The Growth of Ordnance
32pdr 6m Smooth-bore, Muzzle-loader
Weight 3600 lbs. Muzzle Energy, 642 Foot-tons
U S (Dahlgren) 440pdr 15m Smooth-bore, Muzzle-loader
Weight 42000 lbs. Muzzle Energy, 7273 Foot-tons
Italian (Armstrong) 2000pdr 17in Rifle, Breech-loader
Weight 101.5 tons, Muzzle Energy, 51930 Foot-tons
U S Naval 1100pdr 13in Rifle, Breech-loader
Weight 60 tons, Muzzle Energy, 33627 Foot-tons
PLATE V.
The resistance which spherical projectiles met from the air, their deviation in flight, owing to the frequent lack of coincidence of the centres of gravity and form, their excessive “windage,” and their light weight relatively to calibre, led to the adoption of the rifled gun and the cylindrical projectile. The principle of the former—making the shot act as a screw-bolt and the bore as a screw-thread—is very old, there being at Woolwich a barrel of this type bearing date of 1547. The objects aimed at in rifling are to give a pointed cylindrical shot rotation on its axis that it may keep steady during flight, and secondly, to obtain increased weight in the projectile from its elongated form. As to the latter consideration, it may be noted that the old 32-pounder smooth-bore was of 6-inch calibre, while the United States 6-inch rifle of to-day throws a shot of 100 lbs. weight.
France, during the Crimean War, brought out the first heavy rifled gun. In 1860–61, Armstrong rifles were introduced in the British navy. The labors of Krupp met such success that at Paris, in 1867, he exhibited a rifle weighing 50 tons with a projectile of 1080 pounds. The Parrott rifle was brought out about 1856 in the United States, and was so developed that in 1862 it was the most powerful gun, for its weight and size, in existence. The adoption of rifling was the first great step on the road which engineering had laid toward the growth in power of modern ordnance.
Having thus secured a projectile of great weight and moderate calibre which would bore through the air a true path to the distant mark, there remained to seek but four chief elements in the magnificent advance made within a generation by the naval artillery of our day. These factors were: 1st. Increased strength in the material of the gun. 2d. A method of construction which would not only permit enormous pressures in the powder-chamber, but would make possible the continuous acceleration of the projectile during its passage through the bore. 3d. An explosive which would satisfy the objects of the method of construction; and, 4th. A system of loading which would enable guns of great length to be charged with ease. The mounting of ordnance of any weight, its control, and its rapid and facile handling were but minor matters of engineering.
In a paper such as this, of limited length and addressed to laymen, it is possible to give but a glance at the progress in the various elements of gun-construction which have been noted. Of material, little need be said. The rifle of Crimean days was a cast-iron piece; Parrott ordnance was of cast and wrought iron; and the first Armstrong gun was built of wrought iron and steel. Cast and compound materials, however, have vanished with the past. Steel—hardened and toughened to the last degree by every refinement of manufacture—forms the “reeking tube” for the “iron shard” of the century’s close.
The method of construction is the “built-up” process, shown by the partial section on [Plate V]., the barrel being reinforced by tubes which are shrunk on—like the tire of a wagon-wheel—so as to produce initial compression. The explosion in the powder chamber strains and expands temporarily the barrel, and the application of the shrinkage principle enables a portion of the strength of the tubes to be employed in preliminary internal pressure. The barrel thus supported can be strained by the charge, not only to its own limit of safety, but to an additional amount equal to this initial compression. The all-steel, built-up gun has a possible rival in wire-wound ordnance, a system which replaces the tubes, to a greater or less extent, by layers of wire, wound while in tension around the barrel.
Powder is the soul of the gun; it transforms the huge inert mass into a flaming engine of death. The great development of explosives began but a generation since. The researches of Robins and Rumford in the last century, and of Hutton in the dawn of this, formed the world’s knowledge of the gun’s internal ballistics until the year 1870. To the genius of Noble and Abel is due the stimulus to growth since then. The powders have kept pace with gun-construction in its advance. The increased strength of the chamber has been met by heavier and slow-burning charges—cocoa, brown prismatic, and the like—which have given not only greater initial velocity, but a continuous acceleration through bores whose maximum length has exceeded 47 feet. Indeed, to the production of this lingering combustion is due the great linear dimension and power of modern guns. Initial pressure had its limit; advance lay only in the subsequent acceleration given by late ignition of a portion of the charge.