My stepfather was a co-pilot of one in N Africa during WWII. The only GV kill they got was by knocking the track off a tank with a near miss. He said that hitting anything smaller than a ship was very difficult but not impossible.
He also said that the recoil was significant and that it felt like the plane would stop in mid air.
That said I think that, if introduced to AH it would be a real GV killer since us virtual flyiers have much, much more practice at shooting maneuvering objects than they had.