At one time .454 dia. bullets were the norm and guns were made to suit. But as time went on .452 dia. bullets became the norm, perhaps as these revolver's were selling, manufacurer's were slow to change (Colt still hasent changed). Add to the mix non handloaders had very few factory ammo options, mainly Remington and Winchester with 250gr bullets, these were loaded with soft .455 dia. bullets that would fit the oversize throat's and then swage down in a .452 bore and work rather well. Reloaders would just deal with the problem with properly matched bullet choices to suit the firearm being used.

__________________
Stay safe people!