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Thread: Is there a way to calculate pressure in cases?

  1. #1
    Boolit Master Kev18's Avatar
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    Is there a way to calculate pressure in cases?

    I have an 1886 in 40-82. I shoot quite alot, so I have a few loads.

    260 grains, 28 grains 4198, 1500fps
    260 grains, 50 grains 3031, 2000fps

    Now I want a higher fps load with a 300-310 grain bullet.
    300 grains and 2000 fps... but how do I know how much powder I need?

    I know that a documented load of 34 grains of 3031 with a 260 and 300 grain bullet is 1500 fps.

    How can it be if the bullet is heavier?

    Is there an equation I can do or is it just add a few grains, shoot at a chrono, and test over and over? I dont own a chronograph

  2. #2
    Boolit Master
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    Is there a way to calculate pressure in cases?

    Your safest bet is to stick with published load data.
    R/Griff

  3. #3
    Boolit Grand Master
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    Regards
    John

  4. #4
    Boolit Master

    Rcmaveric's Avatar
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    We have things like Quickloads or GR Tools. But even those are not for the inexperienced and can be dangerous. They are only as good as the accurate information inputted. Even then they are only smart wild guess. It can be off and all information when calculating ballistics needs to he approaches with caution. Published loads from reputable sources are always proven safe and reliable (lawyers and stuff).

    Unless you have a chamber pressure guage you really don't know whats going on in there.

    Sent from my SM-N970U using Tapatalk
    "Speak softly and carry a big stick; you will go far."
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    Boolit Master Bazoo's Avatar
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  6. #6
    Boolit Master


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    Deep water without a life preserver...not good.

    Do not be tempted by using a load some yahoo has posted on a forum...any forum...including this one.

    The best you can do is use something like Quickloads to see what powders might get you there and then work up very slowly. I would probably use Federal primers as they seem to have a softer cup and should show pressure signs earlier.

    Good luck!
    Don Verna

    NRA Endowment Member

  7. #7
    Boolit Master

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    if you just have to explore the upper limits, the only safe way is a pressure trace system.
    if you are ever being chased by a taxidermist, don't play dead

  8. #8
    Boolit Grand Master


    Larry Gibson's Avatar
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    Having used the Powley Computer for years, then the Quickload program while I have been actually pressure testing with the Oehler M43 PBL in 30+ cartridges in numerous firearms I have come to the same conclusion as ATK/Alliant (used to be Hercules). Let me quote them from one of their later Reloader's Guide;

    "Even after 80 years of producing and testing powders, ballisticians are unable to calculate and predict exact ballistic results; we must test-fire our powders and each set of comp0nents and record the results. "

    Even at that I have exactly duplicated said tested loads and Lyman's also and have measured sometimes higher psi and sometimes lower psi......I can never predict. Has to do with lot to lot variations of the component and variation of test conditions.
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
    ― Nikola Tesla

  9. #9
    Boolit Master Savvy Jack's Avatar
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    Quote Originally Posted by Larry Gibson View Post
    Even at that I have exactly duplicated said tested loads and Lyman's also and have measured sometimes higher psi and sometimes lower psi......I can never predict. Has to do with lot to lot variations of the component and variation of test conditions.
    Same here, I have tested all of Lymans listed 44-40 bullets with some of the powders they list. Some were higher than they published and some were lower but 90% were a "certain percentage" lower than published...as expected.

    Quick Loads does not work with the lower pressures or at least the 44-40. My data compared to my actual PressuretraceII data were horribly inaccurate.

    John Boy's link looks interesting...wonder how close it can be.

    It is critical to use the exact components used in published manuals. Substituting one bullet for another, even the same weight, can be a huge change in pressures.

    You are correct Larry,

    "Even after 80 years of producing and testing powders, ballisticians are unable to calculate and predict exact ballistic results; we must test-fire our powders and each set of comp0nents and record the results."

    Not only is this true, current factory manufactured loads must be tested and the results must be within SAAMI's MPSM

  10. #10
    Boolit Master Savvy Jack's Avatar
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    Larry, using the Powley Computer, I get the following results in comparison to the PTII results.

    44-40 PTII Tests

    20" barrel
    25.5gr IMR-4227
    Winchester 200gr JSP
    1,735fps @ 19,652 psi

    I estimated this load to be much greater then 22,000 cup due to the inaccuracy of the .846 formula much past 15,000 psi

    Here is what Powley computes which I think is more in line with Sharp's estimated 30,000 CUP estimations.

    Click image for larger version. 

Name:	121475929_2650337328520340_8808461885603873555_n.jpg 
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    I will check out Unique and see what I can get.

