That's the gun. I've not made a chamber cast, but believe it is for a brass case. That is the only way a 13 bore ball would be able to fit in a case loaded in the chamber. Using fibre wads, I hollow out the top of the uppermost one, then hot-glue a .684" ball on top. The ball sticks out the case with over 1/2 of the ball showing, but is firmly held in the plastic. I'll have to search out some brass to try. Note in the picture, the first engraved ball is a 12 bore ball I've hammered into the bore to check land/groove dimensions. The second is a .684" ball that was pushed through the bore showing the rifling engraves 1/2 way on the ball, which will hold the ball from spinning. The third ball is an as-cast .684" ball. As I noted above, I've not fired this gun yet. When I received it, my shoulder allowed no shooting at all. With time, I'll be able to shoot again as things are improving without the DR's. help. It's interesting that every time the Dr's. here are on strike, the death rate seems to fall.