I have a friend who was a FAA pilot during the war. I've just asked him if he has any memories to contribute. His first thought was he didn't have a clue, but he's now had a chance to think about it, he's offered the following. Initially it was down to weight, the .303 being an overall lighter system. He also recollects "There is also the obduracy of the politicians on cost.....", so things don't appear to have changed much.
