Wall thickness, pressure and steel

Discussion in 'Blackpowder' started by Revolver.45, Jan 29, 2020.

  1. Revolver.45

    Revolver.45 Member

    Joined:
    Jan 29, 2020
    Messages:
    10
    Hello.

    I’ve seen old black powder revolvers with very thin cylinder wall thickness, like these cylinders for example:

    ruger-converters.gif

    and this pepperbox has also resonable thin walls:
    medium_item_275418_eeac23b70a.jpg

    Back in the days the quality of steel was inferior, so it got me to wounder about the steels of today.

    What’s the minimum (with a safety factor) thickness of a chamber (or overall barrel for a pepperbox or derringer) in cal .40 containing a 25-30 grain FFFG black powder (or equivalent pyrodex P) load with a 92 grain lead roundball tightly infront of it (+wadding) if it’s made out of a steel with following properties:

    Yield strength min [MPa]
    700

    Tensile strength [MPa]
    900-1050

    Elongation A5 [%]
    12

    Hardness
    270-325 HB

    And how many PSI will such a load described above generate?
     
  2. ofitg

    ofitg Member

    Joined:
    May 17, 2010
    Messages:
    444
    The old 1975 Lyman Black Powder Handbook lists the following data for a patched 92-grain lead ball - 2690 LUP (Lead Units of Pressure) with 25 grains of Gearhart-Owen FFFg, and 3760 LUP with 30 grains of G-O FFFg.
    LUP is not equal to PSI, but it should be in the ballpark.

    I would note that the 1975 G-O powder was produced at the Moosic, PA plant, which was shut down twenty-some years ago. The 1975 G-O powder was apparently comparable to the Swiss or Old Eynsford powders which are available nowadays.
     
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