The M4 Carbine is the U.S. Army's standard issue service rifle, a select-fire 14.5-inch carbine derived from the CAR-15 series. Commercial semi-auto versions designated M4 Carbine are available to civilians with permanently pinned muzzle devices to achieve legal barrel length. Type: Semi-Auto Rifle Action: Gas-Operated Caliber: 5.56x45mm Capacity: 30 Year introduced: 1994, USA Weight: 6.36 oz Overall length: 33" Status: Active Military use: Yes Intended use: Military, Patrol