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Thread: seeking ballistic gel test results with 147 gr loads from a glock 43

  1. #31
    Site Supporter 0ddl0t's Avatar
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    Quote Originally Posted by Ed L View Post
    You do realize that you are lecturing one of the top wound ballistic experts in the business.
    I am not persuaded by appeals to authority when easily verifiable math does not support the assertion.

    But for what its worth, I find the presumed pressure differentials intriguing. The shape of the projectile should affect localized pressures so it would be fascinating to see the pressure modeling for various cavity shapes (something I would expect to play a much, much greater role in expansion than a 17% difference in the medium's density). I wonder if I could get solidworks to model deformation/expansion...
    Last edited by 0ddl0t; 02-26-2019 at 03:02 AM.

  2. #32
    Quote Originally Posted by 0ddl0t View Post
    I am not persuaded by appeals to authority when easily verifiable math does not support the assertion.

    But for what its worth, I find the presumed pressure differentials intriguing. The shape of the projectile should affect localized pressures so it would be fascinating to see the pressure modeling for various cavity shapes (something I would expect to play a much, much greater role in expansion than a 17% difference in the medium's density). I wonder if I could get solidworks to model deformation/expansion...
    That sounds like an awful lot of work just to model the hydrodynamic flow phase (expansion) of the JHP when you could just test the whole penetration event in 10% ordnance gelatin or water and get the whole picture. You could also give ANSYS a try...

    I suppose that you could also modify the Bernoulli pressure equation with the projectile's CD to try to obtain the surface-boundary pressure for a given design....

    ...or go even farther using the modifications to Bernoulli as suggested by Alekseevskii & Tate. (1967, 1969):

    ½ρ(V-U)2 + YP = ½ρU2 + RT where U may be assumed to be equal to Vo ÷ [1 + √(ρT ÷ ρP)]

    The A-T projectile/target pressure interface (U and RT) relationship introduces some computational complication (calculus) into the process, but with that complication (which is mainly in accurately determining the value of RT, which is dependent upon impact velocity) comes some insight, too.
    Last edited by the Schwartz; 02-26-2019 at 02:54 PM.
    ''Politics is for the present, but an equation is for eternity.'' ―Albert Einstein

    Full disclosure per the Pistol-Forum CoC: I am the author of Quantitative Ammunition Selection.

  3. #33
    Quote Originally Posted by 0ddl0t View Post
    I am not persuaded by appeals to authority when easily verifiable math does not support the assertion.

    But for what its worth, I find the presumed pressure differentials intriguing. The shape of the projectile should affect localized pressures so it would be fascinating to see the pressure modeling for various cavity shapes (something I would expect to play a much, much greater role in expansion than a 17% difference in the medium's density). I wonder if I could get solidworks to model deformation/expansion...
    Oh, you will do well here.

    May I inquire about your background and experience?

    Have you worked in wound ballistics or in a trauma center?

    How many people have you treated who were shot in the face?

    Can you detail the military, LEO and government wound ballistics projects that you have worked on?

    Here is some of DrGKR's background:

    "Dr. Roberts is currently on staff at Stanford University Medical Center; this is a large teaching hospital and Level I Trauma center were he performs hospital dentistry and surgery. After completing his residency at Navy Hospital Oakland in 1989 while on active military duty, he studied at the Army Wound Ballistic Research Laboratory at the Letterman Army Institute of Research and became one of the first members of the International Wound Ballistic Association. Since then, he has been tasked with performing military, law enforcement, and privately funded independent wound ballistic testing and analysis. He remains a Navy Reserve officer and has recently served on the Joint Service Wound Ballistic IPT, as well as being a consultant to the Joint FBI-USMC munitions testing program and the TSWG MURG program. He is frequently asked to provide wound ballistic technical assistance to numerous U.S. and allied SOF units and organizations. In addition, he is a technical advisor to the Association of Firearms and Toolmark Examiners, as well as to a variety of Federal, State, and municipal law enforcement agencies. He has been a sworn Reserve Police Officer in the San Francisco Bay Area, where he now he serves in an LE training role."
    Last edited by Ed L; 02-26-2019 at 05:40 PM.

  4. #34
    Site Supporter PearTree's Avatar
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    It seems like every couple of months a blowhard comes in spouting stupidness. Doc comes in as always and politely tells them they have no clue what they are talking about and they start there blowharding even more and then leave pf altogether. @DocGKR I am positive I speak for pf as a whole please disregard these people. We sincerely appreciate your knowledge and expertise and that you choose to participate here.

