WHAT DOES BLACKHORN 209 POWDER IN STOCK MEAN?

I have a CVA optima in stainless steel. I also have the black horn 209 breech plug. I load one hundred grains by quantity of Blackhorn 209 that has a 250 grain Barnes bullet. I have found that you truly need to use a superb primer. Usually do not utilize the primers produced for black powder as it's not black powder. I utilize the CCI magnum primer