GAU-21 to Equip More Marine Choppers

Corps helos to get new machine guns

Eventually, all Marine and Navy assault support rotary wing aircraft will be equipped with the M3M FN Herstal GAU-21 .50-caliber machine gun.

For the Corps, it is now in use on the ramps of the CH-53E Super Stallion, a heavy-lift helicopter, as well as the ramp and windows of the CH-53D, the Super Stallion’s predecessor. But officials at Naval Air Systems Command also are working to integrate a door-mounted GAU-21 onto the CH-53E and the UH-1Y Venom, the Corps’ newest light-utility helicopter.

GAU-21 Ramp Gun

Cpl. Thomas D. Martinez aims at a makeshift target on the desert outside of Al Asad, Iraq, during a test fire with the GAU-21 ramp-mounted weapon system.

Back in 2006 MO noted the first of these joining the Marines:

“The 7.62 round used in the M-240G is too small,” said Harquail, a 26-year-old native of Sea Side, New Brunswick, Canada. “The rotor wash from the aircraft affects the rounds’ trajectory. The .50-caliber is a heavier round. You need a heavy round with a higher volume.”

The rate of fire is over 1,000 rounds per minute compared to about 700 for the M2-based GAU-16.

In addition to putting more rounds down range, the new gun, with a maximum effective range of 21,000 feet, is more accurate due to a new recoil compensation system that also reduces the wear and tear on helicopters. When you fire the GAU-16, the shock rattles all the way down to the airframe, which causes a strong vibration and makes accuracy difficult, said Col. Harry Hewson, the program manager for Marine light/attack helicopters. The new system absorbs that shock in the mount, he said. NavAir also is working to install laser sights for night use.


  1. The “new” GAU-21 is actually the old M-3 aircraft machine gun resurrected combined with a long need shock absorbing mount. That said, why did it take so long? Apparently most have forgotten that the original Browning design was more like a socket set than a single tool and could be readily reconfigured to serve needs. Kudos to our friends at FN Manufacturing in South Carolina.

  2. No, don’t forget the old M85, which replaced the M2 only to be itself replaced by the M2.

    Interesting that the Army is using the .50 3-barrelled GAU-19 for similar purposes.

  3. I had heard from several amtrackers and some of the Marine M-60A1 crewmen that that M85 gun was somewhat of a disappointment. Those who had used both said the M2 gun was much better in its job.

  4. “Somewhat of a disappointment” is kind. “Unreliable piece of crap” was a more common characterization. I’ve heard from lots of dinosaur tankers about having to kick-start their .50s in the M60 cupola.

    M85 is out of the Army inventory; I don’t know if the USMC still uses it on the AAV-7.

    M85 and M2 use incompatible ammunition (different links with different strip directions) … it’s interesting to point our that GD’s XM312 .50 was designed to use the M85 configuration ammunition. That configuration was changed to the M2 when XM312 was resurrected as XM806, and it only took about four years of harping about the potential of re-introducing incompatible ammunition to the logistics system.

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