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Thread: Ken Waters' pressure testing method.

  1. #1
    Boolit Master


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    Ken Waters' pressure testing method.

    I think it was Ken Waters who used a method where you measure the case head diameter of a factory round, the measure it fired. Then you use that amount of expansion (whatever it was) as your top end for handloading.

    Now I've been told on this site that has been found to be inaccurate. I'd like more data, can anyone point me in the right direction please?

    Thanks.


    Cat
    Cogito, ergo armatum sum.

    (I think, therefore I'm armed.)

  2. #2
    Boolit Master
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    I have used that method before; it can work IMO as long as new brass is being used for the handloads.

    I'd have a little difficulty 'betting the farm' with it; would prefer multiple independent confirmations: trusted load data, primer appearance, Quickload modeling, even just chrono data if nothing else.
    Too many people trust one indicator, then get into trouble when ignoring the others.

    It does require a very accurate micrometer, as well as excellent micrometer technique - which is somewhat less common.
    Last edited by Kestrel4k; 09-11-2017 at 05:07 PM.

  3. #3
    Boolit Master

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    Quote Originally Posted by Kestrel4k View Post
    I have used that method before; it can work IMO as long as new brass is being used for the handloads.

    I'd have a little difficulty 'betting the farm' with it; would prefer multiple independent confirmations: trusted load data, primer appearance, Quickload modeling, even just chrono data if nothing else.
    Too many people trust one indicator, then get into trouble when ignoring the others.

    It does require a very accurate micrometer, as well as excellent micrometer technique - which is somewhat less common.
    With so much at stake, I would not trust myself to make that call. Since I don't do max loads, it really is a moot point for me. I remember reading about Ken Water's method many years ago and didn't really understand it then either. Too many other things can enter into those measurements to make them reliable(for me).
    John
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    Boolit Master Hick's Avatar
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    I really don't know much about this, but I do want to make an observation: I have on my reloading bench 4 30-06 cases fired by a friend using reloads made by someone else. The cases all appear to be in good shape with no indication of failure, and my friend assures me he had no trouble firing the rounds. The heads on these 4 cases are so large they will not even fit in a shell holder. I suspect my friend's 30-06 has a very generous chamber. It makes me think that trying to correlate head expansion to load acceptability is risky at best.
    Hick: Iron sights!

  5. #5
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    Quote Originally Posted by Catshooter View Post
    I think it was Ken Waters who used a method where you measure the case head diameter of a factory round, the measure it fired. Then you use that amount of expansion (whatever it was) as your top end for handloading.

    Now I've been told on this site that has been found to be inaccurate. I'd like more data, can anyone point me in the right direction please?

    Thanks.


    Cat
    That is an over simplification of Water's method.

    You had to use the same factory brass to test your reloads in. You had to pull the bullets, dump the powder and deprime. Then load the factory brass with your test loads using the same weight of bullet and a powder that was similar in burning rate. You measured the case at the expansion ring area before firing and then after firing measuring he expansion ring. Water's also used a chronograph to compare the factory velocity with his reloads velocity. The idea was to develop a pressure load that gave equal expansion ring diameter at a similar velocity.

    I have used his method with 3 different cartridges; .223 Remington, .308W and 30-06. I also concurently measured the pressures (Oheler M43) and found his method was fairly close, close enough to be useful if one used the method correctly.

    Unfortunetely many who attempt to use the method do not use it correctly. They use use brass that is already fired (the same factory brass or other), they use an other lot of brass of the same make, they use other brass of different make, they use a different weight of bullet, they use a powder with a burning rate substantionally different than the factory ammo or a combination of these. They also don't use a chronograph chronographing the factory ammo at the begining/same time as the test of the reloads. Any of those or a combination can result in a serious difference in pressure. To be a valid test the same unfired factory brass from the same lot of factory ammuntion must be used.
    Larry Gibson

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  6. #6
    Boolit Master tazman's Avatar
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    What Larry said.

