An ammunition magazine configured to bottom-feed a plurality of ammunition rounds into an upper receiver of a firearm, the ammunition magazine comprising: a magazine housing including: an ammunition reservoir, a proximal guide channel disposed proximal to the ammunition reservoir, a distal guide channel disposed parallel to the ammunition reservoir, and lips disposed on a top surface of the magazine housing, the lips configured to align the ammunition reservoir with a feed ramp of the upper receiver; a spring within the magazine housing; a floor plate retainer disposed at a bottom end of the spring; a floor plate disposed at a bottom end of the magazine housing and reversibly mated with the floor plate retainer; and a magazine follower disposed at a top end of the spring, the magazine follower including: a follower protrusion disposed on a superior portion of the magazine follower, and a bolt catch piston disposed at a proximal end of a body portion of the magazine follower and configured to slide along the proximal guide channel of the magazine housing; characterized by a distal guide piston disposed at a distal end of the body portion of the magazine follower, the distal guide piston having a size and shape complementary to the distal guide channel of the magazine housing and configured to slide along the distal guide channel; wherein the magazine housing further comprises a storage compartment disposed distal to the distal guide channel. a magazine housing including: an ammunition reservoir, a proximal guide channel disposed proximal to the ammunition reservoir, a distal guide channel disposed parallel to the ammunition reservoir, and lips disposed on a top surface of the magazine housing, the lips configured to align the ammunition reservoir with a feed ramp of the upper receiver; an ammunition reservoir, a proximal guide channel disposed proximal to the ammunition reservoir, a distal guide channel disposed parallel to the ammunition reservoir, and lips disposed on a top surface of the magazine housing, the lips configured to align the ammunition reservoir with a feed ramp of the upper receiver; a spring within the magazine housing; a floor plate retainer disposed at a bottom end of the spring; a floor plate disposed at a bottom end of the magazine housing and reversibly mated with the floor plate retainer; and a magazine follower disposed at a top end of the spring, the magazine follower including: a follower protrusion disposed on a superior portion of the magazine follower, and a bolt catch piston disposed at a proximal end of a body portion of the magazine follower and configured to slide along the proximal guide channel of the magazine housing; characterized by a distal guide piston disposed at a distal end of the body portion of the magazine follower, the distal guide piston having a size and shape complementary to the distal guide channel of the magazine housing and configured to slide along the distal guide channel; wherein the magazine housing further comprises a storage compartment disposed distal to the distal guide channel. a follower protrusion disposed on a superior portion of the magazine follower, and a bolt catch piston disposed at a proximal end of a body portion of the magazine follower and configured to slide along the proximal guide channel of the magazine housing; characterized by a distal guide piston disposed at a distal end of the body portion of the magazine follower, the distal guide piston having a size and shape complementary to the distal guide channel of the magazine housing and configured to slide along the distal guide channel; wherein the magazine housing further comprises a storage compartment disposed distal to the distal guide channel.