you also didn't say how far you were shooting, shooter error can also be a factor. It took me a long time to find the right bullet, powder combination, the best shooting rest, a good cleaning routine between shoots, how much powder, what kind of powder, understanding the wind and a hot barrol etc.
what would i suggest? I would read everything i could find on muzzleloader web sites on the muzzleloader i am shooting, from that information i would settle on a bullet and powder and the amount of powder to start with. I would keep notes so you have a record of what you have tried. I would never shoot on a windy day,I would clean the oil out of my barrol before shooting, I would shoot at about 75 yards, foul the barrol with two shots in the air, shoot once, spit patch my barrol on both sides of the patch, then run a dry patch threw on both sides, shoot again and repeat my routine. I take two big breaths, shoot on the slow exhale, use the tip of my trigger finger, and pull so slow that i don't know when the gun will go off. It works for me!