The gun, if/when installed, is an afterthought joke with only 180 rounds for CAS and cannot loiter. A-10s have 1174-1350 rounds for CAS
I don't think the gun is an afterthought, I think it's flat out fraud — it's there so that the F-35 can check "CAS" off on some checklist, and so that the Air Force can again push for retiring the A-10.
One of the things that I've noticed is how it's billed as a can do anything
airframe, despite that it doesn't do anything particularly well (when compared to special-purpose equivalent-tech airframes) and how billions and billions have to be poured into further R & D on actually making it work (the gun being a good example) as cited in this 2014 article… I think this is somewhat confirmed by the political stacking of the deck. (Link1, Link2)
At least the F-22 worked as advertised: Air Superiority.