Lock (firearm)

This flintlock mechanism is distinct from the metal barrel extending to the right, and the surrounding wooden stock encloses and obscures the trigger mechanism connection to the actuation spring.

The lock of a firearm is the mechanism used to initiate firing. It is generally used as a historical term, referring to such mechanisms used in muzzle-loading and early breech-loading firearms, as modern firearms uniformly fire by use of a firing pin to strike the rear of a cartridge. Side-lock refers to the type of construction, in which the individual components of the mechanism are mounted either side of a single plate. The assembly is then mounted to the stock on the side of the firearm. In modern firearm designs, the mechanism to initiate firing is generally constructed within the frame or receiver of the firearm and is referred to as the firing or trigger mechanism.