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Thread: S&W Model 19 (K frame magnum) longevity

  1. #61
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    From SAAMI:

    For many years gun chamber pressure units had been commonly referred to as “pounds per square inch”, which was not technically correct. The older method of pressure measurement involves a piston through the side of the chamber compressing a lead or copper cylinder in which the measurement of the degree of compression is indicative of the maximum relative pressure generated. With the advent of the electronic transducer, it became necessary to indicate by some means the method and equipment used to determine the pressure values given. This is important, since the pressure values determined by one method cannot be mathematically converted to values for another, despite claims to the contrary. Likewise, the limiting pressure values for the different systems are not interchangeable.

    SAAMI created the designations of “Lead Units of Pressure” (abbreviated LUP) and “Copper Units of Pressure” (abbreviated CUP) to clearly indicate the system used in determining pressure results and/or limits. These designations apply only to values with the particular crushers, test gages and methods as outlined in SAAMI technical procedures. The terms LUP and CUP represented a change in name only. The pressure testing equipment, techniques and the numbers themselves are essentially the same as those associated with pressure units expressed as so many “pounds per square inch” prior to the advent of the piezoelectric transducer method. The term “psi” (pounds per square inch) is now reserved for electronic (piezoelectric) methods of measuring pressure, which is the predominant system in use today.
    Last edited by Petrol & Powder; 08-20-2019 at 04:44 AM.

  2. #62
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    S&W Model 19 (K frame magnum) longevity

    Quote Originally Posted by Petrol & Powder View Post
    I don't know how to make this any simpler: PSI and CUP are not interchangeable.
    What I am saying and m tech is saying is much of the current load data is loaded to a lower level than the 1970s and 1980s. Less powder as indicated in m tecs example. Less powder equals less pressure all other things the same. Nobody is arguing the two measurement(psi and cup) are the same or convertible . Regardless of measure system used, many loads are lower pressure than than they used to be because the load data has been reduced.I can’t be more clear than that.


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  3. #63
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    Is there any proof that SAAMI lowered the actual standards for the 357 magnum in the 1970's, 1980's, ???

    There seems to be this nostalgic view that .357 magnum was once much more powerful "back in the day". Almost all of the proof offered to support that view comes from people posting on forums such as this one.

    While there may be some truth that loads were reduced to fall in line with the improved piezoelectric transducer method, I know of no reduction in the actual maximum allowable pressure set by SAAMI.

    The current published SAAMI limits for 357 magnum which were published in 2015 show a maximum limit of 45,000 CUP and a 35,000 PSI.

    If someone has SAAMI published limits for from prior dates that are higher, I would welcome the opportunity to review that.
    Last edited by Petrol & Powder; 08-20-2019 at 09:31 AM.

  4. #64
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    SAAMI did not "lower" the MAP level for any cartridge as is commonly thought. SAAMI established MAP levels for many factory produced cartridges. The method for determining the MAP level is based on several criteria of which, if one is interested, you can find the reasons on SAAMI's web site. SAAMI is a "volunteer" membership organization which does restrict it's membership to larger ammunition manufacturers who can afford to belong. What occurred was, regarding the lowering of reload data, was since SAAMI was the only organization to monitor such cartridge pressures it became, through default, the premier legal authority on such. As such SAAMI established standards became the "standard" that was/is used in legal proceedings both civil and criminal.

    Older manuals which had data that was actually tested and not plagiarized used various methods of their own for determining the max load or, as often mistaken, the max psi for cartridges. When it became necessary because of potential, past or probable litigations the manual publishers, who are also members of SAAMI, decided to adhere to SAAMI standard MAP as the max psi for any of their loads. [Note; all max loads in the manuals are not at max SAAMI MAP levels as there are other considerations, as often explained in the manuals, that indicate a "max load".] Thus when using SAAMI MAP psi standards it was found many of the older manual "max Loads" were over the SAAMI MAP. That is not to say the older loads were "dangerous" just that they were over the SAAMI established MAP. Being members of SAAMI the manual publishers then made decision, based on legal concerns, to adhere SAAMI standards.

    Some manuals still list some loads for cartridges that exceed the SAAMI standards, mostly for older cartridges such as the 44-40, 45 Colt, 45-70 and some others, particularly +P cartridges. They understand in modern firearms those cartridges can be loaded and safely used to higher pressures than SAAMI established.

