I received a cannon barrel from my son as a gift. The barrel is 18 inches long about 4 inches in diameter with a 2 1/4 inch bore. Fires a mini soda can or billiard ball with a 2 oz black powder charge. I am making the undercarriage, a copy of the civil war 12 pound howitzer. It becoming a fun project so far, has anyone else done one of these? Any advise is welcome on this build.