  7. #7
    Boolit Master
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    Do keep in mind this is only a comparison to pressure developed by a factory cartridge which is most likely considerably under SAMMI specs (in America). I use the word "considerably" to indicate an unknown range of values. My suspicion is most of the major manufacturers aim for a maximum average pressure (MAP) about 80-85% of SAAMI maximum MAP. The boutique manufacturers probably get closer to SAMMI max MAP.

    The point of my point is to say if you use Ken Water's method, you should come out with a safe pressure, but it may be considerably under SAAMI specs.
    "Time and money don't do you a bit of good until you spend them." - My Dad

  8. #8
    Boolit Master


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    Ah. Thank you all. I knew I was not stating his full method, but I didn't realize that there were aspects I missed in my study. Thanks Larry, that clears it all up for me.

    I setting about loading the 7.62x39 in a Cz 527. All the loading data I have is for the SKS/AK. They are both considerably weaker actions. I'd like to know where that upper limit is for the Cz. I doubt I will load to it, I'd just like to know.


    Cat
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    (I think, therefore I'm armed.)

  9. #9
    Boolit Master
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    If your primers are falling out after a couple of reloads, you need to back off the throttle! But really, there are several things to watch out for.

  10. #10
    Boolit Master
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    I haven't read Ken Waters' pressure testing method in some time, but the detailed explanation in post #5 is excellent. I think Waters wrote this up in a HANDLOADER article originally and it was re-printed in his PET LOADS book, a necessary reference for any serious handloader. I've used the Waters method. While somewhat comforting in developing loads for obsolete cartridges, etc., there seems to be indications that this method is less (maybe far less) reliable and accurate than we used to think it was.

    Regardless, this non-expert thinks the Waters procedure still retains at least some merit. I don't have a link reference to it, but gunwriter John Barsness wrote up a piece for HANDLOADER some years ago about what may be a more reliable pressure testing method for handloaders. It's well-researched and contains some great information in developing safe handloads.

  11. #11
    Boolit Master
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    He measured the EXPANSION RING that one sees above the head. It is more SENSITIVE to pressure. Therefore more reliable. But the word RELIABLE is used cautiously in this senario. He used it in conjunction with known cases and known loads in the same "lot" of cases of the same brand to compare EXPANSION RING expansion with.
    Still one needs to be caution. Better than using the primer appearance that some uses but then doesn't trust a sensitive mic to record expansion with. Funny isn't it?
    We Know Mass Cannot Be Weighed But It Has Newtonian Weight And That Is Derived From Kilograms And Kilograms Can Be Converted to Pounds. But, Still Mass Cannot Be Weighed. But How is the kilograms obtained? Can Kilograms Be Weighed? Evidentally Yes It Can. But, Still Mass Cannot Be Weighed So Kilograms Must Not Exist. Funny Isn't It.
    One good thing out of this the next time I'm at the doctors and they want to weigh me I'll tell them mass cannot be weighed.

  12. #12
    Boolit Master
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    I've always regarded Ken Waters and Bob Hagel as the best of the gunwriters, regardless of the era. I had forgotten in my earlier post about Bob Hagel's method for pressure testing. Won't get into it here for the sake of brevity, but it shouldn't be difficult to locate. As I recall, there was some disagreement between the two writers on this subject, but both had lots of experience and good reason for their conclusions.

  13. #13
    Boolit Master
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    Obsolete, totally.

    A chronograph is the way to go.

    If your load's velocity exceed that of the max published load for the EXACT combination you are using, you are in dangerous territory.

    No animal/target/gong you shoot will every know you gave up 100 fps.

  14. #14
    Boolit Master Outpost75's Avatar
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    Another method which benchrest shooters have used with varying methods of success for high-pressure cartridges is to start with new brass cases out of the same factory lot, which have been prepped for the rifle, and take that group of five cases, shoot and reload them TEN times at the range, seating primers by hand, and judging by "feel" whether the primer pocket has loosened.

    For a cartridge similar to the .223 Rem. or .308 Win., if you can fire and reload the case TEN times the load is safe.
    If you get perceptible loosening of the primer pocket in less than FIVE reloads, reduce the charge 10% and repeat.
    If you get perceptible loosening after more than five reloads, but in less than TEN, reduce the charge 5% and repeat.

