Tinker, not only hilarious, but exactly what we are looking for!

The gun I mean...

Your assessment is precisely what was discussed on the previous thread. Which "touch" the "ass" prefers, so-to-speak, now that, I do not know, but the principle you describe can be demonstrated in a variety of ways.

On a previous thread, 400ne suggested .078 as a barrel wall thickness of a thin-tubed gun. I'm not sure if it would matter or if that would be a significant detail, but such walls being much thinner than your .090, and assuming such barrels are safe, it would seem to me the thinner walls would give the best possible opportunity for a demonstration of OSR.

Correct?

I do not know what is considered the minimum threshold of safety on a, say, .458 barrel, but a related experiment would be a progressive reduction of barrel wall thickness combined with a firing to destruction of the barrel. I have no idea what diameter would allow for failure, but if the maker took the proper safety precautions it would be an interesting side experiment. Looked at another way, he obviously needs to be prepared {safety} for different demonstrations of material failure {not just relatively benign OSR} if he is going to turn the tubes down beyond known safe diameters.