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.
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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