  5. #35
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    Quote Originally Posted by PearTree View Post
    @DocGKR I am positive I speak for pf as a whole please disregard these people. We sincerely appreciate your knowledge and expertise and that you choose to participate here.
    x2

    We appreciate your patience, Doc, and really appreciate your input.

    Please don’t let the guys who “don’t know what they don’t know” bring you down.

  6. #36
    Andrew's recent comparison of clear gel and 10% ballistic gel is worth watching. 10mm soft point needed an additional 200 fps to expand properly in clear gel.

  7. #37
    Site Supporter 0ddl0t's Avatar
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    Quote Originally Posted by the Schwartz View Post
    That sounds like an awful lot of work just to model the hydrodynamic flow phase (expansion) of the JHP when you could just test the whole penetration event in 10% ordnance gelatin or water and get the whole picture. You could also give ANSYS a try...
    Yeah, a cursory investigation shows that this is beyond my capabilities with solidworks.

    But if it could be done (and maybe ANSYS cfd could), you could test iterative designs far more rapidly than building a physical bullet and testing it in gel then redesigning & repeating. And who knows, the software visualizations might even help inform design improvements (e.g. number and shape of expanding petals).

    I suppose that you could also modify the Bernoulli pressure equation with the projectile's CD to try to obtain the surface-boundary pressure for a given design....

    ...or go even farther using the modifications to Bernoulli as suggested by Alekseevskii & Tate. (1967, 1969):

    ½ρ(V-U)2 + YP = ½ρU2 + RT where U may be assumed to be equal to Vo ÷ [1 + √(ρT ÷ ρP)]

    The A-T projectile/target pressure interface (U and RT) relationship introduces some computational complication (calculus) into the process, but with that complication (which is mainly in accurately determining the value of RT, which is dependent upon impact velocity) comes some insight, too.
    If I was going to do it, I'd want to go far beyond the average pressure on a projectile and look at the localized pressure differentials (the inside of a hollowpoint cavity has to have higher pressures than the outside in order to force the motion of the copper & lead petal). And when you start looking at that level of detail, bernoulli's assumptions begin to fall apart (e.g. you don't have a homogeneous medium, there will also be trapped air which will likely be moving at supersonic speeds in places). That brings you to Navier Stokes and all the associated computational issues. Might make a good grad school project for someone smarter than me.

    I suppose if you had a high definition high speed camera and gelatin with evenly spaced dye particles you could measure the speed of gelatin at various places and from there calculate more localized pressures, but that would be extremely laborious for what would still be a course visualization.

    Quote Originally Posted by Ed L View Post
    May I inquire about your background and experience?
    The laws of physics don't care about my background, why should you? Appeals to authority are invitations to substitute someone else's thought for your own.

    Quote Originally Posted by Velo Dog View Post
    Andrew's recent comparison of clear gel and 10% ballistic gel is worth watching. 10mm soft point needed an additional 200 fps to expand properly in clear gel.
    You will sometimes find similar discrepancies with things like 357 & 5.7x28 or even unusual configurations of 9x19. For instance 150gr HST doesn't reliably expand from 3" barrels in clear gel - sometimes it does, sometimes it doesn't...

    Personally I find that kind of design... fragility?... unacceptable - especially since the intended target has tissue densities from 250-1750 kg/m^3. I imagine everyone here knows about the ISP "biker incident" where a leather-clad drunk fat perp was unsuccessfully shot something like 13 times with an early expanding 9mm round. It led go the development of the ISP +p+ load to ensure expansion...

  8. #38
    Site Supporter DocGKR's Avatar
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    "It led go the development of the ISP +p+ load to ensure expansion..."
    Which still was not a great load, as it tended to demonstrate 20 to 40% failure to expand in denim testing and was less than ideal against intermediate barriers like auto windshields. I personally would not choose to use it given all the better options currently available. With the exception of the Barnes 115 gr XPB all copper projectile, in general, most 9 mm 115 gr loads of any pressure have demonstrated greater inconsistency, insufficient penetration, poor intermediate barrier capability, and failure to expand in denim testing than other 9mm bullets. For those individuals wanting to use lighter weight, supersonic 9 mm’s, I think a better alternative than the vast majority of 115 gr loads is to use the slightly heavier 124 to 127 gr bullets or the Barnes 115 gr all copper bullet.
    Last edited by DocGKR; 02-27-2019 at 02:21 AM.
    Facts matter...Feelings Can Lie

