I used to work for a smooth bore designer. He would find the peak pressure point in a rifle and then terminate the lands and grooves at this point. He would then replace the removed section with smooth bore with the idea that furthering the L&D portion only acted as retarding friction whereas smooth bore would increase velocity. It was interesting. For myself, I would like to know how to figure this out in a cannon. This is for design reasons. I would not want a thinning cannon portion over a peak pressure area. Does different powder created peak pressures in different areas? Or do different amounts of the same powder create different ares of pressure? Is there a method to figure the pressures being generated? Thanks, to all of you! CANNONMAN