UncleNorby

I guess I would put my hands on lead you know is pure, even a small quantity, and cast some bullets. If they shoot well, you have found your problem. Be sure to start with a moderate charge and work up if you get good accuracy. If they still don't group, then try another bullet, simple as that. Round balls are a good idea, also try conicals. Can you inspect that rifling and determine the number of grooves?