A little clarification on Lee's statement. I would not advise using BH209 unless you are shooting an inline ML. I don't think a #11 cap will reliably ignite BH209. I believe even Sabotloader was having some problems using a 25ACP ignition system.
If you are using a sidelock the following is recommended. Flintlock - black powder only (unless it is a Firestorm model) and if a caplock, you can use black powder, triple 7, or pyrodex.