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 a hundred grains by volume of Blackhorn 209 by using a 250 grain Barnes bullet. I have discovered that you actually really should use a superb primer. Will not use the primers created for black powder as this is not black powder. I make use of the CCI magnum