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Thread: Ballistic gelatin comparisons: Part I

  1. #51
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    Quote Originally Posted by 0ddl0t View Post
    I must have misunderstood. I am aware Speer sold reject ammo very clearly marked "training ammo only" "not for duty use." I am not aware of Speer selling QC reject ammo in normal defensive/LE packaging to unwitting consumers (i.e. the initial run of G2 that wound up recalled).


    And that is why I post here, so folks might be aware of the downsides taking only the word of unquestioned experts, rather than doing any validation testing of their own:

    "The Speer 9 mm 147 gr G2 is very good performing barrier blind ammunition! In fact modern 9 mm ammo like the G2 performs so well, that many large LE agencies are having no issues giving up larger caliber handguns in favor of easier shooting, more durable, higher capacity 9 mm handguns that offer terminal performance that only a few years ago was only possible with larger calibers like .40 S&W and .45 Auto."
    Dr. Gary Roberts 2014
    So, your “problem” is with Dr. Roberts?

  2. #52
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    Quote Originally Posted by Duelist View Post
    So, your “problem” is with Dr. Roberts?
    No. Both he & Charles Schwartz are wealths of information who know more about wound ballistics than I likely every will and they have been very generous in freely sharing their knowledge with us. I just suspect both are more concerned about defending consumers from charlatans than acknowledging, investigating, & correcting the flaws remaining in traditional testing.

    As proof of those lingering flaws I gave the example of 1 bullet design, out of the hundreds Dr. Roberts has reviewed, that performed exceptionally well in his tests but failed so miserably in the real world it was recalled & tweaked before rerelease.
    Last edited by 0ddl0t; 11-16-2019 at 08:13 AM.

  3. #53
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    Fifty posts of math and pudding and it still boils down to this.

    Quote Originally Posted by DocGKR
    The keys are:

    -- Cultivate a warrior mindset
    -- Invest in competent, thorough initial training and then maintain skills with regular ongoing practice
    -- Acquire a reliable and durable weapon system
    -- Purchase a consistent, robust performing duty/self-defense load in sufficient quantities (at least 1000 rounds) then STOP worrying about the nuances of handgun ammunition terminal performance.
    Quote Originally Posted by 0ddl0t View Post
    Shot placement did the job

  4. #54
    Quote Originally Posted by the Schwartz View Post
    Modeling terminal ballistic performance in human tissue is not as simple as firing bullets into a substance of a desired density and then concluding that the terminal behavior seen in that material corresponds with what occurs in a human body. Valid physical models, like 10% ordnance gelatin and water, have been shown through extensive research to correlate strongly with living tissue in terms of their material properties. Since the desired objective is to accurately represent a projectile's terminal performance in human tissue, only those specific mediums that can be shown to demonstrate the correct physical properties are valid as a means of modeling such performance. Beyond considering only the mass density of a solid test medium, a solid must also demonstrate the correct shear response within the typical magnitude of strain rates observed in such testing. Data obtained from "different media" that you've suggested above such as butter, margarine, mozzarella cheese, and for that matter, fruits, vegetables, and deli-meats, are not "supplemental" at all; in fact, they are specious and lack evidence that supports their validity as a terminal ballistic test medium that correlates with human tissue.

    The clear, synthetic gel product, with its frequent changes in composition and component sourcing, is also unsuitable not only for the undocumented changes in its formulation but also for the failure of the manufacturer(s) of these products to provide information on how these changes in composition and source compare against previous iterations of their product(s).

    Modeling terminal ballistic performance in fluids/liquids requires more than matching density (ρ) to achieve dynamic equivalence with soft tissue. In order to properly represent terminal performance in soft tissue, the candidate fluid/liquid must also possess the same bulk modulus (K) and internal sonic velocity (c) which are all related to one another in the Newton-LaPlace formula— c = (K/ρ)

    The internal speed of sound in isopropyl "rubbing" alcohol, C3H8O, is c = 1,205 ms-1, its density is ρ = 786 kg/m³ so by extension of the Newton-LaPlace formula, its bulk modulus is K = 1.141 GPa.

    Compared to the respective values of c, ρ, and K in water, 10% ordnance gelatin, and human soft tissue—

    H2O: c = 1,497 ms-1, ρ = 999.87 kg/m³, K = 2.24 GPa
    10% ordnance gelatin: c = 1,494 ms-1, ρ = 1,040.00 kg/m³, K = 2.32 GPa
    Typical values for human soft tissue: c = 1,540 ms-1, ρ = 1,020 kg/m³, K = 2.42 GPa

    —isopropyl alcohol does not compare favorably with any of these materials' values and therefore is not an acceptable candidate fluid (mixed with water or by itself) for modeling terminal ballistic response as it occurs in human tissue. No such research suggesting otherwise exists.

