Locked breech
From Wikipedia, the free encyclopedia
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.
![Thumb image](http://upload.wikimedia.org/wikipedia/commons/thumb/c/c2/Blow-Back_firearm_operation.png/320px-Blow-Back_firearm_operation.png)
![Thumb image](http://upload.wikimedia.org/wikipedia/commons/thumb/1/1a/Gas_operated_breech_with_locking_rollers.jpg/640px-Gas_operated_breech_with_locking_rollers.jpg)
![Thumb image](http://upload.wikimedia.org/wikipedia/commons/thumb/a/ab/Sig-Sauer_Short_Recoil_Locking_System.png/320px-Sig-Sauer_Short_Recoil_Locking_System.png)
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 creates a high-pressure pocket of gas that expands, pushing the projectile (bullet) out of the chamber and down the barrel of the firearm. If the high-pressure gas were not confined within certain parts of the weapon, it could damage the firearm or injure the shooter. A 'locked breech' barrel confines the high-pressure gas to the barrel, allowing the gas to expand and cool without risk of damaging weapon or shooter. Because of the pressure drop, a breech block can be opened in a self-reloading firearm due to the recoil inertia generation by the movement of the projectile.