Doc, here is a nice, little 3x3 Mulie I took last year at 236 yds - even further than this years. My deer load in the Bighorn is: 110 grns. pellets pushing a 250 gr. T/C Supergilde bullet w/ yellow sabot. Long range is the goal to aim for. Play around with some of the high end muzzleloaders like Knight or T/C Arms. Once you find an accurate load, you're set. All that's left to do, is to practice, test the penetration of your shot in a ballistics buffalo test to make certain your load has what takes to make a humane & ethical kill, and believe in your shooting. I had 7" of penetration for my deer load and 11" for my elk load both at 210 yds.
I have also taken 5 Elk with my Knight Bighorn. None of them have been under 100 yds.
Longest was a cow at 194 yds. (with a 5x scope of course), and that shot knocked her clean off her toes. I use a 300 gr. Barnes Expander MZ in front of 130 grs of Triple Seven pellets. 150 grs was too much & made the bullet squirrely. At the range, I can stay inside of a 5" circle with that load at 200 yds. all day long.
However, getting there took experimenting with plenty of load combos to find what my rifle liked.
I would highly recommend the Knight Bighorn as an affordable & long range inline rifle. I have also heard good things about the top end T/Cs as 200 yd. guns.
Jim