The C-MAG is a twin-drum, high capacity, ammunition magazine system for rifles, light support weapons, firing port and other specialized weapons in 5.56mm calibre.

During loading the live cartridges are pressed into the feed clip. The column of spacer rounds and live cartridges are, as loading progresses, pushed into the drums. The cartridge column splits at the point where the feed clip joins the storage housing; this allows for the concurrent division of the stored ammunition on each side of the magazine. Further into each drum the cartridges divide into two concentric rows for storage. Loading stops when the maximum number of cartridges has been inserted.

The C-MAG loads and functions just like standard magazines and can be reused repeatedly. The cartridges feed alternately into each drum. Loading can be done by hand or with a loading device. The springs are tensioned during the loading operation, without the need for supplementary operations. The magazine does not need to be empty to be loaded and remains completely operational at all times.

The C-MAG can be used on almost any modern 5.56mm combat rifle or other weapon without modification to the weapon. The C-MAG is currently in production for M16/M4, M249 SAW/FN MINIMI, STEYR AUG, HK G36 and HK 33 weapons. Other models are available as prototypes. With the correct feed clip installed the C-MAG snaps into the standard magazine housing of the weapon in the standard manner and is released by the weapon's magazine catch in the usual way.

The key feature of the C-MAG is the formation of double rows of cartridges in each of the drums. Spacer-round-strings occupy the feed clip when the magazine is empty. The number required is depending on the length and style of the feed clip, which is specific to an individual weapon system. Pusher arm assemblies transfer the spring energy to the cartridges while being loaded and unloaded and serve to maintain the proper orientation of the spacer rounds. The upper half of the top spacer round is tapered so that the weapon bolt will pass over it (when the last round has been fired) and stop in the closed position.

 Use only graphite (dry) for lubrication, no oils or grease. A tube of graphite is located in every pouch. Recommended use of graphite as lubricant: Regularly add graphite to top of spacer rounds prior to loading. The loading process distributes the graphite through the drum housing.

The C-MAG is a twin-drum high-capacity ammunition magazine for sub-machine guns and other specialized weapons in 9 x 19-mm Parabellum calibre. Covered by US and other patents, the main components are constructed of high-impact plastic. A full description of the operating principles can be found in the 5.56mm entry above.

The C-MAG can be used on most modern 9-mm sub machine guns without modification. The C-MAG 9mm is currently available for the Heckler & Koch MP5 and the COLT AR15 9MM sub-machine guns. Other models may be adapted by substituting a feed clip designed for the particular weapon.