For the 50 cal muzzle loader, have you tried 295 grain CVA Powerbelts? My Omega shoots them very accurately, about 4" at 100 yards with open sights. I like full diameter 50 cal bullets with big hollow points. The Powerbelt is an updated Minnie Ball intended for a 1:28 twist barrel like the standard Encore barrel. For 1:48 twist traditional caplocks, I prefer the Hornady Great Plains Hollow Point, which is a lead hollow point, with a thick Minnie Ball skirt. The bullet is soft and hollow point big enough that it should start expanding immediately. You may want to try this bullet as well to see if it works.
I had running deer problems with T/C Maxi Balls and received the following advice from a game warden:
Deer hit with sabots, round balls and Maxi Balls tend to run. Deer hit with big soft hollow points don't go far.
I don't think that his advice is always 100%, but he checks in deer shot by other hunters every year which puts him in a unique position to evaluate effectiveness.