Technically speaking, just about all 7.62 NATO ammo made for the past couple of decades is MG ammo, and in the case of US made M80 is no hotter than the M80 that was used in the M14. Just about all of the M80 equivalent I've ever chronographed has been in the 2750-2800 fps range.
SSGSAD, MG brass expands more because MGs have generous chambers to improve reliability in austere conditions, not because the brass is different.
Mine is now drilled, tapped, with a red dot, a recoil pad, and a cheek riser. It looks crazy, but they are crazy rifles to begin with!