I’ve really enjoyed running this Overt Industries 11.5 Suppressor Dedicated upper. You can run it as hard or fast as you like (I’ve run the GMR SS on it without issue), and have very minimal gas blowback. Overt isn’t the only game in town…I also really liked my Sionics 11.5 ERGP barrel. Of course, you can accomplish a similar result with flow through cans, AGB gas blocks, etc, but there’s something to be said for simplicity. What do you think?