Machine gun, but single shot, not full auto.
It would have to be, ther would be now way you can track the rounds in full auto through a scope with a Ma Duece bucking. Don't care if you have one bolted to a tank with a telephone pole you still have major vibration with one. When I was stationed in Germany we had a hummer with a gun turret with a .50 mounted to it. Parked on a firing range in Graf and after firing a few belts of ammo off we noticed the truck had moved about 2ft back from the recoil. (this was early 90's in a non armored turtle.)