I have the CVA 50 cal Optima V2. I tried every black powder substitute and pellet I could lay hands on. Every thing worked reasonably well. The difference is powder fouling. With Blackhorn 209 you can just keep on shooting until you decide to quit. I am sure it does have some round count where you do need to stop and clean, but it is past 12 shots.
With the others I was cleaning after every shot.
I did come up with some Black MZ I believe it was called. I did not get around to working with it. I believe it was the next best thing to Blackhorn 209 from what I could find out.

Good Luck

Bob R