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Thread: Predictive tests in water

  1. #1

    Predictive Ammunition Performance Testing in Water

    Upon seeing some of the tests performed and posted by other PF members, I hope that I can contribute something of value just as they have.

    One of the more recent tests that I have run is posted below.

    Winchester Bonded 9mm 147 gr. PDX1 JHP (S9MMPDB1)

    Diameter: 0.5787 inch
    Weight: 146.9 gr. (99.93% retained)
    Velocity: 1,006 fps

    Test Firearm: unmodified Glock 17 with a 4.49-inch barrel
    Test Range: 3 meters (~10 feet)
    Test Barrier: 4 layers of 1-ounce cotton T-shirt fabric

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    Analysis:

    Q-model
    DoP: 13.710 inches
    Wound Mass: 1.776 ounces
    Wound Volume: 2.954 cubic inches

    mTHOR
    DoP: 13.300 inches
    Wound Mass: 1.723 ounces
    Wound Volume: 2.866 cubic inches

    Probability of Incapacitation:
    1st-shot P[I/H]: 69.95%
    2nd-shot P[I/H]: 90.97%
    3rd-shot P[I/H]: 97.29%
    ΔE15 : -220.161 fpe

    DoP = maximum equivalent depth of penetration in calibrated ordnance gelatin
    Wound Mass = total weight of tissue damaged/destroyed within the entire wound channel
    P[I/H] = probability of incapacitation per random munition strike to combatant's torso/abdomen: Assault, 30-second time-frame (US Army BRL P[I/H] model, Dziemian, 1960)
    ΔE15 = Amount of kinetic energy (in fpe) expended by the bullet from a penetration depth of 1 through 15 centimeters

    The Winchester PDX1 bonded JHP design is the commercially-available version of the Winchester Ranger Bonded law enforcement product line.

    In fact the Winchester Ranger Bonded test data found here-

    http://winchesterle.com/SiteCollecti...tocol_2016.pdf

    -duplicates quite closely the water-test performance of the ammunition recorded in this test closely matching the terminal expansion of the Winchester Ranger Bonded 147-grain JHP with an average expanded diameter of 0.585" at 995 feet per second (with 100% weight retention) yielding a penetration depth of 14.10 inches and an average 1.75 ounces of wound mass. With a 1st-shot P[I/H] of 69.95%, the Winchester 9mm 147-grain PDX1 JHP is an excellent example of a well thought-out JHP design.
    Last edited by the Schwartz; 08-13-2018 at 10:20 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.

  2. #2
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    Is there an accurate formula for estimating penetration and expanded diameter in gel vs water?

    Does barrier performance with water traslates to gel?

    I find the predicted % of incapacitation amusing, and the energy deposited in the first 15 cm anecdotal...

  3. #3
    Site Supporter Odin Bravo One's Avatar
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    Good to know how my bullets should perform if attacked by a bucket of water!!
    You can get much more of what you want with a kind word and a gun, than with a kind word alone.

  4. #4
    Quote Originally Posted by TiroFijo View Post
    Is there an accurate formula for estimating penetration and expanded diameter in gel vs water?
    Modifying the constants in the Poncelet equation, which assumes that the inertial pressure is a constant, times the Bernoulli flow pressure, ρV2, or alternatively, modifying the Recht equation appropriately, which assigns less intuitive representations of the three components of resisting force (those being inertial pressure which is a function of the wave velocity, U, mass density, ρ, and the speed of the projectile/target interface Vi), are both viable mathematical models. Duncan MacPherson elected to modify the Poncelet constants as he did, and preferring the Poncelet form over the Recht form myself, I also modified those constants albeit in a somewhat different manner. The Poncelet equation is quasi-empirical in that these constants must be determined experimentally and it assumes that the effect of surface friction upon the motion of the projectile is negligible, approximately 3%, as suggested by: Krafft JM. Surface Friction in Ballistic Penetration. J Appl Phys 1955; 26: 1248-1253. My preference for the Poncelet form comes from the fact that the Recht form, besides its tendency to slightly over-predict depth of penetration, is not tunable, within the statistical experimental design that I employed.

    Furthermore, the late (and very much missed) Dr. Martin L. Fackler M.D., for whom the 'Fackler Box' is named, makes the unqualified statement that, "Shots into water cause bullets to expand as they do in gelatin or muscle" in his article, ''Simplified Bullet Effect Testing''. (page 21 of the Journal of the International Wound Ballistic Association Wound Ballistics Review, Fall 2001; Volume 5, Number 2)

    Quote Originally Posted by TiroFijo View Post
    Does barrier performance with water traslates to gel?
    Yes.

