I once had a 20X spotting scope that could not let me see bullet holes in paper at just 100yds. Just want to voice what others have hinted at. I am pretty confident that most would agree that the "perfect muzzleloader scope" is not going to be in the 4-12, or 4-16 x 40-50mm range. Many ML shots are close in where a 2x or even 1x low end will be more useful with its greater field of view. On the far end, even with 200yd shots, 7-9x should be all you need, assuming you have quality optics.

You state your current scope does not have much clarity. I don't know how much you are willing to pay for your new scope but in general you would be better served with putting your money toward a lower power scope with high quality clear optics rather that going up in magnification.