Abstract: A firearm assembly includes a lower receiver having a rear lug housing and a front lug housing, an upper receiver having a central cavity and a rear take down lug, and a barrel secured within the central cavity of the upper receiver. A handguard rail is configured to receive the upper receiver and the barrel therein, and the handguard rail includes a front take down lug. A rear take down pin is disposed through the rear take down lug and the rear lug housing, and a front take down pin is disposed through the front take down lug and the front lug housing. The handguard rail is configured to pivot about the front take down pin when the rear take down pin is removed.

Abstract: A dual use shell casing for use in a 9 mm firearm and for use in 9 mm magazines includes an upper portion, a lower portion, an internal cavity extending between the upper portion and the lower portion, the internal cavity configured to receive gunpowder and a projectile, and a tapered shoulder disposed at the upper portion and transitioning into a reduced diameter neck portion, the reduced diameter neck portion having an inner diameter equal to 0.313 inches. The tapered shoulder is configured to abut an internal shoulder within a barrel chamber of the 9 mm firearm.

Abstract: A combined firearm receiver and rail includes a handguard rail and a receiver housing disposed within the handguard rail. The handguard rail includes one of a takedown lug clearance slot, a handguard magazine port, a handguard continuous rail, a handguard ejection port, an attachment location, accessory attachment points, a handguard charging handle latch retaining slot, a charging handle housing, a charging handle guideway, a bolt catch clearance slot, a barrel cavity, a receiver cavity, an exhaust port, and a handguard section. In one variation, the handguard section does not come into physical contact with a barrel or a barrel nut of the firearm.

Abstract: A combined firearm receiver and rail includes a handguard rail and a receiver housing disposed within the handguard rail. The handguard rail includes one of a takedown lug clearance slot, a handguard magazine port, a handguard continuous rail, a handguard ejection port, an attachment location, accessory attachment points, a handguard charging handle latch retaining slot, a charging handle housing, a charging handle guideway, a bolt catch clearance slot, a barrel cavity, a receiver cavity, an exhaust port, and a handguard section. In one variation, the handguard section does not come into physical contact with a barrel or a barrel nut of the firearm.