According to the Dixie Gun Works catalog, the Pedersoli Sharps Bullet mould uses "stepped bands." The first band, back from the nose is .525, the 2nd band is 530, and the 3rd band is .544. This is the bullet Pedersoli designed for their replica percussion Sharps.
Whatever you do, NEVER, NEVER, NEVER use plastic bullet sabots AND Black Powder in your Sharps.
As Black Powder burns a lot hotter than the "replica Black Powders," I ended up scrubbing long, thin plastic strings from out of my Sharp's bore after shooting a dozen saboted bullets.
If the Hornady Great Plains Bullets are .540 ( don't know their real size) they might even be a bit undersize for your Pedersoli Sharps bore. A Good way to check their size is to oil the bore of your Sharps up and using a wooden or brass dowel, drive a Hornady bullet thru your barrel. After the bullet emerges from the muzzle of your Sharps, you can examine it to see how well it took the rifling.
GOOD LUCK!