; 
 errors, from the centre of impact. 
 
 2. Deviations are not grouped symmetrically about the 
 point aimed at unless this point coincides with the centre of 
 
POINTING PROBABILITY OF FIRE. 503 
 
 impact, while errors are grouped symmetrically about the 
 latter point. 
 
 It is theoretically possible, by carefully correcting for 
 wind, drift, and the various other causes before enumerated, 
 to make the centre of impact coincide with the point aimed 
 at, and the mean trajectory pass through that point. But 
 when this has been done the trajectories will still form a 
 sheaf or cone about the mean trajectory as an axis. This is 
 due to accidental errors which cannot be corrected, and 
 whose consideration requires the application of the doctrine 
 of probability, to be discussed later. 
 
 To find the error of any shot, and the mean errors for n 
 shot, we have given the co-ordinates of the shot and those 
 of the centre of impact, referred to the origin at the lower 
 left-hand corner of the target. 
 
 Let X, Y, Z be the co-ordinates of the centre of impact ; 
 x'j y' , z' , those of a shot ; 
 e x ,e yl e x , the errors in the directions X, Y, Z, respect- 
 
 ively for each shot ; 
 e*, yt e,, the mean errors in range, laterally and ver- 
 
 tically respectively, for n shot. 
 Then 
 
 e x = ^ - X, 
 
 and 
 
 4. ,/ ," etc. 
 
 _ e z + e,' + e," + etc. 
 
 n 
 
 The sums e x + e x + etc., e y + e y + etc., e, -f- */ + etc., if 
 taken with their proper signs, are each equal to zero, accord- 
 ing to the principle previously explained. Hence, in adding 
 these, they must be taken without regard to sign, and the 
 sum of their numerical values obtained. For instance, if 
 
504 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 two shots are fired, and one strikes 10 feet beyond and the 
 other 10 feet short of the centre of impact, the values of 
 e x and e x will be + IO an d 10, respectively, and this sum, 
 considering the signs, is zero. 
 
 But the total error committed in this case is 20 feet for 
 the two shots, and hence the mean error is %- = 10. 
 
 The error, measured from the centre of impact directly 
 to a shot, is called the absolute error. Denoting this error 
 by r, we have 
 
 r 
 
 or = 
 
 and the mean absolute error is 
 
 292. EXAMPLE. Find the errors laterally and vertically 
 and the mean errors for the 3.2O-inch field-gun with the 
 data in the last example. 
 
 TABLE. 
 
 
 Co-ordinates Feet. 
 
 Errors Feet. 
 
 Squares of Errors. 
 
 No. 
 
 
 
 
 Shots. 
 
 
 
 
 
 
 
 
 Lateral. 
 
 Vertical. 
 
 Lateral. 
 
 Vertical. 
 
 Lateral. 
 
 Vertical. 
 
 I 
 
 9.0O 
 
 9.50 
 
 ~ 6.47 
 
 + 1-63 
 
 41.8609 
 
 2.6596 
 
 2 
 
 21.68 
 
 5.00 
 
 + 6.21 
 
 -2.8 7 
 
 38.5641 
 
 8.2369 
 
 3 
 
 14.25 
 
 5.66 
 
 1.22 
 
 2.21 
 
 1.4884 
 
 4.8841 
 
 4 
 
 17.00 
 
 5.00 
 
 + i-53 
 
 -2.8 7 
 
 2.3409 
 
 8.2369 
 
 5 
 
 11.00 
 
 8.66 
 
 -447 
 
 + 0-79 
 
 19.9809 
 
 0.6241 
 
 6 
 
 19.00 
 
 9.82 
 
 + 3-53 
 
 + i-95 
 
 12.4609 
 
 3-8025 
 
 7 
 
 17.00 
 
 10.32 
 
 + 1-53 
 
 + 245 
 
 2.3409 
 
 6.0025 
 
 8 
 
 14.83 
 
 9.00 
 
 0.64 
 
 + 1.13 
 
 0.4096 
 
 1.2769 
 
 
 123.76 
 
 62.96 
 
 25.60 
 
 15.90 
 
 2e y *= 1 19.4466 
 
 2^ a = 35.72o8 
 
 
 F=i 5 47 
 
 Z= 7 .8 7 
 
 6^=3.20 
 
 ,= 1.9875 
 
 
 
 It will be observed that the positive and negative lateral 
 errors balance each other, and also the positive and nega- 
 tive vertical errors, as they should do, for the reasons 
 
POINTING PROBABILITY OF FIRE. 505 
 
 already explained. Also, that the sum of the positive or 
 the negative errors in either column, divided by one half 
 the number of shots, will give the correct values of e y 
 and e z . 
 
 To calculate the range errors and the mean error in 
 range, the same principle applies as for deviations, that is, 
 
 e x = e z cotan GO, 
 e x e z cotan GO. 
 
 In our service a different mean absolute error is some- 
 times used as a measure of the accuracy of a gun. It is 
 taken as the hypothenuse of a right-angled triangle of 
 which the other two mean errors are the sides. Thus for 
 the 3.2O-inch gun in the example the mean absolute error is. 
 
 e m = Ve; + 6,' = V(3.20)< + (1.9875)' = 3-77 feet. 
 
 This differs slightly from the true mean absolute error e r 
 previously explained, which would be in this case 4.003 feet. 
 
 PROBABILITY OF FIRE. 
 
 293. Division of Sheaf of Trajectories Law of Error Probability 
 Curve Principles upon which Form of Curve Depends. 
 
 DIVISION OF TRAJECTORY. Considering the errors in a 
 given number of shots, it is found that they vary in magni- 
 tude according to a certain law. As we approach the centre 
 of impact the shot-marks become more numerous, and as we 
 recede from it they decrease in number. That part of the 
 sheaf of trajectories which contains one half the whole num- 
 ber of shots is called the " nucleus "/ outside of the nucleus, 
 the surrounding part, containing 40 per cent, is called the 
 "envelope" ; and outside of this, the remaining 10 per cent is 
 called the u tailings" 
 
 LAW OF ERROR. Since one half the shot are grouped 
 within a small distance of the centre of impact, it may be 
 inferred that small errors are more apt to occur than large 
 ones ; and since only 10 per cent of the shot lie at any 
 considerable distance from the centre of impact, it may be 
 
506 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY 
 
 inferred that the chances of committing large errors are 
 small, or that very large errors are not likely to occur. 
 
 PROBABILITY CURVE. This law is general and applies 
 not only to errors of shot, but to accidental errors ol any 
 kind. It may be expressed by a curve, called the proba- 
 bility curve, whose form is shown in Fig. 294. 
 
 a O & 
 
 FIG. 294. 
 
 X 
 
 In this figure let O represent the centre of impact, and 
 XX' the direction of the range. Let Oa, Ob, Oc represent 
 errors in range, their magnitude being represented by the 
 lengths of Oa, Ob, etc., measured from O. Then from the 
 law of error it is evident that the smaller error Oa is more 
 likely to occur than the larger one Ob, and this latter than 
 the larger one Oc. 
 
 In a large number of shots, the error Oa will also occur 
 more frequently than Ob, and so on. 
 
 If in 10 shots the error Oa occurs four times, Ob three, 
 and Oc once, the fractions 
 
 measure the probability of the occurrence of these errors 
 respectively. 
 
 Hence if we lay off errors along XX 1 , measuring from O, 
 and at the points a, b, c, etc., erect ordinates proportional to 
 the probability of the corresponding errors, we will obtain 
 the curve in the figure. 
 
 The same discussion applies to lateral and vertical er- 
 rors, as they follow the same law. 
 
 PRINCIPLES UPON WHICH FORM OF CURVE DEPENDS. 
 The form of the curve depends upon the following gen- 
 eral principles : 
 
POINTING PROBABILITY OF FIRE. 507 
 
 1. The number of shots striking at O will be greater 
 than at any other point, or the probability of the error zero 
 will be greater than that of any other error, and hence the 
 maximum ordinate of the curve will be at O. 
 
 2. The number striking in the vicinity of O will be 
 greater than for points farther to the right and left, and 
 hence the ordinates of the curve will decrease slowly 
 near O. 
 
 3. The number of hits will decrease rapidly as the dis- 
 tance to the right and left of O increases, and hence the 
 ordinates of the curve will decrease rapidly in these direc- 
 tions. 
 
 4. For great distances from O, corresponding to large 
 errors, the ordinates will be very small, since great errors 
 are not likely to occur. 
 
 5. The only error that cannot occur is one infinitely 
 great, and hence the ordinate of the curve becomes zero at 
 an infinite distance, or the axis of Jf is an asymptote to the 
 curve. 
 
 6. Since the shot are as likely to fall short of the point O 
 as beyond it, the same error Oa is as likely to occur on one 
 side of O as on the other, and hence the curve is symmetri- 
 cal with respect to the axis OY. 
 
 294. Equation of the Probability Curve Properties of the Curve 
 Limits. 
 
 EQUATION. The equation of the probability curve, de- 
 duced by analytical methods, is (see Johnson, equation i) 
 
 y=*-", (404) 
 
 in which y is the ordinate of the curve corresponding to the 
 
 abscissa x, or the probability of the error x ; 
 h is the modulus of precision, whose meaning and 
 value will be explained ; 
 
 7C= 3.I4I6; 
 
 e = the base of the Napierian system. 
 PROPERTIES OF THE CURVE. Differentiating equation 
 (404) twice, we have 
 
508 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 = -**,-* ....... (405) 
 
 --_e-"^(l-2h^), . . . (406) 
 x Vn 
 
 From equation (405), when x o, we have 
 
 ?=-> 
 
 dx 
 and hence the tangent at y is parallel to the axis of x. 
 
 Placing - o, we have 
 dx 
 
 I 2^V = O, 
 
 or 
 
 ^ = ~\ ....... (407) 
 
 h \2 
 
 hence =y passes through zero and changes its sign for the 
 
 drsC 
 
 value of x given in equation (407). There is therefore a 
 point of inflection for the curve corresponding to this 
 abscissa. 
 
 LIMITS. In discussing the probability of making an 
 error, it is usual to consider this error as lying within certain 
 limits. Hence it is necessary to consider the area bounded 
 by the probability curve, the axis of errors, and an}' two 
 ordinates whose abscissas represent the limits between 
 which the given error lies. The area so determined repre- 
 sents the probability of the occurrence of the error within 
 the given limits. 
 
 The general expression for the area of a curve is 
 
 P = fydx. 
 Replacing y by its value from (404), we have 
 
 ^ dx ...... (408} 
 
POINTING PROBABILITY OF FIRE. 509 
 
 The axis of XX' extends to infinity in both directions as 
 explained ; hence the total area under the curve will be 
 obtained by integrating equation (408) between the limits 
 +00 and oo. That is, 
 
 Place 
 
 hx = of, .-. dx = ; 
 
 hence 
 
 e'^da (409) 
 
 The value of the integral between limits is, from calculus, 
 f + "e- a *da = * / n' J ..... (410) 
 
 ts co 
 
 hence in (409) 
 
 P=l, 
 
 or the total area under the curve is unity. This means that 
 it is certain that the error will be contained between -{-oo 
 and -co . 
 
 Similarly, for the probability that an error shall be con- 
 tained between any limits + x and x, we have 
 
 Since the curve is symmetrical with respect to the axis 
 OY, we have 
 
 x*j 2 h r x -&w j 
 
 x dx=- e hx dx . . (412) 
 
 /Wo 
 
 for the probability that the error shall be less than x re- 
 gardless of its sign. 
 
510 TEXT- BOOK OF ORDNANCE AND GUNNERY. 
 
 295. Modulus of Precision h Use of Table L 
 Assume, equation (404), 
 
 The smallest possible error is zero, 
 the above equation, we have 
 
 Making x = o in 
 
 (413) 
 
 for the probability of the error zero. It is evident that this 
 is the greatest value of y, and gives the maximum ordinate 
 OY. 
 
 Suppose we have another series of shots for which the 
 value of h differs from that for the first series, as h' 2/1. 
 Then the probability of the error zero in the second case 
 will be 
 
 V* 
 
 (414) 
 
 and the ordinate will be twice that in equation (413). 
 
 That is, the probability of the error zero will be twice as 
 great in the second series as in the first. As the accuracy 
 
 increases with the probability of making no error, we con- 
 elude that the second series of shots is more accurate than 
 
POINTING PROBABILITY OF FIRE. 511 
 
 the first. The quantity h is then a measure of the precision 
 of the shots, and hence is called the modulus of precision. 
 
 If we construct the probability curves for the two series 
 of shots, since the areas under them are always unity, we 
 will have those represented in Fig. 295, OY representing 
 the maximum ordinate for the first series and OY' for the 
 second. It is evident, from the above discussion and figure, 
 that for the same error, x, the curve of probabilities will vary 
 with the modulus h. Hence it is usual to change the form 
 of the equation for probability, so as to introduce h as a. 
 factor of the error x, and hence into the limit. Equation 
 (412) is therefore generally written 
 
 e- h ^d(hx) ..... (415) 
 
 The values of P for different values of hx have been cal- 
 culated and tabulated, and are given in Table I. The value 
 of h as deduced analytically is 
 
 (4i6) 
 
 2^V ' 
 
 in which 
 
 n is the number of shots ; 
 
 2e*, the sum of the squares of the errors in any given 
 
 direction. 
 
 USE OF TABLE I. Let it be required to find for the 3.20 
 gun the probability of committing a lateral error less than 2 
 feet,, at a range of i mile. 
 
 The value of 2e y * for this gun is 119.45 (see example, 
 Subject 292) ; hence 
 
 h \ / .1711 ; 
 
 V 2 x 119-45 
 
 hx = .1711 X 2 = .3422; 
 
 Pfor hx = .3422 = .37155; 
 P = about T V ; 
 
 or about four shots in ten will make an error less than 2 feet 
 laterally, at one mile range. 
 
512 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 TABLE I. 
 
 PROBABILITY OF ERRORS, 
 
 hoc 
 
 f 
 
 hx 
 
 P 
 
 hx 
 
 P 
 
 hx 
 
 P 
 
 hx 
 
 P 
 
 0.00 
 
 0.00000 
 
 0.40 
 
 0.42839 
 
 0.80 
 
 0.74210 
 
 1.20 
 
 0.91031 
 
 .60 
 
 0.97635 
 
 .02 
 
 .02256 
 
 .42 
 
 44747 
 
 .82 
 
 75381 
 
 1.22 
 
 9*553 
 
 .62 
 
 .97804 
 
 .04 
 
 .04511 
 
 44 
 
 .46622 
 
 .84 
 
 .76514 
 
 1.24 
 
 .92050 
 
 .64 
 
 .97962 
 
 .06 
 
 .06762 
 
 .46 
 
 .48465 
 
 .86 
 
 .77610 
 
 1.26 
 
 .92523 
 
 .66 
 
 .98110 
 
 .08 
 
 .09008 
 
 .48 
 
 .50275 
 
 .88 
 
 .78669 
 
 1.28 
 
 .92973 
 
 .68 
 
 .98249 
 
 .10 
 
 .11246 
 
 .50 
 
 1 
 
 .52050 
 
 .90 
 
 .79691 
 
 1.30 
 
 .93401 
 
 .70 
 
 98379 
 
 .12 
 
 .13476 
 
 .52 
 
 53790 
 
 .92 
 
 .80677 
 
 1.32 
 
 .93806 
 
 .72 
 
 .98500 
 
 .14 
 
 .15695 
 
 54 
 
 55494 
 
 94 
 
 .81627 
 
 1-34 
 
 .94191 
 
 74 
 
 .98613 
 
 .16 
 
 .17901 
 
 .56 
 
 .57161 
 
 .96 
 
 .82542 
 
 1.36 
 
 .94556 
 
 .76 
 
 .98719 
 
 .18 
 
 .20093 
 
 58 
 
 .58792 
 
 .98 
 
 .83423 
 
 1.38 
 
 .94902 
 
 78 
 
 .98817 
 
 .20 
 
 .22270 
 
 .60 
 
 .60386 
 
 .00 
 
 .84270 
 
 1.40 
 
 .95228 
 
 .80 
 
 .98909 
 
 .22 
 
 .24429 
 
 .62 
 
 .61941 
 
 .02 
 
 .85084 
 
 1.42 
 
 95537 
 
 .82 
 
 .98994 
 
 .24 
 
 .26570 
 
 .64 
 
 63458 
 
 .04 
 
 .85865 
 
 1.44 
 
 .95830 
 
 .84 
 
 99073 
 
 .26 
 
 .28690 
 
 .66 
 
 .64938 
 
 .06 
 
 .86614 
 
 46 
 
 .96105 
 
 .86 
 
 .99147 
 
 .28 
 
 .30788 
 
 .68 
 
 .66378 
 
 .08 
 
 87333 
 
 .48 
 
 .96365 
 
 .88 
 
 .99216 
 
 3 
 
 .32863 : 
 
 .70 
 
 .67780 
 
 .10 
 
 .88020 
 
 .50 
 
 .96610 
 
 1.90 
 
 .99279 
 
 32 
 
 .34912; 
 
 .72 
 
 .69143 
 
 .12 
 
 .88679 
 
 52 
 
 .96841 
 
 1.92 
 
 .99338 
 
 34 
 
 .36936 
 
 74 
 
 .70468 
 
 .14 
 
 .89308 
 
 54 
 
 .97058 
 
 1.94 
 
 .99392 
 
 36 
 
 .38933 
 
 76 
 
 .71754 
 
 .16 
 
 .89910 
 
 .56 
 
 .97263 i 
 
 1.96 
 
 99443 
 
 .38 
 
 .40901 
 
 .78 
 
 .73001 
 
 .18 
 
 .90484 
 
 .58 
 
 97455 j 
 
 1.98 
 
 .99489 
 
 
 
 
 
 
 
 
 
 2.0 
 
 99532 
 
 
 
 
 
 
 
 
 
 3-o 
 
 .99998 
 
 
 
 
 
 
 
 
 
 00 
 
 1 .00000 
 
 296. Probable Error True Mean Error Relation between Prob- 
 able and True Mean Errors. 
 
 Among the errors which may be committed, from zero 
 to infinity, there are two whose values are of constant use 
 and importance. 
 
 These are the probable error and the true mean error. 
 
 PROBABLE ERROR. In Fig. 296, the total area under the 
 probability curve being unity, if the abscissas Op on each 
 side of O be so taken that the area///'/ included between 
 the curve, the ordinates//', and the axis XX' is equal to one 
 half, the error Op is called the probable error. That is, it is 
 the error whose probability is one halt, or the error which is 
 as likely to be exceeded as not. For example, if ten shots be 
 
POINTING PROBABILITY OF FIRE. 
 
 513 
 
 fired, and O be the centre of impact, the probability is that 
 five of these shots will strike within the distance Op from the 
 centre of impact and the other five at a greater distance. 
 It is to be noted that while the probable error is Op, it may 
 
 f o p 
 
 FIG. 296. 
 
 occur on either side of O, and hence it must be measured in 
 both directions from O. 
 
 From Table I, the value of hx for P = % is 
 
 hx 0.4769. 
 
 Hence, calling this error x p , we have 
 _ 0.4769 
 
 Substituting for h its value from (416), we have 
 
 > = 0.6745. 7-^-. 
 
 V n I 
 
 TRUE MEAN ERROR. The mean error has already been 
 calculated for the 3.2O-inch gun for a limited number of 
 shots. If the number of shots be increased, a different value 
 for the mean error would be obtained, and the true value of 
 this mean error can only be found for an infinite number of 
 shots : hence the name. Since it is impossible in practice 
 to fire an infinite number of shots, the value of the true 
 
514 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 mean error must be found by analytical methods from the 
 equation of the curve. This method gives for its value 
 
 . ' X " = Yvn (4 ' 9) 
 
 Substituting the values ol n, and of h from (416), we have 
 
 x m = 0.79788. /-^-- (420) 
 
 V - i 
 
 Dividing equation (418) by (420), we have 
 
 -^ = 0.8453; *, = 0.845 3*,,. (421) 
 
 * 
 
 297. Probable Zone Examples Comparison of Mean and True 
 Mean Errors. 
 
 PROBABLE ZONE. The probable zone is one which will 
 probably contain 50 per cent, or one half, the total number 
 of shots. Hence the probability for this zone is P = %. 
 Now, in considering the probable error, it was shown that 
 it measured a distance on each side of the point of impact 
 within which one half the whole number of shots would 
 strike ; and hence if we lay off a distance on each side of the 
 centre of impact equal to the probable error, and draw 
 through the points thus determined two lines at right angles 
 to the plane of fire and extending indefinitely in both direc- 
 tions, these lines will determine a zone which will contain 
 50 per cent of the shots. 
 
 ** 
 
 FIG. 297. 
 
 In Fig. 297 let O be the centre of impact ; x p Ox p , the di- 
 rection of the range, or line of fire; Ox p , measured in both 
 directions from O, the probable error. Then the zone de- 
 
POINTING PROBABILITY OF FIRE. $1$ 
 
 fined by the parallel lines extending to infinity in both 
 directions is called the probable zone, and will contain one 
 half the whole number of shots fired. The same reasoning- 
 applies to the lateral and vertical probable zones. 
 
 The width of this zone is twice the probable error, or 
 
 / 2S I 2e* 
 
 i X 0.6745^ = i. 3 49y ^-j- 
 
 (422) 
 
 EXAMPLES. Find the probable error, true mean error, 
 and probable zone vertically for the 3.2O-inch gun at one 
 mile range. 
 
 *> = o.67 45 y _^- = 0.6745^ 1A^5 = 1.523 feet ; 
 
 * w = 0.79788A/ - ^- = Q.79788A/ ^^ = 1-802 feet ; 
 2x p 2 X 1.523 = 3.046 feet. 
 
 The same method will give the corresponding errors 
 and zones laterally and in range, 2f differing for the differ- 
 ent directions. 
 
 COMPARISON OF MEAN AND TRUE MEAN ERRORS. The 
 true mean vertical error in this case is X M = 1.802 feet, while 
 the mean error as obtained from eight shots is (see table) 
 1.9875 feet. Hence the mean and true mean errors differ 
 very slightly, and with a large number of shots the differ- 
 ence would be still less. This is true generally, and hence 
 the calculated mean error may be used instead of the true 
 mean error without appreciable error in the result. This 
 leads to a simple method of calculating probable zones, as 
 follows : 
 
 From (421) we have 
 
 x p = 0.845 3* M ; .-. 2*> = 1.69*,,. . . . (423) 
 
 Substituting for x m the calculated mean error e x , e y , or 
 
5 i6 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 -X' 
 
 e g , we have for the probable zone in any one of these direc- 
 tions : 
 
 Range 2x p 1.69 X e x \ } 
 
 Lateral 2y p = 1.69 X ^; v . . . . (424) 
 
 Vertical 2z p = 1.69 X e,. ) 
 
 298 25 per-cent Rectangle Probable Rectangle Rectangles of 
 any Percentage. 
 
 Let O, Fig. 298, be the centre of impact, XX' the 50 per- 
 cent zone for the range, YY f the 50 per-cent zone laterally. 
 
 The intersection of these zones 
 will form a rectangle about the 
 centre of impact, and this rect- 
 angle will contain one fourth or 
 25 per cent of the shots, for 
 
 .50X .50 = .25 
 
 This is called the 25 per-cent 
 rectangle. It is the rectangle 
 formed about the centre of im- 
 FlG - 2 9 8 - pact by the intersection of the 
 
 two 50 per-cent zones ; and since each contains 50 per cent 
 of the shots independently of the other, by the doctrine of 
 probability, when they intersect, their common part will 
 contain a percentage equal to the product of the two. 
 
 PROBABLE RECTANGLE. The probable rectangle is one 
 which is formed by the intersection of two zones of equal 
 probability, and which will probably contain 50 per cent of 
 the shots. That is, its probability is P = . 
 
 Now the probability of any rectangle, as illustrated in 
 the case of the 25 per-cent rectangle, is equal to the product 
 of the probabilities of the two zones whose intersection 
 forms the rectangle ; and denoting the probabilities of these 
 zones by P' and P" respectively, we have 
 
 P = P' x P". 
 
 It is evident, however, that there are an infinite number 
 of zones whose intersection will give a rectangle having the 
 probability P=%, since any two, the product of whose prob- 
 
POINTING PROBABILITY OF FIRE. 
 
 517 
 
 ^abilities is one half, will fulfil this condition. To fix the 
 rectangle, therefore, we impose the condition that the prob- 
 abilities of the two intersecting zones shall be equal. Sub- 
 stituting in the above equation this condition, we have 
 
 i = V X \ f \, 
 
 or the probability of committing an error less than one half 
 of either side of the rectangle is P' = P" = V%. 
 For 
 
 F = i/J = 0.7071 
 
 we have, from Table I, 
 
 hx 0.7438 ; 
 
 hence 
 
 07438 
 It ' 
 
 (425) 
 
 Substituting for h its value from (416), we have 
 
 /~^7~ 
 
 = I.0524/ -. 
 
 V n I 
 
 This is the value of one half the side of the rectangle. 
 Hence 
 
 Calling the sides of this rectangle in the horizontal plane 
 
 A x and A yt and in the vertical plane A y and A t , we have 
 
 i 
 
 1 x =2.io 4 \/^-; 
 V n i 
 
 4, = 2.i04\/ - ; 
 V n i 
 
 = 2.104 
 
 . (426) 
 
 RECTANGLES OF ANY PERCENTAGE. By similar reason- 
 ing we can find the probable rectangle which will contain 
 
5l8 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 any given percentage of shots. For instance, required the 
 rectangle which will contain twelve out of twenty shots 
 fired from the 3.2 gun at one mile range. 
 We have 
 
 |-| = 60 per cent. 
 
 The probability of this rectangle must then be 
 
 P=.6, 
 and hence the probability of its sides P' V.6, since 
 
 From Table I the value of hx corresponding to 
 
 P' = t/"6 = .7746 
 is 
 
 hx .8572 ; 
 hence 
 
 x - 
 
 Substituting for h its value from (416), we have 
 
 TW 
 
 = \.2\2\ - 
 
 V n I 
 
 X 
 
 and 
 
 2X 
 
 = 2.424\/ - , 
 
 V n I 
 
 ;/ i 
 
 / - 
 
 2Z = 2.424\/ -, 
 
 V n i 
 
 and so on for a rectangle of any percentage. 
 
 299. Examples Measure of Accuracy of Guns Calculation of 
 
 Probable Rectangle from Mean Error. 
 
 Find the 25 per-cent rectangle, the probable rectangle, 
 and the 60 per-cent rectangle for the 3.20 gun, in the vertical 
 plane, at one mile range. 
 
POINTING PROBABILITY OF FIRE. 519 
 
 1. The 25 per-cent rectangle : 
 
 The probable zone vertically is (see subject 297) 
 
 22 p == 3.046 feet. 
 The probable zone laterally is 
 
 V2e y * /i 19.45 
 
 ^f-j: = i.349y --y 1 = 5-57 feet 
 
 Hence the 25 per-cent rectangle is 
 
 3.046 x 5-57 = l6 -97 sq. feet. 
 
 2. The 50 per-cent rectangle : 
 
 / ^ e v / II 9-45 
 
 A y = 2.io4\/ - = 2.104*7 ~= = 8.69 feet; 
 
 4, = 2.i04y ^-^- = 2.io4y -^ = 4-75 feet 
 
 Hence the 50 per-cent rectangle is 
 8.69 x 4-75 = 4I-3 1 s q 
 3. The 60 per-cent rectangle : 
 
 /"SFr 
 
 4 / = 10. 
 V i 
 
 2y 2.42447 - - = 10.01 feet; 
 
 7 "^ c * 
 
 22 = 2.424*7 - - = 5.48 feet. 
 \ n i 
 
 Hence the 60 per-cent rectangle is 
 
 10.01 X 5.48 54.82 sq. feet. 
 
 COMPARISON OF ACCURACY OF GUNS. The probable 
 or 50 per-cent rectangle, is generally used to compare the 
 accuracy of different guns, and may be taken either in the. 
 horizontal or in the vertical plane. For small arms and 
 high-power guns the vertical rectangle is the more accurate 
 means of comparison. It is evident that for high-power 
 
520 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 guns, with flat trajectories, the horizontal rectangles will be 
 larger than for guns with high-angle or curved fire. Hence 
 if we compare guns and mortars by their horizontal rect- 
 angles, the mortar will appear the more accurate. On the 
 other hand, for high-angle or curved fire, horizontal targets 
 should be used as a means of comparison. The most accu- 
 rate method for all guns is to take the plane of the target 
 .at right angles to the trajectory at the point of impact, but 
 this is generally impracticable. 
 
 CALCULATION OF PROBABLE RECTANGLE FROM MEAN 
 ERROR. The mean error of a given number of shots may 
 be readily obtained as previously shown. 
 
 For the side of the 50 per-cent rectangle we have, equa- 
 tion (425), 
 
 From (417), 
 
 *=^: ........ (428) 
 
 and from (421), 
 
 *> = 0.8453*.. ........ (429) 
 
 Substituting the value of x p from (429) in (428), we have 
 
 k _ 0.4769 t 
 0.8453*"' 
 
 and this value of h in (427) gives 
 
 A x = 2x = 2.636 X x m . .... (430) 
 
 300. Use of Probable Error in Calculating Probabilities Use of 
 Table II Example. 
 
 The probable error is generally used as a standard of 
 comparison for other errors, since it represents an error 
 which is as likely to be exceeded as not. 
 
 For the probable error we have, equation (417), 
 
 _ 0.4769 
 ' 
 
POINTING PROBABILITY OF FIRE. 
 
 521 
 
 Using this as a unit of comparison, the ratio of any other 
 
 error x to this is 
 
 x hx 
 
 (43I) 
 
 In Table I we have given, values of P corresponding to 
 Jix, or, conversely, values of hx corresponding to P. Divid- 
 ing the values of hx in Table I by 0.4769, we have the cor- 
 
 * 
 
 responding values of . 
 x p 
 
 Finding the values of P, from Table I, corresponding to 
 
 these values of , we can form a new table, giving the values 
 
 x p 
 
 of P corresponding to , or the values of corresponding 
 
 x p x p 
 
 to P. 
 
 This table is called Chauvenet's Table, and is given 
 below. 
 
 TABLE II. 
 
 PROBABILITY OF ERRORS. 
 
 P 
 
 
 
 1 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 0.0 
 
 o 
 
 .02 
 
 .04 
 
 .06 
 
 .07 
 
 .09 
 
 .11 
 
 .13 
 
 15 
 
 17 
 
 .1 
 
 .18 
 
 .20 
 
 .22 
 
 .24 
 
 .26 
 
 .28 
 
 30 
 
 32 
 
 34 
 
 36 
 
 .2 
 
 38 
 
 .40 
 
 41 
 
 43 
 
 -45 
 
 47 
 
 .49 
 
 
 53 
 
 55 
 
 .3 
 
 
 
 .61 
 
 .63 
 
 6S 
 
 .67 
 
 .70 
 
 72 
 
 74 
 
 .76 
 
 .4 
 
 .78 
 
 .80 
 
 .82 
 
 .84 
 
 .86 
 
 89 
 
 91 
 
 93 
 
 95 
 
 .98 
 
 .5 
 
 1. 00 
 
 1.02 
 
 1.04 
 
 1.07 
 
 1.09 
 
 1. 12 
 
 1.14 
 
 1.17 
 
 1.19 
 
 1.22 
 
 .6 
 
 1.25 
 
 1.27 
 
 1.30 
 
 1-33 
 
 1.36 
 
 1.39 
 
 1.42 
 
 1-45 
 
 1.48 
 
 I.5I 
 
 .7 
 
 1.54 
 
 1.57 
 
 1. 60 1.64 
 
 1.67 
 
 I.7I 
 
 1-74 
 
 1.78 
 
 1.82 
 
 1.86 
 
 .8 
 
 1.90 
 
 1.94 
 
 1.98 1 2.03 
 
 2.08 
 
 2.13 
 
 2.18 
 
 2.24 
 
 2.30 
 
 2-37 
 
 .9 
 
 2.44 
 
 2.52 
 
 2.60 
 
 2.69 
 
 2.78 
 
 2. 9 I 
 
 3-4 
 
 3.22 
 
 3-45 
 
 3.82 
 
 USE OF TABLE II EXAMPLES. 
 
 i. Required the probability of committing a lateral error 
 with the 3.2 gun, at i mile range, of less than 4.354 feet. 
 
 The probable error laterally, for this range, is 2.785 feet, 
 hence 
 
 y _ 4-345 _ I 6 
 
 y> 2.785 
 
$22 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 From Table II, P for 2- = 1.56 is 
 
 P= 0.707 1 = i/JT 
 
 2. The probable lateral error of the 3.2 gun at i mile 
 range is 2.785 feet. 
 
 The probability of committing an error less than x, is 
 
 /> = VJ = 0.7071. Find the value of x. 
 From Table II, for P = 0.7071 we have 
 
 ' = 1.56, .-. y = 1.56 x 2.785 = 4.345 feet. 
 
 301. Probability of Hitting any Plane Figure. 
 
 By the previous methods it has been shown how to deter- 
 mine the sides of a rectangle which will contain any given 
 percentage of shots. By the use of Table II we can readily 
 determine the probability of hitting any plane figure of a 
 given size and shape. 
 
 As the simplest case, consider first a rectangular object. 
 
 A 
 
 K" 
 
 M 
 
 1 
 
 { 
 
 B 
 
 TT" 
 
 
 
 
 I 
 
 ij 
 
 ti 
 
 \r 
 
 
 L 
 
 
 
 Y 
 
 I 
 
 JT'" 
 
 
 O 
 
 
 F 
 
 a * 
 
 TT' 
 
 rt 
 
 h __. 
 
 
 
 
 rt 
 
 C 
 
 K'" 
 
 r 
 
 FIG. 
 
 ? f 
 
 299. 
 
 C 
 
 D 
 
 Let O, Fig. 299, be the centre of impact, OF and OZ the 
 rectangular axes, and suppose vertical errors to be measured 
 along OZ, and horizontal errors along OY. For the given 
 gun and range, the probable errors horizontally and verti- 
 cally will be known by firing a certain number of shots and 
 calculating the probable errors by equation (418). 
 
 I. What is the probability of striking the rectangle 
 ABDC ? 
 
POINTING PROBABILITY OF FIRE. $2$ 
 
 From Table II we find the probability of committing the 
 error OG by taking out the value of P corresponding to 
 
 yp y* 
 
 From the same table we find the probability of commit- 
 ting the error OM by taking from this table the value of P 
 corresponding to 
 
 OM 
 
 and the probability of hitting the rectangle ABCD is the 
 probability of committing these two errors simultaneously, 
 or the product of the above separate probabilities. 
 
 2. What is the probability of striking the rectangle 
 OGBMl 
 
 From the fact that the shot are grouped symmetrically 
 about O, owing to the law of probability, it follows that the 
 number of hits in OGBM will be \ of those in the rectangle 
 ABCD. Hence the probability of hitting the rectangle 
 OGBM is | that of hitting the rectangle ABCD. 
 
 3. What is the probability of striking within OMKF ? 
 This is found exactly as for the rectangle OMBG, Find 
 
 from Table II the probabilities corresponding to and 
 
 yp 
 
 -, and multiply these probabilities together. The result 
 
 will be the probability of striking within the rectangle 
 K"KK'K'", and \ of this will be the probability required. 
 
 4. What is the probability of striking FKBG ? 
 
 It is the difference between the probabilities for OGBM 
 and OFKM, which have already been found. 
 
 5. What is the probability of striking OGHL ? 
 
 Find from Table II the probabilities for and - ; mul- 
 
 y* Z P 
 
 tiply these probabilities together and take J of the prod- 
 uct for the probability required. 
 
 6. What is the probability of striking FGHI ? 
 
524 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 It is the probability of striking OGHL minus the proba- 
 bility of striking OFIL. 
 
 7. What is the probability of striking IKBH ? 
 
 It is the probability of striking OMBG minus the sum of 
 the probabilities of striking OGHL and LIKM. 
 
 In the same way any figure may be divided into rect- 
 angles, approximately, whose centres coincide with the 
 centre of impact. 
 
