300BLK works fine. Never tried 5.56.

by Slow Hand , Indiana, Tuesday, January 22, 2013, 04:20 (4269 days ago) @ John K.

John, I didn't know you we're a .300 blk shooter! I built an AR when barrels were first coming out. Mine is a 16" with a pistol has system that is just itching to be SBR'ed to 8"! It has worked pretty well with everything from 125's to some cast 240's. I shot some traditional gas checked bullets in the 220 range but I've switched over to the mold lee made for AAC. It's a tumble lube that mimics the SMK shape and feed great in my AR. I've also got a Stevens boltgun I rebarreled with a 16" tube available from a local wildcatter. With my SAS can and subsonic handloads it's barely louder than my suppressed .22 boltgun! I was making hits on propane cylinders out at 350 yards last October at Cannon's place. Pooht......THUNK!!