MANUFACTURE OF ORDNANCE IN TIIE UNITED STATES.—The first forged-steel gun made in this country was a 6-in, breech-loading rifle. The tube was annealed metal, but the jacket was of oil-tempered steel, imported. The two guns following were also 6-in., of annealed metal, the forgings being of domestic manu facture, as all have since been, with the exception of those above mentioned.
Notwithstanding the con siderable delays made by waiting for the first deliv eries of the forgings, and the lack of machinery and plant for the new and su perior quality of work de manded, guns and their carriages are now being turned out as fast as the new vessels are ready for them. Finished guns have been subjected to the proof required by law, which constitutes a series of 10 rounds fired with all possible dispatch. All guns have thus far stood the firing tests perfectly and have given satisfaction in service. The 6-in, guns, as mounted in broadside aboard the men-of war, are shown in Fig. 3. The carriage is known as a gravity return ; the gun after fired runs down the slide (a) on the carriage trucks (b b b the training is done at (c) by the cogs, and the elevating at (d).
In their main features the army and navy guns are alike, the most important difference in construction being that, in the navy guns, the trunnion hoops are made of oil-tempered and annealed castings, and are screwed on cold, while in the army these hoops are forged and assembled by shrinkage. In the matter of charges, also, the practice differs, in that the rule in the navy is to use a charge of powder equal to about one-half the weight of the shot, whilst in the army the weight of projectile is made proportionately much heavier. The lighter projectile gives a high velocity with a relatively flat trajectory, which is best adapted to the conditions of naval combat. There is certainly no mechanical difficulty in making these guns which cannot be overcome. The machinery of the finished surfaces requires less care than is exercised in making paper rolls. A variation of 0003 of an inch is usually allowed in turning the shrinkage surfaces for a gun, and the shrinkages required to produce the maximum resistance of a gun built up of several layers, may be obtained by a relatively heavy shrinkage on the first layer, and a relatively light shrinkage for the second layer, and so on. or the reverse.
The division of the gun into many parts has all the advantage of procuring the very best of material, because of the thorough working which each part receives, and the facility for examination of the quality of the material which is afforded. In the construction of these gulls, the different parts are assembled to give great economy of material. The jacket affords all the requisite longitudinal strength. The methods pursued in the manufacture and application in the gun structure, essentially fit them to afford the kind of resistance required. The tube in a built-up gun is subjected to the greatest strains in the struct
ure, and there is always left a margin of elastic strength in the outside parts, which, should the tube be heated to excess, would be equivalent to a case of a gun assembled with a greater shrinkage. So that in firing, the place of most dangerous strain in the gun—that is, at the surface of the bore of the tube—would be under a less, instead of a greater, strain.
Breech ilechanicm.—The system of breech mechanism in use is that of the slotted screw, which is the type in use in France, Italy, and England the 1)e Bange gas check, with mushroom head and plastic obturator, has also been quite generally adopted with heavier calibers in this country. The details of this mechanism vary in different countries, only the main fea tures being preserved. Gas-check rings replace the plastic check in Italian and in the Armstrong guns, and they differ in details from each other, and from the De Bange mechanism. The differ ent parts will be readily understood from the illustration, (Fig. 4): mush room head, slotted screw, breech plug, catch, sight bar, and handle. The Krupp mechanism has been adopted by Russia and Germany. In regard to these two systems, so thoroughly tested and proved, it may he remarked that the slotted screw has been generally received by gun makers with more favor than the Krupp, and probably the principal reason for this is that the latter requires a forging of larger diameter for the block-carrying cylinder than the former, which may even be attached in the tube forging itself, Tests of Ordnance,—Three of the systems contemplated in 1883—the built-up steel, the simple cast-iron, and the multi-charge—have been subjected to trial ; another, the combined east-iron and steel, has been submitted to partial trial only, in the proof of a 12-in, muzzle loading rifled mortar hooped with steel, whilst the rifles made on the same system, and the wire-wound guns, are in a more or less forward state of completion. The principal feature of the multi-charge gun consists in the accelerating principle as applied to the action of the powder upon the projectile, which is sought to be obtained by using a series of powder charges placed in pockets at intervals along the bore near the breech, which are intended to be ignited by the inflamed gases of the breech charge following the passage of the projectile over the opening of each pocket in the bore. The breech charge is relatively light, to give a gradual impetus to the projectile, which is placed immediately in front of it, and in rear of all the pockets. Higher energy and greater penetration than this gun has been able to show are matters of every-day record with guns using a single charge of powder, and with a much safer pressure on the gun.