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When Did 357 SAAMI Pressure Change?

Discussion in 'Handguns: Revolvers' started by Jaywalker, Dec 24, 2012.

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  1. Jaywalker

    Jaywalker Member

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    I understand the SAAMI pressure for the 357 changed in the 1980s or 1990s, down to its present 35,000. Does anyone know what year?
     
  2. murf

    murf Member

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    1992, or 1993.

    murf
     
  3. Guillermo

    Guillermo member

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    Was it 37000 before?
     
  4. ArchAngelCD

    ArchAngelCD Member

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    I think it was 40,000 PSI.

    I think SAAMI changed the pressures when the ultra light .357 Magnum carry guns became popular. (think 12oz S&W M340)
     
  5. Guillermo

    Guillermo member

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    Thank you ArchAngel
     
  6. Jaywalker

    Jaywalker Member

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    Thanks. I'd read that S&W wanted it reduced due to the problems with the 125 gr in the K-frames, M-19 and M-66, but I suspect its use in the J-frames had a influence. It could also have been the presence of better pressure transducer equipment that showed peaks instead of averages showed much higher pressure than they'd thought for years.

    I'd also heard it was 47,000 somethings (psi, lup, cup, etc.) before dropping to 35K, but that doesn't mean what I read was right.

    I'd shot both the 19 and the 66 with those older, higher pressure 125 gr loads. They were accurate enough, but I couldn't see using it for SD - too much flash, blast, and recoil for follow-up. Since I'd moved to semi-autos I had not heard about the reduced pressure until recently. Today's pressures might change me back.
     
  7. CraigC
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    CraigC Member

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    My info says 46,000CUP (43,500psi) to 35,000psi in 1995. Which was approximately a 25% reduction.
     
  8. 2zulu1

    2zulu1 Member

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    If you handload, VihtaVuori (2006) loads to the European standard of 43,500psi, same for the 41mag. :)
     
  9. skidder

    skidder Member

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    Thanks for the info guys.
    My reloading manuals also verify there was a change. According to the copyright dates it looks to be somewhere in the 90's.
     
  10. BaltimoreBoy

    BaltimoreBoy Member

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    So, Jaywalker, you are implying that because S&W was manufacturing revolvers that didn't stand up well to the existing standard, they had SAAMI change the standard rather than fix the problem?

    I knew about the 70's reduction in 38Special. Somehow this reduction in 357 had escaped me.
     
  11. rcmodel

    rcmodel Member in memoriam

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    I doubt it had anything to do with S&W K-Frames.

    .44 Magnum & .357 Magnum were both reduced at the same time.

    I suspect it had more to do with more accurate pressure measurement methods when electronic transducers took over from copper cylinders getting hammered shorter.
    And they found out what the pressure really was.

    rc
     
  12. Jaywalker

    Jaywalker Member

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    BaltimoreBoy,

    I don't know - we see all sorts of conspiracy issues on the internet, and one I read suggested Smith might have lobbied for a change based on the K-frame very real problems with the 125 gr. 357 load. It's possible, but I think it's more likely the change in the testing methodologies cup/lup to psi using strain gauges and piezo-electric methods led to a more accurate representation of pressure. I'm certain, however, there would be no changes to any of the testing methodologies or resulting pressure standards by SAAMI without agreement by large industry manufacturers, including Smith.
     
  13. Steve C

    Steve C Member

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    The SAAMI pressures measurements changed units from CUP (Copper Units of Pressure) to PSI (lbs per sq in). CUP's where determined using the old copper crush method that is less precise form of measurement of peak pressure and has no direct correlation to PSI. PSI measurements are determined by electronic Piezo transducers which is much more precise in determining peak pressure.

    Comparing old SAAMI CUP pressures to current PSI is similar but not precisely like comparing English to Metric measurements and trying to determine if the numbers indicate a real change.
     
  14. Guillermo

    Guillermo member

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    Steve C

    The change in measuring scale came in the late 60's...not 1995.