    Since the test projectile traverses the barrier prior to impinging upon the test medium, why not? When considering the passage of a projectile through clothing (and skin), this model-

    https://ndiastorage.blob.core.usgovc...ay/hudgins.pdf

    -does not consider ''post-barrier'' effects either. Given Dr. Fackler's position, which matches other research reaching that same conclusion, there is no reason to expect otherwise.
    Last edited by the Schwartz; 08-14-2018 at 10:35 AM.
    ''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.

  5. #5
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    Thanks Schwartz

    I'm an engineer and understand and like math models myself, but I still don't think that water would accurately predict bullet behaviour, compared to say 10% gelatin. Sure Fackler said "Shots into water cause bullets to expand as they do in gelatin or muscle", but he didn't say "exactly as much as" or he would not had bothered to father and champion the 10% gelating tests.

  6. #6
    Quote Originally Posted by TiroFijo View Post
    Thanks Schwartz

    I'm an engineer and understand and like math models myself, but I still don't think that water would accurately predict bullet behaviour, compared to say 10% gelatin. Sure Fackler said "Shots into water cause bullets to expand as they do in gelatin or muscle", but he didn't say "exactly as much as" or he would not had bothered to father and champion the 10% gelating tests.

    You're welcome. I understand and do appreciate your skepticism.

    Besides my work, you might wish to look into MacPherson's book for a more technical explanation of the phenomena in Chapter 5 of Bullet Penetration under the section titled ''Tissue Simulant Requirements''.

    Additionally, you might find very interesting, recent research by-

    Bresson F., J Ducouret. Experimental study of the expansion dynamic of 9mm Parabellum hollow-point projectiles in ballistic gelatin. Forensic Science International 219 (2012) 113–118

    -in which the authors conclude, that, ''the expansion law of the projectile is almost insensitive to small variation of the gelatin weight ratio", which varied from 0% (pure water) as well as 5%, 10% and 20% concentrations by weight.
    Last edited by the Schwartz; 08-14-2018 at 11:07 AM.
    ''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.

  7. #7
    Site Supporter Odin Bravo One's Avatar
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    Never mind.
    Last edited by Odin Bravo One; 08-14-2018 at 11:06 AM.
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  8. #8
    Since TiroFijo asked some really good questions about the predictive ability and accuracy of these models (both here and via email), I think that it seems only fair that I share an example of the test data that I have relied upon in correlating these models to actual terminal performance in calibrated 10% ordnance gelatin with the SDE. I really do welcome and appreciate such healthy skepticism.

    During development of these models, I asked John Ervin, of Brassfetcher.com, to conduct some testing for me involving several different brands and configurations of expanding and non-expanding ammunition.

    In the gelatin test presented below, the Hornady 9mm 147-grain TAP-CQ XTP JHP was fired into calibrated 10% ordnance gelatin with the following results.


    Firearm: 9mm Glock 19, 102mm barrel
    Bare Gelatin: Nominal 10% concentration
    Block Calibration: 3.10 ± 0.05 inches @ 585 ± 0.50 fps
    Block Calibration Temperature: 36.90° ± 0.05 Fahrenheit
    Block Core Temperature: 39.50° ± 0.05 Fahrenheit
    Test Site Conditions: 66° Fahrenheit @ 44% relative humidity
    Time Out of Refrigeration Prior to Shot Impact: 4 minutes
    Range: 10 feet

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    Average Expansion: 0.581 inch
    Recovered Bullet Length: 0.494±0.0005"
    Recovered Bullet Weight: 146.6 gr. (99.73% retained weight)
    Impact Velocity: 992 fps
    Maximum Penetration Depth: 13.70 ± 0.05 inches
    Maximum Cavitation Depth : 10.80 ± 0.05 inches

    Entering the average expansion, recovered weight, and the impact velocity from the test above into models gives the predictive yields of the models as seen below.
    From this comparison, it can be seen how closely these models can predict/emulate the terminal performance of bullets in 10% gelatin.

