The FN® M3M (GAU-21) is a .50 caliber (12.7x99mm) single barrel rapid-fire machine gun suitable for rotary-wing aircraft applications providing defensive firepower ranging out to nearly 2000 meters. The FN M3M™ was designated by the U.S. Navy as the GAU-21 in 2004.

The M2 machine gun or Browning .50 caliber machine gun (informally, " Ma Deuce ") [13][14] is a heavy machine gun that was designed near the end of World War I by John Browning.

The M3M is a weapon system rather than just a machine gun. The system has three parts: The Machine Gun, the Medium Pintle Head (MPH) or "Soft Mount", and the Cradle, which is used to integrate the weapon into a particular aircraft or vehicle.

May 5, 2023 · The M3M can be fitted to Wildcat and Merlin helicopters and is adapted for aircraft use, featuring a firing mechanism that fires from the open bolt, internal recoil spring and a perforated barrel jacket.

Apr 15, 2011 · 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...

Sep 1, 2007 · Suitable for aircraft, naval and ground vehicle applications, the .50 caliber FN M3M combines high rate of fire with exceptional accuracy. The weapon is designated as the GAU-21 for Navy and Marine rotary-wing assault aircraft. Photo courtesy of FN Herstal, S.A.

ACME produces GAU-21 (M3M) machine gun simulators that give the full-force, full rate of recoil feel of the actual weapon in a full scale gun replica that can be mounted on any aircraft, watercraft or vehicle simulator.

FN Herstal takes advantage of the FN ® M3M airborne proven machine gun technology and offers the most powerful weapon system for land and sea applications combining lightweight and compactness.

Sep 1, 2001 · With its high rate of fire, soft recoil and levels of reliability, the M3M heavy machine gun is ideally suited for helicopters, for pedestal mounting on light ground vehicles and on light patrol vessels.

An evolution of the M3AN .50-caliber machine gun, it produces 1,100 rounds per minute cyclic rate of fire using an open-bolt operation and a dual recoil buffer system.