    Due to the frequent and unknown changes in its formulation, it is also difficult to ascertain values of c, ρ, and K of the clear, synthetic gel. The only physical property of the clear, synthetic gel that is known has been subject to some variance at different times within the same source ranging from 790 kg/m³ - 824 kg/m³ with no known values for either its internal sonic velocity or bulk modulus.

    Given the lack of supporting research that "ensures the consistency" of any of the "different media" that you've suggested, their use is likely to yield dubious data at best. At worst, relying on that data leads to inaccurate, and possibly dangerous, conclusions being drawn about the ammunition tested in those uncorrelated mediums.
    Thanks for this post. You don't even have to check the math to see your point, it's pretty clear and well laid out.

    And thanks to @DocGKR also for pointing out that the search goes on for better test mediums.

    I've been a ballistic geek wannabe since the '80s...

  5. #55
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    Quote Originally Posted by 0ddl0t View Post
    That's true if mixing data. Here the data is siloed. If a bullet passes traditional fbi/iwba tests, then it is supposedly good to go, right? So what difference is it to John Moses Browning if I subselect only those with blue primer sealant or only those that expand when shot through a cantaloupe?
    A silo full of shit still stinks at half a mile.

  6. #56
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    Quote Originally Posted by 0ddl0t View Post
    Within reason (e.g. shooting water not ice), the properties that affect expansion are density & velocity. For this supplemental test I'm not interested in correlating penetration depth, just checking for a robust margin of expansion.
    I knew I'd read the above somewhere, but it took me until now to find the source:


    Penetration of a 9mm bullet at 1000 ft/sec is resisted by an inertial force of about 800 pounds; it is obvious that the presence or absence of a 3 to 5 pound shear force makes no practical difference in the penetration at this velocity. This also explains why the fact that gelatin fractures more easily than tissue does is not important.

    The extension of these dynamics to soft tissue variation is obvious. Different types of tissue present different resistance to finger probing by a surgeon, but the surgeon is not probing at 1000 ft/sec. Different tissue types do have differences in the amount of shear force they will support, but all of these forces are so small relative to inertial forces that there is no practical difference. The tissue types are closer to one another than they are to water, and bullet expansion in water and tissue are nearly identical at velocities over 600 ft/sec where all bullet expansion takes place (See Bullet Penetration for a detailed explanation of bullet expansion dynamics).

    Since inertial forces depend on accelerating mass, it makes sense that these forces should be lower at lower velocities (because the penetrated material cannot be accelerated to a velocity higher than the bullet). Shear forces have little velocity dependence, and as a result, shear forces are a much larger fraction of the total when bullet velocity is below the cavitation threshold. This low velocity effect is the reason that total bullet penetration depth is much different in water and in tissue or a valid tissue simulant.

    As a result of the penetration dynamics, most soft solids with a density very near soft tissues (i.e., near the density of water) are satisfactory tissue simulants when shear forces are not important. However, total penetration depth depends significantly on dynamics at velocities below 400 ft/sec, so most materials do not properly simulate penetration depth. The total bullet penetration depth in tissue and a valid tissue simulant should be the same; standard practice is to use calibrated gelatin to insure this. In effect, gelatin calibration is done to ensure that the shear forces in the gelatin are the same as in typical soft tissue (as described in Bullet Penetration, the technical parameter used in the dynamic is viscosity).

    -- “Wound Ballistics Misconceptions.” (Duncan MacPherson, Wound Ballistics Review, 2(3): 1996; 42-43)


    ...Just posting for those lurking 3rd parties with open minds...

  7. #57
    The bolded portion of the quoted text—

    Quote Originally Posted by 0ddl0t View Post
    I knew I'd read the above somewhere, but it took me until now to find the source:


    Penetration of a 9mm bullet at 1000 ft/sec is resisted by an inertial force of about 800 pounds; it is obvious that the presence or absence of a 3 to 5 pound shear force makes no practical difference in the penetration at this velocity. This also explains why the fact that gelatin fractures more easily than tissue does is not important.

    The extension of these dynamics to soft tissue variation is obvious. Different types of tissue present different resistance to finger probing by a surgeon, but the surgeon is not probing at 1000 ft/sec. Different tissue types do have differences in the amount of shear force they will support, but all of these forces are so small relative to inertial forces that there is no practical difference. The tissue types are closer to one another than they are to water, and bullet expansion in water and tissue are nearly identical at velocities over 600 ft/sec where all bullet expansion takes place (See Bullet Penetration for a detailed explanation of bullet expansion dynamics).

