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LUP to PSI Conversion

Discussion in 'Shooting Related Threads' started by minnship8, Dec 22, 2011.

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  1. minnship8

    minnship8 Well-Known Member

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    Looking at some reloading recipes and the pressure is displayed as LUP instead of PSI. What is the formula for conversion?

    Thanks,

    Chip
     
  2. skeet_man

    skeet_man Well-Known Member

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    There is none, it is impossible. In other words, your trying to convert inches to pounds, or vice versa.
     
  3. Calkidd

    Calkidd Well-Known Member

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    Ditto
     
  4. halfmile

    halfmile Well-Known Member

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    The relationship is not stable enough to convert. It's not even logarithmic.

    The only constant is that the upper limit is a higher number if you use PSI.

    Use only published data, and pay close attention to whether the pressure is PSI or LUP. That one can sneak up on you.

    HM
     
  5. likes-to-shoot

    likes-to-shoot Well-Known Member

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    I had ask the same question a while back and got the same answers. I was even hoping for some sort of graph that would give a person an idea of what numbers are close to each other.

    You would think that the powder company would up date the data to all psi.
     
  6. kene

    kene TS Member

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    along the lines of "dram equivalent". LUP won't go away --- just be sure you are comparing apples to apples and not apples to grapes when making some sort of decision ...
     
  7. minnship8

    minnship8 Well-Known Member

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    Looking at some reloading recipes and the pressure is displayed as LUP instead of PSI. What is the formula for conversion?

    Thanks,

    Chip
     
  8. skeet_man

    skeet_man Well-Known Member

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    There is none, it is impossible. In other words, your trying to convert inches to pounds, or vice versa.
     
  9. Calkidd

    Calkidd Well-Known Member

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    Ditto
     
  10. halfmile

    halfmile Well-Known Member

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    The relationship is not stable enough to convert. It's not even logarithmic.

    The only constant is that the upper limit is a higher number if you use PSI.

    Use only published data, and pay close attention to whether the pressure is PSI or LUP. That one can sneak up on you.

    HM
     
  11. likes-to-shoot

    likes-to-shoot Well-Known Member

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    I had ask the same question a while back and got the same answers. I was even hoping for some sort of graph that would give a person an idea of what numbers are close to each other.

    You would think that the powder company would up date the data to all psi.
     
  12. kene

    kene TS Member

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    along the lines of "dram equivalent". LUP won't go away --- just be sure you are comparing apples to apples and not apples to grapes when making some sort of decision ...
     
  13. minnship8

    minnship8 Well-Known Member

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    The bizarre part, is that the Hodgdon site, for example, will have load recipes expressed in both terms on the same page, depending on the wad choice.

    Thanks for the explanations,
    Chip
     
  14. timb99

    timb99 Well-Known Member

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    Just remember, regardless of whether its psi or lup, as long as its in the data tables, it is a safe load.

    The reason why they probably don't update the lup's to psi is simple. They'd have to test all those loads (for which there is already reliable data, albeit in lup) all over again, and that costs time and money.
     
  15. JACK

    JACK Well-Known Member Supporting Vendor

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    great comment Tim.
     
  16. hmb

    hmb Well-Known Member

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    Simple but wrong. LUP is a pressure measurement over time, and PSI is a momentary peak pressure measurement. HMB
     
  17. Neil Winston

    Neil Winston Well-Known Member

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    No, Howard, the result of deformation in the lead is somewhat sensitive to how fast the pressure peaked, but it's hardly a "pressure measurement over time". It would be much more reasonable to say that piezoelectric transduction give you pressure over time, since that what it does, relating time to pressure rather than just reporting the peak as lead does.

    The big difference is that the crystal returns to its former state after the force is removed and the lead doesn't. So you use what the transducer gives you. The crystal gives you electricity and the lead a length difference.

    One way you can compare LUP and PSI is to accept big numbers (in printed reloading guides, not in forums) as a lot of pressure but safe, and lower numbers a is less pressure which promises the advantages & problems that may bring. Beyond "lots of pressure" and "not so much pressure," it's pretty much splitting hairs to me.

    Neil
     
  18. hmb

    hmb Well-Known Member

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    Neil, see I told you so. Thanks Ed. HMB
     
  19. BigM-Perazzi

    BigM-Perazzi Well-Known Member

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    How far is it from Vandalia to Sparta, in gallons.....
     
  20. Border Bandit

    Border Bandit Well-Known Member

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    To me it seems Tim's explanation the most plausible, and, perhaps I could expand. It appears, from looking at some data, especially when we notice that occasionally there's a printing error or mistake showing a lesser charge producing greater pressure or velocity, or both, in the next value on a chart; that those data are intended to be used as a guide, and not facts, because of the many variables. I suspect, using Tim's example of time and money issues there's a fair amount of extrapolation published, and since, apparently, LUP testing is antiquated art, just like Dram Equivalents. Assuming the publisher is using extrapolated data, it's easier for him to make an educated guess and plug in an LUP value, that no one can question, than to put down a PSI value that someone could test.

    best... mike
     
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