The metal or plastic case that holds the [[bullet]], gunpowder, and primer as part of [[gun|firearm]] [[ammunition]]. Together the parts are called a round or [[cartridge]], though commonly 'round' and 'bullet' are used interchangeably (the bullet is technically only part of a round). 

On Danbooru, most often seen empty, being ejected one at a time from a semiautomatic firearm or [[shotgun]], in a rapid sequence from an [[machine gun|automatic firearm]], or manually ejected from a [[revolver]] cylinder (all at once, typically six at a time).

h4. See also

* [[bullet]]
* [[cartridge]]
* [[casing ejection]]
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