a magazine including an elongated containing body and a closure member defining a cavity adapted to receive and hold cartridges, the closure member being longitudinally slidably mounted on the containing body for longitudinal sliding movement between an extended position that opens a side of the containing body to allow cartridges to be loaded into the containing body and a closed position where the cartridges are retained within the containing body, the closure member having opposing sidewalls and a transverse wall defining a C-shaped cross section forming an integral handle surface that can be grasp to slide the closure member longitudinally to the extended position for loading cartridges into the containing body and to the closed position for retaining the cartridges therein, wherein the closure member is longitudinally curved, and wherein the sidewalls and transverse wall define at least about 10% of the cavity and further define a three dimensional surface for receiving a user's hand while the user grips the sidewalls with their thumb and fingers to facilitate the longitudinal sliding movement, and further wherein the containing body and the closure member include formed overlapping flanges that form a track and further that strength the containing body and the closure member and further that sealingly engage each other and do not include uncovered openings when in the closed position upon attachment to a firearm such that the magazine is resistant to dust intrusion when attached to the firearm.