An interesting weapon accessory adopted by many combat troops (especially Special Forces and commandoes) is the hundred round M-16 magazine. The C-Mag is sold only to military and police buyers and is built to military durability specifications. Empty, it weighs 2.2 pounds, loaded, it weighs about six pounds. So an M-16 with a C-Mag weighs nearly 14 pounds. The purpose of the C-Mag is not to turn every M-16 or M-4 into a machine-gun, but to have more ammunition available when the action gets very hot. Well trained troops will fire single shots most of the time. But when you do need automatic fire, you need it. Overheating is not a problem, except for the short barreled M-4 version of the M-16. You can use an M-4 to fire off a C-Mag on full auto in under ten seconds. This will make that short barrel very hot, and it is not recommended that you try and fire another C-Mag right away, or the M-4 will likely jam. The light-machine-gun version of the M-16, the M-249 (actually a different design that fires the same ammo), weighs 12.6 pounds, but can fire belts of ammo, which slows the rate of fire down from 900 rounds a minute to about 750. That, plus the heavier barrel, allows the M-249 to fire over a thousand rounds in a few minutes without overheating. The C-Mag has been around for 15 years and has never been officially adopted by the American military, but many units, especially Special Forces, buy them out of the special funds they have for such equipment. Other army and marine units do the same.