Quote Originally Posted by militarymoron
if it's this one, the MB556A, it's VERY loud to someone at the side, and quite the flamethrower (this is coming from a source i trust who test fired one of them).
That could be it but there's no numerical designator mentioned in the article and the pics are taken from far enough away that I'm not positive. Realistically though, it probably is. I doubt Surefire would release two separate muzzle brakes.

Denny Hanson was the author, he wrote:

"I have been on the line next to shooters whose rifles were equipped with muzzle brakes, and the blast is often very extreme. I stood within three feet of the muzzle as Barry [Barry Dueck, Director of Surefire's Suppressor Division]fired an AR-15 equipped with the new Surefire brake. In all honesty, I was expecting an intense blast of pressure, but all I felt was a gentle (though forceful) surge of air. The brake does its job while not making someone to the side of it combat ineffective. I was impressed."