Quote Originally Posted by Beleriphon View Post
And the percussion cap was, or is I suppose, the rough equivalent of a modern round without the bullet in the casing (so its primer and powder in one unit) right? And these were used well into the 19th century yes?
No. The percussion cap was just the primer, it was an explosive designed to detonate on impact, usually a "fulminate" of some sort. The main charge of gunpowder still had to be loaded independently.

On some breechloader designs (Sharps carbine and rifle), a paper cartridge containing the powder and bullet could be loaded into the gun as a unit, but a percussion cap still had to be placed on the "nipple". For muzzle-loading weapons, if paper cartridges were being used they were opened, the powder poured down the barrel, then the bullet inserted (either with the remainder of the paper, or squeezed out of it -- depending upon drill manual used).

The percussion cap, is in my opinion, a huge revolution. Or at the very least the first step in a revolution. It allowed for the concept of a "self-contained cartridge", in which all the ammunition components are bundled together in a single unit.

The first designs were paper cartridges, with gunpowder and bullet sandwiching the percussion primer. Soon metallic cartridges were invented -- they solved the problem of gas-seal by being able to expand when fired, then contracting slightly allowing for extraction of the spent cartridge.

At this point magazines start to become feasible, as well as automatic weapons, etc.