PSIs Versus LUPs

Discussion in 'Reloading' started by J E Custom, Mar 4, 2013.

  1. J E Custom

    J E Custom Well-Known Member

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    Jul 29, 2004
    I was looking for some king of comparison chart between Lead Units of Pressure and Pressure per squair Inch.

    The method now used is PSIs and should be more accurate but a loot of the older loads and firearms are rated using the LUP method.

    I know that 55,000 PSI is not the same as 55,00 LUP but I was just wondering if anyone had or knew
    of such a conversion .

    Any help would be greatly appreciated.

    J E CUSTOM
     
  2. Kevin Thomas

    Kevin Thomas Well-Known Member

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    Feb 16, 2009
    J E,

    Sorry, but there is no conversion factor for this, as it's not a linear transition. LUPs, or Lead Units of Pressure are still used in some applications, and are similar in nature to the CUP (Copper Units of Pressure) that was long used for most metallics. LUPs were generally used for shotguns, and other very low pressure applications that couldn't be accurately measured by the CUP method.

    CUPs, because of the higher numbers involved, are often assumed to be translatable to PSI, but again, it's not linear, and these numbers can't be traslated like this. In some instances the same cartridge measured by both methods may show a higher CUP figure than it does PSI. Others within a different pressure range may show exactly the same numbers in both PSI and CUP, while in a different pressure range, others may show the PSI having a much higher figure than the equivalent load tested in CUP. Different measurement methods, different results, and no direct way to correlate the three other than on a case by case basis.
     

  3. J E Custom

    J E Custom Well-Known Member

    Messages:
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    Joined:
    Jul 29, 2004
    Thanks Kevin.

    I typed LUPs and meant CUPs (I had shotguns on my mind).

    I had hoped there was some kind or relationship between the two so I could use some of the old
    load data that I had.

    It is not an issue because Pressure signs show up at some point but it would be nice to have a
    reference especially with older rifles and loads that require less than 44 or 45,000 CUPs maximum.

    Any other comments are welcome.

    Thanks again.

    J E CUSTOM