Locked breech is the design of a breech-reloading firearm's action. This is important in understanding how a self-reloading firearm works. In the simplest terms, the locked breech is one way to slow down the opening of the breech of a self-reloading firearm when fired. The source of power for the movement is recoil.

The principle of firing a projectile from a firearm is that when the propellant in a bullet's casing is ignited, the propellant burns quickly for a very short time. This