north florida here, 59 retired& tired, vermont transplant,,, wally is the name and i hope this post works, i had a bit of trouble finding things , well any how Wildhorsecannon@webtv.net is my email address, i build metal Spudguns, firecracker cannon, black powder cannon , golf ball cannon, propane cannon, noize makers,and the neatest is a beercan mortar,I have photos i can send,,, THE latest thing is i need help with the size of the wall on a oxygen tank of about 29-29.5 inch cirumferance , and some spects of a co2 tank mortar, dont know if an oxygen tank and co2 tank are the same , this thing i'm going to build i;m going to use a trailer ball to plug the end of the tank where the valve was the threads are the same size but tapped different the valve has a taper to it, so the threads in the tank will have to be chased out and then legs in the front , and a ground plate to set the ball into , drill a fuze hole just above or below the ring on the tank end, kaboom,have built a few mortars, but none this big , saw one at a machine gun shoot , loved it have to have one ,email me i'll send you a link to the stuff i build