Abstract: A hybrid firearm receiver includes a receiver body having a first end, a second end opposite the first end, a substantially planar bottom surface extending from the first end to the second end and transitioning to two upwardly extending opposing sidewalls, and a top end, the receiver body extending along a longitudinal axis from the first end to the second end. The first end is integrally formed with the receiver body and includes a first outer face and a rail interface that facilitates receiving a clamping mount of a gunstock between side edges of the rail interface and the first outer face. The rail interface has a plurality of flats disposed along a first plane that is transverse and non-perpendicular to the axis. The top end, the two opposing sidewall, and the first end form trough extending transverse to the axis.

Abstract: A customizable firearm lower receiver includes a lower receiver body having a forward end and a rearward end, the forward end having a first lateral sidewall and an opposing second lateral sidewall, with a forward end wall between the first lateral sidewall and the second lateral sidewall. The opposing lateral sidewalls at least partially surround a magazine well. A mounting surface is configured on the lower receiver body along one of the forward end wall, first lateral sidewall, and second lateral sidewall. A custom face is removably attachable to the mounting surface.

Abstract: A hybrid firearm receiver includes a receiver body having a first end, a second end opposite the first end, a substantially planar bottom surface extending from the first end to the second end and transitioning to two upwardly extending opposing sidewalls, and a top end, the receiver body extending along a longitudinal axis from the first end to the second end. The first end is integrally formed with the receiver body and includes a circular first cavity and a smaller circular second cavity below the circular first cavity. The second end includes an aperture. The axis extends through a center of the circular first cavity and through the aperture and is below the top end. The circular first cavity may be configured to receive a portion of an AR-15 rifle stock assembly. The aperture may be configured to receive an AK pattern rifle barrel.