You might be on to something with the shape of that drum. I have noticed that when I shoot black powder the rifle is a dream to shoot. Pyrodex does well also. But APP and triple seven give this rifle fits. I need to try this same test again with a more powder friendly rifle. I have a New Englander that I think would shoot dirt if it were combustible. I even shot pellets with a #11 cap out of that New Englander. So I will try this test all over again. Maybe when the weather gets a little better.