 The probability of striking the rectangles or parts of 
 rectangles about the centre of impact may be readily calcu- 
 lated by Table II, and the probability of striking those parts 
 whose centres do not coincide with the centre of impact 
 may be determined by subtraction. 
 
 302. Right-line Method. 
 
 The area under the probability curve being unity, and 
 the curve being symmetrical with respect to the axis OY y 
 
 the area under each branch is . If a right line BC, Fig. 
 300, be drawn so that the area of the triangle OBC = J, and 
 the abscissa of its centre of gravity be at a distance Om from 
 O, equal to the true mean error x m < then the right line BC 
 may be substituted without appreciable error lor the prob- 
 ability curve. 
 
 In this case the greatest possible error is OC and the 
 greatest possible ordinate is OB, and to show that the right 
 line may be substituted for the curve it is necessary to 
 prove : 
 
POINTING PROBABILITY OF FIRE. $2$ 
 
 1. That the probability of the error OC does not differ 
 sensibly from that of the error oo , which is the greatest 
 possible error in the case of the probability curve. 
 
 2. That the ordinate OB does not differ sensibly from 
 the maximum ordinate O Y of the curve. 
 
 i. Probability of the error OC. 
 
 Since in a triangle the centre of gravity is situated at a 
 distance from its base equal to its height, we have 
 
 oc= 
 
 but, from (419), 
 
 Om = x m = 
 hence 
 
 and 
 
 h X OC = hx -4= = 1.6925. 
 
 VTT 
 
 From Table I the value of P corresponding to hx = 1.6925 
 is 
 
 ^=.983. 
 
 j 
 
 The value of P for Ar = oo is 
 
 P= 1 .00, 
 
 hence the probabilities of the extreme errors in the two 
 cases are as 
 
 .983 : i.oo. 
 
 That is, out of 100 shots 98 will make an error less than OC. 
 
 2. Value of the ordinate OB, as compared with OY. The 
 maximum ordinate OY oi the probability curve is found 
 by making x = o in equation (404). The value thus ob- 
 tained is 
 
526 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 or since 
 
 we have 
 
 X 
 
 (432) 
 
 From the triangle OBC, since its area is J and its base 
 3^r w , we have 
 
 i _ ((9^X3-0. 
 2" 2 
 
 hence 
 
 OB = jiht (433) 
 
 Comparing (432) and (433), we see that the numerators of 
 the values of OY and OB are the same, and the denomina- 
 tors differ but slightly, and hence OB may be taken for OY, 
 or the right line may be substituted for the curve without 
 appreciable error. 
 
 303. Value for Probability by the Right-line Method. 
 
 In Fig. 301 make 
 
 Ox =*; 
 
 Om x m ; 
 
 xx p' . 
 
POINTING PROBABILITY OF FIRE. $2? 
 
 v'x" 
 
 Then the area OBC -~~ = 
 
 
 From the similar triangles OBC and xx ' C we have 
 OB'.OC :: xx' : OC - Ox, or / : x" : : p' : x' ' x ; 
 hence 
 
 /' = x n ; 
 
 but 
 
 hence 
 
 pf=y 3 ^7 (435) 
 
 Substituting in (434) for p' its value from (435), we have 
 area OBx'x = JL^-JL-^ . . . ( ^ 6) 
 
 Now the probability of an error less than Ox = x is the 
 ratio of the area of the triangle OBC to that of the trape- 
 .zoid OBxx'\ hence, dividing (436) by the area of the triangle 
 
 , we have 
 
 2 
 
 (437) 
 
 In this equation, having the value of the true mean error 
 given by the equation (420), or that of the mean error ob- 
 tained as explained from a number of shots, we can find the 
 probability of any error x without using the probability 
 tables. 
 
 This discussion of probability may be extended to include 
 the methods for hitting circles or ellipses, and also for de- 
 termining the number of shots necessary to produce a given 
 result, such as to make a breach in a wall, etc., but the 
 discussion is too extensive for the present course. 
 
CHAPTER IX. 
 
 PORTABLE ARMS. 
 
 304. Division Hand Arms Cutting Arms Principles Light 
 Artillery Sabre. 
 
 DIVISION. Portable arms are those which are carried by 
 the individual soldier, and are divided into 
 
 1. Hand arms. 
 
 2. Small arms. 
 
 HAND ARMS are those which are used for attack and de- 
 fence at very short distances, and are divided according to 
 their mode of action into 
 
 1. Cutting arms. 
 
 2. Thrusting arms. 
 
 3. Thrusting and cutting arms. 
 
 CUTTING ARMS PRINCIPLES. A cutting arm is one 
 which acts by its edge, and, being used entirely against ani- 
 mate objects, is based upon the following general principles: 
 
 1. Since the object to be cut is elastic and fibrous, the 
 blow must be struck so that only a few points of the cutting 
 edge at a time will come in contact with the body, and in 
 order to prevent the fibres or the muscles from mutually 
 supporting each other, they must be cut one at a time. 
 
 For these reasons the edge of a cutting weapon should 
 be curved, and the blow oblique rather than direct. 
 
 The kind of curvature of the edge (convex or concave) 
 will depend on the direction in which the weapon is moving 
 at the time of the blow. If moving toward the object, the 
 edge should be convex ; if from it, concave. 
 
 Extreme examples are seen in the Turkish sabre, a, and 
 the Arab yataghan, b, Fig. 302. 
 
 2. In order to give force to the blow, the centre of 
 
 528 
 
PORTABLE ARMS. $2$ 
 
 gravity should be well forward ; an example is seen in the 
 axe. 
 
 3. For facility of handling, the centre of gravity shouM 
 be near the hilt. 
 
 a 
 
 FIG. 302. 
 
 As these two principles are conflicting, a compromise is 
 generally effected by throwing the centre of gravity well 
 forward in a cutting weapon, and well to the rear in a 
 thrusting one, and giving it an intermediate position where, 
 as in the cavalry sabre, the two functions are combined. 
 
 LIGHT ARTILLERY SABRE. This is the only distinct cut- 
 ting weapon in service, and it has a short curved blade with 
 a comparatively light hilt (Fig. 303), the centre of gravity 
 being well forward. The cross-section is grooved for 
 lightness and strength. 
 
 FIG. 303. 
 
 305. Thrusting Arms Principles Straight Sword Bayonet Lance 
 Cutting and Thrusting Arms Cavalry Sabre. 
 
 A thrusting arm is one which acts by its point, and is 
 based upon the following principles : 
 
 1. Its penetration depends on the power of the wedge at 
 its point, and hence this point or wedge should be as sharp 
 as possible consistent with strength. 
 
 2. For a given power of wedge, the penetration also de- 
 pends on the position of the axis of the wedge with reference 
 to the thrusting force. Hence the blade of a thrusting 
 
530 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 weapon should be straight, to prevent the turning aside of 
 the point by the oblique component of this force. 
 
 3. For facility of handling, the centre of gravity should 
 be well to the rear, and the blade should be light. 
 The principal thrusting weapons are 
 The straight sword ; 
 The bayonet ; 
 The lance or pike. 
 
 THE STRAIGHT SWORD (Fig. 304), as its name indicates, 
 has a straight blade and sharp point, and the centre of grav- 
 ity well to the rear in accordance with these principles. 
 
 o 
 
 FIG 304. 
 
 THE BAYONET. This is intended to convert the gun into 
 a pike. It was formerly employed very extensively, but its 
 use has gradually decreased as ranges and velocities have 
 increased. It is still supplied with the latest model guns, 
 ;and is shown in Fig. 305. 
 
 FIG. 305. 
 
 It is fixed to the muzzle of the gun by a spring clasp, a, 
 engaging over a stud on the upper band, and by a ring, b, 
 which encircles the muzzle. 
 
 a 
 
 ,~~c 
 -b 
 
 FIG. 306. 
 
 The older form of bayonet in use on the Springfield 
 Rifle cal. .45 is shown in Fig. 306. Its cross-section is 
 shown in the figure, and is such as to give lightness and 
 stiffness. 
 
SMALL ARMS. 53! 
 
 The parts are : the blade a, neck or shank b, socket c, 
 clasp d y and groove e. Its method of attachment to the gun 
 is well known. 
 
 THE LANCE OR PIKE. This is still used in some foreign 
 services, and is a sharp steel blade fixed to the end of a long 
 wood handle. This handle is provided with a loop at the 
 centre of gravity, for convenience in carrying and guiding. 
 It has the advantage of greater length than the other thrust- 
 ing weapons, but is inconvenient to carry and handle. 
 
 CUTTING AND THRUSTING ARMS CAVALRY SABRE. 
 These weapons combine the functions of the other two classes 
 and hence exhibit features common to each class. 
 
 THE CAVALRY SABRE (Fig. 307) is the only weapon of this 
 
 FIG. 307. 
 
 class in service, and the following points may be noted. As 
 it is used both for cutting and thrusting, its blade is longer 
 and less curved than that of the light artillery sabre ; the 
 hilt is heavier, to bring the centre of gravity further to the 
 rear, and the hand is better protected by the guard. 
 
 SMALL ARMS, 
 
 306. Principal Parts The Barrel Calibre Recoil. 
 
 PRINCIPAL PARTS. The essential parts of all breech-load- 
 ing small arms are : 
 
 The barrel ; 
 
 The receiver ; 
 
 The breech mechanism ; 
 
 The firing mechanism ; 
 
 The sights ; 
 
 The stock and mountings ; 
 and for magazine arms 
 
 The repeating mechanism. 
 
53 2 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 THE BARREL CALIBRE. The determination of the cali- 
 bre of a small arm involves the consideration of recoil, initial 
 velocity, and various other questions which will be discussed 
 in detail. 
 
 RECOIL. Experience has shown that a certain amount of 
 recoil can be borne by the soldier without fatigue. The 
 fatigue caused by recoil will vary not only with the weight 
 of the arm and the velocity of recoil, but also with the 
 nature of the powder, the inclination of the small of the 
 stock, the area of the stock resting against the shoulder, etc. 
 
 For convenience of carrying and to avoid fatigue the 
 weight of a small arm should not greatly exceed 9 Ibs. This 
 fixes the weight of the barrel, and for a given weight of 
 barrel, or of gun, we conclude generally that the fatigue 
 due to recoil increases with the velocity of recoil. We have 
 for the velocity of recoil while the projectile is in the bore, 
 equation (65), Interior Ballistics, 
 
 >=?(<+ 1). 
 
 Since P, the weight of the gun, is fixed by other con- 
 siderations, as above explained, the velocity of recoil can be 
 reduced only by decreasing the initial velocity v or the 
 weight of the bullet/. 
 
 Objections to Decreasing Initial Velocity. These are 
 obvious. The object of all improvements in modern guns 
 is to obtain as great an initial velocity as possible, keeping 
 the maximum pressure within safe limits, as this increase of 
 velocity gives greater energy, longer ranges, flatter trajec- 
 tories, etc., as will be explained. It is evident, therefore, 
 that the fatigue due to recoil can only be reduced and kept 
 within proper limits by decreasing the weight of the bullet. 
 
 Advantages of Decreasing Weight of Bullet. Considering 
 the equation 
 
 it is evident that for an allowable value of v' , since P is 
 
SMALL ARMS. 533 
 
 constant, a decrease in the weight of the bullet /, will in- 
 crease the initial velocity v. 
 
 Therefore a decrease in weight of bullet gives a value 
 for the recoil which can be easily supported by the soldier, 
 and it also increases the initial velocity of the projectile, 
 which is the object sought. Whether this increase in initial 
 velocity will be advantageous at different ranges depends 
 on the manner in which the weight is reduced, and it is 
 necessary therefore to consider the best method of doing 
 this. 
 
 307. Reduction of Weight of Bullet First Method Decreasing the 
 Length, keeping the Diameter Constant. 
 
 The weight of the bullet may be decreased : 
 
 1. By decreasing its length, keeping the diameter con- 
 stant. 
 
 2. By decreasing the diameter, keeping the length con- 
 stant. 
 
 3. By changing both length and diameter. 
 
 To determine which of these methods is best, assume the 
 equations 
 
 dv P 
 
 dt=W' ........ (438) 
 
 Cdv 
 v = d* ........ (439) 
 
 (440) 
 
 v* 
 
 =gcos 0. ....... (441) 
 
 Equations (438) and (439) are from Mechanics. In (438) 
 P is the total pressure acting to produce acceleration, and 
 M the mass of the projectile. In (439) v is the velocity of 
 the projectile at any time /, and in the present case is the 
 initial velocity. Equations (440) and (441) are from Exterior 
 Ballistics. In (440; R is the retardation of the projectile 
 due to the resistance of the air, and the quantities in the 
 second member are all defined in Exterior Ballistics, d and 
 
534 TEXT-BOOK OF ORDNANCE AND GUNNERY, 
 
 W being the diameter and weight of the projectile. In 
 (441) v is the velocity of the projectile at any point of its 
 trajectory, P the radius of curvature at that point, and 
 the inclination of the tangent, g being 32.2 ft.-seconds. 
 
 DECREASING LENGTH OF PROJECTILE, DIAMETER CON- 
 STANT. In equation (438), 
 
 dv___P_ 
 dt ~ M' 
 
 the total pressure P = p' X i^ 2 , p' being the pressure of 
 the powder per unit of area of base of projectile. 
 
 For constant values of/' and d, P will remain constant. 
 Hence if the length of the projectile be decreased, the 
 diameter being constant, Mwill decrease, and from equation 
 
 (438) i-, or the acceleration, will increase. 
 In equation (439), 
 
 *<fc 
 
 = fi 
 
 dv 
 since increases, v, or the initial velocity, will increase. 
 
 In equation (440), 
 
 since ^decreases while ^remains constant, R will increase. 
 This will cause z> to decrease for all points of the trajec- 
 tory, and hence in equation (441), 
 
 ft ~^ C 
 
 p will decrease, or the trajectory will be more curved. 
 
 If /, the pressure of the powder per square inch, be 
 increased, P in equation (438) will increase, and hence also 
 dv 
 . This, in equation (439), will cause an increase in v, but 
 
 since from (440) the retardation is still great, the velocity 
 
SMALL ARMS. , 535 
 
 will fall oft rapidly, arid from (441) the trajectory will be 
 very much curved. 
 
 The results obtained by decrease of weight of bullet, by 
 the method of shortening it, and keeping the diameter con- 
 stant, are, therefore : 
 
 1. The velocity of recoil is decreased; 
 
 2. The initial velocity is increased ; 
 
 3. The remaining velocity at different points falls off very 
 rapidly ; 
 
 4. The curvature of the trajectory is increased. 
 
 From the 3d and 4th results we conclude that this 
 method of reducing the weight of the bullet should not be 
 adopted. 
 
 308. Reduction of Weight of Bullet Second Method Decreasing 
 Diameter, keeping Length Constant. 
 
 In equation (438), 
 
 dv__ P^ 
 dt ~~M> 
 
 we have as before 
 
 Suppose/' fixed and ^ decreased. Then, since the area 
 of cross-section of the projectile decreases in this case, P 
 will decrease directly with it, and the mass M will also 
 decrease directly with the same area, the length being con- 
 
 p 
 stant, and hence the ratio -jr= will not change. The same 
 
 may be shown for an increase in diameter, the length being 
 
 constant. 
 
 W 
 The sectional density of a projectile is --^ (see Projec- 
 
 tiles, subject 164). Substituting for IV its value, we have 
 
 W 
 
 */ 1 
 
 ' ' 
 
 or the sectional density varies with the length. Hence 
 when the length is constant, the sectional density is con- 
 
TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 stant, and from the above we conclude that for the same 
 pressure per square inch, and the same sectional density of 
 projectile, no increase of velocity is obtained by reducing 
 the weight, assuming the same pressure curve in the two 
 cases. 
 
 In equation (440), 
 
 since T^and v do not change, there is no change in retarda- 
 
 tion, and consequently there is no change in curvature, 
 equation (441). 
 
 Therefore the only effect of reducing the weight of the 
 projectile by decreasing the diameter and keeping the 
 length constant, or, in other words, keeping the sectional 
 density constant, when the pressure per square inch p' re- 
 mains constant, is to diminish the velocity of recoil. 
 
 Suppose, however, that/' is increased. 
 
 Then in equation (438), 
 
 M, as before, will decrease directly with the area of cross- 
 
 p 
 section, but P will increase, and hence the ratio -^ will 
 
 increase. This will cause -=- to increase. 
 
 at 
 
 In equation (439), 
 
 v will increase. In equation (440), 
 
 R remains constant, since ^ does not change ; or it may 
 even decrease, owing to the increase in v, and the conse- 
 
SMALL ARMS. 537 
 
 quent change in the exponent of f(v) from 3 to 2 (see 
 Mayevski's experiments, Exterior Ballistics), v therefore 
 will be greater for all points of the trajectory, and in 
 equation (441), 
 
 g cos & 
 
 p will be greater, and hence the curvature of the trajectory 
 will be less, or it will be flatter. 
 
 Hence by decreasing the weight of the bullet by the 
 second method, that is, by reducing the diameter and keep- 
 ing the length constant, and at the same time increasing the 
 pressure per square inch of the powder-gas, we obtain : 
 
 1. A decrease in velocity of recoil ; 
 
 2. An increase in initial velocity ; 
 
 3. No increase in retardation, and perhaps a reduction ; 
 
 4. A flatter trajectory. 
 
 309. Reduction of Weight of Bullet Third Method Changing 
 Length and Diameter Smokeless Powder Advantages of 
 Reduction of Calibre Flatness of Trajectory. 
 
 The method at present adopted is to vary the pressure 
 per square inch, the length, diameter, and weight of projec- 
 tile, so as to obtain the best ballistic results. This has led 
 to a reduction of the calibre from 0.45 to 0.30 inch, a de- 
 crease in the weight of the bullet from 500 to 220 grains, 
 the length being very slightly changed, and an increase of 
 pressure per square inch from a maximum of 30,000 Ibs. to 
 a maximum of 45,000 Ibs. per square inch, an increase of 
 initial velocity from 1300 to 2000 ft.-seconds, with a reduc- 
 tion of velocity of recoil from 14 to 9.6 ft.-seconds, and of 
 energy of recoil from 27 to 1 1 foot-pounds. 
 
 SMOKELESS POWDER. It is evident that to obtain any bal- 
 listic advantage from a reduction of calibre, the pressure per 
 square inch on the projectile must be increased. When the 
 calibre of small arms was first reduced, various attempts 
 were made to obtain this increase of pressure by the use of 
 the old black powder in various forms, such as larger charges 
 compressed, slower burning, etc., but the results were un- 
 
538 TEXT- BOOK OF ORDNANCE AND GUNNERY. 
 
 favorable, giving high and irregular pressures, increase of 
 fouling, etc. The effort to overcome these difficulties led 
 to the introduction of smokeless powder. Its advantages 
 have been explained in High Explosives, one advantage of 
 great importance being that, as the smokeless powder burns 
 more slowly and regularly, it acts upon the projectile like 
 the slow-burning powders already described in large guns, 
 and hence for a given initial value of /' we obtain a greater 
 initial velocity than would be produced by the same initial 
 value of/' with the old black powders. 
 
 ADVANTAGES OF REDUCTION OF CALIBRE. The princi- 
 pal of these are : 
 
 1. Flatness of trajectory, and increase of range ; 
 
 2. Decrease in weight of cartridges ; 
 
 3. Increase of accuracy of fire ; 
 
 4. Decrease of recoil ; 
 
 5. Increased penetration. 
 
 FLATNESS OF TRAJECTORY. The advantage of this may 
 be illustrated as follows : Assume, equation (441), 
 
 g cos 6' 
 
 Let Hj Fig. 308, be the height of a man, and suppose 
 this height to be the maximum height of the trajectory. 
 The total range in this case is called the maximum contin- 
 uous dangerous space, and is frequently used in comparing 
 the ballistic qualities of guns. 
 
 The value of cos = i at the summit of the trajectory; 
 hence 
 
 for this point It is evident that p increases rapidly with v. 
 
 Hence for a low velocity we will have the trajectory 
 
 AB, and for a high velocity, A'B', the maximum continuous 
 
SMALL ARMS. 539 
 
 dangerous spaces beinsr the horizontal distances AB and A' B' 
 respectively. The flat trajectory, then, gives a greater con- 
 tinuous dangerous space A'B', and this is true when the 
 dangerous space is not continuous, as in the case of the ob- 
 ject H'\ the dangerous spaces being H'B and BB' respect- 
 ively. 
 
 An error in estimating distance is also of less importance 
 with a flat trajectory ; as in the figure, an error H'B for the 
 curved trajectory, and BB' for the flat one, may be com- 
 mitted, and the target will still be struck. The distances 
 AB and A' B' for the calibres .45 and .30 are 418 and 600 
 yards respectively. 
 
 310. Advantages of Reduction of Calibre Decrease in Weight of 
 Cartridges Increase of Accuracy of Fire Increased Pene- 
 tration. 
 
 DECREASE IN WEIGHT. The number of rounds carried 
 is limited by the physical endurance of the soldier, just as 
 the weight and recoil of his piece are fixed by the same 
 conditions. A reduction in the weight of the cartridge in- 
 creases the number of rounds that can be carried, and this 
 increase is very important owing to the great increase in 
 rapidity of fire with modern breech-loaders, and the dif- 
 ficulty of supplying the fighting-line w r ith fresh ammunition. 
 This reduction in weight is due not only to the reduction 
 in calibre, but also to the introduction of smokeless powder, 
 by which the weight of the charge has been reduced nearly 
 one half. 
 
 INCREASE OF ACCURACY OF FIRE. Owing to the greater 
 velocities at all points of the trajectory, the small-calibre pro- 
 jectile is less affected by the wind and other deviating causes, 
 and the drift is not greater than with the old projectile. 
 Hence the horizontal deviations are less than with the old 
 projectile. As has already been shown, the flatness of trajec- 
 tory makes it more accurate in a vertical direction, and hence 
 its absolute accuracy, which is taken to be the radius of the 
 circle containing one half the whole number of shots, is 
 greater than with the old bullet, the radius of the circle 
 being less. 
 
54 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 There is, however, one exception to this. Owing to the 
 relative increase in length of the new bullet, it is necessary 
 to give it greater velocity of rotation about its longer axis 
 to insure stability, and hence the pitch of the rifling is more 
 rapid for the new small calibre. 
 
 This increases the passive resistances in the bore, and, 
 with the greater pressure per square inch on the projectile, 
 causes increased vibration of the barrel. The result is that 
 for short ranges the accuracy of the small calibre is slightly 
 less than that of the old arm. 
 
 Beyond these ranges the small calibre is more accurate. 
 
 INCREASED PENETRATION. This is due to increase of 
 velocity, and also to the fact that the exterior of the bullet 
 is covered with a jacket of harder metal, such as copper, 
 German silver, or nickeled steel. This jacket holds the 
 projectile together and prevents deformation on striking. 
 It is stated that the bullet of the 8-mm. rifle has pierced a 
 tree 17 inches in diameter, and afterwards passed through 
 the bodies of five men. The penetration of the cal. .30 bullet 
 with steel jacket is in sand 14 inches, and in oak from 16 
 to 24 inches, the target being 3 ft. from the muzzle. The 
 penetration of the cal. .45 bullet under the same circum- 
 stances is 3.3 inches in oak. 
 
 Numerous experiments have been made upon human 
 bodies to test the effect of the small-calibre bullet, with the 
 general result that the wounds are less serious and the shat- 
 tering effect on the bones less than with the old projectile. 
 The shock or stopping power is also less as the calibre 
 decreases, unless the bullet acts explosively, and hence it has 
 been proposed for the very small calibres to remove the 
 jacket from the point of the bullet, thus causing it to spread 
 out in front on striking. 
 
 311. Disadvantages of Reducing the Calibre. 
 
 The principal of these are: 
 
 i. The decrease in weight of bullet, and hence the rela- 
 tive increase in its length, necessitates a more rapid twist of 
 rifling to give it stability in flight, and this increase of twist 
 increases the passive resistances in the bore and gives rise 
 
SMALL ARMS. 541 
 
 to greater vibrations of the barrel. These vibrations, as 
 stated, decrease the accuracy for short ranges. A test with 
 the barrel confined in a fixed rest showed greater inaccuracy 
 at 500 yards than with the cal. .45. A heavy barrel cal. .30, 
 made expressly for the purpose, was then tried in the fixed 
 rest under similar conditions, and remarkable accuracy, 
 greater than ever before recorded, was obtained. This 
 shows that the inaccuracy is due to vibrations of the barrel, 
 and it is probable that when the gun is fired from the 
 shoulder in the ordinary manner the targets will be much 
 better than when a fixed rest is used, as the barrel in this 
 case will not be rigidly held, and consequently its vibrations 
 will be less. 
 
 The increase in twist also renders the projectile more apt 
 to strip in the bore; that is, to be forced across the lands 
 without taking the rifled motion, with the result that the 
 bore is scored or fouled by the metal, and the projectile 
 rotates about its shorter axis in flight, or tumbles. This 
 has been remedied by the use of a harder metal jacket. 
 
 2. The cleaning of the bore is more difficult. Since the 
 introduction of smokeless powder this objection has less 
 weight. 
 
 3. The manufacture is more difficult. 
 
 This has been a serious objection, as it is a very difficult 
 operation to bore and rifle accurately such a small calibre, 
 and any inaccuracy here is fatal to the accuracy of fire. 
 This difficulty has also been overcome, and guns below 0.30 
 calibre are now successfully made. 
 
 4. The pressure in the bore is greater. 
 
 The necessity for this has been shown, and it has been 
 difficult to provide steel of sufficiently high elastic qualities 
 to withstand this pressure. It has also caused the abandon- 
 ment of nearly all the old forms of breech mechanism, in 
 order to obtain a secure fermeture. 
 
 In spite of these objections, the great advantages of a 
 reduction of calibre have led to its universal adoption in all 
 countries, and the tendency now is to go below the .30 
 calibre. This has been done in some countries. One of 
 the points still in doubt is the effect of the small-calibre 
 
54 2 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 bullet upon the nervous system, and whether a wound from 
 this bullet, when not fatal, will stop a man. 
 
 This can only be solved in actual war, and hence in our 
 service it has been thought best not to go below the cal. .30 
 at present. 
 
 312. Rifling Pitch Number of Grooves and Lands Width 
 Depth Direction of Twist. 
 
 PITCH. The pitch of the rifling in small arms is alw r ays 
 uniform, because, when fired, the bullet is molded accurately 
 into the grooves and lands, and the length of the surface of 
 the bullet in contact with the bore is great. If the pitch be 
 uniform, no change of form of the molded surfaces takes 
 place during the passage of the projectile from breech to 
 muzzle ; if the pitch be increasing, a change of form is con- 
 stantly occurring, resulting in increased resistance, deform- 
 ation of projectile, and inaccuracy. 
 
 It has been found necessary in practice to increase the 
 twist as the calibre decreases, as already explained (see sub- 
 ject 163). 
 
 In the Springfield cal. .45 the twist is one turn in 48.9 
 calibres, in the new cal. .30 it is one turn in 33^ calibres, or 
 one turn in 22 and 10 inches respectively. 
 
 NUMBER OF GROOVES AND LANDS. The number of 
 grooves has no effect apparently upon the accuracy of fire, and 
 hence for convenience of manufacture, cleaning, and strength, 
 these are as few as possible. The cal. .45 has three grooves 
 and lands, the cal. .30 four. As a general rule the number 
 has varied from three to seven. 
 
 WIDTH OF GROOVES AND LANDS. The width depends on 
 the kind of bullet. When of hardened lead, the bullet is 
 slightly upset by the shock of discharge and forced into the 
 grooves, the lands cutting into the projectile. As this metal 
 offers comparatively little resistance, and the twist is not 
 rapid, the grooves and lands in the cal. .45 are of equal width. 
 
 With the jacketed bullet, the resistance to 'deformation 
 being much greater, the grooves are wider and the lands 
 narrower, since these latter do the work of cutting into the 
 
SMALL ARMS. 
 
 543 
 
 projectile. In the U. S. cal. .30 the grooves are three times 
 the width of the lands. 
 
 DEPTH OF GROOVES AND LANDS. If the depth of groove 
 is too great, there is too much work lost in forcing the projec- 
 tile, and the forcing may not be perfectly accomplished. 
 This latter will cause erosion and inaccuracy. If the depth 
 is too small, the groove may be easily filled by fouling. The 
 depth also varies with the kind of bullet. The depth of 
 groove in the Springfield cal. .45 is .005 inch, and in the 
 cal. .30 it is .004 inch. 
 
 The exterior diameter of the lead bullet is 0.457 inch, 
 that of bore at bottom of grooves .455 inch (see Fig. 309). 
 
 Hence with the Springfield rifle, in addition to the work 
 done by the lands in cutting into the projectile, the latter 
 -exceeds the diameter of the bore at bottom of grooves by 
 .002 inch. This, added to the upsetting action of the pow- 
 der, gives a very energetic forcing, and insures its accom- 
 plishment, but without great strain on the gun. The 
 cannelures or grooves in the bullet also assist in reducing 
 the work. With the cal. .30 the exterior diameter of the 
 bullet is 0.308 inch, and that of the bore at the bottom of 
 grooves the same. Hence the bullet exactly fills the bore 
 from groove to groove, and there is no forcing in the 
 grooves, aside from what may be due to upsetting of the 
 metal by the action of the powder and the pressure of the 
 lands. 
 
 FIG. 309. 
 
 FIG. 310. 
 
 In general the grooves have the same depth from breech 
 to muzzle. In the case of the Martini-Henry rifle recently 
 used in the English service, the depth of groove decreased 
 
 1II7B- 
 
 
 
544 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 from breech to muzzle, to make the forcing more gradual, 
 and thus decrease the pressure at the origin, ana conse- 
 quently the vibrations. 
 
 Figs. 309 and 310 show the cal. .45 and cal. .30 grooves 
 in section. 
 
 DIRECTION OF TWIST. This has no influence upon the 
 accuracy of fire, as it produces " drift," which can be allowed 
 for. All small arms are rifled with a right-hand twist, and 
 the resulting drift is to the right as already explained. 
 
 A case occurs in the French service, where the vibrations 
 of the barrel, owing to the peculiarity of the breech mech- 
 anism, caused the bullet to deviate to the right, and to 
 correct this the gun was rifled with a left-hand twist. 
 
 313. Profile of Chamber Thickness and Length of Barrel. 
 
 FIG. 311. 
 
 PROFILE OF CHAMBER. The chamber is made slightly 
 conical to facilitate the extraction of the cartridge-case. 
 That for the cal. .30 rifle is shown in Fig. 311. The chamber 
 must be free from all cuts or scratches, since the cartridge- 
 case will be forced into them on firing, and will either stick 
 or rupture. All dimensions must be exact, and very little 
 variation can be allowed. 
 
 THICKNESS OF BARREL. The case is that of a single 
 cylinder under extension, the exterior pressure being zero 
 (see " Elastic Strength of Guns "). For the thickness of the 
 cal. .30 rifle-barrel just in front of the powder-chamber, 
 assume, equation (205), 
 
SMALL ARMS. 545 
 
 We have 
 
 r, .30 
 
 -#o = = ^S* 
 
 B o = 61,500 Ibs., 
 P = 40,000 Ibs., 
 
 which values substituted in the above equation give 
 R l R = .3429 inch = 1.14 calibres. 
 
 The actual thickness is 0.34 inch = 0.49 0.15 = 0.34. 
 
 For the thickness at various points along the bore the 
 pressure curve must first be calculated, but other considera- 
 tions, such as stiffness to resist vibrations and to prevent 
 bending in service, etc., enter, and the exterior is given the 
 general form of a conical frustum, the thickness at the 
 muzzle being 0.53 calibres, 0.16 inch. 
 
 LENGTH OF BARREL. This is so adjusted that the rear- 
 rank man can fire over the shoulder of the man in front 
 without danger to the latter, and for the small-calibre rifle 
 this length is fixed at 30 inches (100 calibres). 
 
 Experiment shows that increasing this length gives very 
 little increase of initial velocity, while it increases weight 
 and difficulty of manufacture. The length of the cal. .45 
 barrel is 32.6 inches. The length of travel of the projectile 
 in the bore for the cal. .30 is 28.19 inches (94 calibres), and 
 for the cal. .45, 30.445 inches (67.6 calibres). 
 
 314. The Receiver General Features Receiver for Springfield 
 Rifle. 
 
 THE RECEIVER is a distinctive feature of breech-loading 
 small arms, and forms an extension of the barrel, for the 
 purpose of receiving the cartridges and breech mechanism. 
 
 GENERAL FEATURES. The shape of the receiver depends 
 on the breech mechanism, and also upon whether the gun 
 is a single-loader or a magazine arm. 
 
 In general it must have the following features: 
 
 1. A method of attachment to the barrel. 
 
 2. A method of attachment to the stock. 
 
546 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 3. An opening through which cartridges are inserted, 
 empty shells extracted, and in which the breech-block or 
 bolt works. 
 
 4. An axis about which the block rotates, or guide- 
 grooves for regulating the motion of the bolt. 
 
 5. A recess or groove for locking the block or bolt. 
 
 6. An arrangement for ejecting empty cartridge-shells ; 
 and for a magazine arm in addition to the above 
 
 7. An opening for the admission of cartridges from the 
 magazine. 
 
 8. A " cut-off " by which this opening may be used or 
 not at will. 
 
 RECEIVER FOR SPRINGFIELD RIFLE. Fig. 312 shows the 
 receiver for the Springfield rifle. 
 
 FIG. 312. 
 
 It is attached to the barrel B by the screw-threads a ; to 
 the stock, by a screw, b, passing through the tang c\ d is 
 the opening through which the cartridges are fed, and in 
 which the breech-block works ; // is the axis about which 
 the breech-block rotates; g, the recess into which the breech- 
 block is locked by its cam-latch, to be described ; / is the 
 ejector spring and spindle. The cartridge-case is loosened 
 in its seat by the positive action of the extractor E, which 
 rotates in the direction of the arrow. The axis of the 
 spindle of the spring /is at first above the axis of rotation, 
 H, of the block and extractor. After a small rotation of E, 
 the axis of the spindle is carried below the axis H, and the 
 spring / then acts to rotate E quickly, and throw out or 
 eject the empty case. As the case moves backward, it 
 strikes the inclined stud /, and is, by it, deflected upward 
 out of the receiver. 
 
SMALL ARMS. 547 
 
 -315. Receiver for Cal. .30. 
 
 This is shown in Fig. 313. 
 
 It is attached to the barrel by a screw-thread, and to the 
 stock by the sere ws Jf and Fpassing through the trigger-guard 
 
 FIG. 313. 
 
 into it from below (see Fig. 336) ; z is the opening through 
 which the cartridges are fed when the gun is used as a 
 single-loader, and z' when used as a magazine arm. The 
 left side, r, of the opening z, is parallel to the axis of the 
 bore and, together with the surface, r* ', on the right, forms 
 a guide for the bolt when moving forward or back. A 
 second groove, h, forms a recess for the operating-handle of 
 the bolt to rest in, when this handle is rotated to the right 
 in closing the breech. The forward shoulder or cam, s, in 
 front of the groove, k t is so shaped as to give a screwlike 
 motion to the bolt in closing, thus moving it slowly forward 
 to its seat against the breech. The rear shoulder, /, arrests 
 the forward motion of the bolt in closing. A third groove, 
 k, prevents the firing mechanism from turning with the bolt 
 in closing the breech. 
 
 The groove a locks the bolt, a lug on the latter entering 
 it. When in the firing position, the pressure of the gas is 
 transmitted to the surface of the groove a ; the surface s, and 
 the rear surface of the groove //, acting as safety-supports. 
 
 The empty shell is ejected as follows: The bolt is drawn 
 slowly backward at first, by the action of the inclined sur- 
 face, /, of the groove /*, against the operating-handle. The 
 extractor, which is on the bolt, and engaged with the rim 
 of the cartridge, draws the case back slowly, due to this 
 motion of the bolt. When the bolt is free to move along 
 
54 8 TEX 7 '-BOO K OF ORDNANCE AND GUNNERY. 
 
 the axis of the receiver, it moves quickly, drawing back the 
 empty case. 
 
