The US Navy will equip its assault support rotary wing aircraft with the M3M FN Herstal GAU-21 .50-calibre machine gun.

The navy and marine corps heavy-lift helicopter CH-53E Super Stallion CH-53D will be equipped with the new machine guns.

Officials at Naval Air Systems Command are also integrating a door-mounted GAU-21 onto the CH-53E and the UH-1Y Venom, the corps’s newest light-utility helicopter, according to

The GAU-21 can fire more than 1,000 rounds a minute and replaces the M2 Browning GAU-16/A machine gun, which can fire 700 rounds a minute.

Navy Captain Brian Corey said the GAU-21 offers double the rate of fire of its predecessor.

The new machine gun has a maximum effective range of 21,000ft and is more accurate due to a new recoil compensation system which also reduces the wear and tear on helicopters.

With the new machine guns the helicopter will provide additional firepower that will allow it to remain on station for longer and provide more close-air support to grunts.

The door-mounted GAU-21s are expected to enter operational testing by the end of the summer 2010 at Naval Air Weapons Station China Lake, California.

The accuracy and safety test of the new guns will be conducted by the Marine Air Test and Evaluation Squadron 9 at the Weapons and Tactics Instructor Course in Yuma, Arizona.

The machine guns, worth $60,000 each, including the mount system, will be fielded on both the CH-53E and the UH-1Y within a year.