I have an original Knight Disc (they had 22 inch barrels)...With 80grs of Goex FFF she stacks the .430 Hornady XTPs on top of each other...I've killed 4 deer with it this year...Previous to this I had also killed deer with the 250 SSTs and the 300gr Barnes MZ...Accuracy is better than most can hold as long as a fellow knows how to work up a load...

I don't see a disatvantage to a shorted barrel, to really stoke up a muzzleloader you need to go smokeless and that doesn't appeal to me...