 At the end of the travel of the bolt, the short arm, e, of 
 the ejector-lever, 'in the bottom of the receiver, is struck by 
 a shoulder at the end of a groove in the bolt, and the long 
 arm,y, is thrown up, striking the empty case and ejecting 
 it. The opening m is the magazine, which will be explained 
 later. 
 
 The cut-off for the magazine, Fig. 314, is a pin or rod, 
 the rear part, a, of which is round, and the front part, r, is 
 
 cut away partly, as shown. The 
 cut-off is inserted in the left-hand 
 side of the receiver, parallel to 
 its axis (see Fig. 313, C), the cut- 
 F away portion, c, projecting over 
 
 the opening z' of the magazine. 
 When the magazine is in use, the flat part of the cut-off 
 forms a portion of the surface z' of the magazine opening. 
 When the rnagazine is to be cut off, the rod is rotated by 
 turning the handle C. This brings the rounded part of c 
 into such a position that it projects into the opening z' and 
 forces the cartridges down slightly, so that the bolt will 
 pass over without touching them. 
 
 The cut-off is held in the open or closed position by the 
 spring C', which works in a groove in the receiver. 
 
 316. Breech Mechanism General Classification Sliding Mech- 
 anism. 
 
 The functions of the breech mechanism are to open, close, 
 and lock the breech, extract the empty cartridge-case, and 
 for magazine arms, in addition, to operate the repeating 
 mechanism, and insert the cartridge. 
 
 GENERAL CLASSIFICATION. Breech mechanisms may be 
 classified generally into : 
 
 1. Those which operate by sliding. 
 
 2. Those which operate by rotation. 
 SLIDING MECHANISM. The sliding may take plac 
 i. By the motion of the barrel parallel to its axis. 
 
SMALL ARMS. 549 
 
 This arrangement is now obsolete, and is unsuitable for 
 ^a military weapon on account of the weight of the barrel. 
 
 2. By the motion of the breech-block parallel to its axis. 
 Guns with this mechanism are called bolt-guns, and the 
 
 mechanism resembles in its action the bolt of a door, whence 
 the name. All magazine arms at present in use belong to 
 this system. It presents the following advantages : 
 
 a. Extreme simplicity, great strength, and small number 
 of parts. 
 
 b. Secure locking against the effects of discharge. 
 
 c. Ease of extraction of empty case. 
 
 d. Better adapted to magazine arms than any other sys- 
 tem. 
 
 The objections to the system formerly were : 
 
 a. Danger of blowing out the bolt by premature dis- 
 charge, before the breech was securely locked. 
 
 b. Liability to explode the cartridge when pushing it 
 home, either by striking it a blow, or by the projection of 
 the firing-pin striking the primer in the cartridge-case. 
 
 These objections have been overcome. 
 
 3. The block may slide at right angles to the axis of the 
 barrel. An example in seen in the Krupp fermeture. 
 
 The advantage of this system is that it is not liable to 
 blow out, as the direction of the pressure is normal to the 
 bearing surfaces of the block ; the disadvantages are that it 
 tends to guillotine the cartridge, does not push it home, and 
 renders extraction of the empty case difficult. 
 
 317. Rotating Mechanism. 
 
 The rotation may take place 
 
 1. Around an axis parallel to the axis of the gun, and at 
 one side. This is now obsolete. 
 
 2. Around an axis parallel to the axis of the gun, and 
 below it; example, revolvers. 
 
 This system is objectionable for a military arm,, on 
 account of the weight of the revolving cylinder, and also 
 because of the break in the barrel at the junction of the 
 cylinder and barrel proper, through which gas may 
 escape. 
 
550 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY, 
 
 3. Around an axis at right angles to the axis of the gun,, 
 above that axis, and at the front of the block ; example, the 
 Springfield rifle cal. .45. 
 
 This system has the following advantages: 
 
 a. The block acts to push the cartridge home in clos- 
 ing. 
 
 b. It forms, in connection with the extractor, a strong 
 lever for extracting the empty case. 
 
 c. It is simple and has comparatively few parts. 
 Its disadvantages are : 
 
 a. It does not securely and positively lock the block, and 
 the tendency of the pressure, is to force it strongly against 
 the breech-recess ; hence for high pressures, as in the present 
 small calibre, it is difficult to open after firing. 
 
 b. It is not adapted for a magazine arm. 
 
 4. Around an axis at right angles to the axis of the bore,, 
 above that axis, and in rear of the block ; example, the 
 Martini-Henry recently used in the English service (Fig. 
 
 315). 
 
 \ 
 
 FIG. 315. 
 
 The advantages of this system are: 
 
 a. It is simple and solid, and the block is well protected 
 against accident. 
 
 b. The pressure does not tend to blow open the block. 
 Its disadvantages are : 
 
 a. A space must be left between the front of the block 
 
SMALL ARMS. 551 
 
 and the rear of the chamber to allow for rotation of the 
 block, and hence the chamber cannot be tightly closed. 
 
 b. The extraction of the empty case is difficult. 
 
 c. The block is liable to guillotine the cartridge, unless 
 the latter is forced completely home before closing the 
 breech. 
 
 5. Around an axis at right angles to the axis of the gun, 
 below that axis, and in front of the block; example, the 
 Remington, Fig. 316. 
 
 FIG. 316. 
 
 This system is simple, but requires an exact adjustment 
 of all the parts, especially of the hammer, as in addition to 
 its ordinary functions it locks the breech-block. 
 
 A system is also used in which the barrel rotates about 
 an axis at right angles to the bore and below that axis ; 
 example, shot-guns. This is not used for military arms, on 
 account of the weight of the barrel. 
 
 318. Requirements of a Good Breech Mechanism. 
 
 A good breech mechanism should fulfil the following 
 requirements: 
 
 1. It should be simple, strong, and safe in action, and 
 should work freely under all conditions which are liable to 
 prevail in active service, even when rusty or covered with 
 dust. 
 
 2. It should be easy to clean, take apart and assemble, 
 
55 2 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 and should be composed of few pieces, which are not liable 
 to break or work loose, and which are interchangeable. 
 Screws are objectionable, as they are liable to work loose. 
 
 3. The motions in loading should be as few as possible, 
 and executed in regular order, and it should be impossible 
 to fire the gun till the breech is securely locked. 
 
 4. To increase the rapidity of fire, the motion of opening 
 and closing the breech should cock the firing mechanism. 
 In general it is preferable to cock the firing mechanism by 
 the motion of opening the breech, as this withdraws the 
 firing-pin so that it will not strike the primer of the cartridge 
 when the latter is pushed home, and in addition, if the mech- 
 anism is cocked in closing, a slip of the hand before the bolt 
 is home will cause the latter to spring back, and either 
 throw out the cartridge which is partly introduced, or, in 
 case of a magazine arm, it may cause the introduction of a 
 second cartridge before the mechanism, and thus produce 
 jamming. 
 
 5. The opening of the breech should automatically eject 
 the empty case. 
 
 6. The working of the mechanism should cause as little 
 fatigue as possible to the firer. 
 
 7. A safety-device should be provided which can be 
 readily seen and operated, and by which the mechanism can 
 be locked in place and accidental discharge rendered im- 
 possible. 
 
 8. It should be impossible to strike a blow on the car- 
 tridge, either by the bolt, or by the firing-pin, while the 
 breech is being closed. 
 
 319. Breech Mechanism of Springfield Rifle, Cal. .45. 
 
 This mechanism belongs to the system in which the 
 block rotates about an axis perpendicular to the axis of the 
 gun, above that axis, and in front of the block. 
 
 Although it is to be replaced by the cal. .30, the arm is still 
 (1895) in service, and is likely to be used in any emergency 
 arising within the next few years, and hence its mechanism 
 will be explained. 
 
SMALL ARMS. 
 
 The principal parts are (Fig. 317): 
 The breech-block D\ 
 The hinge-pin H ; 
 The cam-latch G ; 
 The extractor E ; 
 The ejector spring and spindle /. 
 
 553 
 
 FIG. 317. 
 
 The receiver and ejector spring, spindle, and stud have 
 been previously explained. 
 
 THE BREECH-BLOCK. This has an oblique hole,/, Fig. 
 318, through it for the firing-pin. In front is the hinge-pin 
 hole h, which is elongated parallel to the axis of the bore, 
 and through which passes the hinge-pin H, Fig. 317, around 
 
 FIG. 318. 
 
 which the block rotates. In rear is a recess, k, called the 
 cam-latch recess, for the cam-latch G and its spring K, Fig. 
 317. The shaft of the cam-latch passes through the hole^-'. 
 
 THE HINGE-PIN. This forms the axis about which the 
 block rotates. It passes through two holes in the lugs of 
 the receiver, and is kept from turning by an arm with a stud 
 which fits in a hole on the side of the receiver. 
 
 THE CAM-LATCH. This locks the breech-block in firing 
 by entering a circular recess, g, in the breech-screw C, Fig. 
 317. It is fixed to a shaft one end of which passes through 
 the hole^-', Fig. 318, in the block, and the other end is sup- 
 
554 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 ported by the breech-block cap g", which is removable. 
 The axis of the cam-latch shaft projects on the right-hand 
 side, and to it is attached a thumb-piece by which the cam- 
 latch is operated. This axis fits loosely in the hole g 1 in the 
 breech-block, and also in the corresponding hole in the 
 breech-block cap^-". 
 
 The cam-latch is pressed to the rear into its recess in the 
 breech-screw by the cam-latch spring K. 
 
 THE EXTRACTOR. This is mounted on the hinge-pin, on 
 the left side of the chamber. Part of its lower extremity is 
 cut into such a shape as to form, when in place, a part of 
 the couriterbore of the chamber, in which the rim of the 
 cartridge rests. It has also in front, and slightly above the 
 axis of the hinge-pin, a recess for the reception of the head 
 of the ejector-spindle; and a lug, e, Fig. 317, projects be- 
 yond the upper surface of the receiver, against which the 
 breech-block bears in opening. 
 
 ACTION OF MECHANISM. When the piece is fired, the 
 breech-block slides bodily to the rear, owing to the elonga- 
 tion of the hinge-pin hole k, Fig. 318. Owing to this motion 
 of the block, and to the loose fit of the cam-latch shaft in its 
 holes in the block, the pressure of the powder-gas is trans- 
 mitted directly, through the breech-block and the body of 
 the cam-latch, to the breech-screw C, and there is no strain 
 upon the hinge-pin H or the cam-latch shaft. The block is 
 opened by pressing the thumb-piece forward, which dis- 
 engages the cam-latch from its recess. When the block 
 has nearly completed its rotation upward, it strikes against 
 the projecting lug, e, of the extractor E, Fig. 317, and rotates 
 the latter slowly, thus extracting the empty case. The 
 ejector then acts as before explained, and throws the case 
 out of the receiver. 
 
 320. Breech Mechanism of the Cal. .30 Rifle The Bolt. 
 
 This mechanism belongs to the system in which the 
 block slides parallel to the axis of the bore, and the gun is 
 a bolt-gun. 
 
 The principal parts are : 
 
SMALL ARMS. 
 
 555 
 
 The bolt A Fig. 319; 
 The sleeve /, Fig. 320; 
 The extractor E, Fig. 321. 
 
 THE BOLT, Fig. 319, is a hollow cylinder, closed at the 
 front end except a small opening, /', in the centre, for the 
 
 FIG. 319. 
 
 passage of the point of the firing-pin. Its interior shape is 
 shown in section, Fig. 336. 
 
 The head of the cartridge rests against the front of the 
 bolt, which is hollowed to receive it, and which supports 
 the pressure of the powder-gas, a is the locking-lug, which 
 engages in the locking-recess <z, Fig. 313, in the front part 
 of the receiver ; r is the guide-rib which rests against the left 
 side, r, of the guide-groove, Fig. 313, when the bolt is un- 
 locked and rotated, and guides the motion of the bolt. It 
 also forms a stop to limit the motion when the bolt is 
 rotated in opening. The guide-rib has a shoulder, e, in front, 
 against which a corresponding shoulder on the extractor 
 rests. 
 
 The rear end, s, of this rib rests in front of a correspond- 
 ing shoulder, j, Fig. 313, on the receiver, when the block is 
 locked for firing, and forms a safety-support to resist the 
 pressure, the lug a being the first support. D is the body 
 of the bolt, in one piece with the operating-handle //. This 
 handle terminates at the bolt, in a collar, d, Fig. 319, which 
 only partly encircles the rear end of the bolt. 
 
 This collar serves to connect the bolt with the other 
 parts of the mechanism. 
 
556 TEXT-BOOK OF ORDNANCE AND GUNNERY, 
 
 The rear side, //, of the operating-handle 7i, rests in front 
 of a corresponding shoulder, //, Fig. 313, in the receiver in 
 the firing position, and forms a second safety-support to re- 
 sist the pressure. 
 
 At the rear end of the bolt is a notch, k, one side be- 
 ing straight and the other inclined. This notch cocks the 
 firing-pin when the bolt is rotated in opening, and also 
 allows the cocking-piece, carrying forward the firing-pin 
 and striker, to move down into it, when the piece is dis- 
 charged, as will be explained 
 
 There is also a longitudinal groove, j, its rear end turn- 
 ing to one side, and its front end terminating abruptly in a 
 shoulder. 
 
 This groove works the ejector-lever /, Fig. 313, in the 
 bottom of the receiver. The notch i ' admits a stud, i' ', Fig. 
 
 320, on the sleeve, and the notch / is for the safety-lock /, 
 Fig. 320. 
 
 321. Breech Mechanism Cal. .30 The Sleeve The Extractor. 
 
 THE SLEEVE (Fig. 320) serves to connect the firing 
 mechanism and the bolt, and carries the safety-lock and the 
 extractor. It consists of a single piece of metal, the lower 
 parts, a and c, of which are hollow cylinders, and the upper 
 part, /, an arm of the shape indicated. The firing-pin and 
 cocking-piece Fk, Figs. 323 and 336, pass through the cylin- 
 ders ac, and the slot k, in c, is to allow the hammer to move 
 forward and back in firing and cocking. The stud i' enters 
 the notch /', Fig. 319, in the interior of the bolt, and locks 
 the bolt and sleeve on the interior. The arm / has a cut, 
 d, which embraces the circular collar d, Fig. 319, on the 
 bolt, and locks the sleeve and bolt together on the exterior. 
 
SMALL ARMS. 55/ 
 
 This locking on the interior and exterior, allows the oolt to 
 turn, while the sleeve remains fixed, but does not allow 
 longitudinal motion of the bolt without the sleeve. The 
 fork e in front carries the extractor , which is secured in 
 it by a screw i. The shoulder g forms a seat for the spiral 
 main spring 6", Fig. 323, which surrounds the firing-pin 
 F. The safety-lock is shown in rear. It consists of a 
 thumb-piece, L, and spindle, /. Its object is, first, to lock 
 the bolt in the firing position, so that the breech cannot open 
 accidentally ; and second, to lock the firing-pin in the full-cock 
 position, so that the piece cannot be accidentally discharged. 
 Both these operations are performed at the same time, as 
 follows : 
 
 The spindle /is half cut away, as explained in the case 
 of the magazine cut-off. The thumb-piece L is cut away 
 also, so that when turned to the left the cut-away portion 
 forms part of the interior surface of the cylinder c, through 
 which the cocking-piece can pass freely. When in this posi- 
 tion also, the cut-away part of the spindle / forms part of the 
 interior surface of the cut d, and the collar d, Fig. 319, on 
 the bolt can rotate freely in this cut. When the thumb-piece 
 L is turned to the right, the cut-away part no longer forms a 
 portion of the interior surface of the cylinder c, and hence the 
 cocking-piece cannot enter this cylinder to move forward. 
 At the same time, the rounded part of the spindle /, turns 
 down into the cut d, and its .front end enters the notch /, 
 Fig. 319, in the bolt, thus preventing the latter from rotating. 
 The rear end of the bolt fits against the shoulder o, so that 
 the exterior of the cylinder c and the exterior of the bolt 
 form one continuous surface. 
 
 The cylinder a enters the interior of the bolt. 
 
 THE EXTRACTOR (Fig. 321) is a long bar, E, having a 
 hook, 0, at its extremity which engages over the rim of the 
 cartridge. It is attached at the other extremity to the 
 sleeve /, as already explained, e is a projection which rests 
 against a corresponding shoulder, ^, on the guide-rib r, of 
 the bolt, Fig. 319. q is a recess fitting against a shoulder, r, 
 in the receiver, Fig. 313, in the locked position, and / a 
 spring which acts against the lower surface of q on the re- 
 
558 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 ceiver, to force the extractor down over the rim of the car- 
 tridge. The extractor has a slight motion around the screw 
 i, which is necessary in dismounting the mechanism. 
 
 FIG. 321. 
 
 322. Firing Mechanism General Principles Conditions for Good 
 Firing Mechanism Firing Mechanism of Springfield Rifle. 
 
 The ammunition used with all modern small arms con- 
 tains a central primer of mercuric fulminate, which is ignited 
 by a blow from the firing mechanism. 
 
 The method generally adopted is to transmit this blow 
 through the medium of a firing-pin passing through the 
 breech, mechanism. The pin may be acted on directly by a 
 spring which forces it forward when the trigger is pulled, 
 or it may be acted on by a hammer which is itself acted on 
 directly by a spring: The first method is that now generally 
 adopted for bolt-guns, the second being used in the Spring- 
 field and some older forms of breech-loaders. 
 
 CONDITIONS TO BE FULFILLED BY A GOOD FIRING MECH- 
 ANISM. A good firing mechanism should fulfil the following 
 conditions : 
 
 1. It should ignite the primer with certainty and without 
 piercing it. 
 
 2. It should not be hard to operate, as this causes loss of 
 aim ; nor too easy, as this leads to accidents. 
 
 3. Its parts should be simple, strong, few in number, 
 easily dismounted and assembled, and interchangeable. 
 
 4. It should be cocked automatically by the opening or 
 closing of the breech. The reasons why cocking on open- 
 ing is preferred have been given. 
 
 5. It should have a safety-device to prevent accidental 
 
SMALL ARMS. 
 
 559 
 
 discharge when the piece is carried loaded, and should show 
 clearly whether it is cocked or not. 
 
 FIRING MECHANISM OF SPRINGFIELD RIFLE. The prin- 
 cipal parts of this mechanism are (Fig. 322) : 
 
 The firing pin F\ 
 
 The hammer b ; 
 
 The tumblers; 
 
 The main spring d\ 
 
 The sear e and sear-spring e' ; 
 
 The trigger/. 
 
 FIG. 322. 
 
 The firing-pin F passes through the breech-block Z>, and 
 projects to the rear. The hammer b is fastened to the tum- 
 bler c by the tumbler-screw, and fits on a square arbor or 
 shaft, so that the hammer and tumbler must rotate together. 
 The tumbler has three notches: a full-cock, i ; half-cock, 2; 
 and safety-notch, 3. The main spring d is attached to the 
 tumbler by a swivel, d'. The sear e is a pivoted lever, and 
 is acted on by the sear-spring /, which forces it against the 
 tumbler, and hence it is always ready to catch in one of the 
 notches I, 2, or 3. The trigger f is a pivoted lever, and 
 acts against a projection on the long arm of the sear. The 
 tumbler and sear are held in place, and supported on the 
 inside, by a piece called the bridle, not shown in the figure. 
 
l^EXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 All the parts except the firing-pin and trigger are assem- 
 bled to a flat plate, a, called the lock-plate, which is secured 
 to the right side of the gun by two screws. 
 
 ACTION OF THE MECHANISM. When the trigger / is 
 pulled in the direction of the arrow i, the sear is withdrawn 
 from its notch in the tumbler, and the action of the main 
 spring causes the hammer and tumbler to rotate in the di- 
 rection of the arrowy, striking a blow upon the firing-pin, 
 which is thus driven forward against the primer, explod- 
 ing it. 
 
 323. Firing Mechanism of the Cal. .30. 
 
 The principal parts of this mechanism are (Fig. 323) r 
 The firing-pin F and striker F' ; 
 The main spring G ; 
 The cocking-piece K '; 
 The sear H and sear-spring H' ; 
 The trigger T. 
 
 K 
 
 FIG. 323. 
 
 The firing-pin is composed of two parts, the body F and 
 the striker F ', the method of connection of the two being 
 indicated in the figure. The striker can thus be readily 
 replaced when broken, or removed to permit the replacing 
 of a broken main spring. The firing-pin passes through the 
 sleeve / and the bolt, as already explained, and the main 
 spring G rests between the rear shoulder of the striker F> 
 
SMALL ARMS. 561 
 
 and the front shoulder^- on the sleeve, Fig. 320. It is evident 
 that when the firing-pin is drawn back, the main spring will 
 be compressed, since the sleeve / is fixed with reference to 
 the Din. The cocking-piece K is screwed to the rear end of 
 the firing-pin. The part g is roughened to give a firm hold 
 to the fingers in cocking. The part k carries the full-cock 
 notch i and the wedge-shaped cocking-nose j, all these 
 being in one piece. The cocking-nose j engages in the 
 notch k, Fig. 319, in the rear end of the bolt. 
 
 The sear H is a piece of metal of the shape shown, 
 hinged at a to the receiver, and its nose c, passing through a 
 cut in the bottom of the receiver, engages in the full-cock 
 notch i. It is constantly pressed upward into this notch by 
 the spiral sear-spring H', one end of which bears against 
 the receiver, and the other against the sear. The trigger T 
 is pivoted to the sear. At the rear it rests against the 
 bottom of the receiver, at the point m, and after the trigger 
 is pulled slightly the point n comes into bearing against the 
 bottom of the receiver, the point m losing contact. 
 
 ACTION OF MECHANISM. Suppose the piece fired. 
 When the bolt is rotated to the left by its operating-handle, 
 the inclined side of the notch k, Fig. 319, in the bolt, presses 
 against the corresponding side of/, Fig. 323, and forces the 
 cocking-piece, firing-pin, and striker backward, till the end 
 of j rests against a notch on the rear end of the bolt. The 
 firing-pin is thus drawn back and cocked, the main spring G 
 being compressed. 
 
 After the introduction of the cartridge into the receiver, 
 the bolt is pushed forward and rotated to the right, to 
 lock it. 
 
 In moving forward, the full-cock notch catches against 
 the sear H, and the firing-pin is now held back by the sear. 
 When the bolt is rotated to the right for locking, the slight 
 forward motion completes the compression of the main 
 spring, and the rotation brings the nose/ and part k of the 
 cocking-piece opposite the notch k, Fig. 319, in the bolt 
 When the trigger is pulled in the direction of the arrow, the 
 nose c of the sear is lowered slowly at first out of the full- 
 cock notch i. As the pull of the trigger continues, the point 
 
$62 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 m loses its bearing against the bottom of the receiver, and 
 the point n comes into bearing. The lever-arm being thus 
 increased, the nose of the sear at the last moment, moves 
 quickly out of its notch i ; the firing-pin is forced forward 
 under the action of the main spring G, and the cartridge is 
 fired. If the bolt is not properly locked, the notch k t Fig. 
 319, on the bolt will not be opposite the nosey, Fig. 323, of 
 the cocking-piece, and the latter either cannot move for- 
 ward sufficiently far to allow the firing-pin to strike the 
 primer, or, if the bolt is nearly locked, the forward motion 
 of the cocking-piece will causey to strike the inclined side 
 of the notch k, Fig. 319, and thus cause the bolt to rotate to 
 the right, and completely lock it. This is an additional 
 safety-device. 
 
 324. Sights General Principles Position. 
 
 There are two sights for small arms : 
 
 1. An adjustable rear sight- 
 
 2. A fixed front sight. 
 
 REAR SIGHTS. A good rear sight for a military arm 
 should be simple, solid, easy of repair, graduated so that 
 the marks can be readily seen, and so arranged that when 
 the rear-sight notch is set to any particular graduation it 
 will not be displaced by the shock of firing, or by any other 
 means, except when changed by the firer. The form of the 
 notch should be such as to enable the target to be seen easily. 
 
 It should be out of the way and well protected when not 
 in use, to avoid being broken, and it should contain all the 
 graduations required up to the extreme effective range of 
 the arm. The requisite of simplicity, excludes peep and 
 telescope sights, except for selected marksmen, and the flat 
 trajectories of the small-calibre rifles have greatly simplified 
 the rear sights by reducing their heights, and doing away 
 with corrections for wind, and to some extent for drift. 
 
 Elevations are marked in ranges and not in degrees, as 
 the ammunition is invariable. 
 
 The rear sight generally consists of a leaf which is 
 hinged to a base, the latter being screwed to the barrel of 
 the gun. 
 
SMALL ARMS. $63 
 
 The base carries a flat spring which bears against the 
 lower edge of the leaf and keeps it upright when in use, or 
 folded down against the base when not required. 
 
 The leaf is graduated in ranges (yards) and carries a 
 slide w r hich has a notch cut m it forming the rear-sight 
 notch. 
 
 This slide moves along the leaf, and is clamped at any 
 graduation and held firmly in place. 
 
 FRONT SIGHT. The front sight is generally a stud set 
 at the muzzle, and terminates in a thin edge parallel to the 
 axis of the bore. It should be sufficiently strong, to pre- 
 vent injury by the rough usage of service. 
 
 POSITION. The front and rear sights are generally 
 so placed, that the notch of the rear sight, and top of the 
 front sight, shall be in a plane passing through the upper 
 element of the barrel and the axis of the bore, and at as 
 great a distance apart as possible, so as to give the longest 
 sight-radius attainable, consistently with distinct vision of 
 the target and the two sights. In some arms, as the Spring- 
 field, the rear sight has an arrangement for correcting for 
 wind, and the slide is set with an inclination to the left 
 equal to the permanent angle of drift. 
 
 325. Sights for Springfield Rifle Sights for the Cal. .30. 
 
 SIGHTS FOR SPRINGFIELD RIFLE. Rear Sight. The 
 principal parts are (Fig. 324) : 
 
 The fixed base A ; 
 
 The movable base and spring B\ 
 
 The sight-leaf C\ 
 
 The sight-leaf slide D. 
 
 The fixed base A is screwed to the barrel. The movable 
 base B carries a flat spring, which bears against the lower 
 edge of the sight-leaf C and keeps it vertical or folded 
 down. This movable base rotates about the pivot E, and is 
 moved by the screw F working in a worm on the end of B. 
 The sight-leaf is thus moved to right or left, and corrections 
 made for wind. The sight-leaf C carries the graduations, 
 and is hinged to the movable base at G. It also carries the 
 
564 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 binding-screw //", which can be made to bear against the 
 sight-leaf slide, and thus clamp it in any position. 
 
 The sight-leaf slide D carries the rear-sight notches i, 2, 
 3, 4, and 5. No. 5 is used for ranges up to 200 yards with 
 the leaf down. 
 
 FIG. 324. 
 
 For distinction Nos. i and 3 will be called peep-sights, 
 and Nos. 2 and 4 open sights. 
 
 If the peep-sights i and 3 are to be used, No. i is em- 
 ployed from 200 to 1350 yards, the right-hand arrow on 
 No. i coinciding with the graduations. 
 
 For 1400 yards the leaf-slide is pushed down, and No. 3 
 is used, its mark coinciding with the graduation 14. 
 
 From this to 2000 yards the left-hand arrow on No. i 
 coincides with the left-hand graduations, the sight being 
 taken through No. 3. 
 
 If the open sights 2 and 4 are to be used, No. 2 is 
 employed from 200 to 1400 yards. The leaf-slide is then 
 pushed down, and No. 4 is used, the left-hand arrow on No. 
 2 coinciding with the left-hand graduations. The correc- 
 tions for wind are marked on the fixed base, and the leaf- 
 
SMALL ARMS. 
 
 565 
 
 slide is set at an inclination to the left equal to the perma- 
 nent angle of drift. 
 
 Front Sight. The front sight, Fig. 324, consists of a thin 
 blade, /, set in a stud. 
 
 FIG. 325. 
 
 SIGHTS FOR CAL. ,.30. Rear Sight. The principal parts 
 are (Fig. 325) : 
 
 The fixed base and spring A ; 
 
 The leaf 5; 
 
 The leaf-slide C. 
 
 The fixed base is screwed to the barrel, and carries the 
 flat spring which bears against the lower edge of the leaf 
 B, and keeps it upright or folded. The leaf B is hinged to 
 the base at d and is graduated on both sides, beginning with 
 700 yards. From 300 to 600 yards the fixed base is cut in 
 steps, and the steps marked as in the figure. For ranges up 
 to 600 yards, the leaf is folded down, and the slide C rests 
 upon the corresponding step, the sight being taken through 
 the notch e. Beyond 600 yards the leaf is upright, the top 
 surface of the slide coinciding with the graduation, and the 
 sight is taken through the notch/. The slide C is clamped 
 in place by a serrated piece contained in the slide, and acted 
 on by a spiral spring which presses it constantly against 
 notches on the right-hand inner edge of the leaf. 
 
566 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 A pressure on the button g releases this catch, and the 
 slide may be moved up or down. The arrangement is shown 
 in section in the figure. 
 
 The notch e is set slightly to the left of the axis of the 
 bore and corrects for drift at 500 yards. For distances less 
 than 500 yards this correction is too great, and for those 
 greater than 500 yards too small. 
 
 The notch /is similarly set to the left of the axis of the 
 bore and corrects for drift at 1000 yards. For distances less 
 than this the correction is too great, and for distances 
 greater than 1000 yards, too small. The notches on the leaf 
 and slide are exactly similar to those on the sight of the 
 Springfield rifle. 
 
 FRONT SIGHT. This is shown at F. It resembles the 
 Springfield front sight, and differs from it principally in 
 "being higher. 
 
 326. The Stock and Mountings. 
 
 THE STOCK. The stock is that part of the arm to which 
 all the other parts are assembled, and it serves 
 
 1. To facilitate the handling and pointing, to diminish 
 the shock of recoil by distributing it over a greater area at 
 the shoulder, and to stiffen and protect the barrel. 
 
 2. In some magazine arms to carry the supply of am- 
 munition required for rapid fire, and in all arms to carry 
 certain parts necessary for the service, security, or preserva- 
 tion of the piece. 
 
 For lightness it is made of wood, and for strength this 
 wood should be of close grain, and it should be well sea 
 soned to prevent warping ; walnut is generally used. 
 
 It is widened at the butt, a, Fig. 326, to distribute the" 
 
 ^~~ 
 
 FIG. 326. 
 
 pressure of recoil over the shoulder, and is crooked at the 
 small of the stock, b, for convenience of aiming. This crook 
 
REPEATING OR MAGAZINE ARMS. $6? 
 
 must not be excessive, as it causes rotation about the 
 shoulder, with a lever-arm, ac, which increases with the 
 crook, and may cause inconvenience. It also weakens the 
 stock, since the wood is cut across the grain at this point. 
 
 In some cases, to avoid this weakening and give room 
 for the mechanism, the stock is made in two distinct parts, 
 called respectively the butt-stock and the tip-stock. With 
 smokeless powders, the barrel becomes excessively heated ; 
 and to prevent contact with the hand, the upper part of the 
 barrel, at the rear, is also covered with wood. 
 
 Under the head of mountings are included the wiping, 
 rod, the bands and tip, the butt-plate, trigger-guard, swivels, 
 and the various pins and screws by which these parts are 
 secured to the gun. 
 
 The wiping-rod is screwed into its seat for a short dis- 
 tance, to avoid displacement in firing. 
 
 The bands assemble the barrel to the 
 stock, and are not continuous, but split, Fig. 
 327, and are assembled by a screw, a. They 
 can thus be readily adjusted to the stock 
 and barrel, and any undue binding prevented, 
 as this might cause vibration in firing. 
 
 The butt-plate and trigger-guard preserve 
 the butt and trigger respectively from wear 
 and accident, and the swivels are used for FIG. 327. 
 stacking and to support the gun-sling. 
 
 REPEATING OR MAGAZINE ARMS. 
 
 327. Advantages of Magazine Arms Definition Conditions to be 
 fulfilled by a Good Magazine Arm. 
 
 ADVANTAGES. In ordinary breech-loaders three opera- 
 tions are necessary to prepare for firing : 
 
 1. Open the breech ; 
 
 2. Insert the cartridge ; 
 
 3. Close the breech. 
 
 The longest of these is the time required to take the 
 cartridge from the box or belt and insert it in the gun. 
 
568 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 The rapidity of fire is therefore greatly increased if the 
 cartridges can be automatically introduced, and the three 
 operations reduced to two, viz., opening and closing the 
 breech. 
 
 As, however, the cartridges so introduced must be carried 
 by the piece in some convenient receptacle, it is evident that 
 the number so carried is limited, and hence automatic intro- 
 duction of the cartridges cannot be continuous beyond a 
 few shots. 
 
 The advantage of a magazine arm is, then, that it can 
 furnish a certain number of shots in a very small interval of 
 time ; and in order to make use of this advantage it is neces- 
 sary to be able to reserve this supply till needed, and ordi- 
 narily to use the arm as a single-loader. 
 
 This leads to the conclusion that a good magazine arm 
 should be also a good single-loader, and should fire as 
 rapidly, when used as such, as any good single-loader, since 
 the arm is- used habitually as such, and only in emergencies 
 as a magazine gun. 
 
 DEFINITION. A magazine or repeating arm may then be 
 defined as one in which a certain number of cartridges are 
 introduced in succession, automatically and rapidly, into the 
 receiver. 
 
 CONDITIONS TO BE FULFILLED BY A GOOD MAGAZINE 
 GUN. A good magazine gun should fulfil the following 
 conditions : 
 
 1. When used as a single-loader it should fire as rapidly 
 as any ordinary single-loader. 
 
 2. When used as a magazine 'arm it should give the 
 greatest possible rapidity of fire, and the mechanism should 
 work well and regularly when rapidly used. 
 
 3. It should allow the change from single-loader to 
 magazine fire to be readily and quickly made, and the de- 
 vice for making this change should be readily seen, so that 
 no mistake can be made ; and so placed that it cannot be 
 accidentally operated. 
 
 4. It should afford an easy and rapid method of recharg- 
 ing the magazine. 
 
 5. The cartridges in the magazine must not be damaged 
 
RE PEA TING OR MA GA ZINE A RMS. 
 
 569 
 
 or deformed by firing or by handling the piece, or be liable 
 to explode by the shock of discharge. 
 
 6. The weight of the piece with magazine and cartridges 
 must not exceed that usually allowed for small arms. 
 
 7. It should afford a ready view of the number of car- 
 tridges in the magazine at all times, so that the supply may 
 not be exhausted before they are needed. 
 
 328. Classification of Repeating Mechanism. The Detachable Maga- 
 zine Lee Magazine Advantages and Disadvantages of De 
 tachable Magazines. 
 
 CLASSIFICATION. The repeating mechanism includes the 
 magazine in which the supply of cartridges is carried, and 
 the means by whic'h the supply is fed to the receiver. As 
 these are generally combined, it is customary to classify the 
 mechanisms according to the magazines used. 
 
 Magazines are classified into 
 
 1. Detachable ; 
 
 2. Fixed. 
 
 DETACHABLE MAGAZINES. The detachable magazines 
 are generally box-shaped, and are placed in rear of the 
 barrel and below the receiver. They are called detachable 
 because they may be readily detached from the gun. They 
 
 ,b a 
 
 are generally made of thin sheet steel, and contain a spring 
 or some device by which the cartridges are constantly 
 pressed upward toward the receiver. The top of the 
 magazine is folded over for a short distance at the rear, a, 
 Fig. 328, and these folds hold the cartridges in place against 
 
570 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 the action of the spring. When the bolt is drawn to the 
 rear over the cartridge, a portion, b, of its rim projects be- 
 yond the folds. As the bolt is pushed forward, it strikes 
 the rim b and pushes the cartridge forward beyond the folds, 
 out of the magazine and into the receiver and chamber. 
 This device in some similar form is found in all box maga- 
 zines. 
 
 LEE MAGAZINE. The Lee magazine is a good example 
 
 of this system, and is shown in Fig. 329 with its method, of 
 attachment to the gun. 
 
