Shirley I do not jest. You tube has many people who delight in making improvised shotguns. Iron pipe slide firing, plastic flare gun modified to handle shot shells, etc, etc. That stuff is tremendous fun. Scope to try all sorts of ideas and find out stuff for yourself. Make a 12 gauge barrel from a piece of PVC pipe. Reinforce with couplings, then turn down the outside diameter until it blows. Informative fun. Every thousand added to wall thickness has an effect. From ignition to projectile clearing the muzzle the intervening space is just a pressure vessel. People have been fooling with this stuff for ages. You, well maybe not you exactly, could figure out the hoop strength of the shotgun chamber. Then figure out the hoop strength of the shell case and add it to the former. At one time there were people who doubted that the Earth was a sphere.
