M4 Carbine

The M4 carbine is a shorter and lighter variant of the M16A2 assault rifle. The M4 is a 5.56×45mm NATO, air-cooled, direct impingement gas-operated, magazine-fed carbine. It has a 14.5 in (370 mm) barrel and a telescoping stock.

The M4 carbine is extensively used by the United States Armed Forces and is largely replacing the M16 rifle in United States Army and United States Marine Corps combat units as the primary infantry weapon and service rifle.

The M4 is also capable of mounting the M203 grenade launcher. The distinctive step in its barrel is for mounting the M203 with the standard hardware. The M4 is capable of firing in semi-automatic and three-round burst modes.