 FIG. 329. 
 
 a is the magazine, b a projection on its rear end, c the 
 magazine-catch operated by the U-shaped sear-spring d, e a 
 folded spring which pushes the cartridges upward. The 
 filled magazine, containing five cartridges, is inserted from 
 below, in a cut made for it in the stock and receiver, and 
 pushed upward till the magazine-catch c snaps under the 
 projection b. When the magazine is empty it is released by 
 pressing on the magazine-catch c, and withdrawn. 
 
 ADVANTAGES. These are : 
 
 1. Since they can be used only when fixed in place, it is 
 always evident whether or not the magazine supply is being 
 employed. This does not, however, apply to those which 
 are lowered vertically to cut off the supply. 
 
 2. A number of these can be carried loaded, and as they 
 
REPEATING OR MAGAZINE ARMS. $?I 
 
 can be inserted quickly, the rapid fire can be kept up con 
 tinuously for some time. 
 
 DISADVANTAGES. i. The magazine has considerable 
 weight and adds to the burden carried by the soldier. This 
 additional weight could otherwise be utilized to increase 
 the number of cartridges carried. 
 
 2. The magazines are apt to be thrown away or lost 
 when empty, and when lost the gun cannot be used as a 
 magazine arm. 
 
 3. The cut through the bottom of the receiver is incon- 
 venient when the gun is used as a single-loader, and when 
 the magazine is attached it must generally be used ; that is, 
 the gun cannot be used with facility as a single-loader. 
 
 To remedy the inconvenience of the cut in the receiver, 
 the Lee gun has a spring slide which closes this cut as soon 
 as the magazine is withdrawn, and the insertion of the 
 magazine pushes this slide out of the way. In some guns 
 of this type a cut-off is arranged by which the magazine is 
 lowered vertically, so that the cartridges will be out of the 
 way of the bolt when the gun is to be used as a single- 
 loader. 
 
 329. Fixed Magazines Classification Description of the Jarmann 
 Magazine. 
 
 CLASSIFICATION. Fixed magazines may be classified 
 according to their shape into 
 
 1. Tubular; 
 
 2. Box. 
 
 Tubular magazines may be placed either under and 
 parallel to the barrel, in the front part of the stock ; or in 
 the butt, in rear of the barrel. 
 
 Box magazines are placed in rear of the barrel, and 
 directly in front of the trigger-guard. 
 
 TUBULAR MAGAZINE UNDER BARREL JARMANN MAGA- 
 ZINE. The Jarmann magazine-gun, formerly used in Nor- 
 way, may be taken as an example of the tubular magazine un- 
 der the barrel. In Fig. 330, a is the barrel ; b the magazine ; c 
 the spiral spring which forces the cartridges to the rear ; d 
 the piston attached to the end of the spring ; e the carrier 
 
572 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 which lifts the cartridges from the mouth of the magazine 
 to the receiver ; / the carrier-spring, which is fork-shaped 
 and rests on two pins,^-, pressing the carrier down ; h the pin 
 by which the carrier is attached to the receiver, and around 
 
 FIG. 330. 
 
 which it rotates ; i a shoulder on the rear end of the carrier, 
 projecting above the bottom of the receiver when the carrier 
 is down ; j a corresponding shoulder and recess on the lower 
 side of the front of the bolt, which, as the bolt is drawn back 
 allows the carrier first to drop under the action of the spring 
 /, and immediately afterward, as the bolt moves further 
 back, strikes against i and raises the carrier ; k is a projec- 
 tion from the lower front end of the carrier, whose object is 
 to work the cartridge-stop and hold back the next cartridge 
 in the magazine. This projection k, carries a pin, /, which 
 works the cartridge-stop. 
 
 ACTION OF MECHANISM. Suppose the piece fired. The 
 breech is then closed by the bolt, the carrier e is held up in 
 the position shown in the lower figure by the bearing of the 
 lug i on the bottom of the bolt. The carrier thus forms a 
 part of the bottom of the receiver. The cartridges are held 
 back in the magazine against the action of the spring c, by 
 the projection k of the carrier, bearing on the head of the 
 rear cartridge. 
 
REPEATING OR MAGAZINE ARMS. 573 
 
 As the bolt is withdrawn, the carrier e remains in the 
 position just described, because its lug i bears continually 
 against the bottom of the bolt. When the bolt, in its back- 
 ward motion, reaches a position such that the cut/ comes 
 over the lug i of the carrier, the latter is free to rotate, and 
 moves downward under the action of its spring/. During 
 its downward motion the cartridges are kept in place by 
 the bearing of the front of the carrier e against the head of 
 the rear cartridge. At the last moment of the rotation of 
 the carrier, when it occupies the position shown in the 
 upper figure, this bearing is removed, and the rear cartridge 
 is forced by the spring c, out of the magazine, and on the 
 carrier. As soon as this is done, the downward rotation of 
 the carrier being completed, the pin /, on the projection k, 
 strikes the cartridge-stop m, and causes it to rise and partly 
 close the mouth of the magazine, thus preventing the other 
 cartridges from being forced out. All this occurs while the 
 cut/ in the bolt is over the lug z of the carrier. As the bolt 
 is pulled backward still further, the shoulder of/ strikes the 
 shoulder of / and raises the carrier e with its cartridge 
 quickly to the mouth of the chamber. The bolt is then 
 pushed forward and the cartridge inserted. It will be re- 
 membered that at this time the cartridges are held back in 
 the magazine by the cartridge-stop. To release this stop, 
 the bolt, in moving forward, strikes the long lever n of the 
 cartridge-stop, which is situated on the right-hand side of 
 the receiver. This pushes the lever n forward, lowers the 
 stop, and frees the mouth of the magazine, and under the 
 action of the spiral spring c, the cartridges move forward till 
 the head of the rear one comes into bearing against the pro- 
 jection k, which is now in the position shown in the lower 
 figure, the bolt being closed. 
 
 The principles explained here are found in modified 
 forms in all magazines of this type. The magazine has a 
 cut-oft by which the carrier is locked in its upward position 
 and the gun may then be used as a single-loader. 
 
574 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 330. Objections to Tubular Magazines under the Barrel Advan- 
 
 tage. 
 
 OBJECTIONS. The objections to tubular magazines under 
 the barrel are : 
 
 1. The cartridges lie with the primer of one against the 
 bullet of the next, and hence the shock of discharge is liable 
 to explode the primer, or to upset and deform the point of 
 the bullet. With modern smokeless powders, although the 
 bullet is not so liable to be deformed, owing to its harder 
 jacket, it is more liable to be driven down into its case, 
 since any excessive crimping of the bullet to the case, which 
 would tend to prevent this, increases the pressure in the 
 gun, by increasing the resistance to motion at the origin. 
 If the bullet be forced down into the case, the density of load- 
 ing of the charge is increased, and hence also the pressure. 
 
 2. The spiral spring which forces the cartridges into the 
 carrier, must be long, as it has to act over a great distance. 
 Hence it is tightly compressed at first, and its action be- 
 comes very slight on the last cartridge, and is therefore 
 irregular. 
 
 3. When the magazine is full, the centre of gravity of 
 the system is carried forward, and as it is emptied this cen- 
 tre changes. 
 
 4. The weight of the arm increases considerably when 
 the magazine is loaded. 
 
 5. The magazine is difficult to load, as the cartridges must 
 generally be inserted singly. 
 
 6. The state of supply of the magazine cannot be seen. 
 
 7. Unless the bolt is drawn back to its full extent, and 
 quickly, the carrier will not work properly. 
 
 8. As the magazine-tube is thin, a slight damage to the 
 stock may close up the tube so that it will not feed. 
 
 Its greatest advantage is the number of cartridges car- 
 ried. 
 
 331. Tubular Magazine in Butt Fixed - box Magazines The 
 
 Mannlicher Magazine. 
 
 TUBULAR MAGAZINE IN BUTT. This was the earliest 
 form of magazine, as seen in the Spencer rifle, which was 
 
REPEATING OR MAGAZINE ARMS. 
 
 575 
 
 used during the Civil War. It has been abandoned, however, 
 because it has nearly all the disadvantages belonging to the 
 tubular magazine under the stock, and in addition it 
 weakens the small of the stock and does not carry a large 
 number of cartridges. The Hotchkiss is probably the best 
 example of this type. 
 
 FIXED-BOX MAGAZINE. This type of magazine has been 
 adopted by many of the foreign powers and by the United 
 States. 
 
 THE MANNLICHER MAGAZINE. The Mannlicher maga- 
 zine may be taken as a type of this system used abroad. 
 
 FIG. 331. 
 
 In Fig. 331, a is the fixed box, having the bottom open 
 at b. This box is fixed in rear of the barrel and in front of 
 the trigger-guard, and projects below the stock as in the 
 Lee magazine, c is the carrier-lever ; d the magazine-spring, 
 which pushes the carrier-lever upward against the car- 
 tridges. The cartridges are carried in a packet, e, made of 
 tin, the top and bottom edges being slightly folded over, as 
 shown in Fig. 328. 
 
 This packet carries five cartridges, and is inserted with 
 its cartridges, from above, through the cut in the bottom of 
 the receiver, into the magazine a. It is held in place in the 
 magazine, by the upward pressure of the carrier-lever c on 
 
TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 the cartridges, which is transmitted to the packet e by the 
 folded edges, and as this would push the packet out of the 
 magazine, the catch /, acted on by the spiral-spring h y 
 engages against a lug, g, on the rear end of the packet, and 
 prevents it from rising. 
 
 ACTION OF THE MAGAZINE. When the filled packet e 
 is introduced into the magazine, it compresses the magazine- 
 spring d. The packet is pushed down till the catch /snaps 
 over the lug g. The cartridges being constantly pressed 
 upward by c and d, when the bolt is pushed forward it 
 strikes the exposed part of the base of the upper cartridge, 
 and pushes it forward beyond the folded edges of the case, 
 the surface/ of the receiver guiding the point of the bullet 
 upward and into the chamber. When all the cartridges are 
 exhausted, the carrier-lever c and spring d no longer exert 
 an upward pressure on the packet, and hence the latter falls 
 through the opening b in the bottom of the receiver, and 
 thus indicates that the supply is exhausted. 
 
 The packet may be removed at any time by pressing on 
 the projection i of the catch. 
 
 To cut off the supply the packet must be removed. 
 
 332. Advantages and Disadvantages of the Fixed-box Magazine, 
 Mannlicher Type General Principles of the Cal. .30 
 Magazine. 
 
 ADVANTAGES. The Advantages of the fixed-box maga- 
 zine, Mannlicher type, are : 
 
 1. In common with all box magazines, the cartridges lie 
 so that the spring which moves them acts in the direction 
 of their least dimension, and therefore the great length and 
 irregularity of its action, as in the tubular magazine, are 
 avoided. 
 
 2. The cartridges are not liable to explode, or to be de- 
 formed in handling and firing. 
 
 3- The centre of gravity of the system is not changed. 
 
 4- The magazine is easily charged. 
 
 5- The packets are light, and hence do not add much 
 useless weight to the soldier's burden, and they are cheap 
 and may be thrown away. 
 
REPEATING OR MAGAZINE ARMS. S77 
 
 6. The exhaustion of the magazine is automatically 
 indicated. 
 
 7. The magazine cannot be lost, and is not liable to 
 damage. 
 
 DISADVANTAGES. The objections are : 
 
 1. When the packet is in place the arm cannot be used 
 as a single-loader without great care ; and when the packet 
 is withdrawn the bottom of the receiver is not solid, which 
 is an inconvenience. 
 
 2. The cartridges must be carried in-packets, and cannot 
 be placed in the magazine without them. The packet there- 
 fore becomes a necessary part of the mechanism, just as the 
 magazine in the Lee gun. 
 
 GENERAL PRINCIPLES OF THE CAL. .30 MAGAZINE. The 
 magazine of the cal. .30 remedies the last two defects. 
 
 In this gun the magazine is a fixed box, but, instead of 
 projecting vertically below the receiver, it is partly hori- 
 zontal and partly inclined at the left side, where it opens 
 into the receiver. This gives a solid bottom to the receiver, 
 so that no inconvenience results from using the gun as a 
 single-loader, and the cartridges may be inserted into the 
 magazine either singly by hand or quickly from a packet 
 carrying five cartridges. This latter arrangement is called 
 a quick-loader, and is used in many other box-magazine guns, 
 in which the packet does not form an essential part of the 
 mechanism, as with the Lee, and the Lee-Speed or English 
 gun. 
 
 333. Description of the Magazine for the Cal. .30. 
 
 This magazine is situated under the receiver, in front of 
 the trigger-guard and in rear of the barrel. It consists, 
 Figs. 332 and 333, of the horizontal part m (see also Fig. 313) 
 and the curved part O. 
 
 The horizontal part is in one piece with the receiver, 
 and the curved part is formed by the separate piece O, of 
 the proper shape, secured to the left side of the receiver. 
 
 The opening #', through which the cartridges pass to the 
 receiver, is narrowed at the rear (see Fig. 313) correspond- 
 ing to the folding down of the sides of the magazines in the 
 
578 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 Lee and Mannlicher, and for the same purpose that is, to 
 hold the cartridges in the magazine, against the action of 
 
 M 
 
 FIG. 332. 
 
 FIG. 333. 
 
 the carrier-lever and spring; and as with other box. 
 magazines, the cartridge must be pushed forward by the 
 bolt, beyond this narrow part, before it can rise into the 
 receiver. The bottom of the receiver at z is left solid, with 
 the advantages noted. 
 
 FIG. 335. 
 
 The cartridges are pushed to the left, and into the re- 
 ceiver, by the carrier-lever N, Figs. 334 and 335. This lever 
 has a spindle, a, and lug, e, at its forward end and below, 
 against which rests a flat bow-spring, S. This spring 5 is 
 carried in a small recess, r, below the receiver (see also Figs. 
 332 and 333). The rear end of 5 bears against the side of 
 this recess, r, the front end against the lug e on the carrier- 
 lever, and against the back of the spring rests the lower 
 edge, 5, of the gate M which opens and closes the mouth of 
 the magazine. 
 
 The spring 5 is thus under constant compression, due to 
 the action of the gate, and it forces the carrier-lever to the 
 
REPEATING OR MAGAZINE ARMS. 
 
 579 
 
 left in the magazine. When the gate is opened, as in Fig. 
 332, a lug, //, attached to it, Figs. 334, 335, presses against the 
 carrier-lever and forces it to the right against the action of 
 the spring 5, thus leaving the magazine clear for loading. 
 The spring 5 acts also to keep the gate M open or closed, 
 just as the fiat spring on the rear sight keeps the sight-leaf 
 up or down k 
 
 The gate M, Fig. 334, has a thumb-piece, /, by which it is 
 opened and closed, and it is assembled to the side of the 
 receiver by the pin P, Figs. 332 and 333. The cut-off is 
 shown at c, same figure. 
 
 ACTION OF MECHANISM. To fill the magazine the gate 
 M is opened by the thumb-piece t, and the five cartridges 
 inserted by hand singly, or all at once from a quick-loader, 
 the carrier-lever N being held back as explained. 
 
 When the gate is closed the carrier-lever comes into 
 action, and forces the cartridges to the left and upward. 
 The first four cartridges, by their shape, act to push each 
 other upward as soon as they reach the curved part of the 
 receiver. The fifth cartridge is pushed upward by the 
 shape of the upper side of the follower-lever. If the cut-off 
 
 K 
 
 D G 
 
 FIG. 336. 
 
 is used, it projects as explained into the opening sf of the 
 magazine, Fig. 333, and forces the upper cartridge down 
 sufficiently far to be out of the way of the bolt. 
 
 The assembled mechanism of the cal. .30 rifle is shown in 
 the firing position in Fig. 336. 
 
580 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 334. Revolvers Classification Conditions to be fulfilled by a Good 
 Service Revolver Remarks. 
 
 CLASSIFICATION. The revolver is a weapon for personal 
 defence at short distances, not exceeding 50 or 60 yards, and 
 is employed principally by mounted troops and by officers. 
 
 They are divided into three classes : 
 
 1. Single-action revolvers, or those which must be cocked 
 by hand before each fire. 
 
 2. Self-cocking revolvers, in which by pulling the trigger 
 the cocking and firing are accomplished, till all the chambers 
 are emptied. 
 
 3. Double-action revolvers, which act as single-action or 
 as self-cocking at the will of the firer. 
 
 CONDITIONS TO BE FULFILLED BY A GOOD SERVICE 
 REVOLVER. i. Its mechanism should be simple, strong, 
 easy to dismount and assemble, and interchangeable. 
 
 2. Each chamber which is to be fired should stop exactly 
 in the prolongation of the barrel. 
 
 3. The mechanism should work well whether the revol- 
 ver be fired rapidly or slowly ; this rapid or slow fire being 
 readily employed at will. 
 
 4. The bullet should possess sufficient energy to stop a 
 man at 50 or 60 yards. 
 
 5. It should be easy to load, and the empty cases should 
 be readily extracted. 
 
 REMARKS. The principal points with reference to the 
 working of a revolver are, to insure the stoppage of rota- 
 tion of the cylinder in the proper position, to obtain rapidity 
 of fire when needed and slow fire at other times, and to be 
 able to load and extract easily. 
 
 The stoppage of rotation of the cylinder at the proper 
 time has been successfully accomplished. The rapid and 
 slow firing at will requires a revolver of the third class, or 
 a double-action revolver. The single-action revolver gives 
 the slow fire, but will not fire rapidly, while the self-cocking 
 revolver, although giving a rapid fire, does not give an ac- 
 curate slow fire, because of the prolonged pull upon the 
 trigger, which is apt to derange the aim. The loading and 
 extraction are readily accomplished in the service revolver, 
 
A MM UNI TION. 5 8 1 
 
 all the empty cases being ejected automatically at the same 
 instant, and the chambers can be loaded from a quick-loader. 
 The condition of certainly stopping a man at 50 yards has 
 caused the retention of larger calibres for the revolver than 
 for the rifle, those of the revolver being 0.38 and 0.45 inch. 
 The revolvers adopted for the U. S. service are the Colt's 
 double-action cal. .38 and the cal. .45. The mechanism of the 
 revolver is best explained from a model. 
 
 AMMUNITION. 
 
 335. History Advantages and Disadvantages of Metallic Car- 
 tridge-cases Folded-head Cartridges. 
 
 HISTORY. Small arms were originally loaded by pour- 
 ing in the powder and then inserting the ball, each of these 
 being carried separately and loose. 
 
 The powder-charge was next wrapped in paper, and 
 hence the name cartridges, from charta, paper ; later the 
 powder and ball were united in one package, and the opera- 
 tion of loading was preceded by the tearing open of the 
 paper containing the powder, pouring it into the barrel, 
 and then inserting the ball. These arrangements were used 
 with muzzle-loaders, and continued up to the Civil War. 
 
 With the introduction of breech-loaders, a change in the 
 cartridge became necessary. The gas from the powder 
 escaped through the opening of the breech, occasioning 
 loss of force, and it also clogged the firing mechanism. 
 
 To obviate the defect of the escape of gas through the 
 opening of the breech, various devices were provided, such 
 as the De Bange pad in the French Chassepot rifle, a rubber 
 packing-ring, etc. These devices prevented the escape in 
 the direction indicated as long as they were uninjured by 
 the gas, but did not prevent it from penetrating into the 
 firing mechanism, which was soon clogged. 
 
 To avoid the expense of manufacture, and the increase of 
 weight, which the use of the metallic case entailed, and also 
 to avoid the difficulties of extraction, combustible cartridge- 
 cases were used with the early breech-loaders. 
 
582 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 But the objections already stated caused them to be 
 abandoned and led to the adoption of the metallic case. 
 
 ADVANTAGES AND DISADVANTAGES OF THE METALLIC 
 CASE. The metallic case presents the following advan- 
 tages : the escape of gas is entirely prevented ; the powder 
 is well protected against shock and moisture; the compo 
 nents of the cartridge powder, primer, and bullet are 
 complete and invariable ; the dimensions of the cartridge- 
 case are exact, and there is no difficulty in loading. 
 
 The disadvantages are, the increase of weight of the 
 cartridge and the expense of fabrication. The first is 
 greatly reduced by the use of smokeless powder and the 
 reduction of calibre, and the second by improved processes 
 of manufacture, by which all the parts are rapidly and 
 cheaply made by machinery. 
 
 FOLDED-HEAD CARTRIDGES. The earliest metallic car- 
 tridges were made of copper, with a folded head (Fig. 337), 
 
 the fulminate by which the charge 
 was fired being contained in the 
 fold a. 
 
 These ar,e called rim - fire car- 
 tridges. The objections to them are : 
 i. The fulminate is exposed to 
 shocks, which may cause accidental 
 
 FIG "\vi 
 
 discharge in handling. 
 
 2. The charge of fulminate is larger than necessary to 
 produce discharge, and hence tends to rupture the head of 
 the shell at the fold. 
 
 3. The fulminate is not evenly distributed ; and as the 
 firing was produced by a blow of the hammer on the rim, 
 if this blow fell where there was no composition a miss-fire 
 would result. 
 
 4. The head of the case is not supported by the walls of 
 the chamber b at the fold, and hence, due to this cause and 
 to the excess of fulminate, the head was liable to shear off. 
 
 The principal advantage is that, as it was generally used 
 in arms with tubular magazines, there was little danger of 
 explosion by the shock of firing, since the point of the bullet 
 did not rest against the primer in the magazine. 
 
AMMUNITION. 
 
 336. Folded-head Cup-anvil Cartridge Solid-head Cartridge. 
 
 FOLDED-HEAD CUP-ANVIL CARTRIDGE. To remedy the 
 shearing of the head of the cartridge, due to non-support 
 by the walls of the chamber, and 
 also the defects of the rim fire, the 
 folded-head cup-anvil cartridge, with 
 the fulminate at the centre of the 
 head, was devised. Cartridges with 
 central primers are called centre-fire 
 cartridges. 
 
 This cartridge is shown in Fig. 
 338. In order to prevent the action 
 of the gas upon the fold a, a gas- 
 check cup b was inserted in the head 
 of the case. When the gas ex- 
 panded, its pressure was exerted FIG. 338. 
 upon the cup, and the fold a protected. 
 
 In the rim-fire cartridge, the blow of the hammer upon 
 the fold of the head was resisted by the wall of the chamber, 
 which thus prevented the fold from yielding, and the effect 
 of the blow was transmitted to the fulminate. In this case 
 the wall of the chamber acted as an anvil. 
 
 When the fulminate was placed at the centre of the head 
 it was necessary to provide an anvil as before, to resist the 
 blow of the firing-pin, and this anvil was furnished by the 
 cup, b. As this cup performed both functions, as above ex- 
 plained, it was called a cup anvil. The anvil is a common 
 feature of all primers, and is necessary for the reason stated. 
 
 The cup anvil was held in place by two crimps, c, in the 
 case. The fulminate is at*/, and ee are the two vents through 
 the cup anvil, by which the flame from the fulminate escapes 
 to the charge, the fulminate being fired by the blow from 
 the firing-pin. 
 
 The copper of which the folded-head cup-anvil cartridge 
 is made is objectionable, as it is too soft, and the extractor 
 frequently cuts through it and fails to withdraw the case, 
 and also, owing to its lack of elasticity, it is apt to stick in 
 the chamber after firing. For these reasons brass is prefer- 
 
58 4 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 -d 
 
 able, as it is harder and more elastic, but owing to its 
 hardness the head cannot be folded. 
 
 SOLID-HEAD CARTRIDGES. For these and other reasons 
 the folded-head cup-anvil cartridge of copper was aban- 
 doned, and the solid - head brass 
 cartridge adopted in its place. 
 
 In this cartridge (Fig. 339) the 
 head is formed by pressure, causing 
 the metal to flow into the shape 
 shown. 
 
 The danger of shearing at the 
 head is avoided, since the bottom of 
 the case, a, inside, is in front of the 
 shearing plane, b. 
 
 The primer is inserted from the 
 outside in a pocket, c, in the base of 
 the cartridge, and consists of the 
 cup d, the fulminate e, and the anvil /. The anvil is made 
 of copper, and has a cut, g, across the bottom, and two ver- 
 tical holes, h, at the sides, communicating with g, through 
 which the flame from the fulminate passes to the charge by 
 the vent i in the primer pocket. 
 
 The principal defect of this cartridge is that its walls are 
 thinner in front than in rear, and when the cartridge is 
 fired the front part expands more than that in rear, and is 
 liable to stick. Hence if there is any movement of the case to 
 the rear, it is apt to tear apart. 
 
 337. Components of the Cartridge The Bullet The Powder. 
 
 THE BULLET. For the older arms the bullet was made 
 of pure lead cast in a mold. As improvements were made, 
 the soft lead was found to shear in the grooves and cause 
 " leading." 
 
 Hence the lead was hardened by alloying it with some 
 other metal, such as tin or antimony. The Springfield bullet 
 is an alloy of lead and tin. With the introduction of small 
 calibres, high velocities, and rapid twist, the hardened lead 
 did not present sufficient resistance to shearing, and the 
 
AMMUNITION. 
 
 585 
 
 jacketed bullet was adopted. The jacket at present used is 
 cupro-nickelled steel. 
 
 The casting of the bullet also was objectionable, since the 
 density was not uniform, and the centre of gravity fre- 
 quently did not coincide with the longer axis, giving rise to 
 irregularity in flight. For this reason the bullet was formed 
 by compression between dies, and more uniform density 
 thus obtained. In the Springfield bullet (Fig. 340) three 
 grooves or cannelures are formed at the rear end, and these 
 are filled with vegetable wax for lubrication of the bore. 
 With the cal. .30 bullet (Fig. 341) it is found that these are 
 not necessary, and they have been abandoned. 
 
 The shape of the bullet is cylindro-ogival for the Spring- 
 field and cai. .30. The two bullets are shown (Figs. 340 and 
 341). The weights are: Springfield, 500 grains; cal. .30,220 
 grains. 
 
 FIG. 340. 
 
 FIG. 341. 
 
 FIG. 342. 
 
 Recent experiments have been made with a tubular steel 
 bullet, the Krnka-Hebler. 
 
 This bullet (Fig. 342) is made entirely of steel except the 
 narrow copper rotating band, a, around the middle. On 
 
586 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 the rear end is a sabot, b, made of vulcanized fibre and 
 weighing only a few grains ; its object being to receive the 
 pressure of the powder-gas over a greater extent of surface, 
 and to act as a gas-check, preventing the escape of gas 
 along the sides of the projectile. When the projectile leaves 
 the bore, the pressure of the air upon the front surface of 
 the sabot causes it to drop off. The central hole allows the 
 air to pass through freely in flight, and thus diminishes the 
 retardation owing to the decreased surface presented. An 
 initial velocity of 3000 ft.-secs. has been obtained with this 
 projectile, with a pressure of 46,000 Ibs. per square inch in 
 the gun. 
 
 THE POWDER. Small-arms powder is used in the 
 Springfield rifle, weight 70 grains. It is measured auto- 
 matically in a loading-machine, and after insertion in the 
 case is slightly compressed before the bullet is put in. The 
 charge of smokeless powder varies from 32 to 43 grains, 37 
 of Wetteren or 43 of Peyton powder being at present used. 
 As it is important with smokeless powders to secure the 
 same amount for each charge in order to regulate the 
 pressure, these charges are weighed, and to insure greater 
 regularity the powder is sieved before loading. 
 
 338. Components of the Cartridge The Case The Primer. 
 
 THE CASE. The general features of the cartridge-case 
 have already been described. The rim is for the purpose 
 of extraction, limits the forward motion of the cartridge in 
 
 loading, and fixes its position in the 
 chamber. In certain box magazines 
 the rim occasions some difficulty if 
 care is not exercised in placing the 
 cartridge in the magazine. For ex- 
 FIG. 343."" ample, in Fig. 343, if the cartridges 
 
 occupy the position there shown, it 
 is evident that the top cartridge is held by the rim of the 
 one next below, and consequently the bolt cannot without 
 difficulty push it out of the magazine. To remedy this it 
 has been proposed to make rimless cartridges, as in Fig. 344, 
 the notch a being f or the purpose of extraction. The ob- 
 
AMMUNITION. 
 
 587 
 
 r\ 
 
 r\ 
 
 jections to these cartridges are that their position in the 
 chamber is regulated by the bearing of the shoulder b against 
 a corresponding shoulder in the forward part of the cham- 
 ber, and as it is impossible to make the length cd exactly 
 the same for all cartridges and all chambers, 
 short cartridge will have too much play, 
 and the head of the case, moving to the rear 
 on firing, while the front sticks in the cham- 
 ber, for the reasons already explained, will 
 cause rupture of the case and fouling of the 
 mechanism. In addition, the operation of 
 the extractor is not always certain. 
 
 The case of the cal. .30 cartridge is made d 
 bottle-shaped to reduce its length as much as 
 possible in order to give a longer path for 
 the gas to work over and to diminish wave 
 action, and the exterior is conical to facilitate 
 f~^ extraction in both 
 the Springfield 
 and the cal. .30. 
 
 The contact of 
 the old nitrate 
 powders with the 
 brass case caused FrG - 344- 
 
 deterioration of the latter, and it 
 was tinned to prevent this. 
 
 The effect of the new smoke- 
 less powders on the case is not 
 known, but the cases are tinned 
 as with the old powders. 
 
 THE PRIMER. Its composi- 
 tion has already been explained. 
 With the new smokeless pow- 
 ders some difficulty has occurred 
 in igniting the charge, and the 
 strength of the primer has been 
 increased, with successful results 
 primer is, for safety, sunken be- 
 The old Spring- 
 
 FIG. 345. 
 
 FIG. 346. 
 
 as regards ignition. The 
 
 low the level of the head of the cartridge. 
 
588 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 field cartridge can be reloaded ; the new smokeless-powder 
 cartridge cannot be, except at the arsenals, on account of the 
 danger from excessive crimping, and the high pressures 
 that result from an error in weight of charge, or from in- 
 serting the bullet too far into the case, and also because of 
 difficulty in providing reloading-tools for the small calibre. 
 
 The complete cartridges for the Springfield and the cal. 
 ,30 rifles are shown in Figs. 345 and 346. 
 
CHAPTER X. 
 MACHINE AND RAPID-FIRE GUNS. 
 
 MACHINE GUNS. 
 
 339, Definition Object Advantages Disadvantages Require- 
 ments Kinds of Machine Guns 
 
 DEFINITION. A machine gun is one that is loaded and 
 fired by machinery. 
 
 OBJECT. Its object is to deliver a rapid and continuous 
 fire, and thereby enable a few men to produce the same 
 effect as a larger number armed with the ordinary rifle. 
 
 ADVANTAGES. Owing to the great volume of fire deliv- 
 ered by them, they may be employed at decisive moments of 
 the attack, and to defend defiles, ditches of permanent works, 
 and for their moral effect against mobs and in street-fight- 
 ing. In the Naval Service they are mounted in the tops, to 
 sweep the enemy's decks, drive the cannoneers from their 
 guns, and to repel boarders. 
 
 DISADVANTAGES. These guns are mounted on wheeled 
 carriages, and transported like artillery. They therefore 
 appear naturally to belong to that arm of the service. But 
 as they generally fire small-arm ammunition, they are unable 
 to cope with field-artillery at the fighting range of the latter. 
 
 This limits the use of machine guns in the attack to the 
 infantry arm, and it is generally considered that for pur- 
 poses of attack they are inferior to infantry, as they do not 
 possess its mobility. 
 
 For defence the guns are very useful in holding positions 
 where they may be permanently mounted, and fired in a 
 fixed direction. 
 
 REQUIREMENTS. In order that a machine gun may fulfil 
 its functions, it should, when once pointed in a given direc- 
 
 589 
 
590 TEXT-BOOK' OF ORDNANCE AND GUNNERY. 
 
 tion, retain that direction unchanged by the shock of firing; 
 which requires that there shall be no recoil, and that the 
 mechanical operations of loading and firing shall not inter- 
 fere with the aim or working of the gun. These conditions 
 are very difficult to fulfil, and are perhaps more nearly at- 
 tained in the Maxim automatic gun than in any other. The 
 gun must also be capable of being rapidly directed upon 
 any particular object, and of having this direction quickly 
 changed. This is accomplished in most of them by mount- 
 ing the gun on a fork placed upon the carriage, by which 
 means a quick motion in azimuth, and also around the axis 
 of the trunnions, can be given. 
 
 The gun must be managed by a small number of men, 
 who should be well protected by shields from the enemy's 
 fire. The ammunition should in general be the same as that 
 used by the infantry, to avoid complication, and a large 
 supply must be carried by the gun in a condition ready for 
 feeding, in order to insure rapid and continuous fire. The 
 mechanism should not be liable to jam or get out of order 
 when the gun is fired rapidly ; it should be simple and easily 
 repaired, and the gun should not become heated to such an 
 extent as to interfere with firing. 
 
 KINDS OF MACHINE GUNS. The principal machine guns 
 which have been tried in the United States are 
 
 The Gatling ; 
 
 The Gardner; 
 
 The Maxim; 
 
 The Hotchkiss revolving cannon. 
 
 Of these, the Gatling and Hotchkiss revolving cannon have 
 been adopted for service. 
 
 340. The Gatling Gun Parts Barrels CylindersCasing. 
 
 PARTS. The gun consists, Fig. 347, of a number of breech- 
 loading rifled barrels, B, usually ten, placed around and par- 
 allel to a central shaft, S. These barrels are held in place 
 by two barrel-plates, P, P, called respectively the front and 
 rear barrel-plates. The barrel-plates are circular disks as- 
 sembled to the central shaft 6", and having holes in them 
 
MACHINE GUNS. 
 
 59! 
 
 through which the barrels pass. The barrels and central 
 shaft thus form a cylinder, of which the barrels are the ele- 
 ments and the central shaft the axis. 
 
 In rear of the barrels is the carrier-block C, which is a 
 metal cylinder attached to the central shaft S. On the sur- 
 face of this cylinder are grooves forming extensions of the 
 barrels. These grooves receive the cartridges from the 
 
 feed, and guide them while they are being pushed into the 
 barrels by the bolts, and they also guide the empty shells 
 while they are being withdrawn from the barrels after firing. 
 
 The outer edges of these grooves have projections which 
 act to feed the cartridges, as will be explained. 
 
 In rear of the carrier-block is the lock-cylinder L, a 
 second metal cylinder attached to the central shaft 5, the 
 surface of which forms guides in which slide backward and 
 forward, the bolts by which the breech is opened and closed, 
 and the cartridges fired. 
 
 On the rear end of the central shaft is a worm-gear, G y 
 in which works a worm, W, on the transverse crank-shaft S f . 
 By attaching the crank K directly to the rear end of the 
 central shaft S, a rapid fire is obtained ; when attached as 
 shown, the fire is comparatively slow. 
 
 CASING. The central shaft, with barrels and mechanism, 
 is mounted in a frame, the mechanism being covered by a 
 bronze casing which protects it from dust. The shaft 5 is 
 journalled in this frame and casing in front and rear, so that 
 the shaft, barrels, carrier-block, and lock-cylinder revolve 
 independently of them. 
 
592 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 The trunnions are attached to the exterior of the frame, 
 and the gun is mounted on a fork attached to the carriage. 
 
 The fork has a motion in azimuth, and hence the direc- 
 tion may be quickly changed without moving the carriage 
 as before explained. 
 
 341. The Gatling Gun Parts 
 tion of Mechanism. 
 
 -The Bolts The Cam-groove AC- 
 
 FIG. 348. 
 
 THE BOLTS. There is one bolt for each barrel. Each 
 bolt consists, Fig. 348, of a hollow cylinder, through which 
 passes the firing-pin #, surrounded by its spiral main spring, 
 b. The firing-pin terminates in rear in a head, b' , which is 
 used in cocking and firing. Each bolt has a lug, c, project- 
 ing from its rear end. This lug fits into a groove in the 
 casing, and is the means by which the forward and back- 
 ward motion is communicated to the bolts during the rota- 
 tion of the barrels. Each bolt acts with reference to its own 
 barrel, like the bolt in the cal. .30 rifle, opening, closing, and 
 locking the breech. The extractor, d, engages over the 
 rim of the cartridge before firing, and by the backward 
 motion of the bolt extracts the empty case from its barrel. 
 e is the guide-rib which fits in a corresponding groove in 
 the lock-cylinder, and guides the bolt in its forward-and- 
 back motion. 
 
