Remember me saying the G22 had about 50% more recoil than the G17, well....

This is a discussion on Remember me saying the G22 had about 50% more recoil than the G17, well.... within the Defensive Carry Guns forums, part of the Defensive Carry Discussions category; Originally Posted by Bigpoppa48 Very interesting, although I never came across that formula for recoil while getting my degree in Mathematics that is very interesting ...

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  1. #31
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    Quote Originally Posted by Bigpoppa48 View Post
    Very interesting, although I never came across that formula for recoil while getting my degree in Mathematics that is very interesting though. If you could somehow write a differential equation(s) for the recoil it would probably be a little bit more accurate and be able to take into account a few more variables.
    I suspect you probably didn't cover a huge number of equations while getting your math degree. This wasn't an equation I found, I and an physics professor derived it based on physics principles.

    What would you include other than what I've already included? I'm already better than 10% accurate compared to a software calculator that takes many more things into account than I do.

    The more complicated the formula gets the less likely it is to be used. My formula can be used with a 4 function calculator - that's what I was looking for.
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  3. #32
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    Quote Originally Posted by Tangle View Post
    Absolutely! That's what I said in post number 20. And I do appreciate the post. Sometimes you get to feeling a little isolated and it's always good to see some corroboration.

    I don't know that I agree about the powder. I'm not disagreeing but IF one grain of powder makes it to the muzzle, it is negligent in the 1-2% range. However, as I mentioned in the last post, I'm not sure the powder makes it, en mass, to the muzzle due to the burning. Still all the mass has to be contained within the barrel until the bullet exits, so the mass may actually be accelerate to the muzzle even if in a different form.

    I'm not sure friction is so insignificant. Try pushing a bullet down a barrel. That friction has to be overcome by the pressure of the powder and it would create more push against the gun. That may be the major thing that Fitch's calculator takes into account that produces higher numbers.
    FWIW my 115g 9mm reloads have 6.9g of powder in them.

    The muzzle exit pressure is about 5,800 psi. It creates a short (~33 millisecond) force impulse of about .113 in^2 * 5,800 lb/in^2 which is 655 lbs but it doesn't last very long. +P 9mm cartridge (my reload for the G26 that meets the power floor for IDPA) would have muzzle exit pressures up closer to 6,400 psi which is one reason the +P ammo has noticably more recoil - at least to me it does. Barrel exit time for the bullet with my reloads is around 0.4 millisecond, or 0.0004 second.

    I'm not into pain from shooting handguns, or rifles, but I'm no shrinking violet either. My .45 BlackHawk (40 oz) puts out a 255g LSWC for hunting at a bit over 1,000 fps - which QuickLoad says is a bit over 12 ft-lbs of recoil, and I love shooting that revolver. Haven't gotten a deer or coyote with it yet (haven't seen any close enough), but I'm still lugging it along when I'm hunting. The muzzle exit pressure is lower on the 45 but the area is bigger so the gas reaction force (is higher and longer) than on either the 9mm or .40.

    My G26 recoil is between 7.2 ft-lbs empty and 5.44 ft-lbs with a full clip. The muzzle exit pressure is up around 7,564 psi due to the short barrel and the +P load. The gas impulse is shorter, 28ms but bigger at 734 lb. I haven't modeled a G27, but it's going to be snappier by a bunch.

    Repeat shots are faster if the gun jumps less so recoil is worth understanding.

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  4. #33
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    Great Good Job

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    Quote Originally Posted by Tangle View Post
    Yes! Well, not 50% more 'recoil' energy, but the heavier bullet with the same energy of a lighter bullet has more momentum - on the other end - not 50% more though.
    Okay Mr. Tangle I've got some more work for your brain,
    I'm not trying to go off on a tangent here or hijack your thread but; relating to this, would the momentum of said projectile be affected by the "rigidity" of what/whomever is absorbing the recoil? This is how I'm thinking of it; if you are walking briskly at 5 mph and you are hit in the back with a projectile traveling at 10 mph, or you were at rest and were struck by said projectile traveling at 10 mph the energy released/imparted will be greater when struck at rest, no?
    So, if you have a softer or harder recoil spring, or the "slack" you have in your grip, arms, etc would in effect affect the energy imparted by a bullet...
    I typed all of that and just had an epiphany: this very well may not apply in the least since both objects we are discussing begin at rest...am I making sense? Thanks.

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    Just to belabor the point, We can disregard friction in the barrel, because the net muzzle exit velocity determines recoil. Recoil from a 50BMG must include the exit velocity of the 210gr powder charge, even thought the solid powder has turned into the same mass of gas. That's a lot of weight that can be redirected by a compensator to reduce recoil.

    Perceived or felt recoil is too subjective to measure except by anecdote. For example, a 300 gr cast moly at 1100fps out of my 5 1/2" Old Model Vaquero will cause the gun to rock and rotate up as it comes back. This spreads the deceleration over a much longer time and softens the blow. The gas ports on my 4" 500S&W prevent the muzzle from jumping, but the alternate compensator for cast bullets blocks off the top ports, allowing some recoil softening flip. A bruise in the palm that takes months to dissipate is worse than recoil torqued into the natural shock-absorber in the web of the hand.
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    Quote Originally Posted by azchevy View Post
    When some guy is bearing down on you with a knife or firearm or other melee weapon, recoil will be the last thing on your mind. Shoot what you like, like what you shoot.


