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.
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.