 THE CAM-GROOVE. The rear part of the cylindrical 
 bronze casing surrounding the lock-cylinder contains a 
 groove, called the cam-groove, which may be regarded as 
 formed by the intersection of the interior of the cylindrical 
 casing by a plane, cd, oblique to the axis, as in Fig. 349. 
 
 This gives an ellipse, the upper and lower ends of which, 
 
MACHINE GUNS. 593 
 
 at c and d, are cut off by two planes perpendicular to the 
 
 axis of the cylinder. Hence ^ ^> i a 
 
 the sides cd of the groove 
 are arcs of an ellipse, and the 
 ends a and , arcs of circles, 
 with their planes perpendic- 
 ular to the axis of the cylin- 
 der. The arc b is at a dis- FlG - 349- 
 
 tance in rear of the barrels equal to the length of a bolt, 
 and the arc a at a distance equal to the length of the bolt 
 plus that of the cartridge, with a small allowance for play 
 added. 
 
 ACTION OF THE MECHANISM. When the crank K, Fig. 
 347, is rotated, it causes the central shaft, with the barrels, 
 carrier-block, and lock-cylinder, to rotate in the casing. 
 
 The bolts, being held by the guides in the surface of the 
 lock-cylinder, also rotate with the barrels and other parts. 
 But by the bearing of the lugs c, Fig. 348, of the bolts, in 
 the elliptical groove cd, Fig. 349, in the breech-casing, the 
 bolts on the right-hand side are forced to move forward 
 toward the barrels, and those on the left to move back- 
 ward. 
 
 Fig. 350 shows a development of the cam-groove, barrels, 
 and firing mechanism; cd being the development of the 
 right-hand side of the elliptical groove cd, Fig. 349, and c'd' 
 that of the left-hand side of the same groove, while cc' and 
 dd' are the developments of the circular arcs b and a, Fig. 
 349, respectively. 
 
 When the lugs c of the bolts, Fig. 348, in this rotation, 
 reach the part dd' , called the " loading flat," the cartridges 
 drop from the feed into the grooves in the carrier-block, in 
 front of the bolts ; as the rotation continues, each right- 
 hand bolt is forced forward by the inclined groove cd, 
 pushing its cartridge into the barrel. When the cartridge 
 is completely inserted, the lug c of its bolt has reached the 
 part cc' , called the " firing-flat," and the bolt thus closes the 
 barrel, just as the bolt of the cal. .30 rifle. 
 
 While the bolts are thus moving forward, a groove R on 
 the right-hand side of the casing, catches the head of the 
 
594 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY, 
 
 firing-pin and retains it, thus compressing the spiral main 
 spring and cocking the firing pin. 
 
 This groove R is called the cocking-rib, and is essentially 
 a short arc of a circle whose plane is parallel to those of cc f 
 and dd'. This arc ends abruptly, so that when the firing-pin 
 
 FIG. 350. 
 
 is cocked and the barrel closed, as in the figure, a continua- 
 tion of the rotation causes the head of the firing-pin to 
 pass out of the cocking-rib. The firing-pin then moves for- 
 ward under the action of the spiral main spring and fires 
 the cartridge. The rotation still continuing, the bolts are 
 withdrawn by the left-hand groove c'd', and as they move 
 back, the empty cases are drawn out by the extractors on 
 the bolts. 
 
 342. The Gatling Gun Feeds Tin Feed-case Objections Bruce 
 Feed Objections. 
 
 FEED. The feed is the method of supplying the car- 
 
MACHINE GUNS. 
 
 595 
 
 tridges to the gun. Various feeds have been used with the 
 Gatling gun, and changes have been made in them to cor- 
 rect defects as they developed. 
 
 TIN FEED-CASE. The first feed consisted of a tin case, 
 
 A, Fig. 351, of trapezoidal cross-section, con- | } 
 
 taining 40 cartridges. 
 
 The cartridges were placed horizontally 
 in this case, lying one above the other, and 
 were held in the case by a spring, s, at the 
 lower end, the upper end being closed. 
 
 A weight, w, at the upper end rested 
 on the column of cartridges, and was provided 
 with a projecting thumb-piece, /, the whole 
 sliding along the case in a groove, -, cut in the 
 side. When in use, the lower end was placed 
 in an opening over the carrier-block, the case 
 being in a vertical plane, and the spring s 
 which closed the lower end being forced 
 aside by the operation of inserting it. 
 
 The cartridges then fell of their own 
 weight into the grooves in the carrier-block, 
 and were pushed forward by the bolts. The 
 sliding weight w, and thumb-piece /, were intended to aid 
 the fall of the cartridges, especially at high angles of eleva- 
 tion. 
 
 OBJECTIONS. The objections to this feed were, that it 
 did not work regularly for different angles of elevation, 
 since the component of gravity parallel to the case varied 
 with the angle of elevation. Also, the cartridges did not 
 always fall parallel to the guide-grooves, and hence jam- 
 ming was liable to occur, and in very rapid firing the car- 
 tridges did not fall quickly enough to supply the barrels. 
 For these reasons a second feed was introduced. 
 
 THE BRUCE FEED. This is a gravity feed, but is in- 
 tended to force the cartridges to fall parallel to the guide- 
 grooves and hence avoid jamming. It consists, Fig. 352, 
 of an upright bronze standard, a, to which is pivoted a 
 swinging piece, b y having two grooves in it. Below the 
 grooves is a fixed mouth, , and below this a wheel, d, turn- 
 
 FIG. 351. 
 
596 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 ing freely on its axis. When in use the feed is inserted in 
 an opening in the breech-casing directly over the carrier- 
 block e. The paper box containing the cartridges, the 
 
 top being removed, is placed in 
 the fixed standard a, with the heads 
 of the cartridges to the rear. The 
 heads of the cartridges engage in 
 the grooves of the swinging-piece 
 b, and the paper box may then be 
 pulled off. In the position shown in 
 the figure, the left-hand column of 
 cartridges passes at once directly 
 into the fixed mouth c, and as each 
 cartridge strikes the wheel d, its 
 weight causes the latter to revolve 
 and present a new groove for the 
 reception of a cartridge. The car- 
 tridges thus delivered to the wheel 
 d are in turn carried round by it 
 and deposited in the grooves in the 
 carrier-block e in the proper position. 
 As soon as the left-hand column of 
 cartridges is exhausted, the weight 
 of the right hand column causes the 
 swinging-piece b to rotate to the left, 
 and thus brings the right-hand col- 
 umn over the fixed mouth c. This 
 operation is repeated as long as the 
 supply 'of cartridges is kept up. 
 
 OBJECTIONS. This feed delivers 
 the cartridges parallel to the barrels, 
 and thus avoids jamming ; but as it 
 depends on gravity, its action is 
 variable for different angles of eleva- 
 tion, as with the old tin case, and this objection has been 
 overcome by the introduction of the Accles feed-drum. 
 
MACHINE GUNS. 
 
 597 
 
 343. The Gatling Gun The Accles Feed Advantages and Objec- 
 tions. 
 
 This feed consists (Fig. 353) of a drum, with two heads 
 of brass, connected by a sheet-brass casing. The distance 
 apart of the two heads is equal to the length of a cartridge. 
 
 FIG. 353. 
 
 The inside of each head is grooved in a spiral form, the 
 spiral beginning at the centre and ending at the mouth or 
 opening of the drum. The central part, a, of the spiral is 
 removed, and its place occupied by the axis or pivot of a 
 set of radial arms, b, which rotate about this axis. The car- 
 tridges are inserted through the mouth c into the drum, 
 the heads of the cartridges entering the spiral of one of the 
 drum-heads, and the point of the buiiet the corresponding 
 spiral on the opposite drum-head. 
 
 The cartridges thus rest in the spirals and between the 
 radial arms. When in use, the feed-drum is inserted in an 
 opening in the breech-casing, directly over the carrier-block 
 d, the opening c of the drum being down, and over the 
 
TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 grooves of the block, and the planes of its heads at right 
 angles to the axis of the barrels. Projections, e, are formed 
 on the outer edges of the grooves of the carrier-block 
 which engage with pins,/, joining the outer extremities of 
 the radial arms of the drum, like the teeth of gear-wheels. 
 
 When the crank k, Fig. 347, of the gun is rotated, the 
 lock-cylinder, barrels, etc., revolve, and the projections on 
 the grooves of the carrier-block cause the radial arms of 
 the drum to rotate. These arms bearing against the car- 
 tridges in the drum force them along the spirals toward the 
 opening c, from which they are delivered to the grooves 
 of the carrier-block parallel to the latter. 
 
 ADVANTAGES AND OBJECTIONS. This drum feeds the 
 cartridges without the aid of gravity and is hence a positive 
 feed, and is independent of the angle of elevation. 
 
 As it is driven by the carrier-block, it supplies the car- 
 tridges as fast as they are needed, and thus the feed is per- 
 fectly regulated ; and as the cartridges are guided by the 
 spirals, they are delivered in the proper position to the 
 carrier-block at all angles of elevation, and jamming is 
 Avoided. 
 
 The objections are the weight of the drum, and the ex- 
 tent of its surface exposed to hostile fire. A bullet striking 
 the drum would render it useless. For these reasons a new 
 feed has recently been introduced. 
 
 344. The Gatling Gun Latest Improved Feed. 
 
 The latest feed introduced has a small surface exposed 
 to fire, is independent of gravity, and can therefore be used 
 with equal facility at any angle of elevation, and it is cheap 
 and light. 
 
 Long strips of tin or any cheap flexible metal, Fig. 354, 
 have tongues or slits, a, punched in them, one end of the 
 tongue being left attached to the strips, and the other 
 separated. 
 
 These tongues surround the cartridge and hold it in 
 place on the strip. The small rectangular slots b, are 
 punched completely through, and in these slots fit the rims 
 
MACHINE GUNS. 
 
 599 
 
 of the cartridge-cases, thus preventing any side or longitu- 
 dinal motion of the cartridges with respect to each other. 
 
 a a a a a a\ a ,a a a a a a 
 
 FIG. 354. 
 
 A hopper, a, Fig. 355, is hinged to the frame which sup- 
 ports the gun, just over the carrier-block, and this hopper 
 has an opening, b, on the left side through which the strips 
 holding the cartridges are fed. This opening is narrow in 
 front and wide in rear, in order to prevent the cartridges 
 being introduced with the wrong end to the front. Below 
 
 FIG. 355- 
 
 the opening b is a shelf, c y so shaped as to guide the car- 
 tridges and strips into the opening. Above the shelf is a 
 flat spring, d, which presses the cartridge-strips down as 
 
6OO TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 they pass through the opening. A wedge, e, projects from 
 the opposite side of the hopper and, acting on each car- 
 tridge in turn, forces it out of the strip, the tongues a, 
 Fig. 354, bending downward into recesses provided for 
 them. / is the carrier-block, provided with projections 
 which act like the teeth of a wheel upon the cartridges, 
 forcing the strip to the right. 
 
 When in use the strip containing the cartridges is 
 pushed into the opening b of the hopper. The crank is then 
 rotated, which causes the projections on the grooves of the 
 carrier-block to act upon the cartridges, forcing the strip to 
 the right through the hopper. This action brings each 
 cartridge in succession against the point of the wedge e, and 
 the action of the wedge forces the cartridge out of its hold 
 on the strip by bending downwards the tongues a, Fig. 354, 
 and the cartridge is deposited in the groove of the carrier- 
 block, the empty strips passing out at the right. 
 
 345. The Gardner GunParts The Barrels The Casing The 
 Bolts. 
 
 PARTS. The parts of the Gardner gun are 
 
 The barrels ; 
 
 The casing ; 
 
 The bolts ; 
 
 The firing and extracting mechanism ; 
 
 The cams ; 
 
 The feed-valve and guide. 
 BARRELS. There are two barrels, a, Fig. 356, which are 
 
 FIG. 356. 
 
 parallel and have their axes in the same horizontal plane. 
 They have no motion, and are loaded and fired by the action 
 of the bolts and firing mechanism. 
 
MACHINE GUNS. 
 
 601 
 
 THE CASING. This is of bronze, the front part, b, being 
 cylindrical and forming- a support and protection for the 
 barrels. Two openings, b' t are made in the top and bottom, 
 to permit a current of air to circulate around the barrels 
 and keep them cool in firing. The rear part, <;, of the casing 
 is box-shaped and contains the mechanism. It is closed at 
 the top by a cover, d, which is hinged to the forward part 
 of the casing, and secured by a screw on the neck of the 
 ,cascable, and may be raised, thus allowing the mechanism 
 to be seen and readily removed. 
 
 THE BOLTS. -There are two bolts of U shape > Fig. 357, 
 
 FIG. 357. 
 
 one for each barrel. One side of the U has an arm, a, ex- 
 tending at right angles to its length, and this arm forms the 
 bolt proper, and carries the firing mechanism, and the ex- 
 tractor, b. The U-shaped part of the bolt has a recess, c, into 
 which the surface of the driving cam (a, Fig. 360) fits, at a 
 certain period of its rotation, and it has also a projection, d, 
 which at the proper period in the rotation of the cam, bears 
 against its exterior surface. The sear e, projects in the recess 
 c, and is acted on by the cam, when the latter enters that 
 recess. The bolt as a whole has a backward and forward 
 motion in the casing, running on the truck-wheel /. g is 
 the cocking-lever, whose action will be explained. 
 
 346. The Gardner Gun The Firing Mechanism Action The 
 
 Extracting Mechanism. 
 
 THE FIRING MECHANISM. This consists (Fig. 358) of a 
 hring-pin, h\ spiral mam spring, i\ cocking-lever, g\ sear, 
 
6O2 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 e; and sear-spring,/. The firing-pin has a collar, k, in front, 
 and a toothed sleeve, /, in rear ; the latter sliding longitudi- 
 nally along the firing-pin. The firing-pin terminates in rear 
 
 FIG. 358. 
 
 in a head, m, fixed to the pin ; n is the main-spring com- 
 pressor, and o the cocking-cam. 
 
 ACTION OF FIRING MECHANISM. In the position repre- 
 sented in the figure, the firing-pin is cocked, but the main- 
 spring is not compressed. The head, ;, of the firing-pin, is 
 engaged with the sear, e. As the bolt is moved forward by 
 the cam, the cocking-lever, g, moves with it, and the lower 
 end of this lever bears against the main-spring compressor 
 n, thus causing g to rotate, and acting by its teeth on those 
 of the sleeve /, the latter is forced forward, compressing the 
 main spring h, since the firing-pin is held by the sear e. 
 When the main spring, //, is fully compressed, the cam a, 
 Fig. 360, enters the recess c, Fig. 358, in the bolt, and press- 
 ing on the sear e, releases it. The firing-pin then moves 
 forward through the sleeve, under the action of the main 
 spring, and fires the cartridge. 
 
 As the bolt moves backward under the action of the 
 cam, the lower end of the cocking-lever, g, bears against the 
 cocking-cam <?, and the firing-pin, by the action of the teeth 
 of the cocking-lever on those of the sleeve, is lorced to the 
 rear till its head, *#, catches over the sear. 
 
 THE EXTRACTING MECHANISM. This consists (Fig. 359) 
 of a hook-shaped extractor, b, on the end of the bolt a, which 
 rides over the rim of the cartridge-case s, as tne latter is 
 
MACHINE GUNS. 
 
 60 3 
 
 forced home, and withdraws the empty shell as the bolt moves 
 backward. The ejectors are two levers,/, pivoted to the 
 
 FIG. 359. 
 
 sides / of the casing, the rear or bent ends, q, of which are 
 struck by lugs, r, on the bolts as they move backwards. The 
 cartridge-case being held by the extractor b, the end, u, of 
 the lever, strikes the case, disengages it from the extractor, 
 and throws it out of the casing. The ejectors also act as 
 stops, to prevent the cartridges from dropping through the 
 openings in rear of the barrels, when fed down by the valve. 
 
 347. The Gardner Gun The Cams The Feed-valve and Guide. 
 
 FIG. 360. 
 
 THE CAMS. Motion is given to all the parts by two 
 cams, a, Fig. 360. These cams are attached to three steel 
 disks, b, at opposite extremities of a diameter, and the whole 
 caused to rotate around the axis c by the crank d. As rota- 
 tion continues, each cam acts against the U-shaped portion 
 of its bolt, pushing it forward, and holding it motionless 
 while firing occurs ; then moving it backwards, and holding 
 it motionless while loading occurs. Firing and loading take 
 place when the cams are in prolongation of the axis of the 
 
604 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 arm of the bolt carrying the firing-pin, at which time the 
 direction of the force of recoil passes through the axis c of 
 the cam-disks, and hence there is no tendency to rotate. 
 The bolts are motionless for about \ of a revolution of the 
 cams, to allow for hang-fires, 
 
 THE FEED-VALVE AND GUIDE. The feed is arranged 
 as follows: A vertical bronze guide, g, Fig. 361, resembling 
 
 FIG. 361. 
 
 the Bruce guide already explained lor the Gatling gun, 
 but without the wheel, is fixed to the casing in rear of the 
 barrels, and holds the cartridges as previously explained. 
 Below this feed-guide, the casing is perforated with two 
 holes, for the passage of the cartridges, and below these holes 
 is the feed-valve, v, Figs. 362 and 363, which is a flat plate 
 having two holes corresponding to those in the casing. 
 This valve slides at right angles to the barrels, and is driven 
 by a fork-shaped lever, /, which receives its motion from 
 the bolts d, as they move forward. By this arrangement the 
 cartridges drop from the feed-guide -, through the holes in 
 
MACHINE GUNS. 
 
 605 
 
 the casing, and these holes are alternately opened and closed 
 by the feed-valve v, as it moves to the right and left. When 
 in the proper position, one of the holes in the feed-valve v, is 
 in prolongation of the corresponding hole in the casing the 
 other hole being closed, and the cartridge drops through, 
 and is forced by the bolt into the chamber. The hole over 
 the other barrel is then opened, and a cartridge drops, and 
 is forced forward into that barrel. The details are best 
 explained from the gun. 
 
 FIG. 362. 
 
 FIG. 363. 
 
 The assembled mechanism is shown in Figs. 362 and 363. 
 a the barrels, b the casing, c the breech-cover, d the bolts, 
 e the cams, e' the disks, v the feed-valve, / the feed-valve 
 lever, f the ejectors, h main-spring compressor, i cocking- 
 cam, g feed,/ cocking-lever. 
 
 348. The Maxim Automatic Machine Gun General Principles 
 
 Action of Mechanism Advantage Parts. 
 GENERAL PRINCIPLES. The Maxim automatic machine 
 gun is so constructed, that on firing a single shot, the force 
 
606 TEXT- BOOK OF ORDNANCE AND GUNNERY. 
 
 of the recoil is utilized for opening the breech, extracting 
 the empty case, and effecting the various operations neces- 
 sary to reload and again fire the arm, or prepare it for 
 firing ; so that after the gun has been once fired, all these 
 operations are performed automatically, and the gun con- 
 tinues firing with great rapidity so long as the trigger 
 remains pulled, and the supply of cartridges lasts. 
 
 ACTION OF MECHANISM. The breech mechanism is oper- 
 ated by hand to insert the first cartridge in the barrel, and 
 the trigger is then pulled. The pressure of the powder- 
 gas on the breech-block, causes the latter, with the barrel, 
 to recoil. During this recoil, the breech is opened, the 
 empty cartridge case extracted, the firing-pin cocked, and 
 a loaded cartridge brought into position to be thrust into 
 the chamber. The energy of recoil not consumed in the 
 above operation is stored up in a spiral spring, which by 
 its reaction causes the barrel to return to the firing posi- 
 tion, forces the loaded cartridge into the chamber, and 
 closes the breech. The moment the breech is closed, the 
 gun is fired automatically, if the trigger be held in the 
 pulled position. The rate of fire is about 660 rounds per 
 minute. 
 
 ADVANTAGE. The great advantage of this gun is, that 
 being automatic in its action, the aiming is not interfered 
 with by the operation of a crank or other device to work 
 the mechanism, and hence it can be pointed readilv in any 
 direction, and the direction changed with great facility. 
 
 PARTS. The gun consists practically of two parts a 
 recoiling, and a non-recoiling part. The recoiling part 
 embraces the barrel, the lock, the crank, the breech-block, 
 and an inner frame with guides and bearings, on which 
 these parts move. The recoiling part may be considered 
 the gun proper. 
 
 The non-recoiling part consists of a casing and two side 
 frames, in which the recoiling part moves. 
 
 349. The Maxim Automatic Machine Gun The Barrel and Frame 
 The Breech Mechanism. 
 
 THE BARREL AND FRAME. The gun has a single barrel, 
 
MACHINE GUNS. 
 
 607 
 
 a, Fig. 364, attached to the inner frame b, and is an ordinary 
 rifled one of the desired calibre. It 
 has bearings at c and d, which rest 
 in corresponding supports in the 
 bronze casing, and on these bear- 
 ings the barrel slides back and 
 forth in action. The frame b is 
 open at the top and bottom, and 
 resembles a box. This frame car- 
 ries the breech mechanism, and 
 hence the latter moves back and 
 forth with the barrel and frame, 
 and has also motion with respect 
 to the frame, as will be explained. 
 Near the rear end of the frame, the 
 crank-shaft e passes through both 
 sides, and has a motion of rota- 
 tion in the frame. On the right 
 hand side, this crank-shaft pro- 
 jects, and upon it is fixed a bent 
 lever, ff, of the shape shown. 
 On the left side of the frame b 
 the crank-shaft e projects also, 
 and to it is attached the short 
 crank g. The strong spiral 
 spring h by which the counter- 
 recoil is produced, is attached at 
 h' to the fixed casing, and at h" 
 to the short crank g. Any rota- 
 tion of the crank-shaft e in the 
 direction of the arrows, will there- 
 fore increase the tension of the 
 spiral spring h, which will be 
 wound up around e. Also any 
 backward movement of barrel and 
 frame, with reference to the fixed 
 casing, will increase this tension, 
 since the spiral spring is fixed to 
 the casing at h' . 
 
 FIG. 364. 
 
6o8 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 THE BREECH MECHANISM. This is contained between 
 the sides of the inner frame b. In Fig. 365 let e, as before, 
 
 FIG. 365. 
 
 represent the crank-shaft. Upon this shaft, and between 
 the sides of the inner frame b, is fixed an arm or crank, i y 
 so that any rotation of e, causes i to rotate also. 
 
 At the end of i, a fork-shaped piece or link,/, is attached 
 by an axis,/', and the front end of j is pivoted to the breech- 
 block k at k' . The breech-block is therefore held between 
 the prongs of the forked link j. When the crank-shaft e 
 is rotated in the direction of the arrow, the pivot j' de- 
 scribes the arc of a circle in the same direction. As the 
 breech-block k can only slide back and forth in the direc- 
 tion of the arrow, it is evident that this rotation of the 
 shaft e, as described, will pull the breech-block backward, 
 with reference to the barrel and frame, along the guides m' ', 
 and at the same time the surface / of the fork-shaped link 
 j will describe the arc of a circle around k ', and will, con- 
 sequently, move down along the rear curved surface of the 
 breech-block. 
 
 350. The Maxim Automatic Machine Gun The Breech-block and 
 Carrier. 
 
 THE BREECH-BLOCK AND CARRIER. The breech-block 
 consists of the part k (Figs. 366, 367), which moves back- 
 
MACHINE GUNS. 
 
 609 
 
 ward and forward parallel to the axis of the barrel, the 
 bearing m t sliding in the groove m' in the inner frame b ; 
 and of the part n, called the carrier, which is attached to 
 the front part of the breech-block k, and moves backward 
 and forward with it, but has also a vertical sliding motion 
 along its front. This carrier, n, extracts the loaded cart- 
 ridges from the belt which carries them, feeds them to the 
 barrel, and extracts the empty case after firing. Its action 
 is as follows: When in the firing position (Fig. 366) the 
 
 FIRING. POSITION, 
 
 FlG. 366. 
 
 LOADING POSITION. 
 
 FIG. 367. 
 
 forked link j is nearly horizontal, and the carrier n is at 
 its extreme upward position. After firing, when j rotates 
 downward (Fig. 367), the cam <?, which is a part of j, is no 
 longer in contact with the second cam <?', pivoted to k, and 
 working n. The carrier n is then held up by two guides on 
 the sides of the inner frame, shown in Fig. 371, upon which 
 the arms, q, rest, and is pressed down as the block slides. 
 
6io 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 backward, by two springs, /, attached to the fixed casing, 
 and acting on the two projecting arms, q, on the carrier. 
 When the block moves forward again, the forked link/ rises, 
 and the cam o, acting on o' , raises the carrier at the end of 
 the forward movement of the block. Two grooves in the 
 rear face of n, slide on bearings, q ', on the front of the breech- 
 block k. The front surface of the carrier n is grooved, so 
 that the heads of the cartridges will fit in it. As it rises, 
 these grooves engage the rirn of the cartridge in the cham- 
 ber, and that of a second cartridge above this in the feed- 
 belt. When the piece is fired, the backward motion of the 
 breech-block causes the carrier n to draw the loaded cart- 
 ridge out of the feed-belt, and the empty case out of the 
 chamber. The carrier n is then forced down by the 
 springs /, as explained, which brings the loaded cartridge 
 opposite the chamber, and the empty shell opposite the ejec- 
 tor-tube. A forward motion of the breech-block then de- 
 posits the cartridge in the chamber, and ejects the empty case. 
 351. The Maxim Automatic Machine Gun The Firing Mechanism 
 The Feed. 
 
 FIG. 368. 
 
 THE FIRING MECHANISM. This is contained in the 
 interior of the breech-block k. It consists (Fig. 368) of the 
 firing-pin a, the main spring b, which acts also as a sear- 
 spring, the tumblers, sear d, salety-sear e, and its spring/. 
 
MACHINE GUNS. 6ll 
 
 The action is as follows : When the forked link j (see 
 also previous figures) moves downward, it strikes the pro. 
 jecting end c' of the tumbler c, and causes the latter to 
 rotate in the direction of the arrow. The upper part of the 
 tumbler, bearing in a notch in the firing-pin a, draws back 
 the latter, compressing the mainspring b, till the sear d 
 catches under the notch d' of the tumbler. At the same 
 time, the safety-sear e drops into a notch on the upper side 
 of the firing-pin a. If the firing is to be continuous, the 
 trigger-rod g is kept constantly pulled backward in the 
 direction of the arrow, by pressing with the thumbs on the 
 lever h. If the pressure upon h is relieved, the spring i 
 forces the trigger-rod g forward, and the firing ceases, the 
 trigger being no longer pulled. 
 
 Supposing the trigger-rod to be kept pulled, the sear d, 
 striking against the projection on the trigger-rod g as the 
 lock moves forward, is disengaged from the notch d' in the 
 tumbler, and the firing-pin is held back by the safety-sear e 
 alone. As the forked link / rises in closing the breech, it 
 strikes the projecting end e' of the safety-sear, just as the 
 breech is closed, disengaging e from its notch in the firing- 
 pin, which then moves forward and fires the cartridge. In 
 this case the firing is automatic and continuous. 
 
 If the firing is to be by single shots, the trigger-rod g is 
 not kept in the pulled position. In this case the forked link/ 
 rises and disengages the safety sear e t as before. The firing- 
 pin is now held back only by the sear d and tumbler c. 
 Pulling the trigger-rod disengages d, and fires the cartridge. 
 
 THE FEED. The cartridges are contained in belts, made 
 by uniting two strips of canvas, with intervals between them 
 to hold the former. These belts, with their cartridges, are 
 contained in a box placed below the gun. Over the rear 
 end of the barrel is a box-shaped feed attached to the casing 
 (Fig. 369). 
 
 This feed contains a slide, a, having a pin, b, acted on by 
 a lever, c. The slide has two spring-pawls, d\ and two 
 other spring-pawls, e, are fixed to the feed-box, but not 
 attached to the slide. The belt containing the cartridges 
 is passed into the feed-box, till the first cartridge is caught 
 
612 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 by the spring-pawls d. As the barrel recoils, a projection 
 on the inner movable frame, strikes the lower end of the 
 lever at c f , and causes the slide a to move to the left, by the 
 action of this lever on the pin b. The spring-pawls d, mov- 
 ing with the slide a, push the cartridges and the belt to the 
 left, till a cartridge is in position to be caught by the groove 
 in the carrier as it rises. The lower spring-pawls e, being 
 pivoted to the feed-box, do not slide, and hence hold the 
 
 FIG. 369. 
 
 belt and cartridges in place, while the slide a, with the pawls 
 d, moves back again to the right to engage over another 
 cartridge, /is a wooden roller, over which the belt passes, 
 and the mouth of the feed-box has guides for directing the 
 motion of the belt. . 
 
 352. The Maxim Automatic Machine Gun Action of the Mechanism. 
 The Figs. 370 and 371 show the assembled gun and mechan- 
 ism. On the exterior right side of the fixed casing, is a 
 curved arm, a, a stop, b, and a buffer-spring, c. 
 
 When the gun is fired, supposing the trigger to remain 
 pulled, the barrel, inner frame, and breech mechanism recoil 
 together for a short distance. 
 
 At the end of this recoil the curved arm d of the bent 
 lever strikes against the curved arm a, fixed to the outer 
 case. This causes a rotation of the crank-shaft e, and, as 
 previously explained, the breech-block k is drawn back from 
 the chamber, thus opening the breech, and at the same 
 
MACHINE GUNS. 
 
 613 
 
 time drawing a loaded cartridge out of the belt, and ex- 
 tracting the empty case from the chamber. As long as the 
 rotation of the crank-shaft e continues, the breech-block k 
 moves backward. 
 
 During the last part of its motion, the carrier n is forced 
 downward by the springs /, Fig. 371, and thus the loaded 
 
 FIG. 370. 
 
 FIG. 371. 
 
 cartridge is brought in line with the chamber, and the empty 
 case with the ejector-tube r. 
 
 During this time also, the firing-pin has been cocked, 
 and the strong spiral spring /extended by this rotation of 
 the crank-shaft e, as explained. The rotation of the crank- 
 shaft e continues, till the outer arm g of the bent lever, 
 strikes the buffer-spring c, fixed to the casing. The re- 
 action of this spring, and the tension of the spiral spring/, 
 now cause the crank-shaft e to rotate in the opposite 
 direction, and the spiral spring /also forces the barrel and 
 frame forward. 
 
614 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 As the rotation of e continues, the breech-block k moves- 
 forward, the loaded cartridge is thrust into the barrel, and 
 the empty shell out through the ejector-tube r. As the 
 breech closes, the carrier n rises, and grasps another cart- 
 ridge which has been fed forward by the slide s in the feed- 
 box, as explained, and when the breech is completely closed 
 the forked link j strikes the safety sear e' , and fires the 
 cartridge. 
 
 The barrel is surrounded by a bronze casing, z, which is 
 filled with water for keeping the barrel cool during the 
 rapid firing, and a provision is made for the escape of the 
 steam if the water is heated to the boiling-point. 
 
 353. The Hotchkiss Revolving Cannon General Features Rotating 
 Mechanism Loading Mechanism Extracting Mechanism 
 Action. 
 
 GENERAL FEATURES. This machine gun differs from 
 the others in its weight and calibre, being much heavier, 
 and firing a projectile weighing about one pound, which 
 may be either shell or canister. It resembles in some re- 
 spects the Gatling gun, already described, and is composed 
 of a group of five barrels assembled around a central shaft, 
 the whole revolving in front of a heavy breech, which con- 
 tains all the mechanism. It differs from the Gatling gun in 
 having only one loading, one firing, and one extracting 
 apparatus for the five barrels. 
 
 FIG. 372. 
 
 ROTATING MECHANISM. This consists (Fig. 372) of a 
 cam- wheel, a, operated by a crank, and working against a. 
 series of studs, b, on the rear end of the central shaft c. 
 
 This cam-wheel is mounted in a recess in the breech, 
 
MACHINE GUNS. 615 
 
 and its peculiar feature is that the grooves </, in its surface, 
 are partly screw-threads, and partly planes at right angles 
 to the axis of the cam-wheel shaft. The object of this 
 arrangement will be explained. 
 
 LOADING MECHANISM. On the left side of the solid 
 breech is situated a loading piston. This moves back and 
 forward in a recess, parallel to the axis of the barrels. The 
 piston itself (b, Fig. 373) is cylindrical, and has an arm, a, 
 which is flat, and carries a toothed rack. 
 
 
 a' 
 
 FIG. 373. FIG. 374. 
 
 EXTRACTING MECHANISM. The extractor is also situated 
 in a recess on the left side of the breech, and below and par- 
 allel to the loading-piston. Its shape is shown in Fig. 374, 
 the front end carrying a hook-shaped extractor, the rear 
 end having an arm with a slot, a, and the upper edge form- 
 ing a toothed rack. 
 
 ACTION OF LOADING AND EXTRACTING MECHANISM. 
 When the cam-wheel is rotated by the crank, if the spiral 
 part of its grooves, d, Fig. 372, is bearing against one of 
 the studs, b, the central shaft and barrels rotate. If, how- 
 ever, the plane grooves act against these studs, the barrels 
 do not move, and are held in position by the binding of 
 these plane surfaces against the studs. 
 
 In Fig. 375, a represents the axis of the cam-wheel, b 
 and c the loading-piston and extractor respectively, in their 
 relative positions when assembled. 
 
 The crank d is attached to the axis a, and the toothed 
 wheel e is mounted on an independent axis on the left side 
 of the breech, gearing into b and c. When the axis a rotates, 
 a pin,^-, on the end of the crank d, engaging in the slot/, at 
 
6l6 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 the end of the extractor-arm, draws back the extractor. 
 This occurs while the plane grooves of the cam-wheel are 
 bearing against the studs on the central shaft, and, conse- 
 quently, there is no rotation of the barrels. 
 
 FIG. 375. 
 
 As the extractor moves backward, it withdraws the 
 empty case from the barrel last fired. By the backward 
 motion of the extractor, the wheel e is caused to rotate, and, 
 acting on the rack of the loading-piston, it causes the latter 
 to move forward, thus pushing the loaded cartridge in front 
 of it into the chamber. The loading and extracting are 
 performed while the barrels stand still. As the rotation of 
 the cam-wheel still continues, the pin g in the slot f reaches 
 a part of this slot which is concentric with a. At this time 
 the extractor and loading-piston stand still, while the barrels 
 rotate. 
 
 Continued rotation of the cam-wheel beyond this point 
 of rest, reverses the motion of the loading-piston and ex- 
 tractor, pushing the latter forward, and drawing the former 
 backward, and so on. 
 
 354. The Hotchkiss Revolving Cannon The Feed The Firing 
 Mechanism. 
 
 THE FEED. The cartridges are contained in zinc or tin 
 cases ten in a case. These cases are inserted in a feed- 
 tray, a, Fig. 376, mounted on the left side of the breech ; 
 the act of inserting the case causing it to open and allow 
 the cartridges to enter the tray. Resting against the top 
 of the loading-piston b, is a hinged lid, c, attached to the 
 
MACHINE GUNS. 
 
 6i 7 
 
 breech. As the loading-piston moves forward, pushing the 
 cartridge in front of it into the barrel, this hinged lid pre- 
 vents the entrance of a second cartridge. When the load- 
 ing-piston moves back in rear of the lid, the latter drops 
 
 FIG. 376. 
 
 down by its own weight and that of the cartridges resting 
 against it, and allows a fresh cartridge to drop in front of 
 the loading-piston. The piston immediately moves forward, 
 raising the lid, and keeping back the other cartridges. 
 
 FIG. 377. 
 
