Colt Automatic Rifle or Colt Light Machine Gun is a 5.56 mm NATO, open-bolt, full-automatic-only firearm developed by Colt Defense. It is based on the M16A2/A4, and its handguard has a distinctive squared-off shape, vertical grip, carrying handle and integrated bipod.It is one of many Squad automatic weapon-type firearms that have been developed from the AR-15. Others include the Colt CMG-1 machine gun and CAR-15 Heavy Assault Rifle.