RIFLE, OR RIFLER 



RIFLE, OR RIFLED. 



the lateral deviation u( a rotating projectile being found in practice to 

 in a much grater ratio than the distance : the trajectory 





being in fact a curve of double curvature. This wag very well shown 

 by KobiM, to whom the firet investigation, and indeed the principal 

 portion of our present knowledge of this subject is due, in his experi- 

 ment before the Royal Society in 1746, in the gardens of the Charter 

 lloiiw (ee page 15, Boxer** ' Treatise on Artillery '), where he fired a 

 bullet from a bent gun-barrel through two paper screens, and on to a 

 wait The bullet followed the direction of the bent portion of the 

 barrel in pasting through the first screen and partially through the 

 Moond, but the place where it struck the wall was on the other side 

 of the line of direction of the straight portion of the barrel. The end 

 of the barrel being bent to the left, the bullet in rolling against it in 

 it* |omago out had received a rotatory movement, its anterior hemi- 

 sphere moving from left to right, which for the reasons before stated 

 caused it to deflect to the right, and the velocity of translation 

 diminishing more rapidly than the velocity of rotation, this deflection 

 was in a curve. This curve being combined with the curve canned by 

 the action of gravity gives a curve of double curvature. 



Let us now apply these considerations to the action of an ordinary 

 smooth bore gun, whether musket or piece of ordnniu . 



In order that the shot may be forced down the bore of the gun it 

 must be slightly smaller than the bore, the difference in diameter of 

 the two bang called windage. Windage, besides allowing a great 

 cape and waste of gas, causes deflection in two ways, first the boll 

 resting on the bottom of the bore of the gun is forced down by the gas 

 rushing over it at the same time that it is forced along, and bounding 

 up again from its elasticity it ia carried along the bore, rebounding 

 from side to side, and eventually leaves it, not in the direction of the 

 axis, but in some other direction depending on its last impact. 

 Secondly, from this last impact it will carry away a certain rotatory 

 movement, which for the reasons before given will cause it to deflect. 



The eccentricity of the projectile is another cause of deflection in 

 smooth-bored guns. For the reasons given in the article (ir.vxKiiv, this 

 eccentricity will in the bore of the gun cause rotation, and, as there 

 Uted, the effects of this rotation will be the same in nature as those 

 due to the roughness of surface before considered, while they will be 

 greatly augmented. Roughness of surface and imperfection of form 

 are the last causes of deflection, and they are the means by which 

 rotation causes deflection. 



Windage may be lessened by increasing the size of the shot and 

 various other means, but practically it cannot be destroyed, except in 

 breech-loading guns. 



Eccentricity, arising from the material of the projectile not being 

 homogeneous, is in musket bullets wholly overcome by making the 

 bullets by compression, instead of casting them, as in cooling a void is 

 often left in the interior ; and may to a great extent be avoided by care 

 in the projectiles used in larger ordnance. 



litillcts can never be made perfectly smooth. l:>tatinn can never be 

 avoided in smooth-bored guns. It can to a certain extent be taken 

 under control by making the shot purposely eccentric [GI-NSKRY], but 

 this is a very uncertain process. We come then to the rifle, in which wt 

 have the power of impressing a certain fixed rotation on the bullet ; ; 

 rotation always bearing in velocity a fixed relation to the initiu 

 Telocity of the bullet. And in direction, a rotation which beinf 

 round an axis that during the first portion of the trajectory, at al 

 events, is tangential to it, causes the resistance of the air to be equally 

 distributed round the pole of rotation, and brings any imperfections o: 

 surface rapidly round from one side to the other of the axis, and 

 corrects any deflection arising from them at each half revolution of the 

 bullet. Thus we obtain accuracy in its flight. 



According to the laws of rotatory bodies, the tendency is for th< 

 axis of rotation always to remain parallel to its original direction 

 Hence we have the power of using elongated bullets from rifles 

 bullets, for instance, of a cylindro-conical form, termed picket*. These 

 being made to rotate on their longer axis, constantly present their 

 points to the resistance of the atmosphere, and at the same tiui< 



that they present an area of resistance of the same size as a spherical 

 >ullet of the same diameter, they possess, supposing them to start 

 with the same initial velocity, a much greater momentum to overcome 

 .his resistance. Therefore, the retardation being less [GUNNERY], we 

 obtain a greatly increased range. A cylindro-conicol picket cannot be 

 ired from an ordinary smooth-bored gun, because, assuming a rotation 

 almost immediately on leaving the muzzle round some of the shorter 

 axes, all advantage is lost. 



