I've been happy with my Brevis 7.62 on a 16" 5.56. 16" 6.8, and 24" 260. It's a little louder than a YHM Phantom, which is a few inches longer and a lot heavier.
At 20 ounces, the Brevis is one of the lightest steel rifle silencers. Mirage is no worse than other silencers that I've used. And I've never seen the diameter as a problem.