    That was a political change. Not scientific.
     
  15. ArchAngelCD

    ArchAngelCD Member

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    CIP pressure limits have nothing to do with SAAMI pressure limits. CIP limits are generally higher than SAAMI limits. (in some cases what SAAMI used to be)
    http://www.cip-bobp.org/
     
  16. gamestalker

    gamestalker member

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    I read an article written by S&W some years ago about testing that they did with the 125 gr bullets being blamed for fractured forcing cones on K frames. Apparently they ran 10's of thousands of .357 H110 loads with 125 gr. jacketed bullets and had no cone failures. However, when they tried the same thing with non jacketed bullets, forcing cone failure appeared and fairly quickly, which was apparently caused by lead deposits in the cones causing pressure on the cone to fracture them.

    As for the .357 mag changing max SAAMI pressures, I read that this change was primarily the result of better testing tools such as the electronic transducer, thus eliminating the CUP method and going with the highly accurate transducer pressures to PSI.

    Currently I load with H110 / 296 and have and still do load and shoot gobbs of them 125 gr. jacketed bullets through my K frames with no indications that they are damaging the cones, or anything else, other than my wrists. One of my K's, a 66-2, has had thousands put through it.

    GS

    GS
     
  17. nofishbob

    nofishbob Member

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    There seems to be two different issues being discussed:

    The method of measuring pressure, and reducing damage to guns.

    I contend that if new measuring equipment came along, and more accurate pressure/time information was available, there would be no reason to reduce the loads in the absence of a desire to correct an overpressure situation that had been exposed by gun failures.

    If guns were not failing at a certain load, many of which were used for decades, why reduce them when new pressure info is available?

    After all, measuring chamber pressure is intended to predict a safe load for a particular cartridge.

    No matter what a pressure measurement says, if the guns are failing, the pressure is too high. Conversely, if the guns are reliable at a certain load ( for thousands of rounds), it is a safe load no matter what the pressure readings are.

    I am always struck by the assertion that when psi transducers became available, all .357 loads had to be reduced because all these years we were overloading our revolvers but somehow we were just lucky that the guns did not blow up on us.

    Bob
     
  18. showmebob

    showmebob Member

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    Confused now

    Ok, I'm not following this.
    Since the transducer is more accurate than the crusher method why not just measure and post the pressure of the (then) existing loads for the standard pressure?
    Why reduce the pressure standard unless there was a problem with existing loads? If testing with the transducer and finding the loads were overpressure, why not leave the pressure limits alone and lower the recommended powder charge weights?
    Seems to me the pressure limits were lowered for some other reason.
     
  19. CraigC
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    CraigC Member

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    This is total BS from somebody who admits to never using a cast bullet. If you match your diameter and hardness to your sixgun and velocity range, there is no leading. However, use the wrong size/hardness bullet and you will get leading. Shoot tens of thousands of rounds through a continually leaded bore and I wouldn't be surprised to see some issues crop up. But some people get weird ideas about cast bullets in their head and there's no convincing them otherwise.
     
  20. Steve C

    Steve C Member

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    If there was any change in the 60's it didn't come to light in any of the loading manual publications until the 80's. All my old manuals from the early 70's and most from the 80's quote pressures in CUP's for rifles and handguns and LUP's for shotguns.

    Remember that SAAMI is not a governmental agency but a trade organization of arms and ammunition manufacturers. Politics has little to do with their publications of pressure guidelines in the manufacturing of ammunition.
     
  21. nofishbob

    nofishbob Member

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    Steve, I wonder if the politics mentioned were intended to be the politics between manufacturers within their trade association

    Bob
     
  22. Blue Brick

    Blue Brick Member

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    46,000 cup in 1981
     
  23. Jaywalker

    Jaywalker Member

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    Showmebob, I think all of us wish SAAMI had tested and published equivalent loads using multiple methods, but if they did I'm not aware of it. It sounds like economics and policy, from my experience in corporations. No one wants to repeat a standard test because different results cause confusion. "What should we do? Issue a changed standard?" If it comes out the same, you've just wasted time and crushed another copper cylinder. Too bad, though.

