Eardley Maitland

“ But however well cast-iron may be disposed, it is naturally too weak and brittle for use with heavy guns, and those nations which employ it thus do so because it is comparatively cheap and easy to manufacture, and not because it is the best material. Austria and Russia have of late years made light guns of bronze cast in chill, and subjected to the wedging action of steel mandrils driven through the bore. The several layers of the metal are thus placed in a state of tension as regards the exterior, and of compression as regards the interior. ”

“ The rotation is impressed on the projectile by a force acting tangentially to the surface. This principle would be represented in its extreme form by making the section of the shell to resemble a cog-wheel, the grooves and lands of the gun being bored to fit. With muzzle-loading systems where windage has been necessary, the sides of the projections on the projectile, and of the grooves in the bore, have been sloped to enable the projections to run up the sides of the grooves, and so distribute the windage equally all round. ”

“ The body is of mild steel ; it is stamped out from the BO bar ; it is then drifted through by a slightly tapered bar carrying a succession of cutters on it. The front part of the body is then screwed to suit the screw on the barrel, so that when home it shall fit accurately to the breech end. The lever, and indeed all parts except screws and springs, are stamped out of solid bar. Each part is milled by machinery to a correct fit ; every fitting is interchangeable, and nothing is marked for selection to fit anything else. ”

“ The hammers are abolished altogether, the striker being a needle in the interior, which is driven against the cap of a central-fire cartridge by a spring when the trigger is pressed ; a lever on the top is pushed aside by the thumb, liberating the catch which holds the barrels against the false breech ; the barrels then drop from the hinge, and are open for loading. On raising the barrels, the action snaps to, and holds them fast; the dropping of the barrels causes an extractor to withdraw the empty cartridge cases. A key at the side regulates the cocking and safety of the lock and striker. ”

“ The eroding effects of gas in motion at high pressure are extraordinarily destructive, and constant necessity for repair arises from this cause. It has also been found that in rapid firing the breech screw may be too quickly forced home, nipping the vent piece before it has fallen into its proper position ; the end of the bore is then not sealed, and important and perhaps danger ous accidents occur. Moreover, even with moderate-sized ordnance, the vent piece becomes too heavy for convenient lifting. In the Krupp system (fig. 44) , a slot is cut through both sides of the breech of the gun ”

“ Supposing a given length of groove in the bore to make a known angle with a line parallel to the axis of the gun, determining the arc through which the surface of the shot must turn while advancing the length of the groove, it is evident that the angular velocity attained by the shot will entirely depend on the velocity of translation or forward movement. ”

“ When the projectile has to be pushed down the gun from the front, it must be smaller than the bore ; when it is thrust home from behind, it may be rather larger than the bore. Hence the earlier muzzle-loading shells were provided with ribs or studs which fitted in the grooves, and guided the projectile in its rotatory course ; while the earlier . breech-loading shells were coated with lead, into which the lands of the bore bit sharply as the powder gas forced the projectile between them. All rifled ordnance were formerly rifled with a uniform twist ”

“ Supposing a gun cartridge to be rammed home to the density of water, and entirely converted into gas bofore the projectile began to move, the pressure in the bore would rise to 43 tons per square inch at the breech, an I fall towards the muzzle, as the travel of the shot afforded increasing room for expansion behind it. The column of metal to be moved, even in the heaviest pro jectiles yet known, is only a few pounds to the square inch of base, while the maximum pressure of the powder gas is measured in tons ”

“ The French system, on the other hand, takes up less of the gun, so that in a piece of given length the bore may be upwards of one calibre longer than with Krupp s. In the French system, also, the breech- fittings are less exposed to damage by the enemy s fire, being behind the gun instead of at the side. DESIGNING. A gun, like all other machines, must be Gun designed to fulfil certain definite conditions. Its projectile s g may be required to pierce a given thickness of armour at a given distance ”

“ In producing a piece of ordnance, two distinct sets of conditions are involved those belonging to its actual construction, and those by which its proportions are regu lated. In constructing a gun, the material must be so selected and disposed as economically and safely to sustain the effect of the forces developed by the charge ; in design ing a gun, it is necessary to know the nature and direction of the forces which will combine to produce the desired ballistic results. ”

“ As the shot pass along a barrel driven violently forward by the powder gas, it is probable that the edges of the charge are retarded by friction against the sides of the bore, so that the centre portion extricates itself rather sooner than the edges, and travels with a slightly higher velocity. ”

“ In the case of the twist which begins at 0, the projections have time to expand comfortably, and adapt themselves to the shape of the grooves before they are called on to perform the work of rotation. On the other hand, since the gas presses out the flanges against the bore and into the grooves, and affords them support in this position, it is desirable that its pressure should correspond with their pressure on the driving edges of the grooves. ”

“ Having stopped the gas from getting round the outside of the ring and injuring the gun, we have now to consider the results of escape from X to Y. A channel cut through here would disable ring and wedge, which, though not so bad as disabling ring and gun, would yet be productive of much inconvenience. The insertion of the steel facing-plate A at once saves the wedge and localizes the injury. It allows, moreover, of the introduction of copper discs behind the plate, for the purpose of making up for wear, compres sion of metal of wedge, &c. ”

