What a pain in the keister this has been. Bought a Ruger American 308 compact (18" barrel), threw a scope on it and off to the range. Factory rounds made the muzzle flip up at least 4". Buy a muzzle brake, stick it on then put the gun away while we prepared to move. Get moved and settled,take gun to range only to find I can't get the POA/POI even close. Put scope in vise and find it won't move but about half of what it should have. Replace scope, go to range can't hit 9" paper plate at 25 yds after bore sighting. Frustrated! Placed several pieces of paper side to side and discover it's shooting about 24" right at 25 yds. Remove muzzle brake and voila, it shoots. Inspect muzzle brake under magnification and find what I'm guessing to be a 2mm bump inside the brake. Took a file to it and back out at the range today and I finally have the stinking rifle shooting again! Now I can finally get to the business of working up loads. Sure am glad this doesn't happen very much!