M4 Carbine

The M4 carbine is an American 5.56x45mm shortened, lighter variant of the M16 rifle family, adopted by the United States military in 1994 and issued widely from the late 1990s onward as the standard individual weapon for much of the Army and Marine Corps, particularly for vehicle crews, support troops and units that valued its more compact size in close quarters. Retaining the direct impingement gas system and general layout of the M16, the M4 added a collapsible stock and a flat-top receiver rail allowing optical sights, laser aiming devices and other accessories to be mounted directly on the weapon, features that became standard as American forces gained extensive urban and close-quarters combat experience in Iraq and Afghanistan. Later variants added a heavier barrel profile and other reliability improvements developed from lessons of sustained combat use, and the M4 remains the primary individual weapon of United States ground forces into the present day.