The M2 Aircraft .50 guns in the gun positions and power turrets of the famed B17 Memphis Belle were AC Spark Plug manufactured guns. In the late 1990s I was part of a maintenance survey on what all the old bird needed for a full restoration; other A&Ps and A&P students from Tennessee Tech did the powerplant and airframe [the main spars were nearly corroded and cracked it two, and the bird would have gone nose-down on one end and tail-down at the other had both cracks continued all the way through. Happily, it was caught and fixed in time.
The flight engineer's top turret was a replacement, dropped in but not hooked up, and some major components were missing from the .50s on board, as seen at the time in the pic here. The late Pony Maples, owner of Ramo Ordnance in Tennessee, too care of that at no charge. And since the USAF Museum at Wright-Pat has taken over the restoration, the top turret, and it's ball turret cousin downstairs- and a LOT of other things- work now.
