They shouldn't. The capsules are plastic. They shatter on the ride down the barrel but from my experience with them they leave very little residue. But it never hurts to run a brush through to clean out whatever there may be left in the grooves. What gets screwed up the most is the pattern because of the rifling.Ok dumb question time it has been asked here before but...
Will CCI Shotshell ammo for hanguns screw up the rifling lands and grooves?