I have always wanted to make a brass cannon . The size is not real big on the firecracker cannons , and I have the stock to do it . So thought I would give it a try , should be fun . Included are measurement for any one interested in scaling . Barrel 7in long x 1in dia , taper is 4in long x 2 deg per side 4 deg total. A interesting side note , if you make the last 1/2in of the bore on the breech end a snug fit on the firecracker , the firecracker acts as a effective seal . You can even fire BP in front of the firecracker without it coming back through the breech , very clean. Easy way to test is to wrap several layers of black tape around fuse end of firecracker for a snug fit and try it.