    As to the use of Magnum 357 loads in M19s it was well understood by those of us "back in the day" when the M19s were extremely popular that most practice, plinking, etc. shooting was to be done with 38 SPL target, standard or +P level loads. The 357 Magnum loads were to be used occasional for "duty" or SD carry. That common or "institutional" knowledge was lost, especially on those who insisted on shooting a lot of jacketed magnum level loads in the M19s. Also, as mentioned, when it became common practice for PDs to qualify and practice with duty level 357 magnum ammo the problems with the K framed M19 became more apparent. The Colt Pythons held up so the heavier framed L frame S&W and the Ruger Security series were introduced. They were designed to hold up to constant magnum level loads which the M19 was not.

    I seldom shoot magnums in my own M19 (don't remember the last time I did). I "carry" the Winchester 38 SPL +P 158 LSWCHP (FBI load) in it or my standard practice load with a 358477 or TL358-158-SWC over 3.5 gr Bullseye for practice or general shooting. I shoot the magnum loads out of my Ruger Security Six or Contender.
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  5. #65
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    S&W Model 19 (K frame magnum) longevity

    Bottom line many loads in the manuals have lower powder charge weights with all other parameters kept the same than in previous years in the 357 magnum. This fact leads me to believe those loads have lower pressure than earlier loads with more powder regardless of measurement method. Hence my original observation that some 357 loads have been toned down. My loads for 66s and 19s are usually 25000 to 30000 psi so I am not pounding them too hard.

    What I don’t know is whether a load that is 45000 cup with a copper crusher could be higher than 35000 psi if that same load is measured with piezo technology? Since the two methods are not linear with respect to each and not convertible , I suspect that may be case



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  6. #66
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    Thank You Larry

    I think it would be fair to say that at one time there was some data out there, even some published in manuals, that was over SAAMI limits. However, SAAMI did not lower their maximum pressures for the 357 magnum.
    Just because there was once data published in manuals that was over SAAMI standards doesn't mean that data reflected existing SAAMI standards.

  7. #67
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    [QUOTE=Petrol & Powder;4711059]Thank You Larry

    I think it would be fair to say that at one time there was some data out there, even some published in manuals, that was over SAAMI limits. However, SAAMI did not lower their maximum pressures for the 357 magnum.
    Just because there was once data published in manuals that was over SAAMI standards doesn't mean that data reflected existing SAAMI standards.[/QUOTE]

    That is correct.
    Larry Gibson

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  8. #68
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    "My loads for 66s and 19s are usually 25000 to 30000 psi so I am not pounding them too hard."

    That is the range I have found most 357 Magnum factory loads (made in the last 30 years) to run at.

    "What I don’t know is whether a load that is 45000 cup with a copper crusher could be higher than 35000 psi if that same load is measured with piezo technology?"

    I have tested loads listed at 45,000 CUP and they are, almost always have a higher psi than 35,000 psi. The old "classic" load of 14.5 gr (Hercules or Alliant) 2400 under the 358156 is a good example. That was listed, in years past, as being a max 45,000 CUP load. It runs over 35,000 psi (usually 37 - 38,000) in my Contender test barrel. Using 14 gr 2400 it runs 34 - 35,000 psi.
    Last edited by Larry Gibson; 08-20-2019 at 01:24 PM.
    Larry Gibson

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  9. #69
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    You will know how hot your loads are when:

    1) your gun loosens up, developing more than 0.002" of end shake,
    2) it goes out of time and fails to carry up in DA, or
    3) the forcing cone cracks at 6:00.

    If you enjoy the gun, want it to last and don't want to put as much $$ in gunsmith time and repair parts to keep it going, as you probably paid for the gun 20 years ago, you might re-read the thread, to consider the advice and benefit of experience given.

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  10. #70
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    S&W Model 19 (K frame magnum) longevity

    "What I don’t know is whether a load that is 45000 cup with a copper crusher could be higher than 35000 psi if that same load is measured with piezo technology?"