    Better yet, start explaining the physics of what you are preparing to do to him and he will shoot himself.



    PS. For what it is worth, I like recoil.
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    Quote Originally Posted by Tangle View Post
    The formula for recoil force we both came up with using different approaches is:

    Er = Mb * Eb / Mg

    where,

    Er = recoil energy
    Mb = bullet mass
    Eb = bullet muzzle energy
    Mg = mass of the gun

    Realizing that mass is proportional to weight and that in the formula the mass of the bullet and the mass of the gun is expressed as a ratio, the formula can be simplified to:

    Fr = Wb * Eb / Wg

    where,

    Wb is the weight, instead of mass, of the bullet in pounds, i.e. bullet grains divided by 7000
    Wg is the weight of the gun in lbs.
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  9. #38
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    Quote Originally Posted by BugDude View Post
    Better yet, start explaining the physics of what you are preparing to do to him and he will shoot himself.



    PS. For what it is worth, I like recoil.
    Hmmm, would that work?
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  10. #39
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    Quote Originally Posted by gunthorp
    Just to belabor the point, We can disregard friction in the barrel, because the net muzzle exit velocity determines recoil.
    Actually, I'm not so sure it's so much disregarding the friction as it is that the friction is accounted for by equal and opposite forces over time. The greater the friction, the greater the force required to accelerate the bullet to the same velocity, but it seems to me that the friction is accounted for by the exit velocity.
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    Quote Originally Posted by BugDude View Post
    Better yet, start explaining the physics of what you are preparing to do to him and he will shoot his self
    Now that there is funny, I don't care who you are!
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  12. #41
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    Quote Originally Posted by Crowbait View Post
    Okay Mr. Tangle I've got some more work for your brain,
    I'm not trying to go off on a tangent here or hijack your thread but; relating to this, would the momentum of said projectile be affected by the "rigidity" of what/whomever is absorbing the recoil?
    It's all kind of mixed up together. I suspect a more rigid fixture holding the gun, would increase momentum of the bullet to some degree because the fixture could not move rearward and subtract motion, etc. from the bullet - I think???

    Without doing some serious thinking, I'm not sure I can accurate answer your question about the 'walking' example. What you say seems logical, but some times things aren't as we think they are. For example, consider a car going 60 mph hitting an immoveable object and then a second case where the car going 60 mph hits and oncoming car head on also traveling at 60 mph. Which is generates the heavier impact?

    Most people, or at least most people I've asked, say the two car example would produce the greater impact. The fact is though, they both examples produce the same impact!

    That's considerably different than your example, I'm just saying, things are always as they seem and I don't know for sure, but what you say seems logical. I just haven't crunched the numbers.
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    Quote Originally Posted by Tangle View Post
    1- Neither of us took the reciprocation of the slide into account; unquestionably valid for revolvers since they have no slides. And, I'm not sure the slide reciprocation would make much difference, but even if it did, if we are comparing semi-to semi, i.e. a G22 to a G17 the slide effects would be a wash anyway.
    .
    You could find the spring constant of the recoil assembly (easier with a Gen3 because it doesn't have the multiple spring setup). You can approximate the initial force on the slide using muzzle energy and subtracting thermal losses, then find the work the spring does on the slide. Subtract that work from the energy you found and you'll have a more accurate answer. I don't think the work done by the springs in the G17 and G22 are equal
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    Quote Originally Posted by Walden View Post
    You could find the spring constant of the recoil assembly (easier with a Gen3 because it doesn't have the multiple spring setup). You can approximate the initial force on the slide using muzzle energy and subtracting thermal losses, then find the work the spring does on the slide. Subtract that work from the energy you found and you'll have a more accurate answer. I don't think the work done by the springs in the G17 and G22 are equal
    Maybe, but that would complicate the ease of calculation. We'd have to know the mass of the slide, the spring constant and/or characteristic, and slide travel distance. If the spring were any more than a simple linear spring, we'd need a mathematical model of the spring constant.

    I was looking for something that would give reasonable comparative numbers with minimal complications, especially to compare similarly operating guns of various weights with bullets of various weights and energies.

    I have to say it would be interesting to look at all that, but to go much further, one might be better off to look at the 10 or so pages of the NRA analysis of recoil.
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    Quote Originally Posted by Tangle View Post
    Maybe, but that would complicate the ease of calculation. We'd have to know the mass of the slide, the spring constant and/or characteristic, and slide travel distance. If the spring were any more than a simple linear spring, we'd need a mathematical model of the spring constant.

    I was looking for something that would give reasonable comparative numbers with minimal complications, especially to compare similarly operating guns of various weights with bullets of various weights and energies.

    I have to say it would be interesting to look at all that, but to go much further, one might be better off to look at the 10 or so pages of the NRA analysis of recoil.
    The math certainly does get complex. I was taking a partial differential equations class and we eventually around to doing LaPlace's equation in three dimensions. We looked at fluid flow and heat transfer, so I decided to combine them and model the expansion of gasses as they exit the barrel of a gun. Pretty cool stuff. Let me see if I have my Mathematica graphs
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  16. #45
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    Nevermind. I did it on another computer.
    "Though defensive violence will always be a 'sad necessity' in the eyes of men of principle, it would be still more unfortunate if wrongdoers should dominate just men." - St. Augustine

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