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Thread: Ballistic gelatin comparisons: Part I

  1. #61
    Site Supporter 0ddl0t's Avatar
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    Quote Originally Posted by the Schwartz View Post
    What is the point of any of this?
    ...
    Quote Originally Posted by 0ddl0t View Post
    My point is that the existing tests of 10% gel & 10% gel behind 4 layers of denim are imperfect for many of the popular concealed carry guns on the market. Repeatable tests in other media or with alternate intermediate barriers can illustrate real deficiencies left uncovered by these traditional tests.

    As an example, I give the gold dot 147 from a 3" barrel which is on Doc's list of recommended ammo and which reliably expands in traditional testing with 10% ordnance gel. But if you lower ρ (using lower density media) or V (by adding distance, barriers, etc) even slightly it begins to fail to expand.

    That gold dot 147s are at the lower bounds of their performance window from a 3" barrel is useful information to know & that information can be reliably and repeatedly discerned from non traditional (but scientifically valid) tests.

    Quote Originally Posted by the Schwartz View Post
    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.
    No. I don't. I am not attempting to compare expansion size or penetration depth between dissimilar media. I am doing a Y/N expansion check to help ensure my 147gr jhp doesn't fail to expand if shot from a 3" barrel into a 350 lb man.

    Again:

    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)

    Distilled:
    When a bullet is expanding, the inertial forces (velocity + density) are so very much larger than the shear forces that the shear forces can be ignored.

  2. #62
    Quote Originally Posted by 0ddl0t View Post
    My point is that the existing tests of 10% gel & 10% gel behind 4 layers of denim are imperfect for many of the popular concealed carry guns on the market. Repeatable tests in other media or with alternate intermediate barriers can illustrate real deficiencies left uncovered by these traditional tests.

    As an example, I give the gold dot 147 from a 3" barrel which is on Doc's list of recommended ammo and which reliably expands in traditional testing with 10% ordnance gel. But if you lower ρ (using lower density media) or V (by adding distance, barriers, etc) even slightly it begins to fail to expand.

    That gold dot 147s are at the lower bounds of their performance window from a 3" barrel is useful information to know & that information can be reliably and repeatedly discerned from non traditional (but scientifically valid) tests.
    This is not correct. Since BBI already addressed this inaccuracy in post #22, I'll not bother re-posting it here. I am sure that you can locate his post for review at your convenience.



    Quote Originally Posted by 0ddl0t View Post
    I am not attempting to compare expansion size or penetration depth between dissimilar media.
    Actually, you are doing just that when you admit that you comparing expansion size in dissimilar mediums (namely the 350-pound man vs whatever uncorrelated test medium you are advocating the use of), right here—

    Quote Originally Posted by 0ddl0t View Post
    I am doing a Y/N expansion check to help ensure my 147gr jhp doesn't fail to expand if shot from a 3" barrel into a 350 lb man.

    Other than your posting of the densities of various liquids and soft solids, I am unconvinced that there is a meaningful point to any of this.
    Last edited by the Schwartz; 11-16-2019 at 04:31 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. #63
    Site Supporter 0ddl0t's Avatar
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    Quote Originally Posted by the Schwartz View Post
    This is not correct. Since BBI already addressed this inaccuracy in post #22, I'll not bother re-posting it here. I am sure that you can locate his post for review at your convenience.
    And I've already addressed his response.


    Actually, you are doing just that when you admit that you comparing expansion size in dissimilar mediums (namely the 350-pound man vs whatever uncorrelated test medium you are advocating the use of), right here—
    Nowhere in this thread do I suggest comparing expansion size (or penetration depth). I'm talking about a Y/N validation for whether a bullet expands at all.

    Other than your posting of the densities of various liquids and soft solids, I am unconvinced that there is a meaningful point to any of this.
    As am I with continuing this conversation.

  4. #64
    Site Supporter DocGKR's Avatar
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    Wow....I am stuck working 12+ hours a day and come back to see this mess.

    First--every institution I am aware of that conducts valid terminal ballistic testing for LE and mil purposes performs correlation with shots in living tissue. So far I am unaware of any such valid analysis being performed with clear synthetic test media.

    Second--every institution I am aware of that conducts valid terminal ballistic testing for LE and mil purposes regularly tests alternative tissue simultants, including clear synthetic test media, to see if new advances offer a more effective option than 10% ordnance gel. So far I am unaware of any simulant which has proven to offer superior terminal performance results in the lab than properly fabricated and validated 10% ordnance gelatin.

