Jumpshot
54 Cal.
Yeah, I'd try .433 balls first (Hornady makes them, and there are cast balls available from Track of the Wolf) and see how they work. You'll need to try different patch thicknesses to see what works best. I like Ox-Yoke pre-lubed cotton patches, I get them at my local gun shop. But Track has them, if you're buying online.
If the .433 ball is too big, you can also get .429 and .424, and if it's too small, there's .435, .437, .440, and .445, so you have plenty of options. Since this is your first blackpowder rifle, keep in mind it will take some experimentation (with both ball sizes and patch thicknesses) to figure out what your rifle likes best. It's part of the process of 'learning' a new gun.
If the .433 ball is too big, you can also get .429 and .424, and if it's too small, there's .435, .437, .440, and .445, so you have plenty of options. Since this is your first blackpowder rifle, keep in mind it will take some experimentation (with both ball sizes and patch thicknesses) to figure out what your rifle likes best. It's part of the process of 'learning' a new gun.