Math about pressures, bullet speed/time in the barrel etc

georgelza

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Cross posting, sorry, thinking this deserves a more generic chat/thread.

curious... I've seen a couple of people mention they working out the pressure... comparing they load/pressure against the SAAMI numbers, comparing it to numbers as per attached.

how do you work out the pressure?

I've got a friend that has a spread sheet, where he calculates the burn rate/time, and compare that against the projected speed of the bullet, determining that against the time that the bullet is in the barrel, and relating that to the burn rate, determine how much unburned power goes out the front (aka wastage).
other than quickload and GRT, does anyone have a spread sheet that does this..

Interested in getting to understand, work out the numbers myself.

G
 

ShtrRdy

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    What little I know about ballistics programs I don't see how you could do the same thing as Quickload with a spreadsheet.
     
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    secondofangle2

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    I am very very skeptical of anybody without a highly specialized background making an .xls file that does what QL does. I know there are those guys out there, but then again, why? When QL is there already.

    Even if I could make a .xls file that did what Applied Ballistics does, why would I? Unless I intended to go compete with Bryan....

    I guess in short - and no offense intended - I'm saying you're asking how to embark on a fool's errand
     

    georgelza

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    I am very very skeptical of anybody without a highly specialized background making an .xls file that does what QL does. I know there are those guys out there, but then again, why? When QL is there already.

    Even if I could make a .xls file that did what Applied Ballistics does, why would I? Unless I intended to go compete with Bryan....

    I guess in short - and no offense intended - I'm saying you're asking how to embark on a fool's errand
    Knowing the individual in question, easily in his sphere of doable.
    And no he is not doing this to compete, just one of those guys with the ability and desire to understand it and there is no better way than unpacking it layer for layer using excel.
    G
     
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    308pirate

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    Probably not good enough, but will learn.

    G

    Ok then. It's not something I recommend learning on your own unless you are already a mathematical prodigy.

    In fact, if this interests you, apply at your local university to take basic and advanced calculus, differential equations, engineering dynamics, fluid mechanics, and a deep dive into smokeless propellant behavior to start getting an understanding of what's happening in the barrel

    What you're asking for is akin to using an excel spreadsheet, without any understanding of orbital mechanics, to calculate a spacecraft's trajectory to the moon.

    Everyone wants to do engineer shit until it's time to do engineer shit.
     

    Ledzep

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    I don't know how to start unpacking this. You're in for years of research before you will begin to really understand enough to do what you want to. This is not a trivial project. So much so that it might be more economical to purchase the test equipment and just measure the pressure directly... which is not an economical move at all.

    ETA....
     
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    308pirate

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    let me decide what I want to learn, and up to what level, and whats to difficult for me or not...
    Keen to get to know more.
    G

    We don't give a shit what you try to learn or not.

    Some of us, who are actually engineers and have a basic understanding of pressure v time v volume curves, acceleration, and friction (as in actually able to describe them using equations), are telling you this isn't trivial and that an autodidactic approach will likely end up with you assuming you know what you're doing when in reality you will likely miss several key aspects.

    Then I imagine you'll come back to argue with real ballisticians like Bryan Litz about how they're wrong. Who, BTW, isn't here much any more likely because of that.
     

    308pirate

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    Good thing I don’t actually care what you think I’m allowed to research:explore or not.

    English must not be your strong suit: We don't give a shit what you try to learn or not.
     

    308pirate

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    I've got a friend that has a spread sheet, where he calculates the burn rate/time, and compare that against the projected speed of the bullet, determining that against the time that the bullet is in the barrel, and relating that to the burn rate, determine how much unburned power goes out the front (aka wastage).
    other than quickload and GRT, does anyone have a spread sheet that does this..

    Then ask him
     

    308pirate

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    Stand up member. Let the insults get personal…

    I would also leave the forum if I was not a sucker for some good bits of information from people that care to contribute , help vs you… only value being mastered the skill to insult.

    I gave you a direct, honest answer. You didn't like it because that wasn't what you wanted to hear so now you get pissy.

    That's what we call in the USA an askhole.
     
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    The_Steward

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    Well, if you really want to get into it, look up Gordon's Reloading Tool. On their website is documentation. Within that documentation, they list the books and models that they have based GRT on. That would probably give you enough to chew on for a while.

    Sadly, Gordon passed away, but IIRC there was some community work being done to keep the software going.

    Good luck.
     

    secondofangle2

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    If you’re listening you’re hearing two things: one, is that people think you’re engaging in a fool’s errand; two, Nobody here is going to be able to help you.

