Today’s fifty-cal door gunners now use the M3 .50 caliber, a lighter weight version of the ‘old-but-gold’ M2HB (HB for Heavy Barrel), but in the door gunner configuration it’s officially called GAU-21 (GAU stands for Gun Aircraft Unit).

Apparently the French were the first to mount .50 caliber machine guns, on U.S. made H-34 Choctaw helicopters, during the eight years Algerian War.  The French H-34 ‘Pirate’ has M2HB .50-cals in the small windows on either side of the aircraft.  The gun in the open doorway is a 20mm.

This is a French experimental externally mounted .50 -cal gun turret pod, mounted on the side of an H-34.

The U.S. use of ‘Ma-Deuces’ as helicopter door guns began during the Viet Nam affair.  Besides the forward facing guns and rockets, this U.S. Army (USA) H-34 Choctaw has a door mounted lightweight .50-cal, as denoted by the type of barrel used.

Notice the unique handle/trigger on this H-34 door mount fifty.  I’m not sure if it doubles as the charging handle, or is just blocking the view of the charging handle, or the gun has the charging handle on the left side?

U.S. Marine Corps (USMC) CH-46s armed with .50-cals, location Arizona Territory south of Da Nang, date not given.

The CH-46 could carry up to three ‘fifties’, one on the starboard side, two on the port side.  This one is armed with the M2HB.

UH-1D ‘Nighthawk’ Huey. For night ops, the USA tried mounting fifties to Huey’s with improvised spotlights made from C-130 landing lights.

This Nighthawk Huey has the standard heavy M2HB ‘ground mount’ gun.

One of three ACH-47A gunships lost in Viet Nam.  Two were lost due to freak accidents, ‘Birth Control’ was shot down and then blown up on the ground by Vietnamese mortars. The ACH-47As had as many as six light weight .50-cals in door, ramp and window positions.  Only four ACH-47As were made, the surviving Chinook gunship is at the U.S. Army Aviation Museum. (see also MH-47 Special Ops Chinook, Pocatello Airport)

Since Viet Nam, attempts were made using lighter weight, faster firing .50-cals, their designations are GAU-15, GAU-16 or GAU-18.  The light weight of the guns were problematic, the guns didn’t last long.  The M3 .50-cal GAU-21 was developed and is slowly replacing the older systems. The GAU-21 M3 is claimed to have a rate of fire of 1-thousand-1-hundred per minute, and a 10-thousand round barrel life.

‘Spud Smoke 21’; HH-60G crews, on Gowen Field in Idaho, arm-up for .50 caliber door gunning over the Orchard Combat Training Center (OCTC, formerly Orchard Training Area), 22MAR2021.

This mustachioed Pave Hawk is home-based on Nellis Air Force Base in Nevada, but flew up to Idaho to let off some 12.7×99-mm steam.

Spud Smoke 21 took place between March 8th and 28th, 2021.  It included active duty units from the U.S. Air Force (USAF) and U.S. Army (USA), 11 units in total.

Video, by Senior Airman Blake Gonzales, showing HH-60G Pave Hawk crews uploading their GAUs and heading out over the Idaho Steppes (Orchard Combat Training Center):

More Idaho shoot ’em up video, by Senior Airman Blake Gonzales, 17MAR2021:

If you’re trying to build a helicopter model with a GAU door-gun system you’ll need photos of the specific system you’re modeling because they can differ greatly from between each service of the U.S. military, and between the type of aircraft using it.

GAU-21 equipped MH-60R Sea Hawk onboard USS Antietam (CG 54), somewhere in the South China Sea, June 2019.

Notice the handle/trigger system on the USAF CV-22 Osprey .50-cal tail gun, somewhere over merry ole England, September 2017.

The handle/trigger system is very different than what’s seen on USAF HH-60G Pave Hawks.

July 2017, Kadena Air Base, Japan, USAF personnel tear-down a GAU-18.

When you check out the photos, also notice slight differences in muzzle brakes.

U.S. Navy (USN) .50-cal gunner, positioned on the rear ramp of a MH-53E Sea Dragon helicopter.

Filling the Persian Gulf with 12.7mm ‘lead’, 20APR2017.  Take that you terrorist waters!

Compare this USN/USMC .50-cal handle-trigger system to the types used by USAF crews.

Video by Lance Corporal Christopher D. Thompson, U.S. Marine Corps GAU-21 live-fire training on the Chocolate Mountain Gunnery Refinement Range, California, 01APR2016:

June 2015, tail gunner position on German CH-53GS, which was visiting Davis-Monthan Air Force Base for the Angel Thunder wargame.

It appears the Germans use a handle/trigger system that’s similar to the U.S. Marines.

USMC video, by Lance Corporal Logan Snyder, HMM-774 conducts one last .50-cal gun-run with its retiring CH-46 ‘Phrogs’, 17APR2015:

USMC video by Lance Corporal Jordan Walker, CH-53E Super Stallion making .50-cal gun-runs during Weapons and Tactics Instructor (WTI) Course near Yuma, Arizona, October 2014:

USMC video by Lance Corporal Jordan Walker, showing a MV-22B Osprey tail gunner using the old GAU-16 system, near Yuma, Arizona, 2014:

Here’s a look at the USN/USMC gun mount, sans gun, in a UH-1Y out of Yuma Marine Corps Air Station, 2018.

USMC video by Corporal Rashaun X. James, a CH-53D crew chief loads her window mounted .50-cal for an upcoming mission over Afghanistan, Spring 2011:

A GAU-16 aims out the side window of a CH-53D somewhere over Afghanistan, December 2010.

USMC video of the last days of UH-1N Iroquois gunship operations in Afghanistan, 2009:

Here’s a very simple .50-cal window mount (similar to what was used on the Viet Nam ACH-47A) in a CH-46 Sea Knight, over the Jazirah Desert, Iraq, September 2008.

 

USMC UH-1Y Venom helicopters are usually armed with one GAU-21 and one GAU-17 ‘minigun’.  A UH-1Y somewhere near Yuma, Arizona, December 2007.

Watch out Yuma, Arizona, this CH-53 Super Stallion ‘tail gunner’ could be gunning for you!  December 2007.

Weapon I-D: WYOMING AIR MILITIA 50-CAL LIVE FIRE!

Weapon I-D: MARK 82

Vehicle I-D: IRAQI HUEY