Browning M3M
FN Herstal · Machine Gun · In Production · 2004
Also known as: FN M3M, GAU-21, M3M .50 cal
Overview
The Browning M3M is a .50 BMG (12.7x99mm NATO) belt-fed heavy machine gun developed by FN Herstal as an evolution of the M3 aircraft variant of the legendary Browning M2. Designed primarily for rotary-wing aircraft as a door- or pintle-mounted defensive weapon, it uses a short-recoil, open-bolt action and a dual recoil buffer system to deliver a high cyclic rate of fire of up to 1,100 rounds per minute while reducing felt recoil and barrel wear. Adopted by the U.S. Navy and Marine Corps in 2004 under the designation GAU-21, it equips platforms such as the H-60, CH-53, UH-1, and MV-22, providing suppressive fire out to roughly 1,850 meters.
Specifications
| Weight (empty) | 35800 g (1262.8 oz) |
| Overall Length | 1520 mm (59.84") |
| Barrel Length | 914 mm (35.98") |
| Action Type | Short Recoil |
| Firing Mechanism | Open Bolt |
| Magazine Capacity | 600 rounds |
| Magazine Type | Belt |
| Muzzle Velocity | 880 m/s (2887 fps) |
| Muzzle Energy | 17010 J (12546 ft·lbf) |
| Effective Range | 1850 m (2023 yd) |
| Maximum Range | 6500 m (7108 yd) |
| Rate of Fire | 1100 rpm |
| Barrel Rifling | Right Hand |
| Number of Grooves | 8 |
| Frame Material | Steel |
| Barrel Material | Steel |
| Finish | Phosphate |
Calibers
- .50 BMG · primary · 12.7x99mm NATO — also known as 12.7x99mm, .50 Browning Machine Gun, 12.7mm NATO
Features
- Firing modes: Full Automatic
- Feed systems: Disintegrating Link Belt
- Safety mechanisms: Manual Safety
- Features: Open Bolt Operation, Dual Recoil Buffer, Quick Change Barrel, Soft Mount Compatible, Disintegrating Link Belt Feed
Service history
Operators
- United States Navy · adopted 2004 · as GAU-21
- United States Marine Corps · adopted 2004 · as GAU-21
Conflicts
- War in Afghanistan (2001-2021)
- Iraq War (2003-2011)
Production
Production years: 2004-present
Initial U.S. contract awarded January 2004 for 136 guns plus 24 spares; later orders included 519 GAU-21 machine guns.
Origin
Country of origin: Belgium
Designer: FN Herstal
Notes
Designated GAU-21 by the U.S. military when fitted to aircraft soft mounts. Features a quick-change barrel and disintegrating-link belt feed compatible with 100-, 300-, and 600-round ammunition containers.
Background
The M3M traces its lineage directly to John Moses Browning's M2 of the 1920s; FN Herstal modernized the aircraft-rate M3 variant into a rotary-wing defensive weapon, which the U.S. Navy adopted in 2004 as the GAU-21.