Krupp Gun

The metal used in these celebrated guns is cast steel, a composition of puddled steel and wrought iron. The wrought iron is obtained from the best hematite ores of Europe, the puddled steel from the spathic ore of Siegen, in the immediate vicinity of the works. The proportions of each metal, the details of their preparation, as well as certain ingredients gue ed at but not known, remain a secret with the manufacturers. Manganese in small quantity is supposed to be present and to exercise an important influence. The result is a metal equal in elasticity and tensile strength to the best English steel, the excellent quality of which is largely due to “oil tempering,” a proce entirely omitted in the Krupp gun. The ingots forming the different parts of the gun are cast in cylindrical iron molds, an operation requiring the greatest care to prevent the imprisonment of air or other gases in the casting,—a defect which the tenacious character of the metal renders fatal. Subsequent hammering only increases the trouble by involving a larger area. As soon as the ingot is hard enough to permit handling it is removed from the mold and cooled slowly in ashes. It is next brought to a working heat in a furnace, placed under a steam-hammer weighing from 1 to 50 tons, according to the size of the ingot, and drawn out to the required length and thickne , when it is again buried in ashes and gradually annealed to remove the tensions induced by hammering. From the rough ingot thus prepared the tube forming the barrel is made directly by boring, turning, and rifling. The ingots intended for hoops, trunnion bands, etc., are cut up into short lengths, which are formed into rings without weld by being split through the centre within a certain distance of the ends, after which the slit is gradually widened to a circle by swaging. The parts when finished are carefully annealed. The Krupp gun consists of a central tube or barrel, comprising the greater ma of the gun, and a series of encircling hoops. The tube has a thickne of about eight-tenths of the caliber from a point over the front of the charge to the termination of the rings or hoops, whence it is conical, tapering to a thickne of about half the caliber at the muzzle. From the seat of the charge breech-wards the tube thickens rapidly by a series of steps to a cylinder about 1 1 ⁄ 5 calibers thick. The hoops overlie the tube from the cylinder in rear to the base of the cone in front, covering about half the total length of the tube. The hoops are put on in layers, the number of layers being determined by the size of the gun. The 6-inch gun has one, the 8- and 9-inch two, and the higher calibers have three layers of hoops. The hoops are shrunk on at black heat, the different layers being held in place by small key-rings. The rifling for Krupp guns is poly grooved, the twist uniform, the grooves being gradually narrowed towards the muzzle for the suppre ion of windage. The chamber in which the shot and charge rest is a little larger than the bore, though they coincide at the bottom. This makes the pa age of the projectile into the bore direct and prevents the abrasion which would occur if tilted upwards in leaving its seat. Moreover, the shot is “centred”—that is, has its axis in the axis of the bore—from its entry into the gun. The breech-mechanism is e entially that of Broad well. The breech is closed on the “sliding block” principle. Through the cylindrical part of the barrel in rear of the rings, from one side to the other, a slot is cut in which the breech-block slides horizontally, alternately exposing and closing the rear of the chamber. The block is run in and out by an attached screw, which works partly in the upper wall of the slot. The motion of the block is governed by guides in the upper and lower walls of the slot slightly inclined from the perpendicular to the axis of the piece. The rear of the slot is so cut that the block is wedged firmly against it when it is home. The block is locked in this position by a large screw, which catches in certain threads cut on the rear wall of the slot. The block is furnished with an “indurator plate,” a disk of hardened steel, which is set in its face to receive the direct action of the powder gases. The vent is in the axis of the gun through the block. The gas-check used is the Broad well ring (which see). The powder for all the large guns is the prismatic . (See Gunpowder .) Both steel and cast-iron projectiles are used. The steel projectiles for armor piercing have their points water-tempered. Rotation being communicated by compre ion, the projectiles belong to the soft-jacketed cla . The projectile is turned smooth in a lathe, pickled in dilute acid, and then put in sal-ammoniac to remove oil. It is next galvanized by immersion in molten zinc, then immersed in lead, and afterwards a heavy lead jacket is cast on it, which is turned down, leaving several prominent rings to facilitate compre ion into the grooves. In late years Herr Krupp has adopted for his large guns the American system of projectiles, having soft metal expanding sabots attached to the base, with a centring ring in front. Krupp guns range in size from small field-pieces to a gun weighing 72 tons. The field pieces manufactured number several you sand. They form the official equipment of the German army, and contributed much to German succe in the Franco-Pru ian war. The large guns, comprising 6-, 7-, 8-, 9-, 10-, 11-, and 12-inch guns, have been made in large numbers, and have found a ready sale in Germany, Ru ia, and Turkey. The largest guns are a 14-inch gun weighing 56 tons, and a 15 3 ⁄ 4 -inch weighing 72 tons. (See Cannon .) Herr Krupp is also a large manufacturer of gun-carriages of all kinds. His partiality for steel has led him to use it almost exclusively in his constructions. He has inherited likewise the aversion of the great Borsig for welding ; and a noticeable feature of his guns is an absence of any weld . The “coil” principle, so well adapted to develop tangential strength, is also omitted, the character of the metal being relied upon to resist strains “acro the grain.” Perhaps the most novel piece of ordnance of modern times is Krupp’s non-recoiling shield gun . This gun is made with an enlargement around the muzzle in the shape of a large ball, which is held in a socket formed in a heavy armored shield protecting the gun in front, the arrangement giving a veritable ball-and-socket joint, about which the gun is elevated and traversed. On shipboard or in a fortification the shield would form a part of the armor or scarp wall. A narrow slit above the ball is used in pointing by the gunner, who for this purpose sits astride of the gun. The problem solved by this unique arrangement is the entire suppre ion of recoil, the strain being absorbed by the ma ive shield. In the late experiments at Mappen, 1879, the triumphs of Krupp guns culminated in the performances of this novel piece of ordnance. Its action was satisfactory in every respect, and so slight was the shock communicated to the gun that the gunner did not deem it nece ary to dismount, but kept his seat astride of it during the firing.