308Lite
You can run a heavy buffer with an adjustable block. Nofail was just saying that he's running the JP lo-mass carrier.
I run one of Slash's heavy buffers with an adjustable block on two of my AR-10 carbines. PRI block (JP block on the other), CAR10-XH buffer & spring, UBR, and a standard Armalite bolt carrier.
The combo of the JP lo-mass + the restricted gas + heavy buffer could cause problems. Though.......you would still think that you could find the sweet spot eventually. Haven't played with any of the lo-mass carriers personally yet.