Since it is last year's model I assume it has a 1:20" twist vs the newer 1:30". Try some NoExcuses conicals in 460 grain with about 80 grains of Pyrodex P loose powder. The are .451" in diameter and should be just a bit underbore in that rifle. Shoot fouled and see how it goes. They will pack PLENTY of punch.
http://muzzleloading-bullets.com/page3.html