 THE FIRING MECHANISM. This is arranged as follows, 
 (Fig. 377) : On the right hand lower side of the breech is 
 a strong firing-pin, a, moving in a recess, and acted on by 
 the main spring b. On the shaft of the cam-wheel is a spiral 
 cam, c, which is cut off abruptly at d. The arm e of the 
 firing-pin, bears against this spiral cam, and the pin is con- 
 
6i8 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 stantly pressed forward by the main spring. As the cam- 
 wheel rotates, the spiral cam, acting on the arm e, grad- 
 ually draws back the firing-pin, compressing the mainspring 
 b. When this spring is compressed to its full extent, the 
 spiral ends abruptly at d, and at this time the barrels are 
 standing still. The firing-pin then moves forward, driven 
 by the main spring, and fires the cartridge. Hence the 
 loading, firing, and extraction in this gun are performed 
 while the barrels are stationary. The recoil is borne by 
 the heavy breech, which is made of cast-iron, and is recessed 
 to receive the various parts of the mechanism. 
 
 FIG. 378. 
 
 These parts are strong and not liable to break, and are 
 readily accessible for repair. The various parts assembled 
 are shown in Fig. 378. 
 
RAPID-FIRE GUNS. 619 
 
 RAPID-FIRE GUNS. 
 
 355. Characteristics of Rapid-fire Guns Object History. 
 
 CHARACTERISTICS. A rapid-fire gun is distinguished 
 from a machine gun by having a larger calibre, loading by 
 hand, having generally one barrel, and an artificial means 
 of checking recoil and returning the gun to the firing posi- 
 tion. It uses metallic ammunition, and rapidity of fire is 
 obtained by the use of a simple breech mechanism, which 
 works quickly, cocking the firing-pin, and extracting the 
 empty case, in the act of opening. 
 
 OBJECT. The object of rapid-fire guns is to defend naval 
 vessels against the attack of swift torpedo boats, by deliver- 
 ing a rapid and easily directed fire of projectiles having 
 sufficient energy to penetrate the plates of these boats ; and 
 also for piercing the lighter-armored parts of large ships. 
 In the land service their use is not so well defined. In 
 order to utilize the rapid fire of which they are capable, it 
 is necessary that the aim shall be maintained upon a given 
 object, and not altered by the recoil of piece or carriage. 
 In the naval service, owing to the character of the mount- 
 ing, this object is very readily attained, the gun being 
 mounted on an elastic or spring-return carriage, fixed to 
 the vessel, by which arrangement the gun is brought back 
 to the firing position after discharge without derangement 
 of the aim. In the land service similar mountings have been 
 provided, attached to wheel-carriages, but in general the 
 shock of recoil alters the direction of the piece, due to the 
 mobility of the carnage, and hence it must be redirected 
 after each fire. In the latest mounting for the land service, 
 spring-return devices have been abandoned, and a rigid 
 carnage adopted. This carriage is provided with a spade 
 at the end of the trail, which is forced into the ground by 
 the recoil, and, when fixed, holds the gun and carriage in 
 place. 
 
 HISTORY. The Hotchkiss revolving cannon, already 
 described, was first used when torpedo boats were adopted,, 
 
62O 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 but it was found impossible to give sufficient velocity to the 
 projectiles from this gun to pierce their plates, or to increase 
 the calibre much beyond 1.75 inches, owing to the great 
 weight of the group of barrels. Under these circumstances 
 Hotchkiss invented a single-barrelled rapid-fire gun, with a 
 sliding breech-block, using metallic ammunition, and firing 
 a much heavier projectile than the revolving cannon, with a 
 muzzle-velocity of 1800 ft-seconds. From this time these 
 guns have rapidly developed in power, and many different 
 systems of breech-closing have been devised. 
 
 The principal systems are the Hotchkiss, Nordenfelt, 
 Driggs-Schroeder, Maxim, Gruson, Krupp, and Armstrong, 
 and a few of these will be described as types. 
 
 356. The Hotchkiss Rapid-fire Gun The Gun The Breech 
 Mechanism Action. 
 
 THE GUN. The body of the gun consists of a tube and 
 a jacket, united by shrinkage. 
 
 The jacket extends to the rear of the tube, and is slotted 
 vertically to receive the breech block. 
 
 X 
 
 ? 
 
 y 
 
 
 
 , 
 
 
 c 
 
 
 
 
 d 
 
 
 
 LEFT SIDE. 
 
 FIG. 379. 
 
 ^BREECH MECHANISM. The breech mechanism consists 
 ( Fl g- 379) of a wedge-shaped block, which rises and falls in 
 a vertical direction in the slot at the rear end of the jacket, 
 instead of moving horizontally, as in the Krupp. Its front 
 surface, a, is perpendicular to the axis of the bore, and its 
 
RAPID-FIRE GUNS. 621 
 
 rear surface, b ', is inclined to that axis, so that the block, in 
 rising, gradually moves forward towards the barrel, cc are 
 guide-grooves parallel to the rear face b' , and correspond- 
 ing projections in the breech-slot fit into these grooves, and 
 guide the block in its motion. On the left side of the 
 block is the stop-groove d. A bolt passes through the left 
 side of the breech, and entering this groove, prevents the 
 block from falling out of its recess when the breech is 
 opened. In front of this groove, and on the same side of 
 the block, is the extractor-groove e. The extractor is 
 exactly similar to that already described in the Hotchkiss 
 mountain gun, except that it works in a recess on the left 
 side of the breech, instead of on the top. Its lug bears in 
 the groove e, and as the block falls, the extractor is moved 
 back very slowly at first, extracting the empty case from the 
 chamber, and then very quickly, owing to the sudden 
 change of form of the groove e, ejecting the case from the 
 gun. On the right-hand side of the block is a groove, /, 
 called the stud way. A crank-shaft, g, passes through the 
 right-hand side of the breech, projecting into the breech 
 slot, and to this inner projection is attached the crank h> 
 with a stud, //, at its extremity, working in the groove or 
 studway /. The crank-shaft g is operated by two handles, 
 i, attached to it on the outside. 
 
 ACTION. When the crank-shaft g is turned by the 
 handles i in the direction of the arrow, the stud h' moves 
 at first in a part of the groove /, concentric with g, and 
 hence no motion of the block occurs. During this time the 
 hammer is cocked, as will be explained. 
 
 The stud h' now enters the eccentric part of the groove 
 /, and causes the block to descend. As soon as it is started, 
 it will fall by its own weight, till arrested by the stop-bolt 
 bearing against the top of the stop-groove d. A reversal of 
 the rotation of the crank-shaft g, after loading, causes the 
 block to rise, and the block in rising, forces the projectile 
 home. 
 
 The opening of the breech-block in firing is prevented 
 as follows : When the breech is closed, the weight of the 
 block is supported by the stud //'. At this time the vertical 
 
622 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 plane through the centre of h' is in front of that through the 
 centre of the crank-shaft^. Hence the weight of the block 
 acting vertically tends to keep the latter closed. 
 
 357. The Hotchkiss Rapid-fire Gun Firing Mechanism Action 
 Remarks. 
 
 FIRING MECHANISM. The firing mechanism (Fig. 380) 
 is contained in recesses in the front portion of the block, and 
 consists of a hammer, a, mounted on a rocking-shaft b (see 
 also Fig. 379), a main spring, c, a sear, d, and a sear-spring, e. 
 
 The rocking-shaft b passes through the lower front cor- 
 ner of the breech-block, and projects beyond the right side, 
 carrying on its right extremity, a curved arm or cam, k, Fig. 
 379, called the cocking-toe. The crank-shaft g, which is 
 
 fixed to the breech (Fig. 379), carries a cam, /, called the 
 cocking-cam, which is just above k. 
 
 ACTION. When the handles, i, Fig. 379, are rotated in 
 the direction of the arrow, the cam/ comes in contact with 
 the cocking-toe k, on the rocking-shaft b, Figs. 379 and 380, 
 drawing back the hammer a, and compressing the main- 
 spring c. At this time there is no motion of the breech- 
 block, because the stud h' , Fig. 379, is moving in the con- 
 centric part of its studway, /, as explained. 
 
 The rotation of the handles, t, continues, till the hammer 
 a is cocked, the sear d catching in a notch on the rocking- 
 
RAPID-FIRE GUNS. 623 
 
 shaft b, the block all the while remaining motionless. As 
 soon as the cocking is accomplished, the breech-block falls 
 and opens the breech. The end of the sear d projects be- 
 yond the rear surface of the breech-block, and when the 
 latter is home, the sear is in contact with the trigger t, and, 
 pulling it, fires the charge. The piece cannot be fired be- 
 fore the breech is closed, ist, because the firing-pin of the 
 hammer is not opposite the primer ; 2d, the trigger will not 
 touch the sear; 3d, the cam/ on the shaft g will catch the 
 cocking-toe k before the firing-pin can reach the primer. 
 
 The main spring e is so connected with the rocking- 
 shaft b, on which the hammer is mounted, that its lower leaf 
 acts downward and its upper leaf upward, and hence the 
 pressure and friction of the rocking-shaft in its bearings are 
 very much diminished. 
 
 REMARKS. All parts of the mechanism are readily ac- 
 cessible and easily dismounted. For aiming, a stock, a, Fig. 
 381, is bolted to the left side of the piece if the gun is on a 
 
 FIG. 381. 
 
 rigid carriage, or to the left side of the carriage if the gun 
 recoils. This stock has handles, b, for grasping with the 
 left hand at different elevations, and a rubber tube, c, against 
 which the left shoulder rests in firing. For the naval ser- 
 vice the gun is generally mounted with its trunnions resting 
 in a fork. This fork turns in azimuth in a heavy socket, and 
 this, combined with the vertical motion of the gun around 
 the axis of the trunnions gives a motion in any direction. 
 
624 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 358. The Nordenfelt Rapid-fire Gun The Breech Mechanism- 
 Action. 
 
 THE BREECH MECHANISM. The breech mechanism in 
 this system combines the sliding and rotating motions, so as. 
 to avoid guillotining the cartridge in forcing it home. 
 
 The breech-block (Figs. 382, 383, and 384) consists of two 
 parts, the first part, or block proper, B, and the rear part, or 
 wedge, W. The front part B rotates around the shaft S, 
 which passes through the breech, while the rear part or 
 wedge, W, has at first a vertical downward sliding motion 
 along the back of B, till it reaches the position shown in 
 Fig. 383, the two upper surfaces r r, then forming one con- 
 tinuous cylindrical surface, at which time both parts rotate 
 backward together around the shaft 5, Fig. 384. C is a 
 
 --E 
 
 P' 
 
 FIG. 382. 
 
 FIG. 383. 
 
 FIG. 384- 
 
 cam, fastened upon the shaft 5, and having a slot in it, in 
 which the pin P, attached to the wedge, works. E is the 
 extractor and ejector. 
 
 ACTION. A lever-handle is attached to the right extrem- 
 ity of the shaft 5, outside the breech. After firing, the 
 parts of the block are in the position shown in Fig. 382. As 
 the lever-handle on the shaft 5 is rotated, it causes the cam 
 C attached to 5 to rotate downwards. The slot in the cam, 
 bearing on the pin P, forces the wedge W downwards, till 
 it stands in the position shown in Fig. 383. The pin P is 
 now>at the end of the slot in the cam 6", and a continuation 
 of the rotation of the lever-handle and shaft 5, causes both 
 
parts of the block to rotate together to the rear, opening the 
 breech (Fig. 384). At the beginning of this rotation, the 
 extractor E is moved slowly backward, withdrawing the 
 empty case. This motion afterwards becomes more rapid, 
 ejecting the case from the gun. 
 
 After the loaded cartridge is inserted in the gun, the 
 rotation of the lever on the shaft 5 is reversed. This causes 
 both parts of the block to rotate to the front, till the front 
 part B comes in contact with the breech. The wedge W is 
 then forced vertically upward by the action of the cam C, 
 till it occupies the position shown in Fig. 382, completely 
 closing the breech. The parts are held in position by the 
 pin P, at the last moment of closing, entering a concentric 
 part of the slot in the cam C, which supports the wedge in 
 position. 
 
 359. The Nordenfelt Rapid-fire Gun The Firing Mechanism- 
 Action Remarks. 
 
 THE FIRING MECHANISM. This is arranged as follows 
 (Fig. 385): The firing-pin a passes through the front part, 
 B, of the breech-block. In rear, it has projecting lugs, b t one 
 
 FIG. 385. 
 
 on each side. The middle part of the sliding wedge W is 
 hollowed out, to receive the parts of the mechanism. The 
 
 UII7IRSITT 
 
626 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 main spring c is secured at one end against the rear face 
 of the block B, while the other end bears against the rear 
 faces of the lugs b, of the firing-pin a, and urges the latter 
 forward. 
 
 Two wedge-shaped lugs d, on the sliding part W of 
 the block, one of which is shown, act upon the lugs b to 
 cock the firing-pin, when the sliding part of the block 
 descends. 
 
 The sear e works on a pivot, e\ resting against the rear 
 face of the front part of the block, and catches under the 
 head of the firing-pin as shown, when the latter is cocked. 
 Its lower end projects beyond the rear face of the block, 
 and is in contact with the trigger/ when in the firing posi- 
 tion, g is a safety lug on the wedge, and h the correspond- 
 ing lug on the sear, i is a tappet-trigger, so called, consisting 
 of a shaft working in a bearing on the rear face of the front 
 part B of the block, and having upon it two arms or cranks 
 / and k, set at an angle with each other. There is also a 
 vertical groove on the front of the sliding wedge, not shown 
 in the figure, which ends abruptly in a shoulder, and which 
 works the tappet-trigger. This may be called the tappet- 
 trigger groove. 
 
 ACTION. In the position shown in the figure, the parts 
 are ready for firing. On pulling the trigger/, the firing-pin 
 a moves forward, under the action of the main spring c, ex- 
 ploding the cartridge. The lever on the main shaft 5 is 
 now rotated, and the sliding wedge descends. As it moves 
 down, the wedge-shaped lugs d, engage in front of the pro- 
 jecting lugs b of the firing-pin, and force the latter back 
 against the action of the main spring c. When the firing- 
 pin is forced back to its full extent, the shoulder of the 
 tappet-trigger groove on the wedge W, acting on the army, 
 causes the shaft of the tappet-trigger i to rotate, and forces 
 the inner crank-arm k backward against the sear e, retaining 
 the latter in the cocked position. The cartridge is now 
 inserted, the lever-handle reversed, and the breech closed. 
 As the wedge Arises into its closed position, the wedge- 
 shaped lugs d rise above the firing-pin, and the projecting 
 part of the sear e comes in contact with the trigger/. The 
 
RAPID-FIRE GUNS. 627 
 
 firing-pin is now held back by the sear e, which in turn is 
 held by the arm c f , of the main spring c, bearing on the lug 
 e". A pull on the trigger /depresses the projecting end of 
 the sear e, disengages the sear from the firing-pin, and allows 
 the latter to move forward and fire the cartridge. 
 
 REMARKS. The cartridge cannot be fired before the 
 breech is completely closed, for the following reasons : 
 
 ist. While the wedge is rising, the lugs, d, are in front of 
 the projections, b, on the firing- pin. Hence, if the firing- 
 pin moves forward at this time, the projections, , will strike 
 against the lugs, d t and prevent the firing-pin from reaching 
 the cartridge. 
 
 2d. The lugs, d, clear the projections, b, on the firing- 
 pin before the breech is completely closed. At this instant, 
 however, the safety lug g on the wedge comes just in front 
 of the corresponding safety lug h on the sear, so that the 
 sear cannot be moved till the breech is completely closed, 
 at which time g rises above h. 
 
 360. The Driggs-Schroeder Rapid-fire Gun The Breech Mechanism 
 Action. 
 
 This gun is an American invention, and its breech sys- 
 tem combines the rotating and sliding movements, as in the 
 Nordenfelt, but its distinguishing feature is that the breech- 
 slot does not extend through the top of the breech, and the 
 block rests in grooves on the top and sides of this slot. 
 This gives greater strength, protects all the working parts, 
 and enables the weight of these parts to be reduced, thereby 
 facilitating the operations of opening and closing the breech. 
 
 THE BREECH MECHANISM. The breech mechanism con- 
 sists of a block, a, Fig. 386, having grooves, b, and projec- 
 tions, c, cut upon its top and sides, which fit into corre- 
 sponding recesses in the top and sides of the breech recess. 
 d is a shaft passing through the sides of the breech, and 
 through the block a, about which motion of the latter takes 
 place, e is a cam attached to the shaft d, and rotating with 
 it ; ff a surface in the interior of the block of the shape 
 shown, which is in contact with the cam e, the rear part of 
 
628 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 /being inclined backward and upward, and the front part/' 
 being circular and concentric with the axis of d. The rear 
 surface/ ends in a cylindrical pin, g. h is an inclined sur- 
 face on the lower rear end of the block, against which the 
 cam e acts at a certain period of its rotation, i is a slot in 
 
 FIG. 386. 
 
 FIG. 388 
 
 the breech-block, which allows the block to slide in a direc- 
 tion at right angles to the axis of d. j is the extractor, 
 there being two of these; k a guide-bolt screwed through 
 the breech-casing, and fitting into the guide-groove / on the 
 side of the block. There are two of these guide-bolts, one 
 on each side. 
 
 ACTION. In Fig. 386 the block is shown in the firing 
 position, in 387 in the partly opened, and in 388 in the fully 
 opened position. When the shaft d is rotated to the rear 
 by hand after firing, the toe m of the cam e passes along 
 the cam surface ff, permitting the block to descend. 
 Should the block not drop freely, the lower face n of the 
 cam, acting on the inclined surface h, forces the block 
 downward, the slot i in the block allowing this motion 
 with reference to the shaft d. The guide-groove / is also 
 so shaped as to allow this motion with reference to the 
 guide-bolts, k. 
 
RAPID-FIRE GUNS. 629 
 
 This vertical motion of the block continues until the 
 block has descended a distance sufficient to disengage the 
 projections, c, from the corresponding recesses in the top 
 and sides of the breech. The block is now resting on the 
 toe m of the cam, and the guide-bolt, as shown in Fig. 387, 
 is just entering the curved portion of the guide-groove. 
 The block now has a double movement, downward by virtue 
 of the toe continuing to move along the surface ff, and 
 rotary owing to the shape of the guide-grooves. This 
 motion continues till the notch o in the cam comes to a full 
 bearing against the cylindrical pin g t when the block will 
 rotate around d as an axis till the breech is open. As the 
 block rotates to the rear, the extractor-groove q strikes the 
 tail p of the extractor j, and rotates it backward, slowly 
 at first, and then more rapidly, owing to the shape of the 
 abutting surfaces ; extracting and ejecting the empty case. 
 The charge is now inserted, and the rotation of d reversed. 
 This causes the block to rotate around d till its projections, 
 c 1 are ready to enter their recesses in the breech, the notch 
 o of the cam e, bearing against the pin g of the block. 
 
 When the rotation of the block is finished, the pressure 
 of the cam on the surface/, causes the block to rise, and seat 
 itself in the recesses in the breech. The toe m .of the cam 
 then passes to the concentric surface f, and supports the 
 weight of the block during firing and keeps it in its seat in 
 the breech. The movement along the concentric surface/' 
 is continued until the toe m of the cam passes over the 
 centre of rotation d, and prevents the downward thrust of 
 the block from having any tendency to turn the cam 
 backward, and it is therefore held rigidly and securely in 
 place. 
 
 361. The Driggs-Schroeder Rapid-fire Gun The Firing Mechan- 
 ism Action Remarks. 
 
 THE FIRING MECHANISM. This consists (Fig. 389) of a 
 firing-pin, a, working in a recess in the block, and having 
 a shoulder, b, in front. 
 
630 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 A strong spiral main spring, c, bears against this 
 shoulder, its rear end resting against a corresponding 
 
 shoulder in the block, g is 
 the full-cock notch ; h, the 
 sear, acting vertically in a re- 
 cess at the rear end of the 
 block ; i, the sear-spring, seat- 
 ed in a recess in the block, 
 and acting against the lower 
 end of the sear to force the 
 latter vertically upward. k 
 is a projecting lug on the 
 firing-pin a, which bears in a 
 circular recess,/, in the front 
 upper surface of the cam e. 
 
 ACTION. When the cam e 
 is rotated to the rear by the 
 shaft d, the surface of the cir- 
 cular recess /, acting against 
 
 FIG. 389. 
 
 the projecting lug k on the firing-pin, withdraws the point 
 of the latter through its hole in the block, so that it will 
 allow the block to descend freely. As the rotation of the 
 cam e continues, the firing-pin is drawn back still further, 
 compressing the spiral main spring c, till the firing-pin is 
 fullv cocked, at which time the sear h, acted on by its 
 spring i, rises, and engages in front of the full-cock notch 
 g, and the firing-pin is thus retained in its cocked position. 
 When the breech is closed, the cam e is rotated forward, 
 and the lug k is no longer in contact with the surface of the 
 groove j. The sear h, being pulled vertically downward 
 by a lanyard attached at/, is disengaged from the full-cock 
 notch, and the firing-pin a moves forward, firing the car- 
 tridge. 
 
 REMARKS. The cartridge cannot be fired before the 
 breech is completely closed, because until it is closed the 
 groove j in the cam e is in such a position as to catch the 
 lug k of the firing-pin if the latter should move forward, 
 and thus prevent the firing-pin from striking the cartridge. 
 
RAPID-FIRE GUNS. 
 
 362. The Maxim Semi-automatic Rapid-fire Gun The Breech Mech- 
 anism Action. 
 
 This gun differs from those previously described in 
 being- semi-automatic ; that is, the firing of the cartridge 
 causes the barrel and breech mechanism to recoil together, 
 opens the breech, cocks the firing-pin, and thus prepares the 
 gun for the insertion of a fresh cartridge. The act of in- 
 serting the cartridge closes the breech, and if the trigger be 
 kept pulled, fires the piece. 
 
 FIG. 390. 
 
 FIG. 391. 
 
 THE BREECH MECHANISM. This consists (Figs. 390 and 
 391) of a breech-block a, hollowed out at b to receive the 
 firing mechanism. This block moves vertically upward and 
 downward in a slot in the rear part of the barrel. 
 
 Attached to a projection on the lower side of the barrel 
 is the shaft c, about which motion of the breech-block takes 
 place. Two arms d, one on each side, are attached to the 
 shaft c and rotate with it. These arms are connected in 
 rear at their upper ends, by a pin e, which passes through 
 the breech-block a, and works in a slot / in the block. 
 This slot is at first concentric with the axis of c, and is after- 
 wards eccentric to that axis, g is a handle attached to the 
 shaft c, outside the gun, for the purpose of starting the 
 mechanism, and can be readily detached, h is the extractor 
 and ejector, having two projections z, one on each side, 
 which fit in corresponding recesses/ in the breech-block. 
 k is a strong spring, one end of which bears against the pin 
 
632 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 I on the short arm of the lever d, and which presses the 
 long arm of d constantly upward, m is a cam fastened to 
 the shaft c, and n is a catch pivoted to the jacket, and hav- 
 ing no motion in the direction of recoil. It is constantly 
 pressed downward by the spring, o. 
 
 ACTION OF THE BREECH MECHANISM. The parts as rep- 
 resented in Fig. 390 are in the firing position, the breech 
 being closed. Before firing, the operating handle g is re- 
 moved from the shaft c. When the piece is fired, all the 
 parts except the catch n, with its spring o, move to the 
 rear in recoil, the barrel sliding in the jacket, which remains 
 fixed. 
 
 As they move to the rear, the cam m slides along the 
 fixed catch n, till the projecting corner of m has passed be- 
 yond the end of n, when the spring o forces n downward. 
 When the end of the recoil is reached, a strong spring, not 
 shown in the figure, acts to draw all the parts back to their 
 former position. As the parts move forward, the project- 
 ing toe or corner of the cam m, strikes against the end of 
 the catch n, and as the forward motion of the parts con- 
 tinues, m is forced to rotate backwards. 
 
 This causes the arms d to rotate downward, carrying 
 with them the pin e, which passes through the slot/ in the 
 breech-block. As the front part of this slot is concentric 
 with reference to c, no motion of the breech-block occurs at 
 first, but at this time the firing-pin is cocked. 
 
 As the forward motion of the parts continues, the toe or 
 corner of the cam m is freed from the catch n by the up- 
 ward motion of m, which strikes against n. When the pin 
 e enters the eccentric part of the slot f the breech-block 
 descends. In its descent it forces the extractor backward, 
 slowly at first, and afterwards more rapidly, by the action of 
 the studs s on the sides of the block which bear on the tail 
 of the extractor. This downward motion of the block, and 
 backward motion of the extractor, continues, till the lugs i 
 on the extractor, catch in the recesses/, of the block. The 
 breech is now open (Fig. 391) and ready for loading. When 
 the long arm of d rotates downward, the short arm moves 
 upward, and compresses the spring k. This spring tends 
 
RAPID-FIRE GUNS. 
 
 633 
 
 to raise the breech-block by its action on the short arm ot 
 d, but the block cannot rise, because it is held by the pro- 
 jections i of the extractor bearing in the recesses j oi the 
 block. When the cartridge is inserted, its rim strikes 
 against the extractor, and frees the lugs i from the recesses 
 j, and the pressure ol the spring k on the short arm of the 
 lever d causes the block to rise, thus completely closing 
 the breech. 
 
 363. The Maxim Semi-automatic Rapid-fire Gun The Firing 
 Mechanism Action Remarks. 
 
 THE FIRING MECHANISM. This consists (Figs. 392 and 
 393) of a hammer E t rotating around a shaft a, which passes 
 
 E 
 
 ^ A? K ts's 
 
 FIG. 392. FIG. 393. 
 
 through the breech-block. This hammer is pressed con- 
 stantly lorward by the main spring 5, the upper branch of 
 which acts against the lower bent end e' of the hammer. 
 The firing-pin G is a separate piece, which is held in place 
 
634 TEX r f-BOOK OF ORDNANCE AND GUNNERY. 
 
 by the bolt P passing through a slot in it, this slot allowing 
 the pin to move backwards and forwards for a short dis- 
 tance. In front, the firing-pin is acted on by a spiral spring, 
 which forces it backward as soon as the pressure of the 
 hammer E is removed. The sear / rotates around a shaft 
 c in the breech-block, and is constantly pressed upward by 
 the spring s, which is a fork of the lower branch of the main 
 spring S. The safety-sear C also rotates around the same 
 shaft c, and is constantly pressed downward by the spring 
 s', which is also a fork of the lower branch of the main 
 spring 5. The hammer E has two notches e" and e'" 
 which engage in the corresponding notches i of the sear 1 
 and c' of the safety-sear, C respectively. 
 
 The sear / is attached to a lever K, which is pivoted 
 around c, and extends to the rear, where it comes in contact 
 with a trigger, T, Fig. 393. 
 
 ACTION OF FIRING MECHANISM. As represented in 
 Fig. 392, the charge has just been fired. When counter- 
 recoil begins, the pin e which passes through the slot / in the 
 breech-block, and which connects the upper extremities of 
 the arms attached to the main shaft, begins to move along 
 the concentric portion of the groove/. During this time 
 there is no vertical motion of the block, as explained, but the 
 pin e strikes against the lower part, e' , of the hammer, and 
 depresses it, thus drawing back the upper part, E, and com- 
 pressing the main spring 5. This continues till the hammer 
 is fully cocked, at which time the notch e" on the hammer 
 E is in front of the corresponding notch i of the sear /, and 
 the notch e'" on the hammer is engaged in the notch c' of 
 the safety-sear C. The hammer is now held back by the 
 safety-sear C, this latter having been lowered by the action 
 of the spring s' till it is in front of the slot /. As soon as 
 the hammer E is withdrawn from the firing-pin G, the latter 
 is forced back by its spiral spring, and the block is now free 
 to descend. 
 
 When the cartridge is inserted the breech-block rises. 
 
 As it does so, the pin e moves up along the slot /, and 
 strikes the end of the safety-sear C, which projects in front 
 ol the slot/, and is therefore in the path of the pin e. This 
 
RAPID-FIRE GUNS. 635 
 
 disengages the notch c' of the safety-sear from the notch e'" 
 ot the hammer E. The notch e" of the hammer E then 
 engages with the notch i of the sear, and the hammer is now 
 held back only by the sear /. Pulling the trigger disen- 
 gages the notch i of this sear from the notch e' ! of the ham- 
 mer, and fires the piece. If the trigger be kept pulled, it is 
 evident that the piece will fire on the closing of the breech, 
 because the hammer E is then held back only by the safety- 
 sear C, and the pin e strikes this safety-sear in closing, as 
 explained, and frees its notch c' from the notch e'" of the 
 hammer. 
 
 REMARKS. The piece cannot be fired before the breech 
 is completely closed, ist, because the firing-pin is not oppo- 
 site the primer; and 2d, because firing cannot take place till 
 the safety-sear is disengaged, and this is done only by the 
 act of closing, and cannot be accomplished till that time. 
 
 364. Ammunition for Rapid-fire Guns Projectiles Cases. 
 
 The ammunition for the different systems of rapid-fire 
 guns is similar in almost every respect, differing only in the 
 kinds of fuze used, each system having its own, but all being 
 of the same type. All these guns use metallic ammunition. 
 
 PROJECTILES. The projectiles are of four kinds : com- 
 mon shell (Fig. 394), made of cast iron ; steel shell (Fig. 395) ; 
 shrapnel (Fig. 396) ; and canister (Fig. 397). The two kinds 
 of shell are similar in construction except that the base of 
 the steel shell is an independent piece screwed in, and hav- 
 ing its inner surface concave, so that it will tend to form a 
 gas-check when the bursting-charge explodes, and retain the 
 gases till they acquire sufficient pressure to rupture the 
 walls. The point of the steel shell is made sharp for armor- 
 piercing, while that of the common shell is cut off, and the 
 two may always be distinguished by this difference in their 
 points. The fuzes are placed in the base, leaving the point 
 and head solid. Many of the steel projectiles are made by 
 electro-welding. 
 
 The shrapnel (Fig. 396) is composed of a body, a head, 
 and a base. The body is made of a steel tube weakened 
 longitudinally by six cuts, in order that it may rupture 
 
6 3 6 
 
 TEXT-BOOK OF ORDNANCE AND GUNNERY. 
 
 readily. The head is of brass, fitted with a combination 
 fuze, and the upper end of the body is crimped into a recess 
 
 FlG - 398- FIG. 399. FIG. 400. 
 
 in the head. The base is a steel plug forced into the body 
 under pressure, or screwed in. The interior is rilled with 
 
RAPID-FIXE GUNS. 
 
 637 
 
 bullets, the layers being separated by cast-iron disks, as ex- 
 plained in the U. S. shrapnel for field-guns. The bursting- 
 charge is contained in a tin 'cup in front. 
 
 The case-shot (Fig. 397) consists of a thin sheet-brass 
 case, with a conical head, and a bottom of soft brass acting 
 as a rotating band. The bottom is strengthened on the 
 inside with a loose plate of sheet iron. The case is filled 
 with hardened lead balls packed in sawdust. 
 
 CASES. These are of three kinds : 
 
 1. The solid drawn case (Fig. 398), made as described 
 under small-arm ammunition. 
 
 2. The built-up case (Fig. 399), consisting of a drawn 
 tube of brass, bent inward at the head, and furnished with 
 an inner and an outer cup of brass, which are riveted to a 
 sheet-iron disk on the outside to strengthen the construction. 
 In some cases the sheet-iron disk is omitted, and the outer 
 cup used. 
 
 3. The wrapped case (Fig. 400), consisting of a sheet of 
 brass of trapezoidal shape wrapped into a cylinder, and the 
 head formed as in a built-up cartridge. 
 
 The latter case is now abandoned except for the Hotch- 
 kiss revolving cannon. All the cartridges are centre- 
 primed. The projectile, fuze, charge, and case are assembled, 
 forming a complete cartridge, the only limit in size being 
 the weight readily handled by one man. On this account, 
 for the larger calibres the projectile and case are separated. 
 
 The assembled cartridge is shown in Fig. 401. 
 
 FIG. 401. 
 
INDEX. 
 
 A 
 
 PAGE 
 
 A and B, value of 54 
 
 Absorbents classified, dynamite 115 
 
 Absorbents, inert, dynamite 115 
 
 Accles feed 597 
 
 Accuracy of fire, increase of 539 
 
 Accuracy of guns, comparison of , 519 
 
 Acid, Emmens .....-... ... 118 
 
 Acid, picric , 118 
 
 Action of breech mechanism, seacoast guns , 266 
 
 Action of drill-press 1 74 
 
 Action of gunpowder in a gun , t . . . . 31 
 
 Action of lathe 169 
 
 Action of mechanism, 3.6-inch mortar 249 
 
 Action of milling-machine 175 
 
 Action of planer 171 
 
 Action of shaper 172 
 
 Action of teeth 158 
 
 Adjustments, Le Boulenge 93 
 
 Advantages of Noble gauge 102 
 
 Advantages of reduction of calibre 538 
 
 Air-packing 101 
 
 Air-space, initial, reduced length of , 40 
 
 a and ft characteristics 55 
 
 aand ft, determination of r 67 
 
 Ammonium nitrate powders 126 
 
 Ammonium picrate 1 18 
 
 Ammunition-chest 413 
 
 Ammunition for rapid-fire guns 651 
 
 Ammunition, history of 581 
 
 Ammunition, small arm ....... 581 
 
 Amount of heat, Noble and Abel's experiments, 24 
 
 Annealing gun-forgings - 152 
 
 639 
 
640 INDEX. 
 
 Annealing of gun-steel I 4 I 
 
 Angle of departure 34$ 
 
 Angle of elevation 34& 
 
 Angle of elevation in recoil 45 l 
 
 Angle of fall , 34* 
 
 Angle of inclination 378 
 
 Angle of sight 347 
 
 Angle of traces 4O2 
 
 Anti-friction washers and springs, seacoast guns 261 
 
 Apparatus, Letard's IO 3 
 
 Apparatus, Noble and Abel's experiments 20 
 
 Application of Noble and Abel's pressure curve 38 
 
 Arrangement of wires, Le Boulenge 87-90 
 
 Area of orifice, constant orifice, hydraulic buffer 459 
 
 Area of orifice, variable orifice, hydraulic buffer 4^3 
 
 Armor 3^7 
 
 Armor, backing for 3 2 i 
 
 Armor, chilled cast iron 3 T 7 
 
 Armor, compound 3 J 7 
 
 Armor, effect of projectiles on 320 
 
 Armor, improved fastenings for 323 
 
 Armor, kinds of .*.... 317 
 
 Armor, old, fastenings for. 322 
 
 Armor, penetration of 325 
 
 Armor-piercing shell 281 
 
 Armor-plates, tests of 324 
 
 Armor, steel, history 318 
 
 Armor, steel, improvements , 319 
 
 Arms, cutting 528 
 
 Arms, cutting and thrusting 531 
 
 Arms, hand 528 
 
 Arms, portable 528 
 
 Arms, small 531 
 
 Arms, thrusting 529 
 
 Artillery-carriages, classification 389 
 
 Artillery-carriages, the axle 389 
 
 Artillery sabre, light , 529 
 
 Assembling gun 180 
 
 Assembling, operations after 182 
 
 Assembling tube and jacket . . 181 
 
 Attachment of horses 403 
 
 Attachment of traces 403 
 
 Auxiliary ballistic formulas 367 
 
 Auxiliary ballistic tables 371 
 
 Auxiliary ballistic tables, examples 372 
 
 Axle-arms - 3go 
 
 Axle, artillery-carriages 389 
 
INDEX. 641 
 
 B 
 
 PAGE 
 
 Backing * 406 
 
 Backing for armor 321 
 
 Ballistic coefficient C 35^ 
 
 Ballistic formulas, auxiliary c 367 
 
 Ballistic formulas, simplification of 361 
 
 Ballistic functions, calculation of 362 
 
 Ballistic problems, table of 388 
 
 Ballistic superiority of smokeless powders, cause of 132 
 
 Ballistic tables, auxiliary 37I 
 
 Ballistic tables, auxiliary, examples of use of 372 
 
 Ballistic tables, explanation of . , 369 
 
 Ballistic test of projectiles 317 
 
 Ballistics, exterior /. 347 
 
 Ballistics, interior 31 
 
 Ballistics, practical problems 374 
 
 Ballistite 127 
 
 Bands, copper 307 
 
 Bands or belts 159 
 
 Barrel, length of, in small arms 545 
 
 Barrel, small-arm 532. 
 