    Since inertial forces depend on accelerating mass, it makes sense that these forces should be lower at lower velocities (because the penetrated material cannot be accelerated to a velocity higher than the bullet). Shear forces have little velocity dependence, and as a result, shear forces are a much larger fraction of the total when bullet velocity is below the cavitation threshold. This low velocity effect is the reason that total bullet penetration depth is much different in water and in tissue or a valid tissue simulant.

    As a result of the penetration dynamics, most soft solids with a density very near soft tissues (i.e., near the density of water) are satisfactory tissue simulants when shear forces are not important. However, total penetration depth depends significantly on dynamics at velocities below 400 ft/sec, so most materials do not properly simulate penetration depth. The total bullet penetration depth in tissue and a valid tissue simulant should be the same; standard practice is to use calibrated gelatin to insure this. In effect, gelatin calibration is done to ensure that the shear forces in the gelatin are the same as in typical soft tissue (as described in Bullet Penetration, the technical parameter used in the dynamic is viscosity).

    -- “Wound Ballistics Misconceptions.” (Duncan MacPherson, Wound Ballistics Review, 2(3): 1996; 42-43)


    ...Just posting for those lurking 3rd parties with open minds...
    —does not affirm the validity of relying upon "lower-than-water-density" test mediums. In fact, because they misrepresent maximum terminal penetration depth, the bolded text that you've quoted above is actually an indictment of the use of "lower-than-water-density" test mediums since the accurate representation of maximum terminal penetration depth is one of the most important metrics considered when undertaking such testing.

    More specifically, the mass densities of the clear, synthetic gel (790 - 824 kg/m³), butter, margarine, and mozzarella cheese are all far enough below that of water that they do not qualify as having "a density very near soft tissues" or "near the density of water". If anyone wishes to substantiate the dynamic equivalence of these "alternative test mediums", then it is incumbent upon those claiming "validity" to support that position. This is easily accomplished by supplying the respective bulk moduli (K), mass densities (ρ), and internal sonic velocities (c) so that the respective physical properties of these "alternative test mediums" may be evaluated against those of human soft tissue (c = 1,540 ms-1, ρ = 1,020 kg/m³, K = 2.42 GPa) using the physical relationship that is set forth in the Newton-LaPlace formula: c = (K/ρ) .

    Of course, you are free to provide the respective mass-densities, bulk moduli, and internal sonic velocities of these "alternative test mediums" in support of your assertion that they are indeed "valid".

    If you cannot support your assertion with these physical parameters, then all you are really doing is debating in a vacuum.
    Last edited by the Schwartz; 11-16-2019 at 01:17 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.

  8. #58
    Quote Originally Posted by 0ddl0t View Post
    I knew I'd read the above somewhere, but it took me until now to find the source:


    Penetration of a 9mm bullet at 1000 ft/sec is resisted by an inertial force of about 800 pounds; it is obvious that the presence or absence of a 3 to 5 pound shear force makes no practical difference in the penetration at this velocity. This also explains why the fact that gelatin fractures more easily than tissue does is not important.

    The extension of these dynamics to soft tissue variation is obvious. Different types of tissue present different resistance to finger probing by a surgeon, but the surgeon is not probing at 1000 ft/sec. Different tissue types do have differences in the amount of shear force they will support, but all of these forces are so small relative to inertial forces that there is no practical difference. The tissue types are closer to one another than they are to water, and bullet expansion in water and tissue are nearly identical at velocities over 600 ft/sec where all bullet expansion takes place (See Bullet Penetration for a detailed explanation of bullet expansion dynamics).

    Since inertial forces depend on accelerating mass, it makes sense that these forces should be lower at lower velocities (because the penetrated material cannot be accelerated to a velocity higher than the bullet). Shear forces have little velocity dependence, and as a result, shear forces are a much larger fraction of the total when bullet velocity is below the cavitation threshold. This low velocity effect is the reason that total bullet penetration depth is much different in water and in tissue or a valid tissue simulant.

    As a result of the penetration dynamics, most soft solids with a density very near soft tissues (i.e., near the density of water) are satisfactory tissue simulants when shear forces are not important. However, total penetration depth depends significantly on dynamics at velocities below 400 ft/sec, so most materials do not properly simulate penetration depth. The total bullet penetration depth in tissue and a valid tissue simulant should be the same; standard practice is to use calibrated gelatin to insure this. In effect, gelatin calibration is done to ensure that the shear forces in the gelatin are the same as in typical soft tissue (as described in Bullet Penetration, the technical parameter used in the dynamic is viscosity).