  9. #39
    Quote Originally Posted by 0ddl0t View Post
    The laws of physics don't care about my background, why should you? Appeals to authority are invitations to substitute someone else's thought for your own.
    Okay, so on one hand we have a world renown wound ballisticiian who "is currently on staff at Stanford University Medical Center; this is a large teaching hospital and Level I Trauma center were he performs hospital dentistry and surgery. After completing his residency at Navy Hospital Oakland in 1989 while on active military duty, he studied at the Army Wound Ballistic Research Laboratory at the Letterman Army Institute of Research and became one of the first members of the International Wound Ballistic Association. Since then, he has been tasked with performing military, law enforcement, and privately funded independent wound ballistic testing and analysis. He remains a Navy Reserve officer and has recently served on the Joint Service Wound Ballistic IPT, as well as being a consultant to the Joint FBI-USMC munitions testing program and the TSWG MURG program. He is frequently asked to provide wound ballistic technical assistance to numerous U.S. and allied SOF units and organizations. In addition, he is a technical advisor to the Association of Firearms and Toolmark Examiners, as well as to a variety of Federal, State, and municipal law enforcement agencies. He has been a sworn Reserve Police Officer in the San Francisco Bay Area, where he now he serves in an LE training role."

    On the other hand we have an anonymous internet poster whose postings contradict said expert and is complaining about appeals to authority; whose claims of "physics" do not match up with the Subject Matter Expert's extensive first hand experience that when compared to ballistic gelatin a certain tissue simulant "One has been correlated with living animal and human tissue; one has not."
    Last edited by Ed L; 02-27-2019 at 02:43 AM.

  10. #40
    Site Supporter 0ddl0t's Avatar
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    This will be my last response to you. I probably should just let it go, but I object to your miscategorization of my prior posts:
    Quote Originally Posted by Ed L View Post
    On the other hand we have an anonymous internet poster whose postings contradict said expert and is complaining about appeals to authority; whose claims of "physics" do not match up with the Subject Matter Expert's extensive first hand experience that when compared to ballistic gelatin a certain tissue simulant "One has been correlated with living animal and human tissue; one has not."
    I have no doubt that DocGKR knows more about wound ballistics than I ever will and I don't question any of the mechanics he's illuminated here. But he erroneously disputed my claim that the results of one video showed a high correlation between calibrated clear & organic gel. I backed up my claim with the relevant statistics in post #25. DocGKR did not dispute my numbers. As a world renown wound ballistician he undoubtedly has access to a much larger sample of data from which he could check correlation coefficients for expansion & penetration of standard low speed handgun ammo in calibrated clear & organic gel.

    I'm right; he's smart. If he hasn't already, he'll come around. But petty disputes over this sort of minutiae are what make academia insufferable. He misused a statistical term on an informal internet message board; it is not a big deal worthy of this protracted discussion. Even professional statisticians are terrible statisticians - here's an anecdote from Daniel Kahneman's book, "Thinking Fast & Slow," where he discusses the time the authors of two statistics textbooks failed to correctly answer a basic stats question on sample size:

    Amos told the class about an ongoing program of research at the University of Michigan that sought to answer this question: Are people good intuitive statisticians? We already knew that people are good intuitive grammarians: at age four a child effortlessly conforms to the rules of grammar as she speaks, although she has no idea that such rules exist. Do people have a similar intuitive feel for the basic principles of statistics? Amos reported that the answer was a qualified yes. We had a lively debate in the seminar and ultimately concluded that a qualified no was a better answer.

    Amos and I enjoyed the exchange and concluded that intuitive statistics was an interesting topic and that it would be fun to explore it together. That Friday we met for lunch at Café Rimon, the favorite hangout of bohemians and professors in Jerusalem, and planned a study of the statistical intuitions of sophisticated researchers. We had concluded in the seminar that our own intuitions were deficient. In spite of years of teaching and using statistics, we had not developed an intuitive sense of the reliability of statistical results observed in small samples. Our subjective judgments were biased: we were far too willing to believe research findings based on inadequate evidence and prone to collect too few observations in our own research. The goal of our study was to examine whether other researchers suffered from the same affliction.

    We prepared a survey that included realistic scenarios of statistical issues that arise in research. Amos collected the responses of a group of expert participants in a meeting of the Society of Mathematical Psychology, including the authors of two statistical textbooks.As expected, we found that our expert colleagues, like us, greatly exaggerated the likelihood that the original result of an experiment would be successfully replicated even with a small sample. They also gave very poor advice to a fictitious graduate student about the number of observations she needed to collect. Even statisticians were not good intuitive statisticians.
    And since you seem hung up on resumes, Daniel Kahneman won the Nobel prize in Economics (despite being a psychologist). Among other things, the other man was the subject of the world's shortest IQ test (the sooner you realized Amos Tversky was smarter than you, the higher your IQ).
    Last edited by 0ddl0t; 02-27-2019 at 08:23 AM.

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