I've fired thousands of rounds in full auto. M-16, M-60 (.308), Browning .30 cal,(.30-06) Browning MA2,(.50 cal BMG) Thompson (.45ACP)
Effective full auto fire requires a belt fed mounted gun with tracers every five rounds. Even low powered full auto in a heavy shoulder fired weapon (11 lb Thompson in .45ACP) is very difficult to control. M-16 is no better in full auto.
Now give me a mounted gun with tracers and you don't want to be a target anywhere inside 1,000 yards, maybe twice that with a .50.