>>64222491
A dream of mine is that, if the MG registry is ever reopened, I'd want to get an Auto Ordnance M1A1 and then convert it into an open-bolt machinegun, and I'd like to see if I could get .45 Super loads running in it without safety issues or wear problems.
Might need to drill the bolt and add in tungsten weights. Maybe also a nice and squishy buffer pad in the back of the receiver.

A .460 Rowland converted Thompson would also be baller, but, uh, I'm not quite brave enough to do that experiment myself, and then you would 100% need a muzzlebrake. Not for the same reason as for automatic pistols, where the brake adds more weight to the barrel and also pushes it down longer, for dwell time, but because the Thompson has such a dropped stock and it would climb like crazy blasting .460 if you don't tame the muzzle.