Thanks for the extra effort Rob. Those wall thickness numbers are well within the CIP recommendations

Commission Internationale Permanente pour l'Epreuve des Armes Feu Portatives (C.I.P)
Standard CIP proof pressure of 850 kg per sq. cm. (BAR) = 13,920 psi proof pressure = 10,730 psi service pressure (SAAMI)
Shotgun recommended minimum wall thickness (p.4) for Standard Steel with tensile strength 700 - 849 N/sq. mm = 101,526-123,137 psi
http://www.cip-bobp.org/sites/default/files/new_file/A-4-1_EN.pdf

10 & 12g
End of chamber - .079
4 from breech - .075

https://sites.google.com/a/damascusknowledge.com/www/home