The modifications of the preceding forms, shown in Figs. 8 and 9 were used in the Crimea by the Sardinian army which also used a smoothbore musket with solid ball as per Fig. 10. The French army Zouaves used a solid cylindro-conical grooved ball, as in Fig. 11, in a tige rifle.

The 1856 Austrian rifle used a solid cylindro-conical ball, "with two deep grooves cut in the cylindrical part such that the parts between the grooves are forced together and outwards, or upset by the explosion of the powder, to fill the bore and the rifle grooves," as in Fig. 12. Fig. 13 illustrates the same principle as used by the Saxon army.

Other forms used at the time by the various Powers are illustrated in Figs. 14, 15, 16, 17, and 18. But it was an open question as to which was the best form, no Power being fully satisfied.

It may be noted here that as the breech-loading rifle had not up to this time been sufficiently perfected, all the above bullets were for muzzle loading rifles. Breech-loading arms had been known for over two centuries but were as yet unreliable, clumsy, and generally imperfect.

Fig. 19. The Lancaster Gun.

The early methods adopted in the construction of cannon to impart to the projectile the desired rotary motion are as interesting as the early methods adopted in the construction of the projectile. Heavy rifled artillery was introduced in 1856 against Cronstadt. The English artillery at Sebastopol used the Lancaster Gun, illustrated in Fig. 19. The form of the bore section of this gun was that of an ellipse of 8" and 85/8" diameters, the bore being generated by the section of such an elipse making a revolution of about one-quarter turn in the length of the bore, the center of the section always co-incident with the longitudinal axis of the gun, forming thereby a continuous elliptical cylinder, the greater axis at the muzzle lying in the vertical plane and gradually becoming horizontal at the breech section, or in other words, the whole length and section of the bore was a rifle twist of one quarter of a turn in its length.

The projectile was a wrought iron shell of the form and size indicated in Fig. 20, as ascertained by measurement of one found in the trenches at Sebastopol.

Fig. 20

The use of these guns in the siege was by no means satisfactory, giving neither precision of fire nor extraordinary range, while the gun more often failed by bursting than other types. The principle, however, met with favor and was studied and improved upon.

Another method of applying the rifle principle to heavy guns consisted in casting a segment of a sphere (nearly) on the side of the cylinder part of the shot with corresponding grooves in the bore of the gun, making about one turn in twenty feet. It is somewhat like the principle of the solid musket ball, Fig. 7 with a difference in the shape of the projections, as shown in the annexed Fig. 21, giving the form and size (nearly) of the shot.

Guns of this pattern were adopted for many of the gunboats fitted out by France for operations in the Baltic in 1856, some with four and others with two guns each.

The bore of the gun had a circular section of 6½" diameter with two grooves cut in it, as shown in Fig. 22, which in the length of the bore had a twist equal to one turn in six meters.

Figures 23 and 24 represent cast iron shot "of very peculiar shape, intended apparently, as a substitute for the rifle groove. They were cylinders of about four inches diameter, with a flattened spherical head from which three spiral openings communicate with the open interior of the cylinder. The cylindrical part was formed with grooves...."

The Modern Type of Gun

From these earliest examples the development of artillery has been gradual until the present day of the built-up gun with an energy and range undreamed of in the earlier days. The built-up gun of today has attained to a calibre of 16 inches, a length of nearly 50 feet, a weight of 124 tons, and an extreme range at 42° elevation of 20.9 miles with a maximum height of trajectory of over 5¾ miles. The projectile, too, has increased in size from a few pounds to the one ton or 2,240-pound mass used in the above gun. The energy imparted to it at the muzzle amounts to 6,408-foot tons assuring a penetration at the muzzle of 33.8 inches of steel, or at 3,500 yards of 27.5 inches, the muzzle velocity being 1,975-foot-seconds and powder charge 640 pounds of smokeless. The maximum pressure in the powder chamber allowed is 37,000 pounds per square inch.

Briefly the modern gun is a built-up piece, constructed by fitting or shrinking super-imposed hoops or cylinders one over the other in size and number as diagramatically explained in Fig. 25, sufficient to re-inforce the bore to withstand the varied pressures.

Fig. 25. 13-inch B.L.R. (Total Length, 40 feet.)

Fig. 26

The twist or rotary motion is imparted to the projectile by means of the "rifling" in the bore. Fig. 26 shows the cross-section of an 8-inch gun with the dimensions of the rifling, which is composed of two elements, the "groove" or spiral cut made in the bore and the "land" or space between two adjacent grooves. To take these grooves "rotating bands" of soft metal, generally copper, are fitted to the projectile as will be explained under "Manufacture of Projectiles."

Classification of Projectiles

Projectiles are classified according to their calibre, type of gun for which they are intended, material of which they are made, etc., as per the following scheme used in the U.S. Army for marking cases of projectiles: