Locked breech

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.

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.

Recoil is described by Newton's third law of motion, which states that for every action there is an equal and opposite reaction.

It takes the form of a quick sharp push away from the path the bullet is flying in and directly against the hand or shoulder of the shooter.

In the late 19th century, firearms makers learned how to use this mechanical force to create "self-loading" weapons, whether they were in artillery, rifles, shotguns, or handguns.

Some designers handled this problem by making the moving parts of the firearm heavier and the strength of the recoil spring much greater.

Beretta solved this problem with a tilting barrel which allowed loading without having to pull the slide to the rear.

In large firearms such as the Browning M2HB .50 caliber machine gun a similar system called long recoil is used.

The amount of mass of the components, the strength of springs,[6] and the distance the barrel and slide are allowed to recoil is carefully calculated and tested to ensure safety.