Been running them on 3 AR's for a long while. It's the best of both worlds. While the Battle Comp is giving the FSC556 a serious run for it's market, I don't see where having one or both would be going wrong.

As many have noted, the muzzle blast is significant and to some, annoying when they are online with the shooter. Look at the angle of the tangs and you'll see where the "blast" area is going to be. The reduction in muzzle rise is very noticeable, especially in lighter or shorter weapons.

I also personally don't worry about anyone being besides me and getting bothered by the blast. I'm just inconsiderate that way I guess