Abstract: A cartridge magazine for a gun includes a machined magazine body having an open edge and open bottom and a separate edge plate slidably attachable to the magazine body to cover the open edge and a floor plate slidably attachable to the magazine body to cover the open bottom and to lock the edge plate in place. A cylindrical coil spring is held in position in the magazine body and has a cartridge follower on one end and a spring base plate on the other which base plate has a detent member for locking to the floor plate for holding the cartridge magazine together. The process selects the components and assembles them by positioning the spring in the spring supporting portion of the magazine body, sliding the edge plate into position and then sliding the floor plate into position to lock the edge plate, floor plate and follower spring together.