 Barrel, thickness of < 544. 
 
 Barbette carriages . . 418 
 
 Base-plate 420 
 
 Bases, chemically active, dynamite 1 16- 
 
 Bases, high explosive, with dynamite 117- 
 
 Bashf orth target 97 
 
 Bayonet 530 
 
 Belleville springs , 398 
 
 Bellite 120 
 
 Belts 159 
 
 Belts or bands 159 
 
 Berthelot's theory 106 
 
 Binomial formula, limit of use of 62 
 
 Binomial formula, Sarrau's 53 
 
 Blasting, use of dynamite in 116 
 
 Blasting, use of gun-cotton in 113 
 
 Blasting, use of n itro-glycerine in..., 115 
 
 Blending and marking gunpowder 2 
 
 Blow-holes in gun-steel 140 
 
 Bolt, cal. .30 555 
 
 Bore, length of 45 
 
 Bore of tube 180 
 
 Boring and turning 152 
 
 Boring- and turning-lathes 179 
 
 Boring, finish 182 
 
 Boring tube, first 177, 
 
642 INDEX. 
 
 PAGE 
 
 Bormann fuze 33 2 
 
 Boxer oblong shrapnel . 290 
 
 Boxer spherical shrapnel 289 
 
 Brake, Buffington 397 
 
 Brake, Hotchkiss 395 
 
 Brake, hydraulic, with constant orifice. . . - 456 
 
 Brake, Lemoine 395 
 
 Brake, necessity for 453 
 
 Brake, Nordenfelt 396 
 
 Brake with variable orifice 460 
 
 Brakes 394 
 
 Brakes and buffers 453 
 
 Brakes, classes of , 454 
 
 Brakes, conditions for good 454 
 
 Brakes, elastic 397 
 
 Brakes, friction 394 
 
 Brakes, friction, for seacoast guns 454 
 
 Brakes, hydraulic 399~455 
 
 Brakes, hydraulic, classification 456 
 
 Breech-block, field-artillery 237 
 
 Breech-block, seacoast guns 260 
 
 Breech-block, Springfield 553 
 
 Breech-loading projectile 306 
 
 Breech-loading projectile, rotating device 306 
 
 Breech, maximum pressure on 55 
 
 Breech mechanism 548 
 
 Breech mechanism, action of, seacoast guns 266 
 
 Breech mechanism, cal. 30 544 
 
 Breech mechanism, classification , 548 
 
 Breech mechanism, Farcot 270 
 
 Breech mechanism, field-guns, action of 249 
 
 Breech mechanism, improved, continuous rotation 269 
 
 Breech mechanism, improvements in 269 
 
 Breech mechanism, Krupp's 274 
 
 Breech mechanism of field-artillery 236 
 
 Breech mechanism of siege-guns 252 
 
 Breech mechanism, requirements 551 
 
 Breech mechanism, rotating 549 
 
 Breech mechanism, seacoast guns 259 
 
 Breech mechanism, sliding , 548 
 
 Breech mechanism, Springfield rifle 552 
 
 Breech mechanism, 12-inch mortar , 268 
 
 Breeching 408 
 
 Breger's improvements 94 
 
 Brinell's experiments.. . . 154 
 
 Broadwell ring 276 
 
 Brown powder 7 
 
INDEX. 643 
 
 PAGE 
 
 Brown segmental gun 220 
 
 Bruce feed 595 
 
 Brugere's powder 118 
 
 Buffer, Englehardt 397 
 
 Buffers, 8-inch ' 442 
 
 Buffers and brakes 453 
 
 Buffi ngton brake 397 
 
 Buffington-Crozier disappearing carriage 430 
 
 Built-up guns, general principles 205 
 
 Bullet 584 
 
 Bullet, cal. .30 585 
 
 Bullet, Hebler 585 
 
 Bullet, reduction of weight of 535-537 
 
 Bullet, Springfield 585 
 
 Burning of spherical grain under pressure 50 
 
 Bursting-charge of shell 284 
 
 Bursting-charge of shrapnel, position of 292 
 
 Bursting of shell '. 284 
 
 Butler projectile 305 
 
 c 
 
 Calculations for compound cylinder 206 
 
 Calculation of ballistic functions 262 
 
 Calculation of pi 212 
 
 Calculation of shrinkage 214 
 
 Calculation of value of r 65 
 
 Calibre, advantages of reduction of 538 
 
 Calibre, effect of, smokeless powder 123 
 
 Calibre, reduced, disadvantages of 540 
 
 Calibre, .30, breech mechanism 554 
 
 Calibre, .30, bullet 585 
 
 Calibre, .30. firing mechanism 560 
 
 Calibre, .30, magazine] for 577 
 
 Calibre, .30, receiver 547 
 
 Calibre, .30, sights for 565 
 
 Calibres of seacoast guns 254 
 
 Calipers 226 
 
 Calipers, eccentric 316 
 
 Cam-latch 553 
 
 Canister 285 
 
 Canister, Sawyer 286 
 
 Cannon, classification of 232 
 
 Cannon, description of 232 
 
 Cannon, Hotchkiss revolving 614-616 
 
 Cannon powder 5 
 
 Cannon, targets for 84 
 
644 INDEX. 
 
 PAGE 
 
 Carbo-dynamite TI 7 
 
 Carriage, direction of 46 
 
 Carriage, 8-inch barbette - 4*8 
 
 Carriage, Hotchkiss mountain 409 
 
 Carriage, howitzer 4 10 
 
 Carriage, siege-mortar 4 1 7 
 
 Carriage, 3.6-inch mortar 4! 
 
 Carriages, artillery /. 39 
 
 Carriages, barbette 4 T 
 
 Carriages, casemate 4 
 
 Carriages, disappearing 428 
 
 Carriages, field-artillery 409 
 
 Carriages, field, 3.2-inch 4 11 
 
 Carriages, mountain-artillery 409 
 
 Carriages, old U. S. seacoast 432 
 
 Carriages, seacoast 418 
 
 Carriages, siege 4 1 5 
 
 Carriages, turret 428 
 
 Carriages, wheeled, recoil of 450 
 
 Carrier-ring 242 
 
 Cartridge-case 586 
 
 Cartridges, folded head 582 
 
 Cartridges, folded head cup anvil 583 
 
 Cartridges, solid head : 584 
 
 Case, cartridge 586 
 
 Case-shot 584 
 
 Case-shot, definition of 284 
 
 Case, spherical U. S 288 
 
 Casemate carriages.. 428 
 
 Cases in pointing 467 
 
 Casting ingots 146 
 
 Casting projectiles 313 
 
 Casting, treatment after 149 
 
 Causes affecting resistance of air 351 
 
 Causes of deviation in pointing 476 
 
 Cavalry sabre 531 
 
 Centre of impact 499 
 
 Chamber, profile of, cal. .30 , 544 
 
 Changes in black powders 121 
 
 Changes of velocity, pressure constant 70 
 
 Characteristics a and /? 55 
 
 Chassis, 8-inch .' 420 
 
 Chauvenet's table 521 
 
 Chemical action of smokeless powders 131 
 
 Chemical composition of gun-steel 136 
 
 Chemical formula for combustion of powder 19 
 
 Chilled cast-iron armor 317 
 
INDEX. 645 
 
 PAGE 
 
 Chilled shot 280 
 
 Chromium in gun-steel 137 
 
 Chronograph, Le Boulenge 85 
 
 Chronoscope, Schultz 95 
 
 Classes of brakes 454 
 
 Classification of artillery-carriages 389 
 
 Classification of breech mechanism 548 
 
 Classification of cannon 232 
 
 Classification of fuzes 328 
 
 Classification of projectiles 279 
 
 Classification of repeating mechanism 569 
 
 Classification of smokeless powders 126 
 
 Close vessel, combustion in 19 
 
 Cocoa powder 7 
 
 Cocoa powder, velocity of emission for 16 
 
 Coefficient, ballistic, C 354 
 
 Cooling jacket 182 
 
 Combination fuzes 337 
 
 Combination fuze, Frankford Arsenal 337 
 
 Combustion in a close vessel 19 
 
 Combustion of gunpowder, chemical formula for 19 
 
 Combustion of gunpowder in air 9-10 
 
 Combustion of gunpowder in air, laws of 10 
 
 Combustion of gunpowder in a gun 31 
 
 Common electric primers . . 343 
 
 Common features of field-guns 234 
 
 Common features of seacoast guns 254 
 
 Common features of siege-guns 251 
 
 Common friction-primers. ... , 342 
 
 Comparator, standard 221 
 
 Comparison of mean and true mean errors 515 
 
 Composition of gunpowder I 
 
 Composition of products, Noble and Abel's experiments 23 
 
 Compound armor 317 
 
 Compound cylinder, calculations for 206 
 
 Compound cylinder, longitudinal strength of 209 
 
 Compounds, explosive 105 
 
 Compounds, nitro- substitution 106 
 
 Compression, smokeless powder 124 
 
 Conditions for good brake 454 
 
 Conditions for good magazine-gun 568 
 
 Conditions to be fulfilled by smokeless powders 129 
 
 Cone of dispersion, cause affecting it 287 
 
 Cone of dispersion, shrapnel 286 
 
 Cones, speed 160 
 
 Connection by cords 161 
 
 'Connection, hydraulic 161 
 
646 INDEX, 
 
 PAGE. 
 
 Console < 26 3 
 
 Constant orifice, length of recoil 45& 
 
 Constituents, other, of gun-steel J 36' 
 
 Construction of spherical shrapnel 288 
 
 Contact, rolling , 1 5& 
 
 Contact, sliding J 57 
 
 Continuous rotation, improved breech mechanism 269 
 
 Copper bands 37 
 
 Core of projectile 3 11 
 
 Cored shot 2 79 
 
 Cordite 128 
 
 Cords, connection by 161 
 
 Correction for drift 49 
 
 Cover, vent 247 
 
 Crane 140 
 
 Cranes - 149 
 
 Crozier gun 220 
 
 Crucible process 145 
 
 Crusher-gauge, Noble's . . 101 
 
 Curve of stresses in cylinder 193 
 
 Curve of total recoil 449 
 
 Curve, pressure, Longridge 78 
 
 Curve, pressure, Mayevski 78 
 
 Curve, pressure, Noble and Abel's 77 
 
 Curve, pressure, Sarrau 80 
 
 Curve, probability 506 
 
 Curved fire 348 
 
 Curves, pressure, in guns 76 
 
 Cut-off, magazine, cal. .30 548 
 
 Cutting-arms 528 
 
 Cutting- and thrusting-arms % 531 
 
 Cutting-tools 164 
 
 Cutting up smokeless powder 125 
 
 Cutters, milling 165 
 
 Cylinder, compound, calculations for 206 
 
 Cylinder, curve of stresses in 193 
 
 Cylinder, maximum strains in 198 
 
 Cylinder, method of strengthening , 196 
 
 Cylinder, pressure in 465 
 
 Cylinder, pressure in, constant orifice 459 
 
 Cylinder, states of ... 206 
 
 D 
 
 Dangerous space 381 
 
 De Bange obturator 238 
 
 Decrease in weight of cartridge 530, 
 
INDEX. 647 
 
 PAGE 
 
 Deduction of final equation of motion of projectile in bore < . 50 
 
 Defects of gun-steel 140 
 
 Definition of case-shot , , 284 
 
 Definition of fuze 328 
 
 Definition of gun-steel 136 
 
 Definition of machine 155 
 
 Definition of shell 281 
 
 Delayed-action fuzes 340 
 
 A constant, o3 and r variable .' 71 
 
 Density, influence of, gunpowder 18 
 
 Density of dynamite No. i 116 
 
 Density of explosive gelatine 117 
 
 Density of gun-cotton 112 
 
 Density of loading 2 1 
 
 Density of loading, French measure for 22 
 
 Density of mercury fulminate 119 
 
 Density of nitro-glycerine 114 
 
 Density, sectional , 296 
 
 Density, spherical , 310 
 
 Depression range-finders 481 
 
 Depth of grooves 543 
 
 Description of cannon 232 
 
 Description of gun 176 
 
 Description of latch 243 
 
 Description of Le Bouleng6 chronograph 86 
 
 Description of modern shrapnel 292 
 
 Designolle's powder 1 1 8 
 
 Detachable magazines 569 
 
 Details of modern rotating band 308 
 
 Determination of a and ft. 67 
 
 Detonation by influence 108 
 
 Detonation of dynamite ... 1 16 
 
 Detonation of explosive gelatine 118 
 
 Detonation of gun-cotton 113 
 
 Detonation of mercury fulminate 119 
 
 Detonation of nitro-glycerine 115 
 
 Detonating fuze 108 
 
 Detonators 107 
 
 Deviations 498 
 
 Deviations, how measured 498 
 
 Deviations in pointing, causes of 476 
 
 Devices, elevating 399 
 
 Devices, rotating 302 
 
 Diameters, exterior, measuring 226 
 
 Diameters, interior, measuring 230 
 
 Difficulties in making time-fuzes 328 
 
 Direct fire ." 348 
 
648 INDEX. 
 
 PACE 
 
 Direction of carriage ' 406 
 
 Direction of traces 45 
 
 Direction of twist 44 
 
 Disadvantages of reduced calibre. 54 
 
 Disappearing carriages * 428 
 
 Disappearing carriage, Buffington-Crozier 430 
 
 Disappearing carriage, Gordon 431 
 
 Discussion of formula for pressure of gunpowder 28 
 
 Dish of wheel 39 1 
 
 Disjunction 89 
 
 Disjunction, fixed 89 
 
 Disjunction reading, fixed, Le Boulenge 93 
 
 Disjunctor 91 
 
 Distance-rings, rollers and 420 
 
 D istances by eye 478 
 
 Distances by sound 478 
 
 Distances, estimating 477 
 
 Distribution of energy in shops 162 
 
 Division of trajectory. 505 
 
 Division of work of gunpowder 41 
 
 Double position, rule of 382 
 
 Draught 401 
 
 Draught-harness 408 
 
 Draught-horse 402 
 
 Drift 348, 350, 385 
 
 Drift, correction for 469 
 
 Drift, permanent angle of 473 
 
 Driggs-Schroeder rapid-fire gun 629 
 
 Drill-press 173 
 
 Drill press, action of 174 
 
 Drill-press, parts of 173 
 
 Drills and reamers 165 
 
 Drying and dusting gunpowder 2 
 
 Drying smokeless powder 125 
 
 Dynamic method 102 
 
 Dynamic method, pressure by, Noble and Abel's 102 
 
 Dynamite : 115, 116 
 
 E 
 
 Eprly shrapnel 288 
 
 Eccentric calipers 316 
 
 Eccentricity of projectiles 315 
 
 Effect of calibre, smokeless powder 123 
 
 Effect of projectiles on armor 320 
 
 Effect of variation of powder, Noble and Abel's experiments 24 
 
 8-inch barbette carriage 418 
 
INDEX. 649 
 
 8-inch chassis 420 
 
 8-inch converted rifle ... 273 
 
 8-inch gun 254 
 
 8-inch top carriage and buffers 422 
 
 Elastic brakes 397 
 
 Elastic strength of guns 185 
 
 Elasticity and elastic limit of gun-steel 137 
 
 Elasticity, modulus of 139 
 
 Electric primer, common 343 
 
 Electric primer, obturating 346 
 
 Elements of loading, variation of 69 
 
 Elevating devices 399 
 
 Elevating devices, 8-inch 423 
 
 Elevating gear, 12-inch mortar carriage 427 
 
 Elevating-screw 399 
 
 Emmens acid 118 
 
 Emmensite 119 
 
 Emission, velocity of, spherical grain 14 
 
 Energy, distribution of in shops 162 
 
 Energy of rotation of oblong projectiles 294 
 
 Energy, relative, of smokeless powders 129 
 
 Englehardt buffer 397 
 
 Equation of motion of projectile in bore 47 
 
 Equation of pressure curve, Noble and Abel's method 33 
 
 Equation of pressure curve, recent hypothesis 37 
 
 Equation of probability curve 507 
 
 Equations A, integration of 358, 360 
 
 Error, law of 505 
 
 Error, probable 512 
 
 Error, true mean 513 
 
 Errors .' 502 
 
 Errors and corrections in general equation of motion of projectile 49 
 
 Errors in height of sight in pointing 485 
 
 Errors in pointing 472 
 
 Estimating distances 477 
 
 Ether, nitric 106 
 
 Eureka projectile '. 305 
 
 Example, rule of double position 383 
 
 Examples of use of auxiliary ballistic tables. 372 
 
 Expanding system, projectiles * 304, 305 
 
 Expansion, furnace for, guns 181 
 
 Expansion, parts of guns 181 
 
 Experiment, pressure by, gunpowder 98 
 
 Experiments, Brinell's 154 
 
 Experiments on resistance of air 351 
 
 Explanation of ballistic tables , 369 
 
 Explosion, modes ot producing 108 
 
650 INDEX. 
 
 Explosion of gunpowder 9 
 
 Explosion, orders of . . 106 
 
 Explosion, temperature of, gunpowder 30 
 
 Explosive compounds 105 
 
 Explosive gelatine 117,118- 
 
 Explosive. high 105 
 
 Explosive, low 105 
 
 Explosive mixtures 1 05 
 
 Explosive, strength of 109 
 
 Explosives 105 
 
 Explosives, flameless 120 
 
 Explosives, principal in 
 
 Exterior ballistics 347 
 
 Exterior ballistics, problem 1 375 
 
 Exterior ballistics, problem 2 376 
 
 Exterior ballistics, problem 3 ,. 377 
 
 Exterior ballistics, problem 4 378 
 
 Exterior ballistics, problem 5 380 
 
 Exterior ballistics, problem 6 381 
 
 Exterior ballistics, problem 7 386 
 
 Exterior diameters, hoops 226, 231 
 
 Exterior of cylinder, strain at 203 
 
 Exterior pressure, method of applying, guns 205 
 
 Exterior pressure, thickness to resist, cylinders 203 
 
 Exterior pressures, limiting, cylinders 201 
 
 Extractor, cal. .30 557 
 
 Extractor, Springfield 554 
 
 Eye, errors of in pointing 485 
 
 F 
 
 Factor of effect, gunpowder 37 
 
 Farcot breech mechanism 270 
 
 Fastenings for armor, improved 323 
 
 Fastenings for old armor 322 
 
 Feed, Accles, Galling 507 
 
 Feed, Bruce, Galling , gor 
 
 Feed-case, tin, Galling ege 
 
 Feed, latest, for Galling ggg 
 
 Feed of lathe !68 
 
 Feeds for Galling guns 504 
 
 Field-artillery, breech-block 237 
 
 Field-artillery, breech mechanism 236 
 
 Field-artillery, principal parts of breech mechanism 236 
 
 Field- and siege-guns, table of 253 
 
 Field-carriage, 3.2-inch 4II 
 
 Field-guns 234, 235 
 
INDEX. 6$I 
 
 PAGE 
 
 Field-guns, common features 234 
 
 Field-limber 412 
 
 Field-shell 283 
 
 5-inch siege-carriage 415, 
 
 5-inch siege-gun 251 
 
 15-inch Rodman smooth bore 274 
 
 Figures of teeth 158 
 
 Final equation, integration of, interior ballistics 53 
 
 Final equation of motion of projectile in bore 52 
 
 Final equation of motion of projectile in bore, deduction of So- 
 Final velocity 348 
 
 Finish-boring 182 
 
 Fire, curved 34$ 
 
 Fire, direct 348 
 
 Fire, high angle 348 
 
 Fire, indirect 34$ 
 
 Fire, mortar 386 
 
 Fire, probability of 505 
 
 Firing mechanism, cal. .30 560 
 
 Firing mechanism, small arms 558 
 
 Firing mechanism, Springfield , 559. 
 
 Firminy process 280 
 
 First boring of gun-tube 177 
 
 Fiske position-finder 483 
 
 Fiske rangerfinder 482 
 
 Fixed box magazine , 575 
 
 Fixed disjunction 89, 
 
 Fixed magazines 571 
 
 Fixed powder-chamber. 72 
 
 Fixing disjunction reading, Le Bouleng6 93 
 
 Flameless explosives 120 
 
 Flanged projectiles 303 
 
 Flask, moulding 312 
 
 Flat grain powder, velocity of emission for 16 
 
 Flatness of trajectory 538 
 
 Flight, time of, projectiles 377 
 
 Fluid-compression, Whitworth's 147 
 
 Fluid-compression theory 148 
 
 Folded-head cartridges 582 
 
 Folded-head cup-anvil cartridges 583 
 
 " Force " of powder 29 
 
 Force or pressure no 
 
 Forces acting on projectile 348 
 
 Foreign guns 274 
 
 Forging, hydraulic, Whitworth's 150- 
 
 Forgings, gun 152, 177 
 
 Forgings, tests of gun 155 
 
652 INDEX 
 
 PAGE 
 
 Form of dynamite No. i ' * 
 
 Form of explosive gelatine l 
 
 Form of grain of gunpowder. 
 
 Form of gun-cotton * 
 
 Form of head of projectile 3 
 
 Form of mercury fulminate "9 
 
 Form of nitro-glycerine I: 4 
 
 Form of picric acid * 
 
 Form of projectile 39 
 
 Forms of pieces in rolling contact J 57 
 
 Formula, binomial, Sarrau's 53 
 
 Formula for burning in air of grains of gunpowder of different shapes n 
 
 Formula for pressure of gases, Noble and Abel's experiments 26 
 
 Formula, monomial, for velocity 6 3 
 
 Formulas, auxiliary ballistic 3^7 
 
 Formulas for whole range - 35 
 
 Formulas, penetration 3 2 5 
 
 Formulas, Sarrau's 4 
 
 Formulas, useful practical 75 
 
 Fouling, smokeless powders I3 1 
 
 4.2-inch Parrott siege-gun 273 
 
 4 5-inch siege-gun 2 7 2 
 
 Frankford Arsenal combination fuze 33 1 
 
 Frankford Arsenal shrapnel 292 
 
 Free acids, effect on dynamite. 116 
 
 Free acids, effect on gun-cotton 113 
 
 Free acids, effect on nitro-glycerine 114 
 
 French measure for density of loading 22 
 
 Frey re obturator 240 
 
 Friction-brakes 394 
 
 Friction-brakes, seacoast 454 
 
 Friction-primer, common 342 
 
 Friction-primer, obturating 344 
 
 Front sight 466, 563 
 
 Front sight, cal. .30 566 
 
 Front sight, Springfield 565 
 
 Fulminate of mercury. . . , 1 19 
 
 Fulminates 119 
 
 Furnace 180 
 
 Furnace for expansion , 181 
 
 Furnace, open-hearth process 144 
 
 Fusibility of gun-steel 141 
 
 Fuze, Bormann , 328 
 
 Fuze, definition of 328 
 
 Fuze, detonating 108 
 
 Fuze, Frankford Arsenal combination 337 
 
 Fuze, Hotchkiss base percussion 336 
 
INDEX. 653 
 
 PAGE 
 
 Fuze, Hotchkiss front percussion 334 
 
 Fuze, mass of 108 
 
 Fuze, Merriam delayed action 340 
 
 Fuze, mortar 330 
 
 Fuze, seacoast 331 
 
 Fuzes and primers 328 
 
 Fuzes, classification 328 
 
 Fuzes, combination 337 
 
 Fuzes, delayed action 340 
 
 Fuzes, old, in use 330 
 
 Fuzes, percussion . 333 
 
 Fuzes, time , ,. 328 
 
 G 
 
 Gas-check, Krupp mechanism 276 
 
 Gas-producer 142 
 
 Gate and riser 313 
 
 Galling gun 590-593 
 
 Galling gun, feeds . 594 
 
 Galling, latest feed < 598 
 
 Gardner machine-gun 600, 601-603 
 
 Gauge, step 227 
 
 Gelatine, explosive 117 
 
 General arrangement of machine-shop 162 
 
 General features of Krupp mechanism 277 
 
 General principles of built-up guns 205 
 
 General principles of measurements, guns 229 
 
 Glazing gunpowder , 2 
 
 Gordon disappearing carriage 431 
 
 Grain, form of, gunpowder . 5 
 
 Graining gunpowder 2 
 
 Grape-shot 285 
 
 Gravimetric density of gunpowder 4 
 
 Grooves, kinds of 301 
 
 Grooves, depth of 543 
 
 Grooves, number of 542 
 
 Grooves, width of 542 
 
 Gruson turrets 317 
 
 Guide-rails, seacoast-guns 264 
 
 Gum-dynamite , 117 
 
 Gunners' quadrant , 491 
 
 Gun, assembled 180 
 
 Gun, Brown segmental 220 
 
 Gun-conslruction, measurements in 216 
 
 Gun-cotton in, 112, 113 
 
 Gun-cotton, modification of , 122 
 
INDEX. 
 
 Gun, Crozier 220 
 
 Gun, description of, general 1 76 
 
 Gun, Driggs-Schroeder rapid fire 627, 629 
 
 Gun, 8-inch 254 
 
 Gun-forgings 152, 177 
 
 Gun-forgings, tests of 153 
 
 Gun, Galling 59. 59 r > 592, 593 
 
 Gun, Gardner 600 
 
 Gun, Hotchkiss rapid fire 620 
 
 Gun, length of 218 
 
 Gun-manufacture 1 76 
 
 Gun, Maxim rapid fire 631, 633 
 
 Gun, Nordenfelt rapid fire 624, 625 
 
 Gun, parts of.... 176 
 
 Gun steel 136, 137, 139. J 4o, 141, 142 
 
 Gun, Woodbridge 219 
 
 Gunpowder, action of in a gun .... 31 
 
 Gun powder, blending and marking 2 
 
 Gunpowder, combustion in air .' 9, 10 
 
 Gunpowder, combustion of in a gun 31 
 
 Gunpowder, composition of i 
 
 Gunpowder, drying and dusting 2 
 
 Gunpowder, explosion of 9 
 
 Gunpowder, form of grain 5 
 
 Gunpowder, " force "of 29 
 
 Gunpowder, formula for burning in air of grains of different shapes n 
 
 Gunpowder, formula for burning in air of spherical grains 12 
 
 Gunpowder, glazing and graining 2 
 
 Gunpowder, gravimetric density 4 
 
 Gunpowder, history of 9 
 
 Gunpowder, ignition of 9 
 
 Gunpowder, incorporating 2 
 
 Gunpowder, inflammation of 10 
 
 Gunpowder, inspection of 8 
 
 Gunpowder, irregular granulation 5 
 
 Gunpowder, laws of combustion in air 10 
 
 Gunpowder, manufacture of I 
 
 Gunpowder, mixing ingredients of I 
 
 Gunpowder, pressing 2 
 
 Gunpowder, proof of 8 
 
 Gunpowder, pulverizing ingredients I 
 
 Gunpowder, regular granulation j 
 
 Gunpowder, Rodman's improvement of 9 
 
 Gunpowder, specific gravity 3 
 
 Gunpowder, work of , . 36, 38, 39 
 
 Guns 136 
 
 Guns, built up, general principles 205 
 
INDEX. 655 
 
 PAGJ 
 
 Guns, elastic strength of. , 185 
 
 Guns, field 234 
 
 Guns, foreign 274 
 
 Guns, machine 589 
 
 Guns, machine and rapid fire 589 
 
 Guns, old, in U. S. service 272 
 
 Guns, rapid fire 619 
 
 Guns, seacoast 254 
 
 Guns, siege 251 
 
 Guns, 10- and 12-inch 256 
 
 Guns, thickness of walls 217 
 
 Guns, wire 218 
 
 H 
 
 Hammer, steam 150 
 
 Hand arms 528 
 
 Handle, lever 246 
 
 Hardening of gun-steel 141 
 
 Hardness of gun-steel 137 
 
 Harness, artillery 406 
 
 Harness, draught 408 
 
 Harvey-process, armor 319 
 
 H eadgear 407 
 
 Head of projectile, form of 310 
 
 Heat, amount of, Noble and Abel's experiments 24 
 
 Heat and cold, effect of on dynamite 1 16 
 
 Heat and cold, effect of on explosive gelatine 117 
 
 Heat and cold, effect of on gun-cotton 113 
 
 Heat and cold, effect of on nitro-glycerine 114 
 
 Hebler bullet 585 
 
 H eight of rear sight 468 
 
 H eight of trajectory 380 
 
 Height of trajectory, maximum 380 
 
 Hellhoffite 120 
 
 Hexagonal powder 7 
 
 H igh-angle fire 348 
 
 H igh explosives 105 
 
 H igh explosives and smokeless powders, table of 133 
 
 High-explosive bases, dynamite 117 
 
 Hinge-pin, Springfield rifle 533 
 
 History of ammunition 581 
 
 History of gunpowder g 
 
 History of rapid-fire guns 619 
 
 History of smokeless powder, early 122 
 
 Holtzer shot 280 
 
 Hooke's law, elasticity 138 
 
656 INDEX. 
 
 PAGE 
 
 Horses, attachment of 43 
 
 Horse, work of 4 O1 
 
 Hotchkiss brake 395 
 
 Hotchkiss base-percussion fuze 33& 
 
 Hotchkiss breech-loading projectile 307 
 
 Hotchkiss front-percussion fuze 334 
 
 Hotchkiss mountain-carriage 409 
 
 Hotchkiss mountain-rifle 232 
 
 Hotchkiss muzzle-loading projectile 304 
 
 Hotchkiss rapid-fire gun 620, 622 
 
 Hotchkiss revolving cannon 614, 616 
 
 Hotchkiss shrapnel 293 
 
 Howitzer carriage 416 
 
 Howitzer, 7-inch 252 
 
 Hydraulic brakes 399, 455 
 
 Hydraulic brake with constant orifice 456 
 
 Hydraulic buffer, 1 2-inch mortar carriage 425 
 
 Hydraulic connection 161 
 
 Hydraulic forging, Whitworth 150 
 
 I 
 
 Ignition of explosive gelatine , 117 
 
 Ignition of gun-cotton 113 
 
 Ignition of gunpowder 9 
 
 Ignition of nitro-glycerine 114 
 
 I. K. powder 6 
 
 Impact, centre of 499 
 
 Improved breech mechanism, continuous rotation 269 
 
 Improved fastenings for armor 323 
 
 Improvements, Breger's, ballistic instrument 94 
 
 Improvements in breech mechanism t . 269 
 
 Inclination, angle of, exterior ballistics 378 
 
 Incorporating gunpowder 2 
 
 Increase of accuracy, small arms 539 
 
 Increased penetration, small arms 540 
 
 Increasing twist 300 
 
 Indirect fire 348 
 
 Indirect pointing 475 
 
 Inert absorbents, dynamite 115 
 
 Infinite expansion, gunpowder 37, 41 
 
 Inflammation of gunpowder 10 
 
 Influence, detonation by . 108 
 
 Influence of passive resistance on velocity and pressure 46 
 
 Ingot-molds I4 6 
 
 Ingots, casting I4 6 
 
 Initial air-space, reduced length of 40 
 
INDEX. 657 
 
 Initial velocity , . . . 348 
 
 Initial velocity by experiment 83 
 
 Inspection and proof of projectiles 314 
 
 Inspection of gunpowder 8 
 
 Integration of equation A 358, 360 
 
 Integration of final equation of motion of projectile in bore 53 
 
 Interior ballistics 31 
 
 Interior diameters 230 
 
 Interior diameters of long hoops 230 
 
 Interior diameters of long tubes 224 
 
 Interior diameters of short hoops, measurements of 222 
 
 Interior pressures, limiting 200 
 
 Interior pressure thickness to resist, cylinder 201 
 
 Irregular granulation, gunpowder 5 
 
 Iron, kind of for projectiles 313 
 
 J 
 
 Jacket, cooling 182 
 
 Jarmann magazine-rifle 571 
 
 Jump 348, 488 
 
 K 
 
 A', value of interior ballistics 57 
 
 KQ, value of interior ballistics 57 
 
 Kieselgiihr , 115 
 
 Kind of iron, projectiles 313 
 
 Kinds of armor . 317 
 
 Kinds of grooves 301 
 
 Krupp mechanism 274 
 
 Krupp mechanism, advantages and disadvantages * / 277 
 
 Krupp mechanism, gas-check : 276 
 
 Krupp mechanism, general features 277 
 
 Krupp mechanism, locking-screw 275 
 
 L 
 
 Ladle, casting 146 
 
 Lame's first law 190 
 
 Lame's second law 191 
 
 Lance or pike 531 
 
 Latch, description of, breech mechanism 243 
 
 Latch, object of field-artillery 243 
 
 Latch, side, seacoast-artillery 265 
 
 Latch, tray, seacoast-artillery 265 
 
 Latest steel plates , 319 
 
 Lathe.. ,. 166 
 
INDEX. 
 
 PACK 
 
 Lathe, action of 169 
 
 Lathe, boring and turning 179 
 
 Lathe, feed 168 
 
 Lathe, parts 167 
 
 Lathe, slide-rest 168 
 
 Law, Hooke's 138 
 
 Law, Lame's first 190 
 
 Law, Lame's second 191 
 
 Law of error 505 
 
 Law of variation of orifice, buffer 463 
 
 Lazy-tongs 401 
 
 Lee magazine 570 
 
 Le Boulenge chronograph 85-88, 93, 94 
 
 Le Boulenge telemeter 478 
 
 Lemoine brake 395 
 
 Length of barrel, small arms 545 
 
 Length of bore, guns 45 
 
 Length of gun 218 
 
 Length of recoil 448 
 
 Length of recoil, constant orifice 458 
 
 Length of recoil, variable orifice. . .-. 461 
 
 Lengths, measurements of 227 
 
 Leonard powder 128 
 
 Letard's apparatus 103 
 
 Lever-handle 246 
 
 Levers, elevating 401 
 
 Light artillery sabre 529 
 
 Light, effect of in pointing 485 
 
 Limber, field 412 
 
 Limit of use of binomial formula , 62 
 
 Limiting exterior pressures , 201 
 
 Limiting exterior pressure on tube 211 
 
 Limiting interior pressures , 200 
 
 Limits of the modulus 75 
 
 Line of fire 347 
 
 Line of sight 347 
 
 Linkwork 160 
 
 Loading, density of 21 
 
 Loading-scoop, 12-inch mortar carriage 428 
 
 Locking-screw, Krupp mechanism , 275 
 
 Longitudinal strength, single cylinder 203 
 
 Longitudinal strength, compound cylinder . . 209 
 
 Longitudinal stress and strain 187 
 
 Longridge's pressure curve 78 
 
 Low explosive 105 
 
JiylS* 
 
 *A OJf 
 
 INDEX. 659 
 
 M 
 
 PAGE 
 
 M, value of 55 
 
 Machine and rapid-fire guns 589 
 
 Machine, definition of 155 
 
 Machine-guns 589 
 
 Machine-gun, Gardner 601, 603 
 
 Machine-gun, Maxim automatic 605, 606, 608, 610, 612 
 
 Machine, milling 174 
 
 Machine, rifling 182 
 
 Machine-shops, general arrangement of 162 
 
 Machine-tools 163 
 
 Machines in general use 166 
 
 Machines used in gun-manufacture 155 
 
 Magazine cut-off, cal. .30 548 
 
 Magazine, fixed box 575 
 
 Magazine for cal. .30 577 
 
 Magazine-gun, conditions for good 568 
 
 Magazine, Jarmann 571 
 
 Magazine, Lee 570 
 
 Magazine, Mannlicher 575 
 
 Magazine or repeating arms 567 
 
 Magazine, tubular 571, 574 
 
 Magazines, detachable 569 
 
 Magazines, fixed 571 
 
 Malleability and ductility of gun-steel 141 
 
 Mammoth powder 6 
 
 Mannlicher magazine 575 
 
 Mandrils, forging 151 
 
 Manganese in gun-steel 137 
 
 Manufacture, gun 176 
 
 Manufacture of gunpowder I 
 
 Manufacture of gun-steel 142 
 
 Manufacture of projectiles 311 
 
 Manufacture of smokeless powder, operations in 123 
 
 Manufacture of smokeless powder, solution 124 
 
 Manufacture, safety and cost of, smokeless powders 131 
 
 Marcel-Deprez registers 96 
 
 Martini-Henry rifle 550 
 
 Mass of fuze 108 
 
 Maxim automatic machine-gun 605, 606, 608, 610, 612 
 
 Maxim rapid-fire gun 631, 633 
 
 Maximum height of trajectory 380 
 
 Mazimum pressure on base of projectile 54 
 
 Maximum pressure on breech 55 
 
 Maximum strains on cylinder 198 
 
 Mayevski's method, resistance of air 354 
 
 Mayevski, pressure curve < 78 
 
66O INDEX. 
 
