Well, you have a 1-48" twist, so why not just load up some .490 round balls and some .015 lubed T/C patches and 50 grains of powder. Lets see, that comes to $14.00 for a pound of Pyrodex RS, or $.10 per shot, then the bullets (Hornady) are $9.00 a box of 100, or $.09 each, then the lubed patches at $5.00 per 100 or $.05 each, and the primers at $.02 each comes to $.26 per shot, about as cheap as you can get, and my gun (CVA Bobcat) will put 3 shots into one big cluster at 25 yds, which would make for fun prairie dog shooting if you got good. You would also be able to adjust your powder charge to match what you are getting with your powerbelts.