automatic carbine

The M4 Carbine is a 5.56×45mm NATO, air-cooled, gas-operated, direct impingement, magazine-fed, select fire carbine. It has a 14.5 in (370 mm) barrel and a telescoping stock. It is essentially a lighter and shorter variant of the M16A2 assault rifle.
The M4 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 (USMC) combat units as the primary infantry weapon and service rifle. The M4 has been adopted by over 60 countries worldwide, and has been described as "one of the defining firearms of the 21st century".Since its adoption in 1994, the M4 has undergone over 90 modifications to improve the weapon's ergonomics and modularity, including the M4A1, which strengthened the barrel and removed the burst-fire option, and the SOPMOD, an accessory kit containing optical attachments and the underbarrel M203 grenade launcher.

View More On Wikipedia.org