lockedbreech

Locked breech refers to a design in which the rear part of the firearm (the breech) remains locked during firing, resisting the high chamber pressure until it is safe to begin the rearward movement of the slide, bolt, or receiver. In a locked-breech system, the barrel and the moving part are held together by locking lugs, blocks, or rotating components and only unlock after a short recoil or gas-activated delay. This unlocking allows the slide or bolt to continue rearward, enabling extraction and ejection of the spent cartridge, while a fresh round is chambered.

Most modern semi-automatic pistols and many rifles use some form of locked breech combined with short recoil or gas operation. Common implementations include locking lugs on the barrel engaging corresponding recesses in the slide, tilting or rotating locking mechanisms, and locking blocks that disengage at a prescribed point in the recoil cycle. The design contrasts with simple blowback systems, where the breech is not locked and relies on cartridge weight, spring strength, and slide mass to manage rearward force.

Advantages of locked breech designs include the ability to safely chamber higher-pressure cartridges and to manage recoil more efficiently, contributing to better accuracy and durability. They, however, introduce mechanical complexity and require precise manufacturing and maintenance to ensure reliable timing of locking and unlocking.

Historically, locked-breech concepts emerged in the late 19th and early 20th centuries and became a standard feature in many military and civilian firearms due to their versatility and performance.