What brand is your revolver? That helps to figure out the right ball diameter.
Most of the .44s seem to have a sweet spot around 22-25 grains of FFFG powder or Pyrodex P. I've never had good luck with Pyrodex and it's just as corrosive as black powder anyway. If you can get real black powder, you might give it a try. I mail order mine in bulk from
powderinc.com.
I'd try .454 balls. You want them to shave off a small ring of lead when you seat them. This creates a tight fit in the chamber for maximum accuracy and it also seals the chamber so that hot gasses from firing doesn't set off the adjacent chambers. If the .454 loads too hard and shaves off a large ring, try .451. If it barely shaves, try .457. Some folks like to put grease over the ball. It makes for some messy shooting and I find this uneccesary if the ball fits tight.
With a charge as light as 22-25 grains, the ball will seat too deep in the chamber for maximum accuracy. It's best to use filler between the powder and ball to get the ball to seat flush with the chamber mouth. You can use lubed felt wads, or just pour in a measured amount of cream of wheat, corn meal or grits. This also helps keep bore fouling down.
For the caps, it probably takes #10, but it might take #11. No way to tell without trying. The caps need to fit the nipples tight to keep hot gasses from entering the chamber and setting off a cross fire. Be sure to push them tightly onto the nipples. You might need to pinch the caps to make them fit also.
For accuracy, the most important aspect, aside from finding the load that your gun likes, is consistency. Do everything the same way each time. Seat all the balls with equal pressure, use the same amount of filler in each chamber, etc.
Good luck and have fun! :grin: