The F-35A is the “normal” version: CTOL (Conventional Take-Off and Landing). It has an internal 25 mm gatlingkanon using boom and receptacle -lufttankning as a starting point.
This version will be used by the US Air Force, the Canadian, Norwegian and many other air forces, including the Air Force, in the event that Denmark chose the Joint Strike Fighter.
The GAU-22/A is a four-barrel version of the GAU-12/U designed for use on the F-35 Lightning II. The CTOL version of the aircraft will carry the gun internally, while the STOVL and naval versions use it in an external gun pod.
The GAU-22/A’s major difference is the use of four barrels, rather than the five barrels on the GAU-12/U.
The GAU-22/A is lighter, has a reduced rate of fire of 3,300 rounds per minute and an improved accuracy of 1.4 milliradians as compared to the GAU-12.
This system is undergoing intensive testing and qualification. The weapon is currently produced by General Dynamics Ordnance and Tactical Systems.
The Nammo 25 mm APEX projectile is being developed for the GAU-22/A