What is a case or casing in relation to a round of ammunition?

The term "case" or "casing" in relation to a round of ammunition refers specifically to the metal or plastic container that holds all the components of the ammunition together. This includes the bullet (the projectile), gunpowder (the propellant), and the primer (the igniter). The casing is crucial as it provides the structural integrity needed to contain the pressure generated when the ammunition is fired.

Understanding this is important because the casing plays a key role in the ammunition's performance and safety. Proper functioning of the casing ensures that the round is securely held and that the internal components work together effectively during ignition and firing. This is distinct from the other components such as the projectile, which is the part that actually exits the firearm when fired, and the charge that ignites the round, which refers to the primer or the propellant itself.