I have 2 Pietta .44 Black powder revolvers (an 1851 Confederate Navy and an 1858 New Army) and I shoot .451 balls out of mine with a 'wonder wad' over the powder. No patches in revolvers. I prefer NOT to use a ton of bore butter or grease to seal the chambers. Black Powder is messy enough without that. I put in the powder charge, place a wad over it, then the ball and crank down the loading lever. The thing is that you want to shave off a little lead from the ball. With the .451 I get a very thin shave all the way around. As long as your getting this you know the ball was large enough to seal effectively. For my revolvers a .454 just means I am shaving more lead...but the size of the ball in the chamber would be the same. To be honest I do not remember what the manual said...but I know I have been shooting this size ball safely for years. Enjoy! !