Synchronized split-bolt breech closure for firearms

Abstract

A synchronized split-bolt breech closure mechanism improves blowback operation for higher pressure cartridges. The mechanism includes a split-bolt assembly with a front bolt half for feeding, chambering, and triggering a cartridge, and back bolt half connected by a variable separation spring separation distance, initiating from an open bolt configuration, where upon cartridge ignition the rearward recoil force on the front bolt half is synchronized with the forward momentum of the back bolt half driven by the main action spring, closing the separation distance which momentum transfer maintains breech closure over a brief interval for the bullet to exit the barrel. The mechanism provides a basis for automatic blowback firearms with enhanced performance over prior art systems, such as the one-piece bolt low pressure blowback of the Thompson M1A1 45 ACP rechambered for the intermediate pressure 50 caliber Action Express, without complex transverse friction or gas-operated closed rotating bolt breech mechanisms.

Dependencies are inferred from the claim text.