WHAT DOES BLACKHORN 209 POWDER IN STOCK MEAN?

I have a CVA optima in stainless steel. I even have the black horn 209 breech plug. I load one hundred grains by volume of Blackhorn 209 by using a 250 grain Barnes bullet. I have discovered that you really should really use a great primer. Don't use the primers created for black powder as this isn't black powder. I make use of the CCI magnum prime