I to saw that old picture in the back of an old Dixie gun works catalog of a barrel being proofed in a tire. Well, it seemed like it would work, but it didn’t, and was one of the most dangerous things that I have experienced in my gun building life. I built a trade gun in 20 gauge. And because the barrel was an old unfinished surplus shotgun barrel, I decided to proof it. I proofed it with a double charge of 2F, and two patched round balls. When the charge went off, the barrel went right through the tire, and traveled about thirty yards across orchard next to my house. I now proof in a heavy wall pipe, well anchored, with a welded cap at the breech.
Hungry Horse