Marine Sgt. fires a GAU-17 "Vulcan" minigun at a fast inshore attack craft during a live-fire exercise on board.
GAU-21 / A .50 cal Machine Gun
The M3M flexible machine gun has been adopted by USN under the designation GAU-21/A for use on helicopters. The GAU-21/A is also being used by the United States Marine Corps to upgrade from the XM218 .50 cal. machine gun for the CH-53E.