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W-O-C is correct. To embellish her answer just a smidge...
There have been several different priming systems for cartridges over the years- the two that have survived in any large numbers are rimfire and center fire.
In a rimfire, the head of the cartridge case is folded to form a rim. The priming compound (stuff that ignites the gunpowder) is placed in that hollow, folded rim, 360 degrees around the rim. The firing pin strikes anywhere on the rim of the cartridge case, pinching the rim, and making the priming compound explode. Rimfire cartridges are smaller and less powerful than centerfire- the design of the case cannot hold heavy pressures. In general, rimfire ammo cannot be reloaded. The only mainstream rimfire cartridges left are the .22s and the .17s.
Centerfire, heavier case. Primer is a separate component at the center of the rear of the cartridge case. Firing pin crushes priming compound against an internal pin (the anvil) exploding it. Flash travels through one or two flash holes into cartridge case, igniting powder. Heavier case can take higher pressures- important now that we use smokeless powder. These can USUALLY be reloaded by pushing out the fired primer, and pressing another primer into the primer well. There are two main types of centerfire primers- Boxer and Berdan.
Boxer was invented by a British soldier, and is now used widely in the US. Each primer has it's own anvil. Berdan was invented by an American, and is widely used in Europe. The anvil is part of the cartridge, not the primer itself. When you look down into a fired Boxer primed case, it has one flash hole in the center. Berdans have 2 or 3 flash holes. Both can be reloaded. Berdan is a PITA to reload.
What we have here is... failure- to communicate.
Last edited by c3shooter; 03-19-2012 at 01:25 AM.