I have nothing intelligent to contribute regarding Lefevers, but it is not at all unusual to find MWT about .020"
PAST 20" in vintage small bore U.S. doubles. Beyond the dent concern, I'm
WAY more concerned about MWT breech to 12", which is rarely reported by dealers. And running a wall thickness gauge quickly down a barrel, usually one pass down the thicker top near the rib, and announcing the MWT is ____ means nothing.
Commission Internationale Permanente pour l'Epreuve des Armes ŕ Feu Portatives (C.I.P)
http://www.cip-bobp.org/ 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.pdf20g End of chamber - .075”
4” from breech - .071”
8” - .041”
12” - .028”
16” - .022”
20” - .020”
Please note the average crolle tensile strength in one study was about
1/2 the CIP "standard strength" barrel. Pre-WWI steel barrels were reported, and a few measured, at 85,000 - 105,000 psi.
