Select fire trigger mechanism for machine guns

A trigger mechanism for a firearm having a bolt carrier that reciprocates and pivotally displaces a hammer when cycled, the trigger mechanism comprising:

• a selector operable between a safe position, an automatic position, and a semiautomatic position;
• a trigger pivotable between a set position and a pulled position;
• a hammer pivotable between a fired position and at least one cocked position, the hammer biased toward the fired position;
• a hammer sear rotatable via the selector between a disengaged position and an engaged position in which the hammer sear is arranged to engage the hammer, wherein the hammer sear is biased toward the engaged position when the selector is in the automatic position;
• and
• a sear trip connected to the hammer sear and movable via the hammer sear between an inactive position and an active position in which the sear trip is arranged to be contacted by the bolt carrier when the bolt carrier reaches a substantially in-battery position, wherein:
• the sear trip is biased toward the active position when the selector is in the automatic position, and
• contact by the bolt carrier with the sear trip moves the sear trip against the bias to disengage the hammer sear from the hammer.

A trigger mechanism for a firearm having a bolt carrier that reciprocates and pivotally displaces a hammer when cycled, the trigger mechanism comprising:

• a selector rotatable between a safe position, an automatic position, and a semiautomatic position;
• a trigger having a trigger sear and pivotable between a set position and a pulled position;
• a hammer pivotable between a fired position, a semiautomatic cocked position, and an automatic cocked position, the hammer biased toward the fired position;
• a hammer sear rotatable via the selector between a disengaged position and an engaged position in which the hammer sear is arranged to engage the hammer, wherein the hammer sear is biased toward the engaged position when the selector is in the automatic position;
• and
• a sear trip connected to the hammer sear and movable via the hammer sear between an inactive position and an active position in which the sear trip is arranged to be contacted by the bolt carrier when the bolt carrier reaches a substantially in-battery position during cycling thereof, wherein:
• the sear trip is biased toward the active position when the selector is in the automatic position, and
• contact by the bolt carrier with sear trip moves the sear trip against the bias to disengage the hammer sear from the hammer and release the hammer toward the fired position;
• wherein pulling and holding the trigger in the pulled position when the selector is in the automatic position, the bolt carrier is in a substantially in-battery position, and the hammer is in the semiautomatic cocked position, releases the hammer toward the fired position and transitions control of the hammer from the trigger sear to the hammer sear.