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Thread: Ballistic gelatin comparisons: Part I

  1. #81
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    Can anybody recommend a BB gun to use for calibration/ validating a gel block at the required 590 fps? I don't have a chronograph to check speeds, so I'm unsure of which model to choose from.

  2. #82
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    Quote Originally Posted by CZ Man View Post
    Can anybody recommend a BB gun to use for calibration/ validating a gel block at the required 590 fps? I don't have a chronograph to check speeds, so I'm unsure of which model to choose from.
    You have to have a chronograph to ascertain velocity of the BB. There's a chart to compare actual velocities to actual block penetration of the BB to make sure the gel block is compliant. I think the Crossman 760 is the popular test BB gun for this, but I'm sure there are others that work just fine.
    Regional Government Sales Manager for Aimpoint, Inc. USA
    Co-owner Hardwired Tactical Shooting (HiTS)

  3. #83
    It appears that Part 3 has been published:

    https://www.policeone.com/police-pro...kEYB93TAd5o6J/

    The following conclusions, some of them oddly phrased, are made in the article:

    1.The clear synthetic gelatin must be calibrated by the user before use.

    2. The clear synthetic gelatin currently demonstrates a tendency to limit bullet expansion and increase bullet penetration, compared to FBI-standard, 10% calibrated organic gelatin.

    3. The clear synthetic gelatin currently does not appear to be a suitable substitute for FBI-standard, 10% calibrated organic gelatin if the bullets will be measured and evaluated according to FBI performance standards.

    4. There is no apparent “conversion” between data derived from 10% organic gelatin and the current version of the clear synthetic.
    Last edited by the Schwartz; 01-14-2020 at 09:49 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.

  4. #84
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    Quote Originally Posted by Wayne Dobbs View Post
    You have to have a chronograph to ascertain velocity of the BB. There's a chart to compare actual velocities to actual block penetration of the BB to make sure the gel block is compliant. I think the Crossman 760 is the popular test BB gun for this, but I'm sure there are others that work just fine.
    OK. Thanks for the suggestion.
    I take it the Crossman 760 doesn't reliably shoot at 600 fps. Hence the need for the chronograph to verify speed?

  5. #85
    Site Supporter 0ddl0t's Avatar
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    Quote Originally Posted by CZ Man View Post
    OK. Thanks for the suggestion.
    I take it the Crossman 760 doesn't reliably shoot at 600 fps. Hence the need for the chronograph to verify speed?
    The FBI specification is a steel BB at 590 +/- 15 fps. You'll probably need to play around with the # of pumps and distance from muzzle to reliably shoot 575-605fps.

  6. #86
    Quote Originally Posted by DMWINCLE View Post
    Part 3

    Unfortunately, our limited test doesn’t indicate a conversion “shortcut” is likely. It would be convenient if we could develop a conversion factor that would equate the organic gelatin and clear synthetic gelatin, but our data indicate that bullet performance is too variable in these mediums to develop a universal “rule of thumb.” Perhaps a skilled mathematician could derive a constant from a more complete sample, but we’re not seeing one lurking in the data.
    While it "might" be possible to derive a scaling constant that "converts" test data for non-expanding/non-deforming projectiles obtained in Clear Ballistics Gel to its equivalent in 10% ordnance gelatin, due to the tendency of CBG to under-drive expansion and over-represent terminal penetration of expanding designs such a scheme is simply not plausible for the projectile designs that are best suited for self-defense.

    Also, not sure how I missed your posting of the publication of Part 3 of the series DMWINCLE...apologies as I wasn't aware of your post prior to mine bringing this to light. I reckon that this is what I get for not reviewing these threads as thoroughly as I could/should.
    Last edited by the Schwartz; 01-17-2020 at 04:52 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.

  7. #87
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    Quote Originally Posted by the Schwartz View Post

    Also, not sure how I missed your posting of the publication of Part 3 of the series DMWINCLE...apologies as I wasn't aware of your post prior to mine bringing this to light. I reckon that this is what I get for not reviewing these threads as thoroughly as I could/should.
    No need to apologize, but thanks. Better to have too many links to the conclusion than none. :-)

    I was glad to see he pulled no punches in his summary.
    Last edited by SiriusBlunder; 01-17-2020 at 05:20 PM.

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