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    Wall thickness recomendations Archived Message

    Posted by Drew Hause on June 2, 2014, 9:49 am

    Steve asked a question about wall thickness recommendations fro Royal steel. Unfortunately, I have not received any segments of Royal, London, Crown or Nitro steel for compostion analysis and tensile strength testing (HINT! HINT! ) so we should start with what we know, then work our way to opinions, which we all have

    1. The Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives (C.I.P) shotgun recommended minimum wall thickness for Standard Steel is defined as a tensile strength 700 - 849 N/sq. mm = 101,526-123,137 psi.

    2. In 1918, Sears advertised the Fulton/Gladiator barrels as "having a tensile strength of 85 to 95 thousand pounds to the square inch.” The ‘LLH’ mark of Laurent Lochet-Habran is frequently found on L.C. Smith Royal, Armor, London, Crown and even Nitro Steel barrels from 1914 to 1948, Hunter Arms Fulton, Gladiator and Ranger for Sears, and also Fox, Ithaca, Lefever, and Baker guns. This figure may therefore reflect the strength of Belgian ‘rough forged tubes’ used by most U.S. makers.


    3. ONE sample of Armor steel had a tensile strength of 101,000 psi

    4. The average tensile strength of both Crolle and Twist is about 54,000, just a bit less than Decarbonized or Siemens steel. There was however only a slight difference in the performance of late 1880s steel vs. pattern welded barrels in the 1891 Birmingham Proof House Report of 1891
    http://docs.google.com/a/damascusknowledge.com/document/d/1dnRLZgcuHfx7uFOHvHCUGnGFiLiset-DTTEK8OtPYVA/edit?pli=1

    5. Modern AISI 4140 Chrome Moly gun barrel steel runs 95,000-100,000 psi

    6. Depending on the load, pressures at 24" are as low as 500 psi.

    Much more information may be found here
    http://docs.google.com/a/damascusknowledge.com/document/d/1LFnSG34k3mBhLEjEgU267wAlIa215MNVQZhIiY62Hx4/edit?pli=1

    SO on to my only slightly informed opinion

    No way would I shoot any barrel, pattern welded or fluid steel, that is deeply pitted and has a wall thickness less than .020" in the distal 1/3 of the barrel because one cannot know the wall thickness at the bottom of those pits.

    I favor as MWT for pattern welded barrels:
    End of chamber - .105"
    Forcing cone - .100"
    9" from breech - .040"
    9" from muzzle - .025"

    As always, nothing here should be construed to indicate that YOUR barrels are safe.

    And donations of barrel segments are still gladly accepted! I would very much like a piece of Meriden Fire Arms/ Crescent 'Armory' steel.

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