Anatomy of a Rifle or Pistol Cartridge
Case (a.k.a. Brass) – Cases can be called brass, empties, shells, reloading brass, spent cases or brass cases. The case is generally made of brass, steel or aluminum designed to contain the powder charge and the primer. Centerfire cases include all pistol and rifle cartridges that have primers in the center of the cartridge base. Rimfire cases have the primer located in the rim of the case. Brass- and nickel-plated brass are reloadable while rimfire, steel and aluminum cases that are not reloadable.
Powder – The term for any chemical compound, normally gunpowder, used to propel the bullet out of the barrel when ignited by a struck primer. Powder is commonly found in two varieties, smokeless and black. Smokeless powder is found in modern ammunition and has a significantly reduced smoke signature. Black powder on the other hand is very smoky and can be corrosive.
Primer – The primer is the small circle on the base of the cartridge. The Primer is made up of the anvil, primer cap and priming compound. When the primer is struck by the firing pin, it ignites the powder contained inside the case through the small flash hole beneath the primer. There are two types of primers: boxer and berdan. The boxer primer is more commonly used and allows the case to be reloaded. A berdan primer is generally used in non-reloadable cases.
Rim – The rim of the cartridge is designed to allow easy extraction of the fired cartridge as well as prevent some cartridges from entering the chamber. There are several types of rims including belted, rimmed, semi-rimmed, rimless and rebated that are used depending on the caliber of ammunition.
Bullet – This is projectile that is fired from the case when the primer is struck by the firing pin, igniting the powder. The bullet is sometimes improperly referred to as the “tip.” The bullet is measured by its diameter in either inches or millimeters.