>>27681473Honestly, you can try this idea out with regular-ass 3/4" steel pipe from home depot. Find some with reasonably thick walls and remotely-test fire them. Schedule 80 is probably safer, but the peak PSI of the ammo and the stated safe PSI of the steel pipe are not directly relevant. PSI in a pipe means steady pressure, where as if used as a gunbarrel, the pressure vents out the muzzle and most of the PSI isn't forced against the chambers.
Shotgun shells are low-pressure. That's why you see modern shotguns with .027" thick barrel walls and thinner.
If you sign a bomb-proof legal liability waiver with a gunsmith, you could probably have such an abomination created without too much issue.
Don't try and re-purpose an antique.