In your rifle, I personally would use Triple Seven 2f or Pyrodex RS. I know a lot of people have fallen in love with BlackHorn 209 and it is a great powder.

Blackhorn 209 -- Is hard to find in some areas. It is more expensive then most powders. If you shoot a lot you will learn about the cost real fast. A stronger primer is needed to set it off. A tight fitting projectile is needed. Also I have been seeing this problem with the breech plug getting plugged. I personally do not like this aspect at all. The good points of BlackHorn 209 is the power of it, the fact you don't have to swab the bore, you clean it with solvent instead of water (which is a good thing to some and not a good thing to others), and is non corrosive which is a plus.

Triple Seven -- A competitive priced powder. A powerful powder. It is an accurate powder. Goes off with any kind of primer. Can be cleaned up with simple water. An easy powder to find locally. But there is a crud ring that can form. A swab material will take that crud ring out. While corrosive, it is not as fast acting as people might believe. Not at all like Pyrodex RS of black powders.

Pyrodex RS -- An excellent powder. Very easy to find on sale or well priced. Able to find almost any where. Provides excellent accuracy. The fouling is soft and easy to swab out or clean. Can be cleaned up with simple soap and water. A very consistent powder to shoot accuracy wise. Most times what shoots for accuracy one day will do the same the next. I have seem some powder really change day to day because of such factors as humidity, temperature, etc. One of my favorite powders.

Black Powder -- Hard to find. Very cost effective if you order it in bulk. So for shooters that shoot several times a week, this is a good deal for the shooter. Very consistent powder when shooting. Fouling is easy to clean. But some claim it is too much of a mess. Cleans with soap and water. Anything will set this stuff off. Even low power primers. Bad points.. lots of smoke, stinks when you shoot it (although I do not think so), and people complain about cleaning it. I never found this to be a problem. The powder I use most often is Goex or Graf's and Sons black powder.

Any of these will work in your rifle. I am sure you will have some excellent accuracy with them.