The rifle motion is communicated by one rotating ring of copper, which is placed at the distance of 1.5 inch from the base of the projectile.
CARTRIDGE CASE AND GRAINS OF POWDER, U.S.N.
The uniform windage for all calibres is .04 inch; thus, taking the 6-inch gun as an example, the diameter of the bore across the lands is 6 inches, the diameter of the shell is 5.96 inches, the depth of the grooves is .05 inch; thus the diameter of the bore across the grooves is 6.10 inches. In order to permit the rotating ring to fill the grooves, it must have a diameter of 6.14 inches; this causes a squeeze of .05 inch between the lands and the rotating ring.
There is no subject in the development of the new naval artillery more important than the powder. That used with the old artillery is entirely unsuited to the new conditions that obtain in the modern high-power guns. A brown powder, introduced first in Germany, has exhibited decided advantages over all others, and the efforts to reproduce it have been thoroughly successful at the Du Pont Mills. It is generally known as “cocoa” powder. Its peculiarity exists in the method of preparing the charcoal; this affects the color, and results in a brown instead of a black powder. With this powder, experiments with the 6-inch gun give a muzzle velocity of over 2000 feet per second with a projectile of 100 pounds, using charges of 50 pounds, and this result is obtained with less than 15 tons pressure per square inch in the powder chamber. The grain is prismatic, with a central perforation, and as regards its rate of burning, is under complete control in the manufacture; the form provides an increasing surface for the flame during the period of combustion, thus relieving the gun from abnormal pressures at the moment of ignition, but continuing the extreme pressure farther along the bore. The progressive nature of the combustion is very apparent when comparing an unburned grain with others partially consumed, blown out from the gun.
COMMON SHELLS, U.S.N.
The gun-carriage, which is a separate study in itself, is carried to a high pitch of perfection, and presents many features being adopted abroad. The importance of a suitable carriage can be appreciated by inspecting the following table, which exhibits the energy that must be controlled by it:
| Gun. | Weight of Charge. | Weight of Projectile. | Muzzle Velocity. | Muzzle Energy. | Penetration in Wrought-iron. | Muzzle Energy per Ton of Gun. | Weight of Gun. | Weight of Carriage. |
|---|---|---|---|---|---|---|---|---|
| Pounds. | Pounds. | Feet. | Ft.-Tons. | Inches. | Ft.-Tons. | Pounds. | Pounds. | |
| 5-inch steel breech-loading rifle | 30 | 60 | 1915 | 1,525 | 10.7 | 552 | 6,187 | 4,200 |
| 6-inch steel breech-loading rifle | 50 | 100 | 1915 | 2,542 | 13.2 | 521 | 11,000 | 6,400 |
| 8-inch steel breech-loading-rifle | 125 | 250 | 2050 | 7,285 | 18.2 | 560 | 28,000 | 14,000 |
| 10-inch steel breech-loading rifle | 250 | 500 | 2100 | 15,285 | 23.7 | 588 | 58,240 | 32,482 |
| 12-inch steel breech-loading rifle | 425 | 850 | 2100 | 25,985 | 27.6 | 591 | 44 tons | .... |
| 14-inch steel breech-loading rifle | 675 | 1350 | 2100 | 41,270 | 32.2 | 550 | 75 tons | .... |
| 16-inch steel breech-loading rifle | 1000 | 2000 | 2100 | 61,114 | 36.8 | 571 | 107 tons | .... |
This energy, total energy, expresses the work that the gun can perform. It is expressed in foot-tons, and signifies that the energy developed is sufficient to raise the weight in tons to a height of one foot. Thus the projectile from the small 5-inch gun, weighing sixty pounds, fired with a charge of thirty pounds of powder, leaves the gun with an energy capable of lifting 1525 tons to the height of one foot! Comparing this with the energy developed by the 100-ton hammer at the forge of Le Creuzot in France, the energy of which is 1640 foot-tons, we have a most striking illustration of the power of gunpowder, and the testimony in the table as to the energy developed per ton of gun more forcibly exhibits the perfection of a manufacture which, with so little weight of gun, can develop such gigantic power.