In one form or another this construction enters into most all modern breech mechanisms. Among the forms used by the United States are the Driggs-Seabury, the Dashiell, and the Vickers-Maxim. To prevent the expanding gases from driving through the crevices of the breech block, expanding or swelling rings, known as gas checks, are arranged on the front of the breech block. De Bange’s patent, No. 301,220, July 1, 1884, covers the most popular form.
FIG. 269.—SIGHTING A SIX-INCH RAPID FIRE GUN.
The elements of efficiency of the modern rapid-fire breech-loading rifle are to be found in the following features: First, in the increased length of the gun, which, for a 6-inch gun is now as much as 25 feet, the increased length lending a longer period of expansion for the explosion of the powder charge, and imparting a correspondingly higher momentum; secondly, in the fixed ammunition, which means a cartridge case in which a metallic shell encloses the powder charge, and is connected with the projectile, and third, in the great improvement and rapidity of action of the breech mechanism, which permits as many as eight rounds per minute to be fired. In [Fig. 269] is shown a 6-inch rapid-fire gun of the United States Navy, loaded, and being sighted for fire. Rapid-fire guns of this class represent the most effective form of modern ordnance. It was largely such rapid fire batteries of Admiral Dewey’s squadron that swept the Spanish fleet out of existence at Manila, and that demolished the fleet of Cervera at Santiago by the awful hail of shells poured into his ships. These relatively small guns throw a shell six miles, and the striking energy of their projectiles at the muzzle is equal to the penetration of iron plate 21 inches thick, or 16 inches of steel. When the gun is loaded, it is held in the forward position by coil springs, inclosed in cylinders and holding a recoil seat for the trunnions, and also has two pistons traveling in cylinders filled with glycerine. When the gun is fired, the recoil causes it to slide back, carrying the pistons, and the recoil is checked by the resistance of the glycerine traveling through an opening past the pistons. After full recoil, the gun is automatically returned to its forward position by the action of the coil springs, which are compressed during the recoil. The gun crew is protected by Harveyized steel plate 4 inches thick, and the gun is so delicately mounted on ball bearings that its great weight of 71⁄2 tons responds readily to the slight pressure in training the same.
FIG. 270.—RANGE OF SIXTEEN-INCH GUN.
Powerful as these guns appear to be, their big brothers in the revolving turrets are far more so. While not so nimble in action, the great power of these guns of the main battery, and the elaboration and completeness of mechanism for operating them, for supplying them with ammunition, and for rotating the turrets, constitute a complete world in ordnance in itself. As the gun increases in size, its cost both in construction and service increases in a greatly disproportionate ratio. A 6-inch breech-loading rifle costs $64.40 for each discharge, while a 12-inch gun costs $458 for each discharge. The largest guns of our battleships are of 13 inch calibre, and about 40 feet long, but larger ones are employed for sea coast defenses. The great 16-inch 126-ton gun, now building for the United States at the Watervliet arsenal, is 491⁄4 feet long, over 6 feet in diameter at the breech, and it will have an extreme range of over twenty miles. Its projectile will weigh 2,370 pounds, and it will cost $865 to fire the gun once. The accompanying view, [Fig. 270], will give graphic illustration of the range of this gun. If fired at its maximum elevation from the battery at the south end of New York in a northerly direction, its projectile would pass over the city of New York, over Grant’s Tomb, Spuyten Duyvil, Riverdale, Mount St. Vincent, Ludlow, Yonkers, and would land near Hastings-on-the-Hudson, nearly twenty miles away, as shown in our map, [Fig. 271]. The extreme height of its trajectory would be 30,516 feet, or nearly six miles. This means that if Pike’s Peak, of the Western Hemisphere, had piled on top of it Mont Blanc, of the Eastern Hemisphere, this gun would hurl its enormous projectile so high above them both as to still leave space below its curve to build Washington’s Monument on top of Mont Blanc, as shown in [Fig. 270].