    Okay, just did 2400 powder Lyman max load. Lyman claims 19,000cup

    20gr of 2400 with a Speer 200gr SJHP (4425)
    My results, 1,672fps @ 15,618 psi (estimated 18,500 cup)

    Powley's results (different measurements)
    25,400 cup, much higher than both mine and Lyman's results

    Using 10gr of Unique with the 200gr SJHP
    Lyman says, 13,300 cup
    Powley's results 12,000 cup

    My results
    11,363 psi which should equal 13,754 cup using the .846 formula

    Again, low pressures are close but once they get above 14k or 15k psi, the formula's folks use go through the roof!
    Last edited by Savvy Jack; 10-17-2020 at 07:23 PM.

  11. #11
    Boolit Master Bazoo's Avatar
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    Maybe contact Dave Turnbull and ask him about it. He says the old 1886 can take higher pressures of modern rounds if you replace the barrel. Maybe he has some idea of how hard you can push your original.

  12. #12
    Boolit Grand Master Texas by God's Avatar
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    50 grs of 3031!!? I hope that’s a typo. The best idea for your 100+ year old rifle is to stick with original level ballistics, in my opinion.

  13. #13
    Boolit Grand Master
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    I missed that 50gr also. Would be best if OP would log on and change typo because that load is immediate Emergency Room if he makes it to the ER
    I sent the OP a PM
    Regards
    John

  14. #14
    Boolit Master Kev18's Avatar
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    Quote Originally Posted by Texas by God View Post
    50 grs of 3031!!? I hope that’s a typo. The best idea for your 100+ year old rifle is to stick with original level ballistics, in my opinion.
    Its is a recorded load... and a very accurate one. Im not posting my loads for fun. They are all from trustworthy sources like books and articles. And all made for antique/ original rifles. None of my rifles are repros.

  15. #15
    Boolit Master Kev18's Avatar
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    Quote Originally Posted by Bazoo View Post
    Maybe contact Dave Turnbull and ask him about it. He says the old 1886 can take higher pressures of modern rounds if you replace the barrel. Maybe he has some idea of how hard you can push your original.
    I was jsut asking a general question for fun. I dont want to get too into it. Im sure he's very knowledgeable. I have pretty much every source of info on the 86 and 40-82. I love the rifle and cartridge.

  16. #16
    Boolit Grand Master
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    Jack, nice to see another reloader use the Powley Calculator. Noted on the screen print you posted, your calculation is for CUP, not PSI ... just check mark the PSI box to change the results
    I don’t use the PSi calculator much. Powley has another calculator that is not on the Internet any more to calculate FPS and twist when I’m to lazy to use a chronograph. Excellent tool for pre 1900 calibers when Sharpe doesn’t have it in his manual. If you want it, PM me your email and I’ll copy the program off my computer and send it to you
    I first used it for the rare Ideal 375166 (38-55), 320 gr bullet where there is zero data to CX the best black powder charge which has become my best go to bullet that is 17.8 in a 18 Twist barrel. It is accurate to 500 meters

    .
    Last edited by John Boy; 10-18-2020 at 12:07 AM.
    Regards
    John

  17. #17
    Boolit Master
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    Quote Originally Posted by Texas by God View Post
    50 grs of 3031!!? I hope that’s a typo. The best idea for your 100+ year old rifle is to stick with original level ballistics, in my opinion.

  18. #18
    Boolit Master
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    If I was that concerned about pressure, I would use case head expansion measurements. I never load any of my older classic guns or modern replica anywhere near what is being talked about here. BP or the same pressure levels in smokeless only for me.

  19. #19
    Boolit Master Savvy Jack's Avatar
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    Quote Originally Posted by John Boy View Post
    Jack, nice to see another reloader use the Powley Calculator. Noted on the screen print you posted, your calculation is for CUP, not PSI ... just check mark the PSI box to change the results
    I don’t use the PSi calculator much. Powley has another calculator that is not on the Internet any more to calculate FPS and twist when I’m to lazy to use a chronograph. Excellent tool for pre 1900 calibers when Sharpe doesn’t have it in his manual. If you want it, PM me your email and I’ll copy the program off my computer and send it to you
    I first used it for the rare Ideal 375166 (38-55), 320 gr bullet where there is zero data to CX the best black powder charge which has become my best go to bullet that is 17.8 in a 18 Twist barrel. It is accurate to 500 meters

    .
    Thanks!! I missed the psi conversion...I'll check again

  20. #20
    Boolit Master Savvy Jack's Avatar
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    I see the psi now (bottom of chart), the psi is higher than the cup and that is incorrect for the low pressure 44-40. I'll check the new program you send me and see what it says.

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