Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives (C.I.P)
http://www.cip-bobp.org/
Shotgun recommended minimum wall thickness p.4
http://www.cip-bobp.org/sites/defaul...e/A-4-1_EN.pdf
Assuming Categorie 1 is Standard Steel, for 12g the MWT numbers are:
Just past the forcing cone/ 4” from breech - .075”
8” - .043”
12” - .030”
16” - .024”
20” - .022”
