I don't think it was the blackhorn that caused therust. I think it was the lack of oil in the barrel. If you had left a centerfire rifle in the same condition with out any oil in the barrel I think it would rust to under the right conditions (Humidity). I would never leave any of my guns without anything in the barrel to protect it no matter what kind of powder I was using.And yes, I do shootBH209 and love the stuff.