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Thread: 7.62 / 6.5 / 5.56 vs concrete block

  1. #1
    Chieftain stanc's Avatar
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    7.62 / 6.5 / 5.56 vs concrete block

    Was intending to put this video in the .308 vs 6.5 Grendel thread, but it appears that got deleted. So, since this section didn't seem busy, I'm putting it here although it ain't your typical target.

    (Mods feel free to move it elsewhere, if you wish.)


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    Moderator bwaites's Avatar
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    Link?
    Gun Confiscation WILL NOT Happen In My Lifetime. Pat Kelley 1998

    NOR IN MINE!

  3. #3
    QuadCam
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    i was thinking the m855 with the steel penetrator core would have penetrated through all the jugs. I guess not.

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    Moderator bwaites's Avatar
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    Quote Originally Posted by QuadCam View Post
    i was thinking the m855 with the steel penetrator core would have penetrated through all the jugs. I guess not.
    855 is a bit of a compromise as an AP. Once it hits something, the jacket seems to come apart. The penetrator sometimes keeps going, as it did in this case, when it exited the side of the jug.

    I would like to see this test with the Barnes solid 110 grain.

    Going to have to give it a try.
    Gun Confiscation WILL NOT Happen In My Lifetime. Pat Kelley 1998

    NOR IN MINE!

  5. #5
    JASmith
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    It appears that the steel core still makes a big difference since it got through at least as well as the others and was the lightest of the bunch.

    The mantra is "bullet construction counts!"

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    Chieftain stanc's Avatar
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    Quote Originally Posted by QuadCam View Post
    i was thinking the m855 with the steel penetrator core would have penetrated through all the jugs. I guess not.
    As Bill noted, bullet construction of M855 is relatively fragile, with a much thinner jacket than larger calibers.

    Also, for tough barriers like this, there's no substitute for mass. Even though the 7.62 and 6.5 MatchKings lack the steel tip of M855, their post-barrier effects were far greater.

  7. #7
    JASmith
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    The core separating from the rest of the bullet should be no surprise.

    They need to do that so the harder material can do its thing.

    It's too early to generalize about the value of mass. While mass and the KE associated with it makes exciting splashes, one needs the bullet to get through in order to get on the table for effects. The lighter M855 core penetrated as far as anything else and was a lot lighter. Hence one could also draw the conclusion that there's no substitute for steel, since the M855 was the only round with a steel core.
    Last edited by JASmith; 08-20-2011 at 06:29 PM.

  8. #8
    Chieftain stanc's Avatar
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    Quote Originally Posted by JASmith View Post
    The core separating from the rest of the bullet should be no surprise.

    They need to do that so the harder material can do its thing.
    Huh?
    It's too early to generalize about the value of mass.
    Too early for you, perhaps, but not for me. In similar barrier penetration testing I did in the past, I observed that heavier bullets always outperformed lighter bullets, despite a velocity differential of 300 fps.

    Rifle calibers (7.62mm 147gr FMJ vs 5.56mm 55gr FMJ) and pistol calibers (.45 ACP 230gr FMJ vs 9mm 115gr FMJ), the result was the same.
    While mass and the KE associated with it makes exciting splashes, one needs the bullet to get through in order to get on the table for effects.
    Uh, don't you realize that the "exciting splashes" were caused by the bullets getting through???
    The lighter M855 core penetrated as far as anything else and was a lot lighter.
    True, but its post-barrier effect was far less than those of the bigger, heavier bullets.
    Hence one could also draw the conclusion that there's no substitute for steel, since the M855 was the only round with a steel core.
    Incorrect conclusion. Note the difference in post-barrier wound trauma of 5.56 M855 vs 6.8 M855-type bullet.



    There is no substitute for mass.

  9. #9
    JASmith
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    I think the difference in how one interprets the information is the focus on a single dimension or effect versus looking at the challenge as a constrained system where trades need to be made.

    As near as I can tell, the context of almost any discussion in this forum is the Grendel. My interest is in what bullet designs, etc. might help it perform better in various encounters.

    To be sure, mass is important, but it is only a part of the system and the Grendel platform puts significant constraints on the mass that can be brought to the problem.

    I will repeat, one has to get through any intervening material before the response in gel (or any liquid) begins to be important.

    Further, the milk jug tests more closely illustrate the dynamic wound cavity than the permanent wound cavity. Martin Fackler and others have shown that the dynamic cavity, while capable of presenting spectacular pictures, does not adequately represent wound potential in torso-sized objects with individual weapons.

    To illustrate, consider the difference in how that milk jug responds to the 5.56 to how a 5 gallon plastic can will. Or to get more graphic, a squirrel coming apart when hit by that round versus a small hole in a deer - both responses from the same bullet at the same velocity. You just can't count on the dynamic cavity causing significant damage unless the body is small enough that the skin (or package) ruptures.

    To repeat:
    1) Hydrodynamic shock, while interesting, is a minor player in the terminal effects the Grendel needs to generate.

    2) When working to get the most out of a cartridge, trades in penetration, energy, and bullet construction are needed.
    Bottom Line: If the purpose of this thread is merely to entertain, then I will read with amusement. If, however, the comments appear to impact the Grendel (or other cartridge) design space, I will likely add more comments.

  10. #10
    Chieftain stanc's Avatar
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    Quote Originally Posted by JASmith View Post
    To be sure, mass is important, but it is only a part of the system and the Grendel platform puts significant constraints on the mass that can be brought to the problem.

    I will repeat, one has to get through any intervening material before the response in gel (or any liquid) begins to be important.
    Does this mean you still don't understand that the 6.5 and 7.62 MatchKings did get through the barrier???
    Bottom Line: If the purpose of this thread is merely to entertain, then I will read with amusement. If, however, the comments appear to impact the Grendel (or other cartridge) design space, I will likely add more comments.
    Comment all you wish. But it'd be nice if you show evidence that supports your claims, instead of just posting your beliefs.

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