akbearhunter,
Clean Shot powder has been out of business for 3 or 4 years now. The new name is American Pioneer Powder, but that wouldn't be my first choice. The Hodgdon 777 in the FFFG (pistol grade) would be my first choice. Pyrodex P (pistol) would be another choice, but is very corrosive. If you go with black powder, use the FFFG grade also.
Hodgdon 777 FFFG will spank your bullets out of the short barrel, and that is what you need for a pistol or short barreled rifle shooting conicals.
The 777 powder is more energetic than the other powders, 85 grains by volume measure is equal to 100 grains by volume of Black Powder, Pyrodex, or American Pioneer Powder. Of course you probably wont want to be shooting that heavy of powder loads out of a pistol, so adjust accordingly. 50-60 grains of powder should work for plinkin', and 70 or so for hunting, if you can get it all to burn in that short tube. The 777 FFFG will let you use less powder by volume while maintaining the same velocities.
I am looking to build a muzzleloading pistol, as soon as I get the legalities all figured out. How much would it cost to get a barrel for an Encore frame?