I did one but SBR'd it. 5.5" QC10 upper with a 8.5" Odin Works hand guard that allows for a little bit longer reach and also allowing a suppressor to go underneath it. I swap the suppressor over to a fake can so I can shoot matches with it. It's not the softest shooting PCC because its set up to run any ammo and not tuned to run a gammer load. Bolt weight installed, 308 carbine spring, Blitzkrieg hydraulic buffer. It can be a little gassy with the suppressor on but apparently that's something you gotta deal with when suppressed.
FYI, I recently built a 4.5" AR22 pistol and think the SBA3 brace is hard to beat.
The 512C works great on this set up.