I purchased the breech plug to shoot BlackHorn 209 from CVA. Remember, when you install it... use the tool and really crank that thing in there the first time.
85 grains would be plenty. You could start her at 65 grains and see what kind of accuracy you get. My optima sweet spots in at 90 grains. Nice bargain by the way. I don't need another rifle but for that price, it would have come home with me too.