Just about any of the commercially sold Muzzle loaders today can be made to shoot well. Just don't think.. it can shoot 150 grains so that's what I need to shoot. Many tune in much lower. For instance my Optima Magnum loves 90 grains of powder. And is very accurate with that load. And that load is plenty.
When you get the rifle post some pictures of it if you can. I love to look at guns.