The XM301 Cannon is an externally powered, three-barrel 20 mm Gatling gun made by General Dynamics for the U.S. Army .  Developed for use with the RAH-66 Comanche stealth helicopter , it is the world's lightest 20 mm Gatling cannon.  The XM301 was designed to be a versatile and accurate lightweight cannon that could serve both an air-to-air and air-to-ground role.  Development and manufacture of the XM301 was cancelled in 2004 along with its parent RAH-66 program. 
The M61A1 and M61A2 produced by General Dynamics Ordnance and Tactical Systems are externally powered six-barrel 20mm Gatling gun systems that offer lightweight, highly lethal combat support for a variety of air, land and sea platforms.
The GAU-19/A is designed for a linkless feed, but can be fed from a standard M9 linked belt if a delinker feeder is used. The rate of fire is selectable to be either 1,000 or 2,000 rounds per minute. The Humvee armament kit version fires at 1,300 rounds per minute. The average recoil force when firing is 2.2 kN . In January 2012, General Dynamics announced they would be delivering a new version designated GAU-19/B . It provides the same firepower in a lighter platform, weighing 48 kg . 
Boeing / Sikorsky RAH-66 Comanche Type: Reconnaissance / Light Attack Helicopter National Origin: United States [ VIEW ] Manufacturer(s): Boeing Helicopters / Sikorsky Aircraft Corporation - USA [ VIEW ] Introduction: 2004 Production Total: 2 [ VIEW ]