1. Attention: We have put together a thread with tips and a tutorial video to help with using the new software. Please take a moment to check out the thread here: Trapshooters.com Tutorial & Help Video.
    Dismiss Notice

LUP ?

Discussion in 'Shooting Related Threads' started by j2jake, Apr 30, 2009.

Thread Status:
Not open for further replies.
  1. j2jake

    j2jake Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    2,284
    Saw this listed rather than PSI in reloading data. Someone please enlighten me to its meaning. Thanks, Jake
     
  2. mixer

    mixer Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    3,386
    Location:
    Coral Springs, Florida
    Lead Units Pressure. Not sure if that term is really used anymore.


    Eric
     
  3. waverider

    waverider Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    1,622
    Location:
    HI
    Lead Units of Pressure, older method of measuring pressure in a shotgun.

    Although there is no direct formula to translate to Pounds per Square Inch. Adding 1,000 to the LUP figure will give you a very rough estimate of PSI.

    Jason
     
  4. Quack Shot

    Quack Shot Active Member

    Joined:
    Mar 14, 2006
    Messages:
    4,003
    It is an older unit of measurement that relates to pressure in relative terms. It is NOT the same as PSI. It was used when a "crusher" type measurement system was the standard. They use a more direct method to measure pressure these days. Some of the older data is still listed as "LUP" or "CUP". Lead units of pressure or Copper units of pressure. CUP, LUP, and PSI are NOT interchangeable, nor can they be converted from one to the other.
     
  5. hoggy

    hoggy TS Member

    Joined:
    May 9, 2006
    Messages:
    1,261
    Makes one wonder why LUP is still used in some load references. Were these stats done so long ago that we should NOT use them for reloading? Why have so many of these loads not been redone in PSI's?
     
  6. j2jake

    j2jake Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    2,284
    Thanks Guys! I knew there was information out there! Jake
     
  7. mixer

    mixer Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    3,386
    Location:
    Coral Springs, Florida
    Copied from Wikopedia:



    "Comparing units
    While CUP and LUP numbers were intended to be comparable to the crushing power of a given pressure in psi, the numbers are not equivalent! Since a longer duration, lower pressure pulse can crush the cylinder as much as a shorter duration, higher pressure pulse, CUP and LUP pressures frequently register lower than actual peak pressures (as measured by a transducer) by up to 20%. For example, the SAAMI maximum pressure for the 7.62 x 51 mm is given as 52000 psi (CUP), or 62000 psi (430 MPa); the .45-70, on the other extreme, is listed as 28000 in both CUP and psi (190 MPa). SAAMI standards for a given cartridge may be expressed in CUP units, LUP units, or in standard units of pressure (psi or MPa).

    CUP and LUP pressures vs. transducer pressures
    Until the invention of measurement transducers in the 1960s, crusher guns were the only reliable method for estimating chamber pressures. With the availability of inexpensive, reliable transducers since the 1960s for actually making chamber pressure measurements, the industry almost universally has begun to move away from crusher guns for estimating chamber pressures, towards favoring making actual measurements. Transducers are also faster to use in practice, as they do not require the careful measuring of the copper or lead cylinders after firing. Additionally, transducers are capable of recording instant-by-instant pressures through the entire firing cycle. Hence, in the long run, using a transducer is less expensive, as it does not require using expendable metal cylinders in a crusher gun, and also reduces the labor required to analyze test results.

    One outcome from this transition to using measurement transducers is, for example, that a Speer reloading manual from 1987 lists all SAAMI pressures in CUP, while current references list nearly all pressures in PSI. Another outcome is that design margins are now better determined, which has the effect of increasing the long-term safety of firing multiple thousands of rounds in a gun. With estimates based on crusher guns, actual safety margins could never be accurately assessed, short of actually firing tens of thousands of rounds in a sample gun."


    Eric
     
  8. Quack Shot

    Quack Shot Active Member

    Joined:
    Mar 14, 2006
    Messages:
    4,003
    hoggy

    I would be more comfortable using later data measured in PSI, rather than to rely on older data expressed and measured in CUPS or LUPS by the crusher method. This older data really does not show the peak pressures encountered as well as the transducer methods used today. The other question of why the data is not redone is simple economics. It's expensive and time consuming to do it over. Much of the data is fine, just that some of the "hotter" loads may not be as accurately measured as was once thought. You will probably see a lot of loads being revised if/when they are actually retested. If you compare some of the older loading manuals to those published with newer current data, you may see many of these loads revised. Unfortunately, some manuals like Lyman tend to use the old data forever. I have one of the much older Lyman manuals and it has a lot of the same data that the new one does. Some newer data has been compiled, but a lot of it has been around as long as a good many trap shooters. Powder companies seem to take a lot of shortcuts as well, so I can't single out just one manual and call it a day.

    One way to remove some of the variables is to have some of your own loads tested and see what they develop in Pressure and Velocity. It may not be as expensive as you thought and there is a little peace of mind knowing what you are shooting.
     
  9. hoggy

    hoggy TS Member

    Joined:
    May 9, 2006
    Messages:
    1,261
    Quack shot I'm talking about 2009 reloading book from Hodgdon. Guess they like Lyman (which I also have as a older reloading manual)they are retrying these loads. JFYI I only load using PSI. I just don't know why reloading manuals today list any loads LUPS especially if there's any chance at all of them being dangerous, which they may not be at all. I just don't trust them.
     
Thread Status:
Not open for further replies.
Search tags for this page

lup loads