I am by far no expert with black powder, but I would think 75 to 80 gr charge with a light bullet in the low 200's might not be a bad combination, hopefully the shot will be closer than further, I have also known guys I've hunted with use a 50cal sabot casing with a 45 cal bullet, maybe a thought, if you can kill one with a 410 slug or 20ga. this combo should be fine, but like I said I am no expert but have killed quite a few with the muzzleloader, maybe more input from others on the board would be good. Hope this helped
Also go with a quality hollow point for more expansion.