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Home > Small Arms Ammunition > Primer Manufacture > Shotshell
Shotshell Primer Mixture, anvil, propellant

Battery cup

Primers for modern shotshells have an additional part; the battery cup supports and adds strength to the primer. Battery cups may be made of copper, brass, or copper-plated steel.

The shotshell anvil is larger than that of a rifle/handgun primer anvil. The anvil is a flat plate mounted perpendicular to the cup. Its leading edge rests against the inside of the battery cup.

Primer cups are charged and compacted similarly to metallic cartridge primers. However, different equipment is employed to press the cup into the large battery cup which, at this point, already contains the anvil.

The battery cup is hollow and holds a significant volume; it is important to prevent finely granulated propellants from entering the cup. If this happens, the added pressure inside the cup at firing can damage the bolt or breechface of a shotgun. Thus, the opening (flashhole) through which flame and gas will pass is sealed with a thin, combustible paper or plastic disk before seating the anvil.

After the primers pass dimensional and sensitivity tests, they are ready for loading.

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