The M2 Cal 0.50 came in at least three varieties. There was an early water cooled version, the M2-HB for ground use that was air cooled and a lighter version for aircraft.
I don't think any of them would go over 850 RPM though. The M2-HBs were more like 550 RPM.
Marines used the M1917 and M1919 .30 cal Brownings, the M2 .50 cal Browning, the BAR Browning automatic rifle (Browning was one of the major saints of projected forces), but none had such high rates of fire. I think the German MG42 was one fo the few that did. An odd weapon used briefly by the Marines was the Johnson rifle, and they stole M1 Garands from the army until they got their own.