    Rather than argue with everyone, the prudent thing to do is to pack up and go somewhere else for advice on how to go about this fool’s errand that you’re set on
     

    ShtrRdy

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    @georgeiza - then I would suggest exploring the internet for equations describing the burning characteristics of smokeless powder, the dynamic and static friction of a projectile, the equations of motion for a mass, as well as other aspects.

    The easiest concept is probably equations of motion. Dig into that topic and let's see if you can build a spreadsheet that can handle varying acceleration over time.

    Yes, this is a homework assignment. 😁
     
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    georgelza

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    @georgeiza - then I would suggest exploring the internet for equations describing the burning characteristics of smokeless powder, the dynamic and static friction of a projectile, the equations of motion for a mass, as well as other aspects.

    The easiest concept is probably equations of motion. Dig into that topic and let's see if you can build a spreadsheet that can handle varying acceleration over time.

    Yes, this is a homework assignment. 😁
    :) already started finding them,

    this is purely for my own education, curiosity. sure I won't get to know everything, sure I'm not an amazing engineer, but eventually I might know enough to keep it interesting for myself.

    G
     
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    georgelza

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    Well, if you really want to get into it, look up Gordon's Reloading Tool. On their website is documentation. Within that documentation, they list the books and models that they have based GRT on. That would probably give you enough to chew on for a while.

    Sadly, Gordon passed away, but IIRC there was some community work being done to keep the software going.

    Good luck.
    Correct,
    I'm in contact with the community, and have the software running in a VM this side.
    Reading their docs as we talk.
    thanks.
    G
     
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    Yondering

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    :) already started finding them,

    this is purely for my own education, curiosity. sure I won't get to know everything, sure I'm not an amazing engineer, but eventually I might know enough to keep it interesting for myself.

    G

    The real answer is that anyone who thinks they can calculate the pressure of their load within any useful degree of accuracy, whether by spreadsheet, Quickload, etc, is FOS. At best, it's a very vague estimate that takes a LOT of correlation to have any value at all. And that's even if you did develop a tool to calculate things accurately. You'll see a lot of people here posting or quoting QL numbers, as if they actually mean something useful; in almost all cases it's people thinking their numbers are useful because they have no idea how far off they can be.

    Minor details and variations in the real world can have significant impact on pressures, and there are a lot of them. None of the current calculators adequately account for all of these, and some, like GRT, don't even accurately account for some of the basics like distance from the lands.

    Good luck, but it'd be wiser to understand that there are much easier and more effective (and efficient) methods of figuring out good and safe loads.
     

    secondofangle2

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    I love threads like this. It's like watching a guy persist in hitting on a girl who is clearly not into it, thinking if he just tries harder he will make the situation better, rather than worse. Makes me chuckle.
     

    georgelza

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    The real answer is that anyone who thinks they can calculate the pressure of their load within any useful degree of accuracy, whether by spreadsheet, Quickload, etc, is FOS. At best, it's a very vague estimate that takes a LOT of correlation to have any value at all. And that's even if you did develop a tool to calculate things accurately. You'll see a lot of people here posting or quoting QL numbers, as if they actually mean something useful; in almost all cases it's people thinking their numbers are useful because they have no idea how far off they can be.

    Minor details and variations in the real world can have significant impact on pressures, and there are a lot of them. None of the current calculators adequately account for all of these, and some, like GRT, don't even accurately account for some of the basics like distance from the lands.

    Good luck, but it'd be wiser to understand that there are much easier and more effective (and efficient) methods of figuring out good and safe loads.
    Not doing this to design my own internal ballistic calculator, not doing this to do load dev, doing this purely out of curiosity.
    Thx
    G
     
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    Yondering

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    Not doing this to design my own internal ballistic calculator, not doing this to do load dev, doing this purely out of curiosity.
    Thx
    G

    I think you may have missed my first paragraph that you quoted. Even if you do learn all the math, and aquire supporting data (that most of us don't have access to) to run the calculations - it's still nearly worthless crap, because the complexity of accounting for everything that matters in real life is astronomical. The worst part is, being someone who doesn't want to listen to experienced input, you'll convince yourself it's meaningful and deceive yourself and other people with your calculations.

    If you want to learn this stuff, start by using QL and GRT, and learn enough to understand why those calculations are wrong and/or inadequate. If you can do that, then you might be able to develop something useful. But that'll require a lot of years of loading experience to do something of any value; without that you're just another optimist failing to understand the obstacles he needs to overcome.
     

    308pirate

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    It definitely makes sense if you like living in a technologically advanced society.

    The Wright brothers succeeded at powered flight. They were somewhat self taught engineers. But it took real engineers to take this
    1668267314536.png


    And turn it into this
    1668267419455.png

    1668267443298.png


    Backyard mechanics that know how to rebuild a Chevy small block can't get it done
     

    Precision Underground

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  • It definitely makes sense if you like living in a technologically advanced society.

