I've owned and shot muzzle loaders for going on fifty years. Several were TC's. Here in the real world, if you can keep three shots under four inches with open sights you're doing very good. "Well under an inch" at fifty yards is a bit of a stretch with any gun and open sights.
The last time someone told me that I challenged him to do it (we were shooting sporting clays and there were a lot of people in the room).
if I do my part