Abstract: An improved magazine construction for gas powered firearms or other single object dispensing unit is disclosed. The expanding gasses from the breech or barrel of the gun are directed into the bottom portion of the magazine where they are introduced into a chamber having varying capacity. The upper portion of the chamber is movable and forms the follower, which includes integral biasing means thereon to provide additional impetus for urging the cartridges upwards into the receiver. The body of the follower also includes spring loaded cammed pins that engage cooperating pin holes in the inner magazine wall to provide a ratcheting action as the follower advances. These pinholes also serve as a excess pressure relief, allowing the gasses to escape through a blow by rail located between the inner and outer magazine walls.