    I have tested loads listed at 45,000 CUP and they are, almost always have a higher psi than 35,000 psi. The old "classic" load of 14.5 gr (Hercules or Alliant) 2400 under the 358156 is a good example. That was listed, in years past, as being a max 45,000 CUP load. It runs over 35,000 psi (usually 37 - 38,000) in my Contender test barrel. Using 14 gr 2400 it runs 34 - 35,000 psi.[/QUOTE]

    Larry, you made my point that others cannot seem to understand. Loads that tested out at 45000 cup almost always have a higher psi than 35000 psi. 35000 psi is or is fast becoming the new standard per saami for the 357 magnum. I doubt any new data is made with cup methods but rather with newer psi equipment and limited to 35000 psi . Obviously, the newer load data has been reduced to conform to the new 35000 psi standard so the max pressure levels have been lowered with the newer psi method. You can bet ammo manufacturers are not going to load to levels greater than 35000 psi like the older 45000 cup loads(because it would be greater than 35000psi).I am not the only one that gets this. Brian Pearce of Handloader magazine who likely has more experience with load development and the industry than any of us by a long shot states this in my previous reference. He is a machine when it comes to generating data and he routinely has it pressure tested.


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  11. #71
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    dogdoc

    That is correct but let us remember there is no direct across the CUP/psi test spectrum correlation between the two methods. We can't say...this much CUP equals that much psi. There is too much variation based on too many variables. Looking at SAAMI MAPs for both CUP and psi (transducer) for example the 9mm CUP MAP is 33,000 while the psi MAP is 35,000. The 38 SPL has 17,000 MAPs listed for both methods. With rifle cartridges, particularly the bottle necks, the difference almost always has the psi MAP higher than the CUP MAP.
    Larry Gibson

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  12. #72
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    Back in the very early 60's I loaded full snort loads in my Smith and Wesson Highway Patrolman and Colt New Frontier. The most popular load, which was also listed in the Lyman Handbook was the Thompson 158 GC SWC over 15.5 grains of 2400. The hollow point version of the same bullet took 16 grains of the same powder.

    I shot several hundred rounds of these loads in my pistols and figured out these loads were hotter than the hinges of hell and back off to 13.5 grains of the same powder. Nothing I ever it with the lower loads ever knew the difference between that and the hotter loads.
    Disclaimer: The above is not holy writ. It is just my opinion based on my experience and knowledge. Your mileage may vary.

  13. #73
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    Know what you mean Char-Gar, my magnum 357 load with the 358156 is 14 gr 2400 which is just under the SAAMI MAP of 35,000 psi. I use it in my Ruger and Contender, not in my M19. The +P 38 SPL loads suffice nicely in my 2 1/2" M19.
    Larry Gibson

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  14. #74
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    We got my dad a m66 2-1/2" years ago. We loaded it with 158gr .357s and each took a turn. "That's kicks stupid bad", said Pop and he was right. I loaded him a supply of 158 Hornady swaged hp @800 fps and that's all he shoots in it since then. If I inherit it, it'll never see hot loads.

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  15. #75
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    Char-Gar;
    I well remember those 16.0 grs. Of 2400. That load seemed to be the “Standard” for serious “business” use. Early on, I pretty much decided that a “medium” load in my .357’s made more sense.

    This thread is an excellent learning tool with special mention of the input of yourself, Larry Gibson, and last, but not least, Outpost75.

    People, listen to these guys!

    Dale53

  16. #76
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    Quote Originally Posted by Dale53 View Post
    Char-Gar;
    I well remember those 16.0 grs. Of 2400. That load seemed to be the “Standard” for serious “business” use. Early on, I pretty much decided that a “medium” load in my .357’s made more sense.

    This thread is an excellent learning tool with special mention of the input of yourself, Larry Gibson, and last, but not least, Outpost75.

    People, listen to these guys!

    Dale53
    I am not in the same class as Larry and Outpost75. They are true science guys with great extensive knowledge. I am just an old shooter who learned what he knows, by pissing on the electric fence.
    Disclaimer: The above is not holy writ. It is just my opinion based on my experience and knowledge. Your mileage may vary.

  17. #77
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    Good reading. Keep it coming!

  18. #78
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    Quote Originally Posted by Char-Gar View Post
    I am not in the same class as Larry and Outpost75. They are true science guys with great extensive knowledge. I am just an old shooter who learned what he knows, by pissing on the electric fence.
    Welcome to the club!
    Dale53

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    I prefer to call it Empirical Knowledge. It's the same thing as learning by pissing on the electric fence ......but it sounds better.

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    Dale53

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check