'Breech action' definitions:

Definition of 'Breech action'

From: GCIDE

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. [Webster 1913 Suppl.]