I bought a used 45lc Ruger Blackhawk that was mfg in 1976. It came from the factory with a .454 barrel. It shot way to the left and real high. You couldn't move the sights far enough to compensate. I sent the gun to Ruger, they put a new barrel on it, (free of course). The new barrel was marked .452; so if Ruger isn't concerned about the size difference, I'm not either. I loaded up some 300gr ,454 bullets with a "healthy" powder load. No problems in either of the pistols or the Marlin rifle.