Bramble, I am not discussing regulating a DR or indeed even getting barrels to print POI, what I want to know is whether it could be detrimental to fire a bolt, single shot, DR or semi auto from a lead sled ? physics seems to ay as long as the rifle CAN recoil, albeit from a much "heavier" start position, it shouldn't be a problem. Lets see if 9threeX57 can bang off a few shots from a big hitter. best, Mike