I recently purchased a rifle with a Primary Weapons Systems FCS 556. I noticed that it did cut down on the recoil a bit. While I do realize the 5.56 round does not have much recoil in the first place I did notice a drop. On the flip side of that, during the day there is a small visible flash of light that comes out of the muzzle. Where as on my other rifle with a birdcage flash hider there is no flash during the day but a bit more recoil. If you are looking for no flash period I find the smith vortex to have minimal flash. Hope this helps.
i have the PWS TTO, and it doesn't really help the recoil, but i noticed the muzzle doesn't flip up as much. it's pretty good for quick follow up shots.