A reciprocating bolt assembly has delayed blowback and a firing pin block. Features prevent out-of-battery firing, when the bolt assembly is not fully engaged to the firing chamber or barrel face, a movable member within a bolt body functions as a blocking member that blocks the firing pin and prevents the firing pin from striking a cartridge. In embodiments, the firing pin has two stop portions that the movable member can engage depending on the cycle status of the firearm. A reverse cam mechanism associated with the firing pin blocking provides a resistance to and delays blowback.

An assembly for holding a bolt of a firearm in an open position is disclosed. The assembly comprises a bolt catch pivotable about a first axis toward and away from a catching position. In the catching position, a portion of the bolt catch is within a path of travel of the bolt. A follower transfer adapter is pivotable about a second axis. The follower transfer adapter includes an engagement portion that is configured to engage a follower of a magazine. Optionally, the follower transfer adapter includes an overhang lip that extends transversely to the longitudinal axis of the firearm and into a path of travel of the follower to define the engagement portion. The engagement portion is positioned between the second axis and the bolt catch along the longitudinal axis of the firearm. A linkage transfers rotational movement of the follower transfer adapter to rotation of the bolt catch.

An assembly for holding a bolt of a firearm in an open position is disclosed. The assembly comprises a bolt catch pivotable about a first axis toward and away from a catching position. In the catching position, a portion of the bolt catch is within a path of travel of the bolt. A follower transfer adapter is pivotable about a second axis. The follower transfer adapter includes an engagement portion that is configured to engage a follower of a magazine. Optionally, the follower transfer adapter includes an overhang lip that extends transversely to the longitudinal axis of the firearm and into a path of travel of the follower to define the engagement portion. The engagement portion is positioned between the second axis and the bolt catch along the longitudinal axis of the firearm. A linkage transfers rotational movement of the follower transfer adapter to rotation of the bolt catch.