Gas operated mechanism having automatic pressure regulator

In a gas operated firearm having an axially elongated barrel including a bore extending therethrough, means defining an annular gas chamber of variable volume surrounding an associated portion of the barrel and including a guide member mounted in fixed position on the barrel and a first reaction member coaxially surrounding associated portions of the guide member and the barrel and supported for limited reciprocal axial movement between first and second positions relative to the guide member and the barrel, said first reaction member having a generally radially disposed first reaction surface defining one end portion of the gas chamber, and a gas port in the barrel opening into the bore and the gas chamber, said first reaction member being movable from its first to its second position in response to the pressure of gases of explosion within the chamber, the improvement comprising a second reaction member supported in coaxial surrounding relation to said barrel by said guide member for reciprocal axial movement relative to said guide member, said barrel and said first reaction member, said second reaction member having a generally radially disposed second reaction surface defining another portion of said gas chamber opposite said one end, means for limiting axial movement of said second reaction member in the direction of said first reaction member, means for biasing said second reaction member axially and in the direction of said first biasing member and to an inactive position, and means defining a vent port for communicating with said chamber and the atmosphere to vent gases of explosion from said chamber, said second reaction member being movable in an axial direction away from first reaction member and from said inactive position to another position in response to gas pressure within said chamber, said second reaction member being further movable in said axial direction away from said first reaction member and from said other position to a venting position in response to gas pressure within said chamber, said venting means being in communication with said gas chamber and with the atmosphere only when said second reaction member is in its venting position.

In a gas operated firearm having a receiver, an axially elongated barrel projecting axially forwardly from the receiver and having a bore extending coaxially therethrough, a slide member slidably supported on the receiver for movement between forward and rearward positions relative thereto, a guide member mounted in fixed position on the barrel, a piston coaxially supported on the barrel for axial sliding movement relative thereto between first and second position, said piston having a head portion disposed generally adjacent the forward end of the slide member when the piston is in its first position and the slide member is in its forward position, the piston having an annular skirt portion projecting axially forwardly from the head portion in radially spaced relation to the barrel, the piston and the guide member cooperating to define a gas chamber of variable volume surrounding an associated portion of the barrel, and gas port defining means communicating with the bore and with the chamber, the improvement comprising a reaction plunger supported by said guide member within said piston skirt, means for biasing said plunger in an axial direction toward said piston head portion and to an inactive position, said plunger being movable from its inactive position in an axial direction away from said piston head and through a range of positions to a venting position in response to gas pressure within said chamber, and vent means defined by said guide member for venting gases of explosion from said chamber to the atmosphere only when said plunger is in its venting position.