John: I believe you mean MINIMUM wall thickness.
I favor as MWT for pattern welded barrels:
End of chamber - .105"
Forcing cone - .100"
9" from breech - .040"
9" from muzzle - .025"
Factory original 20 and 16 gauge small frame guns with Damascus barrels however may have a wall thickness of .090” at the end of the chamber, and less than .020” in the distal third of the barrel, making it critical to use loads that match the ballistics of those originally intended for use in the gun.
More information
https://docs.google.com/document/d/1...vwLYc-kGA/edit