Is that the one with the brass spacer in the stock??? If so, try 75grs of FFF Goex, a .440 ball and a lubed .015 patch...

A .45 round ball will kill deer quite easily, I killed 25 or so with that load out of my flinter back in the 70s and 80s...I had a buddy that had one of those CVAs and if memory is correct it is a 1-66 twist and the above load is what he used simply because it worked in mine...