It says right on the Blackhorn 209 website that it does not work in all muzzleloaders. It has to be able to shoot a full strength shotgun primer, have a sealed primer pocket and it helps to have a recessed breech face to get the powder closer to the primer.
You also have to maintain your breech plug with regular cleaning of the flash channel and flash hole. This is with any propellant, but Blackhorn has a higher flashpoint than others. I have never had hangfires or failures with Blackhorn. Get a drill bit that can lean the flash channel and a torch tip cleaner for cleaning your flash hole and use them about every 10 shots and you will likely never have problems.
I shot this doe last night at 100 yards with a 250 gr. Hornady MonoFlex ML bullet on top of 84 gr (by weight) of BH209. It was 13 degrees with 30 mph winds and my W209 primer obviously did the job lighting it...Blackhorn is the best substitute on the market. You just have to have compatible equipment and maintain it.