I built one. Aero precision receivers, 10.5" barrel, timney trigger, and a folding SBA3 brace. I haven't shot it in a couple years

, but it was pretty quiet with subs through my 9 mil can.
If you're going to be shooting subsonic, 300blk is a better choice because the barrels have faster twist rates than 308 to help stabilize the heavier rounds, plus they cycle good with both supers and subs.
I just ordered a silencerco hybrid 46, so looking forward to trying it with my 300blk. Then next year, I want to load some 425 grain maker rexs for my 450 bushmaster and try to get a deer with it suppressed subsonic.