John: by anyone's recommendations, less than .020" at 8" is inadequate, and extremely unlikely to have left Ithaca that way.
Even
CIP MWT for Standard Steel (Non-alloy AISI 1045) with tensile strength = 101,526-123,137 psi for
20g at 8" is .041"https://docs.google.com/document/d/1ZIo0y746UsSRZIgRuuxwAbZjSBHitO_EanvwLYc-kGA/editWalt Snyder graciously shared a 1919 Ithaca Gun Co. letter from A.P. Curtis, General Manager requested tensile strength testing on a section cut from a barrel made in Belgium to be performed by E.J. Stormer of Racine, Wisconsin. The letter did not indicate if the barrels were Smokeless Powder Steel used on the Field grade, Fluid Steel or Nitro Steel used on the No. 1 and No. 1 1/2, or Cockerill Steel used on the No. 1 Special (discontinued that year).
Tensile strength was reported to be about 70,000 psi. Composition was similar to AISI 1030.
Another careful evaluation might be in order
