Firing rate regulating mechanism

A method for modifying an automatic firearm to provide regulation of a rate of fire of the firearm, the firearm having a frame, a barrel, a bolt assembly that moves along the frame in a forward direction toward the barrel and in a rearward direction away from the barrel, the bolt assembly including a moving firing pin, a hammer constructed and arranged to move against the firing pin when the bolt assembly is adjacent a forwardmost position against the barrel, a trigger sear and a secondary sear that selectively engages and disengages the hammer to, respectively, retain the hammer against movement against the firing pin and to cause the hammer to move against the firing pin, the method comprising the steps of:

• locating a time delay unit comprising a hydraulic cylinder and a piston assembly and having a base and a movable part wherein the movable part moves with respect to the frame of the firearm in a first direction at a first rate and moves in a second direction at a second rate that is slower than the first rate, a movement of the movable part in the second direction being responsive to a spring that biases the movable part away from the base and wherein the spring is compressed by movement of the movable part in the first direction;
• mounting in the frame a movable bolt engagement surface that moves in response to movement of a predetermined portion of the bolt assembly thereover in the rearward direction from an interfering position within a path of movement of the bolt assembly to a non-interfering position remote from the path of movement of the bolt assembly;
• interconnecting the bolt engagement surface with the time delay unit so that movement of the predetermined portion of the bolt assembly in the rearward direction to, thereby, move the bolt engagement surface to the position remote from the path of travel of the bolt assembly causes the time delay unit to move in the first direction, the time delay unit moving in the second direction to, thereby, move the bolt engagement surface into the imterfering position when the bolt assembly subsequently moves in the forward direction back to the forwardmost position adjacent the barrel, a movement of the time delay unit to move the bolt engagement surface into the interfering position occurring at a time delay after movement of the bolt assembly back into the forwardmost position;
• and
• interconnecting the time delay unit with the secondary sear so that movement of the time delay unit in the first direction actuates the secondary sear to engage the hammer to retain the hammer from moving against the firing pin and so that movement of the time delay unit in the second direction actuates the secondary sear to release the hammer to cause the hammer to move against the firing pin after the time delay.

An automatic firearm comprising:

• a frame;
• a bolt carrier movably mounted in the frame including a bolt movably mounted in the bolt carrier;
• a firing pin movably mounted in the bolt;
• a hammer pivotally mounted in the frame constructed and arranged to move toward the firing pin when the bolt is in a forwardmost position, the hammer having a trigger sear shoulder and a secondary sear shoulder;
• a trigger pivotally mounted in the frame and having a trigger sear that selectively engages a trigger sear shoulder;
• a secondary sear constructed and arranged to engage the secondary sear shoulder at predetermined times to retain the hammer against movement toward the firing pin until the bolt is adjacent the forwardmost position;
• a cam pivotally mounted in the frame and operatively connected to the secondary sear, the cam including an upper surface that is movable forwardly into and rearwardly out of a path of travel of the bolt carrier and the upper surface pivoting rearwardly in response to rearward movement of the bolt carrier and the cam including a shoulder for engaging the secondary sear in response to forward pivotal movement of the upper surface;
• and
• a time delay unit operatively connected with the cam, the time delay unit moving to a compressed position in response to a rearward pivotal movement of the upper surface and the time delay unit moving to an expanded position, thereby forwardly pivoting the upper surface into engagement with the sear at a predetermined delay time subsequent to a movement into the compressed position.