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Reload pressure

Discussion in 'Uncategorized Threads' started by blkfin, Sep 21, 2008.

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  1. blkfin

    blkfin Member

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    I have been reloading for a while and am in the stage of trying different loads. I came across some loads with lup instead of psi. I believe this stands for lead under pressure. Does anyone know if it equals or is the same as psi. Thanks for any help. Mike K.
     
  2. Gary Waalkes

    Gary Waalkes Well-Known Member

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    Sorry - it means Lead Units of Pressure. This is the old method and is not the same nor is it at all related to PSI - there are no conversions - LUP is a different animal.
     
  3. blkfin

    blkfin Member

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    Gary, In the 2007 hodgdon book it seems to have lup listed in clays powder data only, And only for some formulas. Where could i find these loads with psi for comparison. Mike K.
     
  4. waverider

    waverider Well-Known Member

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    Mike,

    As others have stated there is no simple formula to convert LUP to PSI. So until Hodgdon retest the LUP listed loads you just have to accept that, the recipes published in Hodgdon's book have been tested and found to be safe to use. If you are trying to compare different loads to find one that has the lower pressure under the misconception that lower pressure means less recoil, just load the various loads up and let your own perception determine what load you find best.

    In Hodgdon's book there should be a formula for calculating recoil, there is no pressure value used.

    11,500 psi is the maximum average working pressure for 12 ga target loads. The highest LUP that you can find would be close to 11,500 psi. A quick look of Win AA recipes showed an Int'l Win 209, WAA12 1 1/8 oz load at 10,800 LUP.

    Jason
     
  5. blkfin

    blkfin Member

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    Jason, Thanks for the reply. I'll take your advice and try different recipes for recoil. Moved back to 26 and would like to get a little more speed without a lot of added recoil if possible. Looking for somewhere around 1200 fps. Thanks Mike K.
     
  6. Quack Shot

    Quack Shot Active Member

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    The main diffeence between LUPS and PSI is the method and equipment used to measure them. The LUPs are determined by a lead crusher method. An actual piece of calibrated material is crushed in a special pressure testing apparatus while the load is fired. PSI refers to a value generated by a pressure transducer, usually a piezo device, when firing the shell. The two parameters are not convertable.

    Pressure, no matter how it was measured, has no real effect on recoil provided the velocity and weight of the ejecta are the same.
     
  7. Quack Shot

    Quack Shot Active Member

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    MIA

    Recoil ENERGY is the issue. Sensation is an entirely different idea and might be different for different shooters. My statement is simple and easy to understand. You can calculate recoil energy and that will be the same under the conditions I stated. Chamber pressure has no real effect on recoil energy given a constant ejecta mass and velocity. Perception is another theory. I don't buy into the "Perception" of recoil theory as some might. Even the "acceleration" differences are probably imperceptable and on the order of 3 or 4/10,000 of a second. Neil had a good graph to illustrate the details.

    I like to keep it simple. I don't get involved in the idea of perception, since I have NEVER seen any evidence that supports the idea that lower chamber pressures will result in less recoil, unless the velocity or ejecta's mass is reduced. It might be an interesting experiment, but my guess is that it would be inconclusive.

    Changing the profile or footprint of a recoil pad would probably have more effect on the "perceived" recoil than the type of powder used and pressures developed.
     
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