When discussing firearms, what does 'casing' NOT include?

In the context of firearms, 'casing' refers specifically to the container that holds all the essential components necessary for firing a bullet, which typically includes the bullet itself, the propellant (or powder), and the primer. The casing is essentially the shell that contains these elements and is often made of metal, such as brass.

The firing mechanism, however, is separate from the casing. It consists of components such as the firing pin, hammer, or striker, which are involved in igniting the primer when the trigger is pulled. This mechanism does not form part of the physical casing that holds the ammunition. Understanding this distinction is crucial for comprehending how ammunition and firearms function together.