This questions has been brought up a few times. People have had good experiences and bad! I have a friend on the forums that had gotten one of the kahntrol breaks and they shipped him the wrong one. It blew off the end of his barrel and left some permanent damage to the end of the muzzle. I think they sent him another one, but I don't know if he still uses it.

Personnaly, I wouldn't run a clamp on on anything larger than the 223 family. Preferably, I would have the barrel threaded. That's me personally though.