The rimfire cartridge was the second enclosed bullet to be developed, and is such a simple and elegant design that it is still used today. The first was the pinfire cartridge, which was only used in pistols due to its unique design.

The rimfire cartridge carries its primer in a lip running around the base. When the weapon's hammer struck anywhere on that rim, the bullet would fire. This was especially useful for early repeating rifle designs like the Spencer Rifle, as the mechanism didn't have to be as precise as that for a centerfire cartridge, which has to be hit in the exact center of the base to fire.