An A2 flash hider with the bottom 3 ports welded up and a washer welded on the end!!! Works like a charm. Probably a thread saver would work just as well?
I suspect most comps on PCCs don't do much unless you use very slow burning powder and with a blowback design just as much gas is escaping out the bolt if not more than is going through the comp. I would like to see some super slow motion video.