A bolt hold open mechanism assembly is disclosed. The bolt hold open mechanism assembly contains a connector rod, a follower lever associated with the connector rod, a bolt stop associated with the connector rod, and a lifter lever comprising at least one protrusion configured to interact with a magazine follower.

An intrinsically safe firearm may include a handle and a frame connected by a pivot pin. One or more latches of the firearm can temporarily fix the firearm in a stowed orientation or a deployed orientation. In the deployed orientation, a magazine of the firearm can be removed from the handle; a slide of the firearm can be removed from the frame; a magazine safety allows a firing pin to strike a primer of a round in the firearm; and a trigger of the firearm is accessible to discharge the round in the firearm. In the stowed orientation, the magazine is not removable from the handle; the slide is not removable from the frame; the magazine safety prevents the firing pin from striking the primer; and the trigger of the firearm is not accessible.

A firearm receiver assembly includes a receiver body, a threaded mount at a rear portion of the receiver body, a magazine release assembly including a magazine release portion on at least one side of the receiver body, a bolt release assembly including a bolt release central portion and a bolt release portion on at least one side of the receiver body, and a safety selector assembly including a safety portion on at least one side of the receiver body. The bolt release central portion translates vertically within a cavity of the receiver body.

Provided is a last round bolt hold-open mechanism for a firearm with a removable ammunition magazine and a longitudinally reciprocating bolt that automatically releases the bolt when a loaded ammunition magazine is inserted. The mechanism includes a frame mountable to a firearm receiver and having a pair of mounting flanges. A catch member is pivotally mounted on a pivot axle oriented transverse to the longitudinal reciprocation of the bolt and carried by the mounting flanges. The catch member has a rearward portion that moves between bolt blocking and bolt release positions and is spring biased toward the bolt blocking position. A forwardly extending finger is configured to be lifted by the presence of at least one ammunition cartridge in the magazine and, when lifted, causes the catch member to pivot to the bolt release position.

Provided is a last round bolt hold-open mechanism for a firearm with a removable ammunition magazine and a longitudinally reciprocating bolt that automatically releases the bolt when a loaded ammunition magazine is inserted. The mechanism includes a frame mountable to a firearm receiver and having a pair of mounting flanges. A catch member is pivotally mounted on a pivot axle oriented transverse to the longitudinal reciprocation of the bolt and carried by the mounting flanges. The catch member has a rearward portion that moves between bolt blocking and bolt release positions and is spring biased toward the bolt blocking position. A forwardly extending finger is configured to be lifted by the presence of at least one ammunition cartridge in the magazine and, when lifted, causes the catch member to pivot to the bolt release position.

An auto-loading firearm having a system for switching between live fire and training modes via a selector switch mounted either on the firearm or on a specially designed training attachment. An action arm is selectively movable in response to movement of the selector switch between a live fire position, in which the firearm is free to operate as normal, and a training mode position where the action arm interrupts operation of the hammer and prevents the firearm from discharging while allowing the trigger and, if present, trigger spring to continue operating.

A magazine safety for a semiautomatic firearm uses two levers connected via a floating pin. The first lever is pivotable into and out of the magazine well. The second lever is spring biased to position a spur extending therefrom into the path of a trigger bar. An end of the second lever is connected to the first lever via the floating pin. In the absence of the magazine from the magazine well the first lever will rotate into the magazine well, thereby permitting the second lever to rotate and position the spur in the path of the trigger bar to prevent discharge of the firearm.

A magazine safety for a semiautomatic firearm uses two levers connected via a floating pin. The first lever is pivotable into and out of the magazine well. The second lever is spring biased to position a spur extending therefrom into the path of a trigger bar. An end of the second lever is connected to the first lever via the floating pin. In the absence of the magazine from the magazine well the first lever will rotate into the magazine well, thereby permitting the second lever to rotate and position the spur in the path of the trigger bar to prevent discharge of the firearm.

A last round hold open (LRHO) apparatus comprising a first lever having a first end and a second end; a second lever having a first end and a second end, the first end of the second lever in contact with the second end of the first lever; a bolt catch in contact with the second end of the second lever, and with a bolt carrier; and a follower in contact with the first end of the first lever, such that when the follower pushes up on the first end of the first lever, the second end of the first lever pushes down on the first end of the second lever, and the second end of the second lever pushes up on the bolt catch, resulting in activation of the bolt catch and opening the bolt carrier to alert an operator of the firearm that the firearm is out of ammunition.

A last round hold open (LRHO) apparatus comprising a first lever having a first end and a second end; a second lever having a first end and a second end, the first end of the second lever in contact with the second end of the first lever; a bolt catch in contact with the second end of the second lever, and with a bolt carrier; and a follower in contact with the first end of the first lever, such that when the follower pushes up on the first end of the first lever, the second end of the first lever pushes down on the first end of the second lever, and the second end of the second lever pushes up on the bolt catch, resulting in activation of the bolt catch and opening the bolt carrier to alert an operator of the firearm that the firearm is out of ammunition.