    Q-model
    DoP: 13.436 inches
    Wound Mass: 1.754 ounces
    Wound Volume: 2.918 cubic inches

    mTHOR
    DoP: 13.032 inches
    Wound Mass: 1.701 ounces
    Wound Volume: 2.830 cubic inches

    Probability of Incapacitation, 1st-shot and cumulative binomial P[I/H] values
    1st-shot P[I/H]: 69.59%
    2nd-shot P[I/H]: 90.75%
    3rd-shot P[I/H]: 97.19%
    ΔE15: -214.987 fpe

    DoP = maximum equivalent depth of penetration in calibrated ordnance gelatin
    Wound Mass = total weight of tissue damaged/destroyed within the entire wound channel
    Wound Volume = volume of the entire wound channel
    P[I/H] = probability of incapacitation per random munition strike to combatant's torso/abdomen: Assault, 30-second time-frame (US Army BRL P[I/H] model, Dziemian, 1960)
    ΔE15 = Amount of kinetic energy (in fpe) expended by the bullet from a penetration depth of 1 through 15 centimeters
    Last edited by the Schwartz; 08-14-2018 at 09:47 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. #9
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    So you are comparing water to bare gel tests. However people aren’t homogeneous and the tests which most closely simulate what we see with bullets dug out of actual bodies is the four layer denim test. Regardless, bullets sometimes just do weird stuff in the real world.

    Even if water does match gel results how much practical application is there ?

  10. #10
    Quote Originally Posted by HCM View Post
    So you are comparing water to bare gel tests. However people aren’t homogeneous and the tests which most closely simulate what we see with bullets dug out of actual bodies is the four layer denim test. Regardless, bullets sometimes just do weird stuff in the real world.
    I agree. Sometimes bullets do indeed, 'do weird stuff'.

    Of course, human beings are not homogeneous isotropic masses of ''stuff'' either, but that is not why gelatin and water are good tissue simulants. The reason that gelatin and water are good tissue simulants is that they are physically equivalent test mediums that duplicate the Bernoulli flow pressure, P = ρTV2, that drives the expansion of JHPs and the resistance (force) that decelerates bullets that occurs when bullets pass through flesh. According to the equation that describes the Bernoulli flow pressure, P = ρTV2, the hydraulic pressure produced at impact is a function of the mass density of the medium, ρT, and the impact velocity (V) of the bullet. Rearranging the Newton-LaPlace formula, C = √(K ÷ ρT), to solve for the mass density, ρT, of 10% gelatin and water, K ÷ C2 = ρT, it is not hard to see that both substances possess nearly identical densities and will therefore produce nearly identical pressures on any bullet that is traversing at the same velocity through either substance. If we take a hypothetical JHP moving at 1,250 fps (381 mps) through water and 10% gelatin, we get the following pressure values that drive the expansion of our hypothetical JHP-

    For water: Pressure = ρTV2 = 999.972 kg/m3 x (381 m/s)2 = 145,156,935.5 N/m2

    For 10% gelatin: Pressure = ρTV2 = 1,040 kg/m3 x (381 m/s)2 = 150,967,440.0 N/m2

    -which means that there is a very small difference in Bernoulli flow pressure, 3.8% - 4.0%, produced by either medium upon our hypothetical JHP. With equal Bernoulli flow pressure, we get equal (or darned close to it) expansion.

    Quote Originally Posted by HCM View Post
    Even if water does match gel results how much practical application is there ?
    Quite a bit. Since the technical burden of maintaining laboratory control of the tissue simulant's properties is eliminated, or largely reduced. Since water produces dynamic forces on transient projectiles that are nearly identical to those produced by calibrated 10% ordnance gelatin, water is an excellent tissue simulant. Water is insensitive to ambient environmental conditions, requires no calibration in order to produce valid test results, and can be used with little difficulty and almost no expense. Ballistic tests conducted in calibrated ordnance gelatin require rigorous environmental control to ensure a valid test outcome. The ease of use and low cost of testing in water make it an attractive option for those individuals seeking a valid, yet cost-effective ballistic test medium.

    This reduction in required technical control is why some experimenters are so attracted to the synthetic simulants, like Clear Ballistic Gel. Water, which is much, much less expensive than Clear Ballistic Gel, reproduces Bernoulli flow pressure that is nearly identical to that of 10% ordnance without the cost associated with Clear Ballistic Gel. Unfortunately, synthetic simulants, like Clear Ballistic Gel (ρT = 865 kg/m3), are unsuitable due to the fact that their mass densities, internal sonic velocity and bulk moduli do not match those of water or 10% ordnance gelatin. Once again, the constraints of the Newton-LaPlace formula, C = √(K ÷ ρT), determine the Bernoulli flow pressure, P = ρTV2, produced upon our hypothetical JHP by the test medium. If the mass density differs significantly (in the case of Clear Ballistic Gel, there is a -16.8% difference between CBG and 10% ordnance gelatin) then the test medium will produce dissimilar pressures that drive expansion. CBG, being one such example, demonstrates less expansion and greater penetration and fails BB validation/calibration as claimed by the manufacturer's website as shown in the video below.


    https://www.youtube.com/watch?v=5pqPBnSYTIc
    Last edited by the Schwartz; 08-15-2018 at 11:13 AM.
    ''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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