An apparatus includes a bolt carrier assembly and a bolt assembly. The bolt assembly includes a bolt body member, the bolt body member having a proximal end portion and a distal end portion, and defining a longitudinal axis extending from the proximal end to the distal end. The bolt assembly includes a guide member attached to proximal end portion and the guide member is parallel to the longitudinal axis. The bolt assembly further includes a bolt chamber interface attached to a distal end portion, the bolt chamber interface nests within an interior wall of a firearm chamber, and the bolt chamber interface limits rotational and axial movement of the bolt assembly relative to the firearm chamber. The bolt assembly includes a bolt nipple connector for mating with a nipple assembly of a magazine assembly.