    -- “Wound Ballistics Misconceptions.” (Duncan MacPherson, Wound Ballistics Review, 2(3): 1996; 42-43)


    ...Just posting for those lurking 3rd parties with open minds...
    Additionallly, submitted for the consideration of those "lurking 3rd parties with open minds", they might also wish to bear in mind that the next line after that which has been bolded in black, which has now been set in bold red, also affirms that "the total bullet penetration depth in tissue and a valid tissue simulant should be the same" and that "standard practice is to use calibrated gelatin to insure this".

    Finally, if the proper representation of total bullet penetration depth is not desired, anyone can simply fire bullets into water to cause them to expand. There is no need to "reinvent the wheel" when water (which already possesses the requisite physical properties) is so easy to use and meets the requirement for being "near the density of water" or having "a density very near soft tissues".
    Last edited by the Schwartz; 11-16-2019 at 01:54 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.

  9. #59
    Site Supporter 0ddl0t's Avatar
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    Quote Originally Posted by the Schwartz View Post
    The bolded portion of the quoted text—



    —does not affirm the validity of relying upon "lower-than-water-density" test mediums. In fact, because they misrepresent maximum terminal penetration depth, the bolded text that you've quoted above is actually an indictment of the use of "lower-than-water-density" test mediums since the accurate representation of maximum terminal penetration depth is one of the most important metrics considered when undertaking such testing.
    Straw man again... No one here is arguing about obtaining valid penetration data from other media.

    More specifically, the mass densities of the clear, synthetic gel (790 - 824 kg/m³), butter, margarine, and mozzarella cheese are all far enough below that of water that they do not qualify as having "a density very near soft tissues"
    Patently false.

    Lung (inflated): 255-604 kg/m^3
    Fat: 812-964 kg/m^3
    Connective tissue 911-1142
    Blood is 1050
    Lung (deflated): 1050
    Cartilage is 1100
    Intervertebral disc 1100
    Larynx 1100
    Bronchi 1050-1147
    Liver 1050-1158
    Muscle 1041-1178

    https://itis.swiss/virtual-populatio...abase/density/

    Rubbing alcohol 790
    Ammonia (max concentration) 880
    Butter is 911
    Cream chesse is 966
    Jello is 980-1050
    Milk is 1030
    Orange juice is 1050-1125
    potato 1090
    mozzarella is 1100
    Bleach (12.5%) 1200
    Salt water (saturated) 1360

    Quote Originally Posted by the Schwartz View Post
    Finally, if the proper representation of total bullet penetration depth is not desired, anyone can simply fire bullets into water to cause them to expand.
    Bullets traveling just over their expansion thresholds for living tissue will expand readily in water, even if they are inconsistent in tissue.

    But if a bullet expands in both rubbing alcohol and bleach - now you can be a bit more confident in the robustness of expansion through the variety of tissue densities it might encounter.
    Last edited by 0ddl0t; 11-16-2019 at 02:15 PM.

  10. #60
    Quote Originally Posted by 0ddl0t View Post
    No one here is arguing about obtaining valid penetration data from other media.
    What is the point of any of this?

    Terminal ballistic testing conducted in an uncontrolled/uncorrelated medium produces expansion and penetration data that is only comparable within the uncontrolled/uncorrelated medium and that is incomparable to all other mediums.

    It is interesting to note that you continue to refuse to provide the other requisite physical parameters (that is, the respective bulk moduli, internal sonic velocities of butter, margarine, mozzarella cheese) required to support your claim that any of these—

    Quote Originally Posted by 0ddl0t View Post
    Rubbing alcohol 790
    Ammonia (max concentration) 880
    Butter is 911
    Cream chesse is 966
    Jello is 980-1050
    Milk is 1030
    Orange juice is 1050-1125
    potato 1090
    mozzarella is 1100
    Bleach (12.5%) 1200
    —are valid terminal ballistic test mediums.

    Once again, mass-density is just one part of the the Newton-LaPlace formula: c = (K/ρ) . You'll need to provide all of the requisite physical properties of these "alternative mediums" to prove that they possess the dynamic equivalent qualities specified by the Newton-LaPlace formula so that they yield data comparable to other mediums.

    Quote Originally Posted by 0ddl0t View Post
    But if a bullet expands in both rubbing alcohol and bleach - now you can be a bit more confident in the robustness of expansion through the variety of tissue densities it might encounter.
    No, you cannot. What occurs in those mediums applies only within those mediums.

    All that you have done so far is post the densities of various substances and refused to provide the physical parameters that would confirm their dynamic equivalence to any other medium (or human soft tissue) and support your claims.
    Last edited by the Schwartz; 11-16-2019 at 03:29 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.

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