The problem with muzzleloaders is that there are zero standards. Bore diametery to bullet diameter is a huge issue. For example, 50 caliber bore diameters range from .499 to .504. Now how are bullet makers supposed to match their bullets with your bore? Well with the sabot of course. That's the biggest variable in accuracy with sabots. Now generally manufacturers bullets will shoot well in their guns. Sometimes when they do not there is a smaller than normal barrel. That can generally be dealt with by lapping. It's better to try other bullets before lapping a barrel however. After all, metal you remove today can not be added back tommorow. That's the biggest reason I do not like lapping. If I need to simply break in a barrel I use powerbelts.