I have a 3 inch cannon made from a seamless oil well pipe...100,000psi tested. I proof tested it with 2lbs of FFG black powder. I shoot 3 inch comets, and 3 inch salutes out of it. I have a low explosives BATF permit, and shoot display fireworks shows. My 16 inch fiberglass morter weighs over 250lbs, and a 16 inch shell weighs about 75lbs. 3 1/2 lbs of ungraded black powder will send a 16 inch 3000 ft up! Once I shot up 3000lbs of black powder in 20 minutes! I fired 20 twelve inch shells, 60 ten inch shells, and 300 eight inch shells in the show.
Douglas George