    If you need to put a piece of tape over the primer to hold it in until you can load the cartridge, ask everybody to move three benches away and say in a loud voice, "here, hold my beer while I try this@!"
    The ENEMY is listening.
    HE wants to know what YOU know.
    Keep it to yourself.

  15. #15
    Boolit Master
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    eldon- The John Barsness article from HANDLOADER that I referred to in post #10 deals with what you mentioned. I'll attempt to locate it when I have time. I think many of the folks who post here have old copies of HANDLOADER.

  16. #16
    Boolit Master
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    HANDLOADER #236, August 2005, p. 62, "Velocity and Pressure", by John Barsness; well worth reading.

  17. #17
    Boolit Master Harter66's Avatar
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    Quote Originally Posted by Eldon View Post
    Obsolete, totally.

    A chronograph is the way to go.

    If your load's velocity exceed that of the max published load for the EXACT combination you are using, you are in dangerous territory.

    No animal/target/gong you shoot will every know you gave up 100 fps.
    I would disagree .
    I have a couple of rifles that reach published data numbers with much lower than suggested charges . A sister rifle comes in under speed for the same load . The slow rifle has almost a match chamber while the other has a long leade and runs 200 fps fast .
    In the time of darkest defeat,our victory may be nearest. Wm. McKinley.

    I was young and stupid then I'm older now. Me 1992

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  18. #18
    Boolit Master
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    I think all the methods discussed here have varying degrees of merit and usefulness. As long as one knows the coarse limitations of each method, they can certainly be used in conjunction with one another.

    A chronograph remains an incredibly useful tool for most handloaders in roughly determining pressure. Most barrels are not "fast" barrels or "slow" barrels. I've had both kinds; they skew results, but fortunately, most barrels are pretty close to just right; figures jive closely with book figures.

    Something I found quite interesting when working up new, safe handloads for a rifle chambered in 7x61 Sharpe & Hart...based on the Barsness research and subsequent article, velocity increases at one-fourth the rate of case capacity. Comparing a 7mm Rem. Mag. case with the S&H case showed an advantage of 6.9% greater capacity for the Remington case. Divided by four, this equaled a 1.7% increase in muzzle velocity for the 7mm Rem. However, most 7mm Magnum barrels are 24" in length while the S&H barrel was 26".

    I took six load manuals and averaged the velocities of popular bullet weights for the magnum. Velocities for the 7x61 should have been 1.7% less. Adding 50 fps for the extra 2" of barrel on the Sharpe & Hart rifle provided very close to the same velocities as the 7mm Rem. Deducting 50 fps, muzzle velocities of the S&H were very close to the 1.7% figure. Importantly, I tailored my load data to get the right velocity figures and avoid high pressure problems.

    This formula worked very well for me in this instance. It's the only time I've used it to date, but would certainly try it again if necessary.

    I couldn't teach a kid to butter bread without making it needlessly complicated, so I tried hard to oversimplify my explanation. I hope I got the point across.

  19. #19
    Boolit Master
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    Micrometer measurements have to be taken at exactly the same spot/orientation ,etc. I go with primer/case head appearance , bolt lift/action cycle and chrono . Also , you got to wonder why and to what purpose are you operating in this area of the envelope of tolerance. Just my.02

  20. #20
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    Quote Originally Posted by Tedly View Post
    Micrometer measurements have to be taken at exactly the same spot/orientation ,etc. I go with primer/case head appearance , bolt lift/action cycle and chrono . Also , you got to wonder why and to what purpose are you operating in this area of the envelope of tolerance. Just my.02
    Would you say your tolerance of load development is any better? Bolt lift, primer appearance, etc., come on now.
    We Know Mass Cannot Be Weighed But It Has Newtonian Weight And That Is Derived From Kilograms And Kilograms Can Be Converted to Pounds. But, Still Mass Cannot Be Weighed. But How is the kilograms obtained? Can Kilograms Be Weighed? Evidentally Yes It Can. But, Still Mass Cannot Be Weighed So Kilograms Must Not Exist. Funny Isn't It.
    One good thing out of this the next time I'm at the doctors and they want to weigh me I'll tell them mass cannot be weighed.

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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