    Here's an interesting wiki on CUP: https://en.wikipedia.org/wiki/Copper_units_of_pressure
    They make an informative point, "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 those who visit that wiki site, note in the references at the bottom a nice paper reference written in 2002, "Correlating PSI and CUP," by Denton Bramwell. In it he finds CUP and PSI "correlated," but not "equivalent," with a good example for the difference being his increasing weight compared to his belt size - as one gets bigger so does the other, but it's hard to say by how much.

    It's clear the use of piezo/strain gauges found higher peak pressures in common loads and so they dialed them back. Why they dialed them back, however, is conjecture, based on your social views, e.g., nasty lawyers, need to keep K-frames running, various conspiracies, real concern for customers, etc. I do note that Smith makes the 357 currently in J-, L-, and N-Frames, but not K, for what it's worth.

    I do wish we had the earlier standard to compare, though.
     
  24. showmebob

    showmebob Member

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    Jaywalker

    Thanks for the info. I read and re-read it.

    Maybe I'm way off this morning as sleep evaded me last night but here's my take for whats its worth.

    If a gun was built to withstand xxx pressure and that pressure was then checked with a transducer and found to be higher than xxx (and the guns were experiencing no failures) then the guns were built to acually withstand xxx+ pressures. Therefore the pressure standards could (and maybe should) have been actually raised to the pressure readings obtained with the transducer. Since the pressure standards were lowered the pressure standard must have been reduced due to gun failures/desires to build lighter guns etc, not due to the accurate transducer readings.

    At least this is the way I'm thinking this morning. All thoughts appreciated.
     
  25. Jaywalker

    Jaywalker Member

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    I'm not an engineer or a metallurgist, but here's my take on engineering/production thinking: you pick steel and processes (forged, cast, machined, etc.) based on expected load, both for individual and cumulative lifetime use), then add in some safety percentage in case you're wrong about the load - a 50% safety margin, for example (just for argument, not even a guess), over the requirement. PSI testing was not available widely until the mid-1960s, so I suspect the engineers at the time created an equivalency between the PSI design characteristics of steel and the LUP/CUP testing methods since direct PSI testing on barrels wasn't available. If you're reputable, you build it so it doesn't explode, and since we have few kabooms, relatively, Smith is by definition reputable.

    While in the case of our 357 example they appear to have been safe instantaneously (no disastrous failures), the more accurately-measured pressures were probably above the basic design requirement and were well into the safety margin to the extent they lessened revolver's lifetime below that particular design parameter. It turned out that CUP/LUP and PSI were not directly equivalent, so something had to change - stronger steel, redesign, or lower pressure. (If the J-frame has less steel, maybe they assumed few people would want to shoot full house loads - I have no opinion.) Smith did introduce the L-frames, then, so they did make use of at least two of the three alternatives.

    I had both a Smith Model 19 and a Model 66 and neither broke, but the problems with that model using 125 gr loads is very real and is documented extensively elsewhere. A problem seemed to be the necessity of milling a flat on the bottom of the facing cone - it was a problem, even when the remaining forcing cone is larger than the original, fully round forcing cone on the J-frame 357. So, I guess what I'm saying is there were pressure problems with your "xxx" load example, and the solution is what we have today.

    That's not to say that Smith drove this particular decision or that it was based on any K-frame problems, but as Smith & Wesson's a part of SAAMI industry group, they would have to have agreed with the need to reduce pressure or it might not have happened.

    You asked for thoughts, but while I have somewhat of a background in production, I'm not an engineer or metallurgist, so if one signs on, I'll defer to him/her for a better explanation. I'm speculating on motivations of a company and engineers from years ago, so I've almost erased this post several times now as it comes close to too many I've read on the internet that have no basis in fact - I'm just stringing together the few things I know. I still may erase it.

    On another issue, has anyone noted that this thread now has over 143,000 page views?
     
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