    Third--like some other projectiles we have tested, including early versions of Gold Dot, Ranger Talon, HST, some lots of G2 had manufacturing QC issues which proved to inhibit bullet terminal performance..........want to guess how these problems were discovered??? (Hint: see photo below showing top row of failed G2 fired through 4LD compared to known control loads)

    Name:  G2 failure.jpeg
Views: 544
Size:  54.8 KB
    Facts matter...Feelings Can Lie

  5. #65

    Ballistic gelatin comparisons: Part I

    Quote Originally Posted by DocGKR View Post
    Wow....I am stuck working 12+ hours a day and come back to see this mess
    I’d actually like to thank you for this alone. Folks at trauma hospitals do not get the respect they deserve.


    Sent from my iPhone using Tapatalk
    Last edited by Sigfan26; 11-16-2019 at 09:54 PM.

  6. #66
    Site Supporter DocGKR's Avatar
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    Also--we typically have done the majority of our pistol ammunition testing out of 4" barrels, but generally see minimal difference in terminal performance results in barrels from 3.5-5".

    The IWBA published some of Gene Wolberg’s initial data on his study of San Diego PD officer involved shootings; he later presented more at an IWBA Conference in Sacramento. When I last spoke with Mr. Wolberg in May of 2000, he had collected data on nearly 150 officer involved shootings which showed the majority of the 9mm 147 gr bullets fired by officers had penetrated 13 to 15 inches and expanded between 0.60 to 0.62 inches in both human tissue and 10% ordnance gelatin. The first third of Mr. Wolberg’s groundbreaking study assessed the SDPD standard issue Winchester 147 gr JHP. SDPD then switched to the Federal 147 gr JHP, so the remaining 2/3 rds of officer involved shooting incidents assessed by Mr. Wolberg used the Federal loading. Interestingly both the Federal and Winchester 147 gr loadings demonstrated the same close correlation between laboratory testing and actual terminal performance in tissue. In Mr. Wolberg’s study, the OIS incident bullet penetration depths are the actual total length of the bullet track in tissue, as measured by the Medical Examiner at autopsy.
    Facts matter...Feelings Can Lie

  7. #67
    Site Supporter DocGKR's Avatar
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    Sigfan26--Thank you! That is refreshing to hear, especially since some ignorant folks insisted that I am "just a dentist"...
    Facts matter...Feelings Can Lie

  8. #68
    Quote Originally Posted by DocGKR View Post
    Sigfan26--Thank you! That is refreshing to hear, especially since some ignorant folks insisted that I am "just a dentist"...
    Lol. My brother is an anesthesiologist that works more hours a week than I do. Doctors are under appreciated!


    Sent from my iPhone using Tapatalk

  9. #69
    Quote Originally Posted by DocGKR View Post
    Wow....I am stuck working 12+ hours a day and come back to see this mess.

    First--every institution I am aware of that conducts valid terminal ballistic testing for LE and mil purposes performs correlation with shots in living tissue. So far I am unaware of any such valid analysis being performed with clear synthetic test media.

    Second--every institution I am aware of that conducts valid terminal ballistic testing for LE and mil purposes regularly tests alternative tissue simultants, including clear synthetic test media, to see if new advances offer a more effective option than 10% ordnance gel. So far I am unaware of any simulant which has proven to offer superior terminal performance results in the lab than properly fabricated and validated 10% ordnance gelatin.

    Third--like some other projectiles we have tested, including early versions of Gold Dot, Ranger Talon, HST, some lots of G2 had manufacturing QC issues which proved to inhibit bullet terminal performance..........want to guess how these problems were discovered??? (Hint: see photo below showing top row of failed G2 fired through 4LD compared to known control loads)

    Name:  G2 failure.jpeg
Views: 544
Size:  54.8 KB
    Thanks for all that you've done here, Doc. Nice to have another voice of reason here. Found, I think, the test data for the image above to be interesting.
    Last edited by the Schwartz; 11-16-2019 at 10:34 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.

  10. #70
    Site Supporter DocGKR's Avatar
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    I am on 24 hour call today and don't know where that data is at the moment--it is not on my current computer. We just finished a kid with a maxillary fracture from a bike accident, are working up an older adult who will need surgery for their bicycle induced orofacial injures, as well as trying to get OR time for a person with a jaw tumor, so I am unsure when I will be able to look for that information

    Our service has never been busier and I have not had less than a 12 hour day in months, with many extending to 18 hours--have very little time for other endeavors at the moment.
    Last edited by DocGKR; 11-16-2019 at 10:34 PM.
    Facts matter...Feelings Can Lie

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