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Thread: Temporary Cavitation Wounding. Rifle vs. Pistol?

  1. #1

    Temporary Cavitation Wounding. Rifle vs. Pistol?

    Hi folks, I have a question for the experts: what is the threshold for temporary cavitation wounding? If it makes it easier, specifically with a bullet with a .355 diameter in the 65-90gr range?

    To give a little context, I was reading this thread on M4carbine which indicates that one of the biggest reasons traditional rifle rounds have much more dramatic wounding in many cases is because of "temporal cavitation wounding" in which there is enough energy and surface area that the temp cavity is moving at velocities which induce actual wounds (first assumption this is predicated on). The consensus seems to be that velocity is more important that mass or size, although those do matter. The other consensus seems to be that once you get rifle projectiles up around 1800-2000fps, this effect starts in earnest. One guy then pipes up that there are some pistol rounds that match or are close in terms of velocity to 5.56 from 10-12in barrels, with similar kinetic energy as well. This reminded me of another thread I'd seen recently on Glock Talk where a guy has revived 38 Casull and is pushing light bullets very fast.

    In sum we have a .357 SIG pushing 65gr 9mm bullets at over 2100fps, a 9x25 Dillon pushing 80gr TACXP's at over 2100fps, and .38 Casull pushing 90gr XTPs at over 2400fps! Which if any of these might be fully into the "rifle" wounding category?

    And the followup: how temp cavity wounding scales with bullet diameter and KE as well as velocity in general? I realize that is asking a lot broader of a question so I narrowed the question above. Thanks!

  2. #2
    Site Supporter Sensei's Avatar
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    Significant temporary cavitation generally occurs at velocities >1400 fps. The problem with most ultralite, ultrafast pistol rounds is that they are poorly constructed. This leads to temporary cavitation in the first 4” of issues and trival temporary or permanent cavities beyond 8-10”. Performance through many intermediate barriers is horrible.

    Contrast this with well-designed rifle rounds that offer significant temporary cavities out to 8-10” and a reasonable permanent cavity(ies) out to 16+”.
    I like my rifles like my women - short, light, fast, brown, and suppressed.

  3. #3
    Modding this sack of shit BehindBlueI's's Avatar
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  4. #4
    Site Supporter DocGKR's Avatar
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    "what is the threshold for temporary cavitation wounding?"
    Depends.

    At LAIR, shots were made in the 6000-6500 fps range and the TC was minimal--like a .38 sp LRN for those projectiles which remained point forward.

    Shotgun slugs and large caliber deforming rifle projectiles (think old school 1800's era calibers) can have velocities below 1500 fps, yet offer quite impressive TC effects.

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    "If it makes it easier, specifically with a bullet with a .355 diameter in the 65-90gr range?"
    As noted, when driven too fast, many expanding projectiles designed for handguns will: over-expand creating too much drag resulting in reduced penetration; hyper-expand and fragment, resulting in limited penetration and poor terminal effects; or cause the expanded petals to fold back against the bullet shank, creating a wadcutter type effect (this often occurs with all copper JHP's).

    This violent perpetrator took 27 hits of 115 gr JHP at around 1400 fps during an active shooter incident--too much expansion and too little penetration resulted in poor incapacitation effects.

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    Facts matter...Feelings Can Lie

  5. #5
    Quote Originally Posted by DocGKR View Post

    This violent perpetrator took 27 hits of 115 gr JHP at around 1400 fps during an active shooter incident--too much expansion and too little penetration resulted in poor incapacitation effects.


    It looks like he still had a very bad day. I'm assuming he didn't survive?

  6. #6
    Site Supporter DocGKR's Avatar
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    Fortunately he did not survive, but he was not easy to stop due to poor bullet performance. NONE of the grossly overexpanded, shallow penetrating body hits reached any vital organs, it was a peripheral neck hit which severed an artery, eventually resulting in hypovolemic shock, unconsciousness, and death.
    Last edited by DocGKR; 02-02-2019 at 10:42 PM.
    Facts matter...Feelings Can Lie

  7. #7
    I think I'd choose a 5.56 rifle over a 9mm SMG every time. Rifles make rifle wounds, and handguns, even ones with stocks and longer barrels, suck.

  8. #8
    Site Supporter Sensei's Avatar
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    Quote Originally Posted by WDR View Post
    It looks like he still had a very bad day. I'm assuming he didn't survive?
    I see a bunch of rib fractures and lead with no chest tubes...probably a post-mortum.
    I like my rifles like my women - short, light, fast, brown, and suppressed.

  9. #9
    Site Supporter DocGKR's Avatar
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    Definitely post-mortem from Medical Examiners office...

    This is one of the seminal incidents that encouraged American SWAT teams to switch from MP5's to AR15's.
    Last edited by DocGKR; 02-02-2019 at 11:09 PM.
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  10. #10
    Site Supporter Sensei's Avatar
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    Quote Originally Posted by WDR View Post
    I think I'd choose a 5.56 rifle over a 9mm SMG every time. Rifles make rifle wounds, and handguns, even ones with stocks and longer barrels, suck.
    The force is strong with you.

    There is very little reason to choose a PCC.

    A 8-9” barreled 300blk or 6.8 SPC PDW is within 2” of a MP5K in terms of size and has vastly superior terminal performance through every intermediate barrier...

    A 10-11” 556 is within 2” of an MP5N and will eat its lunch if fed RA556B or some other barrier blind load.

    I have a bunch of PCCs only for nostalgia and because the Mrs. likes them.
    I like my rifles like my women - short, light, fast, brown, and suppressed.

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