I remember doing this once myself. It was one of those nights when just a few people playing in one of the MAs. I killed an M3 near maproom with an M16 ...then heard tank spawn in so just for fun drove the M16 out to where the panzer was rolling. I got behind it and pumped it full of .50 cal, figuring I was just being annoying but the panzer blew up. It wasn't already damaged because it was the same guy that was driving the M3---he spawned back in with his tank to kill my M16. Nobody else was defending the field so I know it wasn't tank fire and I was just stealing the kill with my .50s. It took several seconds of continuous fire, but I don't remember how many rounds.