The Colt M4 is another member of the M16 family. It is technically called a carbine, having a shortened barrel (15 inches versus 20 inches) than the standard M16. The M4 is slightly larger than the Colt Commando, but shares many of the same features, such as a collapsible stock and full-auto fire. The M4 is often equipped with the Rail Interface System (RIS) from Knights Arms Corporation, which allows the quick attachment of various accessories, such as sights, flashlights, and a shortened version of the M203 40 mm grenade launcher. The U.S. military has taken advantage of this ability and issues SOPMOD kits to its unconventional forces (Special Forces, SEALs, etc.) The M4 is chambered in 5.56 mm NATO and accepts standard M16 magazines.