    The Wright brothers succeeded at powered flight. They were somewhat self taught engineers. But it took real engineers to take this
    View attachment 7997402

    And turn it into this
    View attachment 7997404
    View attachment 7997405

    Backyard mechanics that know how to rebuild a Chevy small block can't get it done
    I wasn’t talking about engineering I was taking about engineers lol. Just busting your balls.
     

    Oldloser

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    What little I know about ballistics programs I don't see how you could do the same thing as Quickload with a spreadsheet.

    Excel is great for solving ordinary differential equations analytically. There is not much difference mathematically between a bullet in motion and converting heat to motion. Both problems have some shorthand methods that are well understood and examples in code for those who know how to read them.

    Ballistics programs core logic is not many lines of code. Some of the original programs were done in BASIC using the Siacci method and are quite close to AB or BDX or 4DOF or TRASOL today. Excel allows for BASIC programs. A clever coder could find a basic ballistic program and convert it to run in excel. Heck you might even publish a worksheet on snipers hide. How hard can it be?

    As for the OT, once you know the specific heat of the gas in the case, and spend some time learning thermo, the rest is easy to derive on your own if you really want to understand it. Or just cleverly read the code that is publicly available. And port to excel.

    The really hard thing that requires original thinking is to deduce the assumptions underlying the tools and the physics. And to then know the box under which the tool works well and where it does not. Or be observant enough to see where the line is crossed and figure out why.

    As for the OP, the code is out there in the public domain. Go do your own excel sheet.
     

    MarkyMark007

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    not-on-google.shit
    Cross posting, sorry, thinking this deserves a more generic chat/thread.

    curious... I've seen a couple of people mention they working out the pressure... comparing they load/pressure against the SAAMI numbers, comparing it to numbers as per attached.

    how do you work out the pressure?

    I've got a friend that has a spread sheet, where he calculates the burn rate/time, and compare that against the projected speed of the bullet, determining that against the time that the bullet is in the barrel, and relating that to the burn rate, determine how much unburned power goes out the front (aka wastage).
    other than quickload and GRT, does anyone have a spread sheet that does this..

    Interested in getting to understand, work out the numbers myself.

    G

    your friend doesnt know what he is doing.
    he only thinks that he is doing it right, but in reality he is doing it wrong.

    if you cant measure pressure, you can only see what is QuickLoad 'predicting'. but QL can be realy realy off !! so dont fully trust QL !
     
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    harry_x1

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    Not doing this to design my own internal ballistic calculator, not doing this to do load dev, doing this purely out of curiosity.
    Thx
    G
    @geirgelza : Hey Man there is a coordinated group of attention seeking jobless assholes on snipershide who spend most of their time throwing shit around...just ignore them. Your question/quest is great, I was looking for a similar approach myself. Will drop you a DM and seek your inputs.
     
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    Doom

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    @geirgelza : Hey Man there is a coordinated group of attention seeking jobless assholes on snipershide who spend most of their time throwing shit around...just ignore them. Your question/quest is great, I was looking for a similar approach myself. Will drop you a DM and seek your inputs.
    You certainly have had no problem seeking advice from the assholes on this site. But the method used for the spreadsheet is probably based on Powley's computer which was a method used by DuPont for the IMR powders or one of the other analytical models , with some additional approximations.
     

    Molon

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    Cross posting, sorry, thinking this deserves a more generic chat/thread.

    curious... I've seen a couple of people mention they working out the pressure... comparing they load/pressure against the SAAMI numbers, comparing it to numbers as per attached.

    how do you work out the pressure?

    I've got a friend that has a spread sheet, where he calculates the burn rate/time, and compare that against the projected speed of the bullet, determining that against the time that the bullet is in the barrel, and relating that to the burn rate, determine how much unburned power goes out the front (aka wastage).
    other than quickload and GRT, does anyone have a spread sheet that does this..

    Interested in getting to understand, work out the numbers myself.

    G

    I'm willing to be that your friend's spreadsheet isn't able to account for the myriad of variables involved in these matters, but I could be wrong. The only way to be certain if the data for pressure, velocity and barrel time is correct is by using actual pressure and velocity test equipment and that type of equipment is cost prohibitive for most people. (Even QuickLoad admits that their predictions can be off by a good percentage.)

    See if your friend's spreadsheet can accurately reproduce the actual pressure, velocity and barrel times shown in the table below. This data is from actual pressure/velocity testing of factory loaded Berger 223 Remington 77 grain OTM ammunition.




    berger_blow_out_pressure_data_table_001b-2708680.jpg


    TTP = time to peak pressure

    AT = time to the bullet exiting the muzzle



    .....
     
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