A last round hold open (LRHO) apparatus comprising a first lever having a first end and a second end, a mag stop component to which the first lever is pivotally affixed at the second end, a second lever disposed proximate the second end of the first lever, the second lever pivotally affixed to the mag stop, a bolt catch affixed to the mag stop and the second lever, and a magazine release extending from the first end of the first lever.

An apparatus and method for creating the apparatus that holds a bolt open after a last round is fired from a magazine is disclosed. A lower receiver may include at least two cavities. A transfer bar may be configured to fit into a first cavity of the at least two cavities. A hold down may be configured to fit into a second cavity of the at least two cavities. At least a portion of the hold down may be configured to overlap with at least a portion of the transfer bar to hold the transfer bar in place. The transfer bar, when a final round is fired from a magazine in the lower receiver, may be pushed up by a bump in the magazine to transfer upward movement to the transfer bar that catches a bolt and holds the bolt open until activation of a release button.

An apparatus and method for creating the apparatus that holds a bolt open after a last round is fired from a magazine is disclosed. A lower receiver may include at least two cavities. A transfer bar may be configured to fit into a first cavity of the at least two cavities. A hold down may be configured to fit into a second cavity of the at least two cavities. At least a portion of the hold down may be configured to overlap with at least a portion of the transfer bar to hold the transfer bar in place. The transfer bar, when a final round is fired from a magazine in the lower receiver, may be pushed up by a bump in the magazine to transfer upward movement to the transfer bar that catches a bolt and holds the bolt open until activation of a release button.

A replaceable slide notch system for a firearm that includes a replaceable slide notch component dimensioned to fit within a corresponding cavity of a slide. The replaceable slide notch component includes a slide lock notch surface that locks the slide when the firearm's ammunition is exhausted. A second replaceable slide notch component has a second slide lock notch surface that locks the slide at a further rearward position than that of the first slide notch component, thus providing greater chambering/operating force when the slide is released.

A replaceable slide notch system for a firearm that includes a replaceable slide notch component dimensioned to fit within a corresponding cavity of a slide. The replaceable slide notch component includes a slide lock notch surface that locks the slide when the firearm's ammunition is exhausted. A second replaceable slide notch component has a second slide lock notch surface that locks the slide at a further rearward position than that of the first slide notch component, thus providing greater chambering/operating force when the slide is released.

A last round hold open (LRHO) apparatus comprising a first lever having a first end and a second end, a mag stop component to which the first lever is pivotally affixed at the second end, a second lever disposed proximate the second end of the first lever, the second lever pivotally affixed to the mag stop, a bolt catch affixed to the mag stop and the second lever, and a magazine release extending from the first end of the first lever.

A firearm preferably permits a user to readily change ammunition type and associated magazine configuration at user discretion. Such a firearm may be optimally practiced as a pistol, rifle, or submachine gun but is not limited to a particular caliber size or configurations. A main receiver body of the firearm is preferably of a monolithic construction whereby the handguard and breech bolt carrying bore can be manufactured from a single piece of material such as, for example, an aluminum extrusion or polymer injection molded component. In at least one or more of these respects, the firearm is of an improved design to both simplify and speed manufacturing and assembly, while simultaneously reducing manufacturing costs normally associated with the firearm industry's usual state-of-the-art (e.g., prior art) methods.

A replaceable slide notch system for a firearm that includes a replaceable slide notch component dimensioned to fit within a corresponding cavity of a slide. The replaceable slide notch component includes a slide lock notch surface that locks the slide when the firearm's ammunition is exhausted. A second replaceable slide notch component has a second slide lock notch surface that locks the slide at a further rearward position than that of the first slide notch component, thus providing greater chambering/operating force when the slide is released.

A replaceable slide notch system for a firearm that includes a replaceable slide notch component dimensioned to fit within a corresponding cavity of a slide. The replaceable slide notch component includes a slide lock notch surface that locks the slide when the firearm's ammunition is exhausted. A second replaceable slide notch component has a second slide lock notch surface that locks the slide at a further rearward position than that of the first slide notch component, thus providing greater chambering/operating force when the slide is released.

An apparatus and method for creating the apparatus that holds a bolt open after a last round is fired from a magazine is disclosed. A lower receiver may include at least two cavities. A transfer bar may be configured to fit into a first cavity of the at least two cavities. A hold down may be configured to fit into a second cavity of the at least two cavities. At least a portion of the hold down may be configured to overlap with at least a portion of the transfer bar to hold the transfer bar in place. The transfer bar, when a final round is fired from a magazine in the lower receiver, may be pushed up by a bump in the magazine to transfer upward movement to the transfer bar that catches a bolt and holds the bolt open until activation of a release button.