Radial delayed blowback operating system for a firearm incorporating a rotational inducing profile established between bolt lugs and a mating receiving pattern within the upper receiver or a trunnion installed within the receiver

Abstract

A delayed rotary blowback mechanism integrated into a firearm bolt and carrier subassembly. A plurality of radial locking lugs are configured at a rear end of the bolt and seat within a mating profile of an upper receiver interior or integrated trunnion in a fully chambered position. A plurality of chamfered locations are configured between the lugs and a receiving profile in the barrel or trunnion for influencing linear to rotational motion of the bolt. A cam pin extends upwardly from the bolt and seats through a circumferentially directed slot configured within the bolt carrier. Upon initiating of the discharge cycle, signaled by the round traveling through and out the end of the barrel, the chamfered configuration results in the bolt and cam pin rotating within the carrier and the lugs subsequently separating from the receiver or trunnion, with the bolt and associated carrier retaining sufficient inertia to cycle through the discharge cycle to the set position concurrent with reloading a subsequent cartridge.