Jerry,

The ammo for the cap and ball pistols came in six packs or six pre made rounds in a box or paper package to keep them from breaking. The rounds were paper or "skin" tubes with powder and ball inside. You could break the round and pour the powder in or, some paper was treated like flash paper, you just drop the cartridge in and ramm it home and when fired all of the paper burned.
You need a pistol cartridge box to keep the cartridge packs in. The leather helps keep the rain out but it will also keep sparks from gunfire away from the ammo...if it goes off it is going to hurt! If a powder flask goes off...well it is a bomb! DON'T carry a flask on you.

Thanks,
Gary D. Bray