The tendency of all rotating bodies to rotate round the shortest 

 axis of greatest moments is on important consideration in the con- 

 struction of rifle pickets. If the cylinder be very long and solid, the 

 t.'iuli nc-y is for the ballot to nptct during its flight. The hollow at the 

 jase of most rifle pickets is therefore of great assistance in retaining 

 iho impressed rotation. There are two other points connected with 

 ihe rotation of the picket, which it may be as well to notice before 

 proceeding to the description of the rifle itself. 



The tendency of the axis of rotation to remain parallel to its original 

 direction is the cause of a peculiar deviation, termed by the French 

 derivation. It was pointed out by Robins, that when the elevation of the 

 piece is high, and the trajectory greatly curved, the axis of the bullet, 

 jr of rotation, does not remain tangential to the trajectory, but very soon 

 begins to moke an angle with it, which angle continues to increase to 

 the end of the range (fy. 3) ; the consequence is, that there is an iu- 



Fig. 3. 



equality in the resistance of the air on different sides of the axis ; the 

 bullet or picket presents an increased rotating surface to the condensed 

 air, that is, there is a greater resistance from friction on one side (below) 

 the axis of rotation than on the other ; the effect of this resistance 

 will, for the reason before given, cause the bullet to deflect or derivate. 

 But this resistance is almost wholly below f and of the same nature as 

 that shown, fy. 1, as acting on the anterior hemisphere of the spherical 

 bullet, whilst little or none of the opposing resistance of condensation 

 of air from the meeting of two currents can be called into play (or rather, 

 it will be in a position where it can have little effect) consequently, 

 the bullet or picket, supposing it to have a right-handed rotation 

 from above downwards, viewing it from behind the piece, will have a 

 derivation to the right. The path of the centre of gravity of the shot 

 will be a line of double curvature, but the axis of rotation will remain 

 constantly parallel to its original direction. Robins proposed that 

 the bullets should be formed like eggs, the longer axis being placed 

 in the direction of the axis of the piece, and the larger end to the 

 front, in order that, the centre of gravity being forward, the greater 

 resistance of the air acting behind might throw the point down, 

 and constantly keep the axis tangential to the trajectory. More 

 recently, caiulimt, grooves cut round the base of a cylindro-conical 

 bullet (see fig. 6), have been proposed by M. Tamissier, and employed 

 with the same object. But a slight consideration will show that 

 the action of this increased resistance behind the centre of gravity 

 is not simply a force tending to produce angular motion in the 

 axis of the bullet in the plane of the trajectory round au axis per- 

 pendicular to it, but is of the nature of the action arising from 

 the friction of the rotating bullet or picket, when its axis is in- 

 clined to the trajectory, and which we have just been discussing. 

 But it must be remembered, that we were then assuming either that 

 the resistance of the atmosphere was equal on both sides of the centre 

 of gravity, or that any slight inequality there might be was not suffi- 

 cient to overcome the effect jof rotation in keeping the axis parallel to 

 its original direction ; whereas now, from the object of the canelures, 

 in order that they may be effective, we must assume that the increased 

 resistance behind tho centre of gravity is sufficiently great to give 

 angular motion to tho axis of rotation. For the same reason, then, that 

 the bullet or picket would in the former case deflect to the right, 

 (Opposing it to have a right-handed twist, in this case the portion 

 behind the centre of gravity would deflect more, proportionately to the 

 greater resistance on it, than the portion in front ; that is, the axis or 

 head of the bullet must turn to the left, making au angle with the 

 plane of the trajectory. In this position the combined forces will tend 

 to depress the head, and BO on, if we consider it in its successive 

 positions, with the forces acting on it, we shall see that the eBect of 

 the increased resistance behind the centre of gravity will be to make 

 tho bullet assume a second motion of rotation one motion of rotation, 

 the original one, being round the longer axis, while the second will be 

 round an axis making an angle with this, and directed to the -left of tho 

 tangent of the trajectory at every moment; though the deflection 

 from this oblique surface would be to the left, and counteracting 

 the deflection it was intended to counteract, yet the wabbling motion 

 the bullet must assume would be very destructive to accuracy and 

 penetration. When from the form of the bullet the resistance is 

 greater in front of the centre of gravity, and sufficient to give angular 

 motion to the axis of rotation, the second axis of rotation will be 



