Gas-operated firearm

Abstract

A gas-operated firearm is disclosed in which the gas port is located in the forward part of the chamber, in the part of the barrel bore wall which surrounds the portion of the bullet projecting from the case of a chambered cartridge. In the disclosed firearm the bolt remains locked in its breech-closing position until the gas pressure resulting from the detonation of a cartridge drops to practically zero (gauge). The bolt, which rides on guide rails in the receiver, is provided with a pivotable locking member constructed and arranged to engage locking recesses in the guide rails when it is pivoted into one of its extreme positions. The locking member can be withdrawn from engagement with the locking recesses in the guide rails, and the bolt impelled rearwardly, when a lug projecting from the locking member is struck by a cam which is pivotably mounted in the receiver. An operating slide, mounted in the receiver for sliding parallel to the sliding motion of the bolt, is driven rearwardly in the receiver by the pressure of the gas resulting from the detonation of a cartridge in the chamber driving a ram from a cylinder and compressing the operating slide return springs. When the gas pressure in the cylinder, resulting from the detonation of the cartridge, has dropped to a very low level or zero (gauge) the operating slide is driven forward by the action of its return springs and the operating slide engages the operating cam, rocking it sufficiently to disengage the locking member from its associated recesses in the bolt guide rails and driving the bolt rearwardly. Extraction and ejection of the spent cartridge and cocking of the hammer and trigger mechanism takes place in the well known manner during the rearward travel of the bolt. When immediately thereafter the bolt is driven forward by its return springs a new cartridge is stripped from the magazine and chambered and the locking member is re-engaged with its cooperating locking recesses in the bolt guide rails by spring action, by the action of a depressor plunger mounted in the bolt which strikes the rear face of the barrel block as the breech is closed by the returning bolt, or both. The firing pin is held out by the locking member when the locking member is in its bolt-unlocked position, so that the arm can be fired only when the bolt is locked in its breech-closing position.

Dependencies are inferred from the claim text.