The Spitfire's guns are now correct. For all those years we had a Frakenstein Spitfire that never existed. The Spitfire F.Mk IX with a Merlin 61 was never equipped with an "e" wing so it never carried .50 cals.
Spitfire LF.Mk IXe's did, and they were powered by the Merlin 66.
The Spitfire Mk LF.XVIe we have in AH is identical to the Spitfire LF.Mk IXe, but powered by an American built version of the Merlin 66, the Merlin 266.