 PAGE 
 
 Mean error, true 513 
 
 Mean radius of grain of powder 6 
 
 Measuring-points 223 
 
 Measuring-rule 92 
 
 Measurement of length 227 
 
 Measurement of surface lengths 228 
 
 Measurements 221 
 
 Measurements, general principles of , 229 
 
 Measurements in gun-construction 216 
 
 Measurements, necessity for 221 
 
 Measurements of interior diameters of long tubes 224 
 
 Measurements of interior diameters of short hoops 222 
 
 Mechanism, breech 548 
 
 Mechanism, breech, classification 548 
 
 Mechanism, firing 558 
 
 Mechanism, rotating 549 
 
 Mechanism, sliding 548 
 
 Melinite 119 
 
 Mercury fulminate 119, 120 
 
 Merriam delayed-action fuze 340 
 
 Metal, quality of, for projectiles 314 
 
 Method of applying exterior pressure 205 
 
 Method of determining resistance of air , 353 
 
 Method of strengthening cylinder 196 
 
 Military purposes, use of dynamite for 116 
 
 Military purposes, use of explosive gelatine for 118 
 
 Military purposes, use of gun-cotton for 113 
 
 Military purposes, use of nitro-glycerine for 115 
 
 Milling-cutters 165 
 
 Milling-machine 1 74, 175 
 
 Mixing ingredients of gunpowder I 
 
 Mixtures, explosive 105 
 
 Modern rotating device for projectiles 308 
 
 Modern shrapnel 291 
 
 Modern shrapnel, description of. 292 
 
 Modes of producing explosion , 108 
 
 Modification of gun-cotton 122 
 
 Modulus, limits of . . 75 
 
 Modulus of elasticity 139 
 
 Modulus of precision 510 
 
 Modulus of quickness 60 
 
 Modulus, pressure as function of 62 
 
 Modulus, velocity as function of 6r 
 
 Molded powder 7 
 
 Molding projectiles 312 
 
 Molds, ingot 146 
 
 Monomial formula for velocity 63 
 
INDEX. 66 1 
 
 PAGE 
 
 Mortar-carriage, 3.6-inch 410 
 
 Mortar-carriage, 12-inch 423 
 
 Mortar fire 386 
 
 Mortar fuze 330 
 
 Mortar powder 5 
 
 Mortar, 7-inch 252 
 
 Mortar, 3.6-inch 235 
 
 Mortar, 1 2-inch, breech mechanism of 268 
 
 Mortar, 1 2-inch cast-iron, steel hooped 259 
 
 Mortar, 12-inch steel , , 258 
 
 Motion of projectile, circumstances of 349 
 
 Motion of projectile in bore, equation of . 47 
 
 Motion of projectile in bore, final equation, deduction 50 
 
 Motion of projectile in bore, final equation of 52 
 
 Motion, transmitted and modified, how 155 
 
 Mountain-carriage, Hotchkiss 409 
 
 Mountain-guns 232 
 
 Mountings, small arms 567 
 
 Muzzle velocity by experiment 83 
 
 N 
 
 Nave 391 
 
 Necessity for brake 453 
 
 Necessity for measurements 221 
 
 Necessity for rotation of oblong projectile 293 
 
 Nickel in gun-steel 137 
 
 Nitre, addition of, to gun-cotton 112 
 
 Nitric ethers 106 
 
 Nitro-benzines 120 
 
 Nitro-glycerine 114, 115 
 
 Nitro- substitution compounds . . . '. , 106 
 
 Noble and Abel's experiments 19, 20, 22, 23, 24, 25, 26 
 
 Noble and Abel's method of determining pressure curve 33, 77 
 
 Noble and Abel, pressure by dynamic method 102 
 
 Noble crusher-gauge 101 
 
 Noble gauge, advantages of 102 
 
 Nomenclature, compound cylinder 206 
 
 Nordenfelt brake 396 
 
 Nordenfelt rapid-fire gun 624, 625 
 
 Number of grooves 542 
 
 O 
 
 Object of latch, field-artillery 243 
 
 Object of Noble and Abel's experiments 22 
 
 Object of rapid-fire guns 619 
 
662 INDEX. 
 
 PAGE 
 
 Object of wheel 392 
 
 Oblong shrapnel 290 
 
 Oblong shrapnel, Boxer 290 
 
 Obturating electric primer 346 
 
 Obturating friction-primer 344 
 
 Obturator, De Bange 238 
 
 Obturator, Freyre 240 
 
 Obturator, seacoast-guns 260 
 
 Oil-tempering steel , 153 
 
 Old armor, fastenings for 322 
 
 Old fuzes in use 330 
 
 Old guns in U. S. service 272 
 
 Old U. S. seacoast-carriages 432 
 
 cS constant, A and r variable 70 
 
 Open-hearth process 142, 143, 144, 145 
 
 Operation, open-hearth process , 145 
 
 Operations after assembling, gun-manufacture 182 
 
 Operations before assembling gun 177 
 
 Operations in manufacture of smokeless powder 123 
 
 Orders of explosion 106 
 
 Orifice, area of, constant orifice, brakes 459 
 
 Orifice, area of, variable orifice, brakes 463 
 
 Orifice, law of variation of, brakes 463 
 
 Orifice variable, brake with 460 
 
 P 
 
 pi, calculation of 212 
 
 /n, true value of 213 
 
 Pack-horse 401 
 
 Palliser shot 280 
 
 Paraffine, effect of on gun-cotton 112 
 
 Parallelopipedon, velocity of emission for 15 
 
 Parrott 4.2-inch siege-gun , 273 
 
 Parrott projectile i 305 
 
 Parts of drill-press 173 
 
 Parts of gun. .. o r 176 
 
 Parts of lathe 167 
 
 Parts of milling-machine 174 
 
 Parts of planer 170 
 
 Parts of shaper 171 
 
 Passive resistances 44 
 
 Passive resistances, influence of on velocity and pressure 46 
 
 Pattern of projectiles 311 
 
 Penetration formulas 325 
 
 Penetration, increased, small arms 540 
 
 Penetration of armor 325 
 
INDEX. 663 
 
 Percentage rectangle , 5 !7 
 
 Percussion fuzes 333, 334 
 
 Periods of recoil 435 
 
 Permanent angle of drift 473 
 
 Permanent gases, volume of, Noble and Abel's experiments 25 
 
 Peyton powder 128 
 
 Phosphorus in gun-steel , 137 
 
 Picrates 118 
 
 Picric acid 118 
 
 Picric acid, powder 126 
 
 Pierted cylinder, velocity of emission for, gunpowder 16 
 
 Pike 531 
 
 Pipes in gun-steel 140 
 
 Pitch of rifling 542 
 
 Placing rotating bands in position , 309 
 
 Plane figure, probability of hitting 522 
 
 Plane of fire 347 
 
 Plane of sight 347 
 
 Planer , 169, 170, 171 
 
 Pointing 466 
 
 Pointing, cases in 467 
 
 Pointing, errors in 472, 476, 485, 486, 487 
 
 Pointing, first case 468 
 
 Pointing, fourth case 473 
 
 Pointing, indirect 475 
 
 Pointing, second case 470 
 
 Pointing, third case 470 
 
 Pole, field-carriage 412 
 
 Pole, support of 404 
 
 Portable arms 528 
 
 Position, rule of double 382 
 
 Position of bursting-charge, shrapnel 292 
 
 Position of projectile in mold 314 
 
 Position of rear band 309 
 
 Potassium picrate 118 
 
 Potential no 
 
 Pouring steel 147 
 
 Powder, B. N. F 127 
 
 Powder-chamber, fixed 72 
 
 Powder, picric acid 126 
 
 Powders, ammonium nitrate 126 
 
 Powders, black, changes in 121 
 
 Powders, progressive 18 
 
 Practical formulas, useful 75 
 
 Practical problems, ballistics 374 
 
 Precision, modulus of 510 
 
 Press, Whitworth's hydrauJic 150 
 
664 INDEX. 
 
 PAGE 
 
 Pressing gunpowder 2 
 
 Pressure as function of modulus. 62 
 
 Pressure by dynamic method, Noble and Abel 102 
 
 Pressure by experiment 98 
 
 Pressure curve, equation of, Noble and Abel's method 33 
 
 Pressure curve, equation of, recent hypothesis 37 
 
 Pressure curve in guns 76 
 
 Pressure curve, Longridge 78 
 
 Pressure curve, May evski 78 
 
 Pressure curve, Noble and Abel 77 
 
 Pressure curve, Noble and Abel's, application of 35 
 
 Pressure curve, Sarrau 80 
 
 Pressure, exterior, method of applying in cylinders 205 
 
 Pressure-gauge, Rodman 100 
 
 Pressure in cylinder, buffer 465 
 
 Pressure in cylinder, constant orifice. . , 459 
 
 Pressure, maximum, on base of projectile 54 
 
 Pressure of gases, formula for, Noble and Abel's experiments 26 
 
 Pressure of gunpowder, discussion of formula for 28 
 
 Pressure on breech, maximum 55 
 
 Pressure or force, explosives , % no 
 
 Pressures, limiting, exterior 201 
 
 Pressures, limiting, interior 200 
 
 Primer 587 
 
 Primer, common electric 343 
 
 Primer, common friction 342 
 
 Primer, obturating electric . 346 
 
 Primer, obturating friction 344 
 
 Primers 342 
 
 Primers and fuzes 328 
 
 Principal explosives in 
 
 Principal parts, breech mechanism, field-artillery 236 
 
 Principles of teeth of wheels 158 
 
 Prismatic powder 7 
 
 Probable error 512 
 
 Probable rectangle 516 
 
 Probable rectangle from mean error 520 
 
 Probable zone 514 
 
 Probability by right-line method M 526 
 
 Probability curve 506, 507 
 
 Probability of fire 505 
 
 Probability of hitting plane figure 522 
 
 Problem i , exterior ballistics 374 
 
 Problem 2, exterior ballistics 376 
 
 Problem 3, exterior ballistics 377 
 
 Problem 4, exterior ballistics 37 8 
 
 Problem 5, exterior ballistics 380 
 
INDEX. 665 
 
 PAGE 
 
 Problem 6, exterior ballistics 381 
 
 Problem 7, exterior ballistics 386 
 
 Problems, practical, ballistics 374 
 
 Process, crucible 145 
 
 Process, Harvey 3^ 
 
 Process, open hearth 142 
 
 Process, Tresidder 319 
 
 Process, Whitworth's, fluid compression 147 
 
 Producer, gas 142 
 
 Products, character of, smokeless powders 131 
 
 Products, composition of, Noble and Abel's experiments 23 
 
 Products, nature of, Noble and Abel's experiments 22 
 
 Profile of chamber, cal. .30 544 
 
 Profile of rib, constant pressure. 465 
 
 Progressive powders 18 
 
 Projectile, Butler 305 
 
 Projectile, circumstances of motion of 349 
 
 Projectile, Eureka 305 
 
 Projectile, forces acting on 348 
 
 Projectile, Hotchkiss breech-loading 307 
 
 Projectile, Hotchkiss muzzle-loading. 304 
 
 Projectile, motion of in bore, equation of 47 
 
 Projectile, necessity for rotation of oblong 293 
 
 Projectile, oblong, energy of rotation of 294 
 
 Projectile, Parrott 305 
 
 Projectile, position of in mold 314 
 
 Projectile, rotation of, general discussion 294 
 
 Projectile, velocity of 43 
 
 Projectile, weight of 310 
 
 Projectile, Whitworth 303 
 
 Projectiles 279 
 
 Projectiles, ballistic test 3 r 7 
 
 Projectiles, breech-loading 306 
 
 Projectiles, casting 313 
 
 Projectiles, classification of , 279 
 
 Projectiles, core 3 11 
 
 Projectiles, eccentricity 3*5 
 
 Projectiles, effect of, on armor 320 
 
 Projectiles, flanged. 33 
 
 Projectiles, form of 309 
 
 Projectiles, inspection and proof of 3 T 4 
 
 Projectiles, kind of iron for 3 T 3 
 
 Projectiles, manufacture of 3 1 r 
 
 Projectiles, pattern 3" 
 
 Projectiles, quality of metal 3 r 4 
 
 Projectiles, shape and dimensions of 3*5 
 
 Projectiles, steel. 3*4 
 
666 INDEX. 
 
 Projectiles, studded 302 
 
 Proof of gunpowder , 8 
 
 Properties of probability curve 507 
 
 Pulley, rounded 160 
 
 Pulverizing ingredients of gunpowder. . * I 
 
 Q 
 
 y, value of, interior ballistics 50 
 
 Quadrant, gunners' 491 
 
 Quality of metal of projectiles 314 
 
 Quickness, modulus of 60 
 
 R 
 
 
 
 Rack-a-rock 120 
 
 Radial stress and strain 185 
 
 Range 348 
 
 Range by trial shots 484 
 
 Range and position finders 482 
 
 Range-finders. . . 479 
 
 Range-finders, class 1 480 
 
 Range-finders, classes 2 and 3 481 
 
 Range-finders, depression 481 
 
 Range-finders, principle 479 
 
 Range, whole, formulas for. . . 365 
 
 Rapid-fire gun, Driggs-Schroeder 627, 629 
 
 Rapid-fire gun, Hotchkiss. . . , 620, 622 
 
 Rapid-fire gun, Maxim 631, 633 
 
 Rapid-fire gun, Nordenfelt 624, 625 
 
 Rapid-fire guns 619 
 
 Rapid-fire guns, ammunition for 635 
 
 Rapid-fire guns, history of , 619 
 
 Rapid-fire guns, object of 619 
 
 Rapidity of reaction, explosives no 
 
 Reaction on explosion of dynamite 116 
 
 Reaction on explosion of gun-cotton 113 
 
 Reaction on explosion of mercury fulminate 119 
 
 Reaction on explosion of nitro-glycerine 115 
 
 Reaction, rapidity of no 
 
 Reamers and drills 165 
 
 Reannealing 153 
 
 Rear band, position of 309 
 
 Rear sight 466, 562 
 
 Rear sight, cal. .30 565 
 
 Rear sight, height of 468 
 
 Receiver, cal. .30 547 
 
INDEX. 667 
 
 PAGE 
 
 Receiver, small arms 545 
 
 Receiver, Springfield rifle 546 
 
 Recoil, angle of elevation 451 
 
 Recoil, curve of total 449 
 
 Recoil, discussion of 437, 438, 440 
 
 Recoil, example 442 
 
 Recoil, length of 448 
 
 Recoil, length of, constant orifice 458 
 
 Recoil, length of, variable orifice 461 
 
 Recoil of wheeled carriages 450 
 
 Recoil, ordinary case 436 
 
 Recoil, periods of 435 
 
 Recoil, problems 446 
 
 Recoil, small arms 532 
 
 Recoil, steps in solution of problem 436 
 
 Recoil, theory of 434 
 
 Recoil, time of, second period 447 
 
 Recoil, velocity of 43 
 
 Rectangle, probable 516 
 
 Rectangle, 25 per cent 516 
 
 Rectangles of any percentage 517 
 
 Reduced calibre, disadvantages 540 
 
 Reduced length of initial air-space 40 
 
 Reduction of calibre, advantages of 538 
 
 Reduction of weight of bullet 535, ^37 
 
 Regenerators 143 
 
 Registers, Marcel-Deprez 96 
 
 Regular granulation, gunpowder -7 
 
 Regulating magnets, Le Bouleng6 93 
 
 Reheating 149 
 
 Reinforce, axle 390 
 
 Relation between x and y, exterior ballistics 364 
 
 Relations between stresses and strains, gun-cylinder 188 
 
 Relative variation of velocity and maximum pressure 74 
 
 Relative variation of velocity and time of combustion 73 
 
 Remaining velocity 348 
 
 Remington rifle 551 
 
 Repeating mechanisms, classification of 560 
 
 Repeating or magazine arms 567 
 
 Requirements of breech mechanism 551 
 
 Rest, system at, gun-construction 210 
 
 Resistance of air, causes affecting 351 
 
 Resistance of air, experiments on 351 
 
 Resistance of air, Maye vski's method 354 
 
 Resistance of air, method of determining 353 
 
 Resistance of compound cylinder in action 207 
 
 Resistances, passive, gunpowder 44 
 
668 INDEX. 
 
 PACK 
 
 Revolvers 580 
 
 Rib, profile of, constant pressure, buffers 465 
 
 Rifle, 8-inch converted 273 
 
 Rifle, Hotchkiss mountain 232 
 
 Rifle, Springfield, receiver 546 
 
 Rifle, 3-inch wrought iron 272 
 
 Rifling 182, 299 
 
 Rifling-machine 182 
 
 Rifling-tool 183 \ 
 
 Rifling, uniform 299 
 
 Right-line method 524 
 
 Right-line method, probability by 526 
 
 Rigidity of trajectory ' 384 
 
 Rim of wheel * 392 
 
 Ring, Broad well 276 
 
 Ring, carrier 242 
 
 Riser and gate 313 
 
 Roburite 120 
 
 Rodman's improvements of gunpowder 9 
 
 Rodman pressure-gauge 100 
 
 Roller-paths, 12-inch mortar carriage 427 
 
 Rollers and distance-rings 420 
 
 Rolling contact 156 
 
 Rolling contact, forms of pieces 157 
 
 Rolling smokeless powder, 125 
 
 Rolling-table 316 
 
 Rotating band, modern, details of 308 
 
 Rotating bands, placing in position of 309 
 
 Rotating devices 302 
 
 Rotating devices, breech-loading projectiles 306 
 
 Rotating device, modern 308 
 
 Rotating device, seacoast-guns 262 
 
 Rotating mechanism, small arms 549 
 
 Rotation of oblong projectile, energy of 294 
 
 Rotation of oblong projectile , necessity for 293 
 
 Rotation of projectile, general discussion . 294 
 
 Rounded pulley 160 
 
 Rule of double position 382 
 
 Rule of double position, example 383 
 
 Rule, measuring 92 
 
 S 
 
 Sabre, cavalry 531 
 
 Sabre, light artillery 529 
 
 Saddle 407 
 
 Safety mixtures, Sprengel's 120 
 
INDEX. 669 
 
 PAGE 
 
 Sarrau's binomial formula 53 
 
 Sarrau's formulas 46 
 
 Sarrau's pressure curve go 
 
 Sawyer canister 286 
 
 Scale of time, Le Boulenge 85 
 
 Scale of time, Schultz 95 
 
 Scale, vernier. 231 
 
 Schultz chronoscope gg 
 
 Scraping-tools 164 
 
 Screw, elevating 39 g 
 
 Seacoast-carriages 4!8 
 
 Seacoast-fuze . . .-. 331 
 
 Seacoast-guns 254 
 
 Seacoast-guns, action of breech mechanism 266 
 
 Seacoast-guns, anti-friction washers and springs 261 
 
 Seacoast-guns, breech-block 260 
 
 Seacoast-guns, calibres and common features 254 
 
 Seacoast-guns, guide-rails 264 
 
 Seacoast-guns, obturator , 260 
 
 Seacoast-guns, rotating devices 262 
 
 Seacoast-guns, table of 271 
 
 Seacoast-guns, translating-screw 264 
 
 Seacoast-guns, tray 263 
 
 Seacoast-guns, vent-cover 266 
 
 Seacoast service, shells for 281 
 
 Sebert's velocimeter 103 
 
 Second boring of tube 178 
 
 Sectional density 296 
 
 Sector, toothed 400 
 
 Sensitiveness of smokeless powders 131 
 
 Setting star gauge 225 
 
 7-inch howitzer 252 
 
 7-inch howitzer carriage 416 
 
 7-inch mortar 252 
 
 Shape and dimensions of projectiles 315 
 
 Shapero . . . . . 171, 172 
 
 Shearingtools 164 
 
 Shell ........ t 28 1 
 
 Shell against decks of vessels 282 
 
 Shell, armor-piercing 281 
 
 Shell, bursting-charge of 284 
 
 Shell, definition of ". 281 
 
 Shell, field 2?3 
 
 Shell for seacoast service 281 
 
 Shell, siege 283 
 
 Shoe 394 
 
 Shot, case 284 
 
6/0 INDEX. 
 
 PAGE 
 
 Shot, chilled 280 
 
 Shot, cored 279 
 
 Shot, Holtzer 280 
 
 Shot, Palliser 280 
 
 Shot, solid 279 
 
 Shot, steel .'.. 280 
 
 Shrapnel 286 
 
 Shrapnel, Boxer oblong 290 
 
 Shrapnel, Boxer spherical 289 
 
 Shrapnel, cone of dispersion 286 
 
 Shrapnel, early 288 
 
 Shrapnel, Frankford Arsenal 292 
 
 Shrapnel, Hotchkiss 293 
 
 Shrapnel, modern 291 
 
 Shrapnel, modern, description of 292 
 
 Shrapnel, oblong 290 
 
 Shrapnel, position of bursting-charge 292 
 
 Shrapnel, spherical, combustion of 288 
 
 Shrapnel, steel welded 292 
 
 Shrinkage, calculation of 214 
 
 Side-latch 265 
 
 Siege-carriage, 5-inch 41 5 
 
 Siege-carriages 4I g 
 
 Siege-gun, 5-inch 251 
 
 Siege-gun, 4. 5-inch 272 
 
 Siege-gun, Parrott, 4.2-inch , 273 
 
 Siege-guns 251 
 
 Siege-guns, breech mechanism 252 
 
 Siege-guns, common features 251 
 
 Siege-mortar carriage 41 y 
 
 Siege-shell 283 
 
 Sight for 3.2-inch field-gun 49 6 
 
 Sight for 3.6-inch mortar 495 
 
 Sight, front 466, 563 
 
 Sight, rear 4 66 
 
 Sight, rear, height of -. 453 
 
 Sights 4 6 6? 562 
 
 Sights for cal. .30 565 
 
 Sights for field-artillery 495 
 
 Sights for 8-, 10-, and 12-inch guns 489 
 
 Sights for 7-inch howitzer 493 
 
 Sights for siege-artillery 493 
 
 Sights, rear 5 6 2 
 
 Sights, Springfield rifle 5 6 3 
 
 Silicon in gun-steel I37 
 
 Simplification of ballistic formulas 3 6i 
 
 Sinking-head I47 
 
INDEX. 671 
 
 PAGE 
 
 Size of grain, density, progressive powders 17 
 
 Size of grain, influence of * I7 
 
 Sleeve, cal. .30 55 6 
 
 Slide-rest, lathe Z 68 
 
 Sliding contact I57 
 
 SHding mechanism 548 
 
 Slow cooling of gun-steel 140 
 
 Small-arms targets 85 
 
 Small arms 53! 
 
 Small-arms powder 5 
 
 Smooth bore, 15-inch Rodman 274 
 
 Smokeless powder, cutting up 125 
 
 Smokeless powder, drying 125 
 
 Smokeless powder, early history of 122 
 
 Smokeless powder, manufacture, operation in 123 
 
 Smokeless powder, manufacture of, solution 124 
 
 Smokeless powder, rolling 125 
 
 Smokeless powders 121 
 
 Smokeless powders, cause of ballistic superiority of 132 
 
 Smokeless powders, classes i, 2, and 3 126 
 
 Smokeless powders, character of products 131 
 
 Smokeless powders, chemical action of 131 
 
 Smokeless powders, classification 126 
 
 Smokeless powders, compression 124 
 
 Smokeless powders, conditions to be fulfilled by 129 
 
 Smokeless powders, fouling 131 
 
 Smokeless powders, relative energies 129 
 
 Smokeless powders, safety and cost of manufacture 131 
 
 Smokeless powders, stability 130 
 
 Smokeless powders, sensitiveness 131 
 
 Smokeless powders, smokelessness 130 
 
 Smokeless powders, velocities and pressures 130 
 
 Smokeless powders, weight and specific gravity 131 
 
 Solid-head cartridges 584 
 
 Solid shot 279 
 
 Solution, manufacture of smokeless powder r^. . 124 
 
 Solubility of explosive gelatine 117 
 
 Solubility of gun-cotton 112 
 
 Solubility of mercury fulminate 119 
 
 Solubility of nitro-glycerine 114 
 
 Sound, distances by 478 
 
 Space, dangerous 381 
 
 Speed-cones 160 
 
 Specific gravity of gunpowder 3 
 
 Specific volume 26 
 
 Spherical case 288 
 
 Spherical density 310 
 
672 INDEX. 
 
 Spherical grain, burning under pressure 50* 
 
 Spherical grain, velocity of emission of 14 
 
 Spherical grains, formula for burning in air ia 
 
 Spherical shrapnel, Boxer. . , 289 
 
 Spherical shrapnel, construction of 288 
 
 Sphero-hexagonal powders 7 
 
 Spokes 391 
 
 Sprengel safety mixtures 120 
 
 Springfield breech-block 553 
 
 Springfield bullet 585 
 
 Springfield rifle, breech mechanism 552 
 
 Springfield rifle, firing mechanism 559 
 
 Springfield rifle, front sight 565 
 
 Springfield rifle, receiver 546 
 
 Springfield rifle, sights 563 
 
 Springs, Belleville , 398 
 
 Springs, 12-inch mortar carriage 424 
 
 Stability of smokeless powders 130 
 
 Standard comparator 221 
 
 Star gauge 224 
 
 Star gauge, setting 225 
 
 Starting and stopping machines 160 
 
 Static method, pressure 98 
 
 States of cylinder, gun-construction 206 
 
 Steel armor 318, 319 
 
 Steel projectile 314 
 
 Steel shot 280 
 
 Steel-welded shrapnel 292 
 
 Step gauge 227 
 
 Stock , 293, 566 
 
 Stock and mountings 566 
 
 Stopping and starting machines 160 
 
 Storage of dynamite 116 
 
 Storage of explosive gelatine 118 
 
 Storage of gun-cotton % 113 
 
 Storage of mercury fulminate 120 
 
 Storage of nitro-glycerine 115 
 
 Straight sword 530 
 
 Strain at exterior of cylinder, gun-construction 203 
 
 Strains in terms of radii and pressures 197 
 
 Strains, maximum, in cylinder 198 
 
 Strap, gun-carriage 399 
 
 Strength, longitudinal, cylinder 203 
 
 Strength, longitudinal, compound cylinder 209 
 
 Strength of an explosion 109 
 
 Stress and strain 185 
 
 Stress and strain, longitudinal. iS; 
 
INDEX. 673 
 
 PAGE 
 
 Stress and strain, radial 185 
 
 Stress and strain, tangential 186 
 
 Stresses and strains, relation between 188 
 
 Stresses in cylinder, curve of 193 
 
 Structure of gun-steel I 39 
 
 Studded projectile 302 
 
 Sulphur in gun-steel 137 
 
 Summit of trajectory 404 
 
 Support of pole 404 
 
 Surface lengths, measurements of 228 
 
 Sword, straight 530 
 
 System at rest, gun-construction 210 
 
 System, expanding, projectiles 304, 305 
 
 T 
 
 T, calculation of value of 65 
 
 r constant, GO and A variable 72 
 
 r, value of for maximum velocity 59 
 
 Table I, probability 511, 512 
 
 Table II, use of, probabilities 520 
 
 Table of ballistic problems 388 
 
 Table of field- and siege-guns 253 
 
 Table of guns and powders 68 
 
 Table of high explosives and smokeless powders 133 
 
 Table of seacoast-guns 271 
 
 Tables, auxiliary ballistic 371 
 
 Tables, ballistic, explanation of 369 
 
 Tangential stress and strain 186 
 
 Tarage 98 
 
 Target, motion of in pointing 486 
 
 Targets, Bashforth 97 
 
 Targets for cannon 84 
 
 Targets, small arms 85 
 
 Teeth, action of 158 
 
 Teeth, figures of 158 
 
 Teeth, principles of , 158 
 
 Telemeter, Le Boulenge 478 
 
 Temperature of explosion of gunpowder 30 
 
 10- and 12-inch guns 256 
 
 Tensile strength of gun-steel 137 
 
 Test for purity of nitro-glycerine 116 
 
 Testing ingots 149 
 
 Tests of armor-plates 324 
 
 Tests of gun-f orgings 153 
 
 Theoretical maximum velocity 58 
 
 Theory, Berthelot's 106 
 
674 INDEX. 
 
 PAGE 
 
 Theory of fluid compression * 148 
 
 Theory of recoil 434 
 
 Thickness of barrel, cal. .30 544 
 
 Thickness of walls of guns 217 
 
 Thickness to resist exterior pressure 203 
 
 Thickness to resist interior pressure 201 
 
 Thickness to resist longitudinal stress 204 
 
 3-inch wrought-iron rifle 272 
 
 3.2- and 3.6-inch field-guns , 235 
 
 3. 6-inch mortar 235 
 
 Thrusting-arms 529 
 
 Time-fuzes 328 
 
 Time-fuzes, difficulties, how overcome 329 
 
 Time-fuzes, difficulties in making 328 
 
 Time of burning for maximum velocity, gunpowder 58 
 
 Time of flight 377 
 
 Time of recoil, second period 447 
 
 Time, scale of, Le Boulenge 85 
 
 Time, scale of, Schultz 95 
 
 Tin feed-cases, Gatling 595 
 
 Tire 392 
 
 Tool for first boring tube 177 
 
 Tool for second boring tube 178 
 
 Tool, rifling !g 3 
 
 Tools, cutting 164 
 
 Tools, machine 163 
 
 Tools, scraping ^4 
 
 Tools, shearing ^4 
 
 Toothed sector 400 
 
 Tongs, lazy 401 
 
 Top carriage and buffer, 8-inch 422 
 
 Total recoil, curve of 449 
 
 Touch, measuring 229 
 
 Toughness of gun-steel 137 
 
 Traces, angle of 402 
 
 Traces, attachment of 403 
 
 Traces, direction of 505 
 
 Trajectory 347 
 
 Trajectory, division of 505 
 
 Trajectory, flatness of 538 
 
 Trajectory, form of , 350 
 
 Trajectory, height of 380 
 
 Trajectory in air 356 
 
 Trajectory, maximum height of 380 
 
 Trajectory, rigidity of 384 
 
 Trajectory, summit of 366 
 
 Transformation of general equation of motion of projectile in bore. ... 48 
 
INDEX. 675 
 
 PACK 
 
 Translating-screw, seacoast-guns ..................................... 264 
 
 Tray-latch. ......................................................... \ 2 ^ 
 
 Tray, seacoast-guns ................................................ 263 
 
 Traversing-gear, 12-inch mortar carriage ............................. 427 
 
 Treatment after casting, ingots ..................................... j 49 
 
 Tresidder process ........... ...................................... 3I9 
 
 Trial shots, range by ............................................... 4 g 4 
 
 Tri-nitro-phenol .................................................. TI g 
 
 True mean error .................................................... c 
 
 True value of f .............................................. ' ..... 2I3 
 
 Tube, bore of ...................................................... x g o 
 
 Tube, first boring .............................. ..................... jyy 
 
 Tube, limiting exterior pressure on .................................. 211 
 
 Tube, second boring ................................................ ^g 
 
 Tube, turning of .................................................... jg o 
 
 Tube, warping of ................................................... !^y 
 
 Tubular magazine .............................................. gyi f 574 
 
 Turret-carriages .................................................... 428 
 
 Turrets, Gruson .................................................... 317 
 
 Turning angle ..... ................................................. 406 
 
 Turning and boring ............... ................................ 152 
 
 Turning tube ....................................................... 180 
 
 25 per cent rectangle ................................................ 516 
 
 12-inch cast-iron mortar, steel hooped ............................... 259 
 
 12-inch mortar carriage ............................................. 423 
 
 12-inch mortar, breech mechanism of ................................ 268 
 
 12-inch steel mortar ................................................ 258 
 
 Twist, direction of ......... . ........................................ 544 
 
 Twist, increasing ................................................... 300 
 
 Twist in terms of calibre ............................................ 300 
 
 Twist, uniform ......................................... ........... 299 
 
 U 
 
 Uniform riflin g ..................................................... 299 
 
 Uniform twist ..................................................... 299 
 
 U. S. percussion fuzes ............................................ 334 
 
 U. S. spherical case ................................................ 288 
 
 Use of Le Boulenge chronograph ... ................................. 94 
 
 Use of mercury fulminate ........................................... 119 
 
 Use of Table I ....................... ............................... 511 
 
 Use of Table II, probabilities .................... . .................. 520 
 
 Useful practical formulas ........................................... 75 
 
 V 
 
 Value of A'. ........................................................ 57 
 
 Value of A'o .................... .................................... 57 
 
 Value of M. ........................................................ 65 
 
676 INDEX. 
 
 PAGE 
 
 Value of modulus of quickness 60 
 
 Value of q 50 
 
 Value of r, calculation of 65 
 
 Value of r for maximum velocity 59 
 
 Values of A and B 54 
 
 Values of a, A, and fJ. for different forms of grain 13 
 
 Variation of elements of loading, effect of 69 
 
 Variation of powder, effect of, Noble and Abel's experiments 24 
 
 Velocimeter, Sebert's 103 
 
 Velocity and maximum pressure, variation of 74 
 
 Velocity and time of combustion, variation of 73 
 
 Velocity as function of modulus 61 
 
 Velocity, change of, pressure constant 70 
 
 Velocity, final 348 
 
 Velocity, initial 348 
 
 Velocity, initial, by experiment 83 
 
 Velocity, monomial formula for 63 
 
 Velocity of emission for cocoa powder 16 
 
 Velocity of emission for flat grain 16 
 
 Velocity of emission for parallelopipedon and for pierced cylinder 15 
 
 Velocity of emission for pierced cylinder 16 
 
 Velocity of emission, spherical grain 14 
 
 Velocity of projectile 43 
 
 Velocity of recoil 43 
 
 Velocity, remaining 348 
 
 Velocity, theoretical, maximum 58 
 
 Velocities and pressures, smokeless powders 130 
 
 Vent-cover 247 
 
 Vent-cover, seacoast-guns 266 
 
 Vernier scale , 231 
 
 Vessels, shells for piercing decks of 282 
 
 Volume of permanent gases, Noble and Abel's experiments 25 
 
 W 
 
 Walls of guns, thickness of 217 
 
 Warping of tubes 177 
 
 Water, effect of on gun-cotton 112 
 
 Water, effect of on mercury fulminate 119 
 
 Weight and specific gravity of smokeless powders 131 
 
 Weight of bullet, reduction of 533 
 
 Weight of cartridge, decrease of 539 
 
 Weight of projectile 3IO 
 
 Welding of gun-steel !4! 
 
 Wetteren powder I2 6 
 
 Wheel, object of 3Q 2 
 
 Wheeled carriages, recoil of 450 
 
INDEX. 677 
 
 PAGE 
 
 Wheels , 39 o 
 
 Whitworth's hydraulic forging 150 
 
 Whitworth's hydraulic press 150 
 
 Whitworth's process, fluid compression 147 
 
 Whitworth's projectile 303 
 
 Whole range, formula for 365 
 
 Width of grooves 542 
 
 Wind, effect of in pointing 476 
 
 Wire guns 218 
 
 Wires, arrangement of, Le Boulenge 87, 90 
 
 Woodbridge gun 219 
 
 Work in terms of " force " and weight, gunpowder 39 
 
 Work in terms of length of travel, gunpowder 40 
 
 Work of gunpowder 36, 38, 39 
 
 Work of gunpowder, division of 41 
 
 Work of horse 401 
 
 Working of Le Bouleng6 88 
 
 X 
 jc andj, relation between , 364 
 
 Z 
 Zone , probable 514 
 
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