Bolt hold open actuator for use with AR-15/M16 type firearms

An actuator for establishing a bolt hold open condition in use with a firearm containing a reciprocating bolt within a receiver upon which said assembly is supported;

• said actuator further comprising:
• a body exhibiting a perimeter defined open interior and which is adapted to being seated upon an upper surface of a receiver in proximity to an exposable location of an inner chamber containing said bolt;
• and
• an actuator bolt catch supported relative to an end of said body and being shaped to be vertically upwardly displaceable relative to the body to establish a bolt hold open condition, said actuator bolt catch including a window and a tab, the tab extending in a direction over the receiver inner chamber and which is adapted to being engaged by a follower of an attachable magazine for establishing a last shot hold open condition;
• and
• an adjustment screw incorporated into a bottom end location of said body and, upon rotating, vertically displacing said actuator bolt catch in either of opposite linear directions to modify a contact location established with a forward edge location of the follower, as well as correspondingly varying a seating location of the catch within the window.

An apparatus for use with a firearm, the apparatus comprising:

• an actuator housing;
• and
• an actuator bolt catch,
• the actuator housing having a rectangular configuration with a first end and a second end connected by a pair of sides, the ends and sides of the actuator housing defining an open interior, the first end of the actuator housing defining slot sized to receive at least a portion of said actuator bolt catch, and the actuator housing being sized so the actuator housing is mountable to a firearm proximate an interior aperture of a magazine well and sized so that the open interior spans at least a portion of an interior aperture of a magazine well when said actuator is mounted to a firearm, and
• at least a portion of said actuator bolt catch being positioned in the slot of the actuator housing and said actuator bolt catch having at least a face orientated away from the open interior, the face including a recess, and the recess being sized to be engaged by a firearm bolt catch.

An apparatus comprising:

• a firearm, and
• an adapter assembly,
• the firearm including an upper receiver, a lower receiver, a reciprocating bolt, a firearm bolt catch, and a magazine, the lower receiver including a magazine well having an internal aperture and an external aperture, and the magazine being inserted into said magazine well through said external aperture, and
• the adapter assembly including an actuator housing and an actuator bolt catch, the actuator housing having a rectangular configuration with a first end and a second end connected by a pair of parallel sides, the ends and sides of the actuator housing defining an open interior for the actuator housing, with the actuator housing being positioned on the firearm so that the open interior spans at least a portion of the internal aperture of the magazine well, and at least a portion of the magazine being received in the open interior, the internal aperture and the first end of the actuator housing also defining a slot dimensioned to receive the actuator bolt catch, which is positioned in the slot and having a face orientated away from the open interior and including a recess, and the recess being engaged by the firearm bolt catch.