In the first practicable form of metallic cartridge, the composition was placed in the rim which formed the base of the cartridge, and which enabled it to be withdrawn after discharge — the rim thus serving two purposes.
These rimfire cartridges answered very well until the powder charges became heavier, when it was discovered that the weakening of the metal by folding to make the rim caused it to sheer off at the edge of the chamber of the gun, and the copper, of which they were made, would expand and render it almost impossible to extract the shell.
And since the fulminate had to be placed entirely around the rim, a greater quantity was used than necessary for firing, and the distribution was imperfect, thus causing misfires.
A pin-fire cartridge was invented, but proved unsatisfactory.
A pin projected from the rim and was intended to be struck by the hammer of the gun; but, of course, any object striking it would cause an explosion, and it was dangerous.
Neither the pin-fire nor the rim-fire cartridges could be reloaded.
On June 25, 1864, the chief of ordnance
of the United States army reported that among the most important changes in firearms evolved from the experience of the war was the metallic cartridge-case.
Linen had been in use, but copper was much superior.
The case formed a perfect gas-check; it gave the benefit of allowing a fulminate to be used in the case itself, which was an advantage over the former method of using a cap; there was a gain of time in that the piece did not have to be recapped with each new load; there was greater ease of loading, and the ammunition was waterproof.
For the field-artillery of both services there were supplied solid shot, case, and shell with time-fuses and with percussionfuses.
Solid shot were designed for destroying the heavy walls of fortifications, or for some similar purpose, but were used also in the field.
The other forms of ammunition were used against troops.
Case was of two kinds-canister, which separated at the muzzle of the piece in consequence of the shock