A groove diameter of .470 in 450, is not that unheard of. 577-450s often have larger diameter grooves than expected. An odd number of grooves is hard to measure, but they normally measure smaller than actual(not larger), unless a special mic or "V" block is used.A paper patched bullet is normally bore sized(or smaller) and patched up from there.A soft lead bullet, as stated above)should "bump up" if black powder is used. If smokeless is used, it won't likely bump up and a groove diameter( or .002-.003"larger)"naked", lubricated would be used.With BP, non petroleum based lube must be used.Even naked bullets in factory BP ammo, usually has undersized bullets( expected to bump up. 43 Spanish ammo bullet is .433, while my groove dia is .439"),but the rifle will tell you what it wants.
Mike
