live,
I think Pglasgow's advise is right on.

Pellets are fineas opposed to loose powder. They do tend to work better if they are NOT crushed though. Pyrodex and 777 come in pellets and two 50 grain pellets of either and a 295 grain PB (or heavier) would be an ok place to start. 70 grains of loose 777 is pretty close to 100 grains of pyrodex, maybe a little less. Other suggestions for projectiles might include Hornady XTPs, Gold Dots, Shockwaves and several others. These can be pushed much faster than the PBs and in some cases are ballistically superior.
After you have been shooting awhile, and refine your needs, you might want to shift to loose powder and more modern sabots. It will increase your range and accuracy.
Good luck.
Hank