Ok I am greener than green about cannons , but I love to look at them and I love reading and watching the history part of them to. I really like the Mountain Howitzer and the 1857 Napoleon cannon styles. I have a small oxygen bottle that failed inspection I want to make a mostly static cannon from to park by my flag pole in the front yard. I thought while I am building it and such how hard would it be to place a thick walled smaller diameter pipe inside the cylinder and encase it with concrete where its in the center for something to shoot just powder blanks with the bread wad from like on the 4th of July. Anyone ever do anything like this? Is it doable? I have read lots on here about making the powder chamber the same thickness as the bore. Or can I just load powder in Tin foil like I read about on here straight down the barrel without building a powder chamber? How big of a bore pipe do I need to make a good size boom with lots of smoke? Again I am new to powder and cannons and such but I do shoot guns a lot....lol? Back when I was young me and my brother used to open up the 12 gauge bird shot shells and take out the led shot and make our own blanks but we all have done stupid stuff before. Ok please be nice to me I just like bang and smoke like the rest of you.