“ A certain portion of this work is expended in heating the gun and projectile, in giving rotation, and so forth ; the remainder appears as the energy of translation of the shot on leaving the muzzle. Large guns realize a greater proportion of the total work than small ones ; the gunmaker knows very approximately by experience what percentage may be expected from certain classes of ordnance with certain descriptions of powder. ”

“ Hence the shell must have 156,800 units of momentum, which may be composed of high velocity and light weight, or low velocity and heavy weight. For breaching purposes, accuracy and penetration are essential qualities ; a shell varying in length from two and a half to three times its diameter will be suitable for the purpose. We have now a neat problem in ballistics, viz., To find the calibre of a shell of the proper length, of such a weight that, with the muzzle velocity required to give a range of 1500 yards at 5 elevation, the muzzle momentum shall be 156,800 units. ”

“ A second improvement gave the shooter the choice of cocking the hammer and firing it in the usual way, if he preferred it. The next step was to make the chambers breech-loading, by boring them right through, and packing the powder and bullet in a strong based cartridge, carrying its own ignition. In pistols constructed on this plan the chamber arriving at the top is brought against a false breech through which the striker is driven by the hammer. In the latest pattern of this pistol, the cylinder and barrel open away from the false breech on a hinge underneath ”

“ The remaining portions ot the gun are termed the furniture. They are the heel plate which covers the butt, the break-off into which the breeching hooks for muzzle-loaders, the trigger plate, the trigger guard, the ham mers, the escutcheons, and bolt fastening the barrel to the stock, &c. For breech loaders the action is a most important part of the furniture. The ingenuity of gunmakers has devised an immense variety of actions, and every day sees progress made in strength and simplicity. ”

“ In France and Italy a combination of cast iron and steel has been introduced with a view to economy. The interior of the gun is a moderately thick steel tube as in the coil guns ; over this is a thick cast-iron body, corresponding to the steel body of the Krupp guns. On the exterior are shrunk steel hoops. Sir J. Whitworth uses his fluid-compressed steel for the manufacture of ordnance. He forces massive hoops over a central tube, and over one another by hydraulic pressure or by shrinkage. ”

“ Rifles for sporting purposes differ from military pieces in being double-barrelled, and in requiring accuracy and penetration at short ranges, instead of a flat trajectory at very considerable distances. Hence they generally re semble the shot-guns in their action, and fire more powder in proportion to the weight of the bullet than military rifles. ”

“ ORDNANCE. riflia; the bore the less is the breech pressure required to produce a given muzzle velocity, and the less is the maximum strain thrown upon the studs, gas check, or other rotating agent ; next, the more forward the general disposition of the metal, the farther from the breech end will be the centre of gravity, j and consequently the trunnions, a position which favours steady shooting and absence of jump ”

“ In his pistol a revolving muzzle-loading cylinder contains a number of chambers, usuilly five or six, bored from the front parallel to the axis ; the back of the cylinder is left solid, and forms the breech ; a nipple is screwed into each chamber. As the cylinder revolves, each chamber arrives at the top, and is then opposite to a barrel ; the pistol is cocked by the thumb, an action which locks the chamber against the barrel, so that the two form a continuous bore ”

“ Now a mixture of best wrought scrap, and sometimes steel scrap with stubs, is preferred, as giving more hardness and durability to the barrels. A description of the manufacture of cast-steel barrels will be found below, in connexion with military rifles. A sham-twist barrel is apt to impose on the purchaser ; plain iron is cheaper than twisted iron, and sometimes a thin coil of twist is rolled round a plain inner tube ”

“ Rifling. Spherical projectiles fired from smooth-bored guns seldom or never pursue the mean trajectory. The centre of the ball s figure will rarely coincide exactly with the centre of gravity, and the pressure of the air during flight will then act with unequal effect on different parts of the surface. ”

“ Each barrel is twice subjected to proof by powder, once before rifling, once after. Sixteen are placed in a cast-iron frame ; a temporary steel screw, furnished with a vent, closes each breech end, which rests against a leaden bar. The barrels are loaded from the muzzle ; a train of powder ignited by a cap fires them simultaneously ; the bullets are caught in a hollow cast-iron receiving frame, shaped like the shell of a snail. The charge for the first proof is 7J drs. ( = 205 grs.) of powder and a bullet weighing 715 grs., secured by a half-inch cork wad forced down over it. ”

“ The flat side forms the bottom of the bore. For loading, the wedge is pulled out to the left side of the piece as far as the stop will allow it to go, the shell and cartridge are thrust up the gun from behind, the wedge is pushed in, and is pressed hard home and secured by an ingeniously- contrived screw with powerful handles. ”

“ We have now a cone slightly larger than the barrel, with a hole through it -433 in. in diameter. This hole is then bored out to 444 inch. Having now got a true inside, the next step is to obtain a true outside from it. The cone is placed vertically in a machine, the lower end fitting accurately on a pin, the upper end passing loosely through a hollow chuck, which revolves round a centre in truth with the centre of the pin and the axis of the bore of the cone ; the exterior of the cone, being slightly irregular, will be out of truth ”