The Collaborative International Dictionary
Breech action
Breech action \Breech action\ The breech mechanism in breech-loading small arms and certain special guns, as automatic and machine guns; -- used frequently in referring to the method by which the movable barrels of breech-loading shotguns are locked, unlocked, or rotated to loading position.
Usage examples of "breech action".
From inside the hollow glassfibre stock he took out a barrel and a breech action and, within thirty seconds, he had assembled the rifle.