The internal 25mm cannon fires up to 50 rounds per second.
On Aug. 13, pilots from the 388th Fighter Wing’s 4th Fighter Squadron fired the F-35A’s 25 mm internal cannon in a strafing run on two sets of ground targets on the Utah Test and Training range. It was the first use of the F-35A’s GAU-22/A in operational training.
The shots that the U.S. Air Force has released after the training event are particularly interesting, as they show the internal gun at work: the GAU-22 gun is hidden behind closed doors to reduce the plane’s RCS (radar cross section) and keep it stealth, until the trigger is engaged.
The F-35’s GAU-22/A is based on the proven GAU-12/A 25mm cannon, used by the AV-8B Harrier, the LAV-AD amphibious vehicle and AC-130U Gunship, but has one less barrel than its predecessor. This means it’s lighter and can fit into the F-35A’s left shoulder above the air intake. The gun can fire at about 3,300 rounds per minute: considered the A model can hold 181 rounds only, this equals to a continuous 4 seconds burst or, more realistic, multiple short ones.
The F-35 GAU-22/A gun has been among the most controversial topics in the past years: not only did some criticise the fact that the Joint Strike Fighter’s gun can only hold 181 25mm rounds, fewer than the A-10 Thunderbolt’s GAU-8/A Avenger, that can hold some 1,174 30mm rounds, but also the accuracy has been disputed because of “a long and to-the-right aiming bias” reported in fiscal year 2017 report by the Office of the Director, Operational Test and Evaluation (DOT&E). It’s not clear whether the accuracy issues have been completely fixed or not.
Noteworthy, the training sortie was flown with the aircraft carrying two external pylons (with a single inert AIM-9X Sidewinder air-to-air missile).
While the F-35A will be equipped with an embedded GAU-22/A gun, the B (STOVL – Short Take Off Vertical Landing) and C (CV – Carrier Variant) variants carry it inside an external pod capable to hold 220 rounds.
According to the 388th FW’s website “Loading and firing the cannon was one of the few capabilities Airmen in the 388th and 419th FWs had yet to demonstrate. The F-35A’s internal cannon allows the aircraft to maintain stealth against air adversaries as well as fire more accurately on ground targets, giving pilots more tactical flexibility.”
Image credit: Air Force photo by Todd Cromar