A bolt hold open linkage incorporated into a lower receiver of a firearm for elevating a bolt catch into contact with a forwardly displacing bolt associated with an upper receiver reciprocating action assembly. An elongated central stem has a forward end and an opposite rearward end, a shoulder being supported, via an extending portion, from the rearward end. A pair of axially aligning mounting pins are supported at spaced apart locations of the lower receiver above a magazine receiving well incorporated into the lower receiver, the pins mounting the opposite ends in pivoting fashion about a centerline extending between the axially aligning pins which is offset from the shoulder. Upon an upwardly displaceable follower, associated with a magazine which is secured to the well, being adapted to elevate into contact with the linkage at a location offset from the axial centerline, the shoulder actuating in a combined pivoting and elevating fashion and adapted to contact and elevate the bolt catch for intercepting the forwardly displacing bolt.