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Thread: 5.56 Water Expansion Testing; 55/70gr GMX, 62gr TBBC, 55/64/75gr GDSP

  1. #21
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    Quote Originally Posted by WS6 View Post
    Buford, your projectiles look like oooollldddd stuff. Like, way old. The stuff i tested previous that shed petals was newer. This last batch im testing is yet the latest revision. Compare this round, fired at something like 40m from a 14.5 (impact at around 2700ish) on water jugs to yours. This is latest gen for this projectile. Attachment 54677
    Holy sh*t. They have obviously changed some internal skiving geometries. Possibly even the alloy itself. Date of purchase? And, if your don't mind, where you got it from? I'm getting ready to grab some more. Feel free to PM if you want. Please and thank you.


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    Good stuff Buford. Thanks for adding some data points for everyone to consider.

    Not sure if you remember but I did a similar test with a few different types of rounds about 5-6 years ago. If you want me to, I can link it for everyone’s benefit. Your call.

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    5.56 Water Expansion Testing; 55/70gr GMX, 62gr TBBC, 55/64/75gr GDSP

    Quote Originally Posted by WS6 View Post
    Velocity IS a wounding mechanism at 1800+. It contributes greatly to secondary projectiles as well. As a matter of fact, this doe (shot with 70gr gmx by me at 78m) had secondary projectiles all through the top 3" of her lungs from her spinal column. Further, expanded bullet shape, etc. Does matter. A large flat meplat will destroy tissue more than a rounded one. Especially at the latter portion of the wound tract. My ra556b at 27m (pix on harddrive, not phone) produced significantly less damage than my 70gr gmx at 23m, from a shorter (14.5 vs 16.1) barrel on the exit side. Very interesting about bullet shape, weight, etc.. the wounds look like they cam from different caliber weapons, and you can see the value of retaining velocity through the target. Lots of blood trail on the 70gmx, none really on ra556b.

    Attachment 54678
    Attachment 54679
    Vicious, I'm tracking.

    WS6, THAT is what I experienced with the 70gr GMX even from my SBR. Granted, I bought almost all my 70gr GMX at one time, early in their initial release. But, I see explosive wound tracks with the occasional punctuate entrance, always a silver dollar or bigger exit, and always guts and blood and organs blown out of the backside of the animal. Blood trail is always strong, even when I tagged a 285lb boar through both cartilage plates and both scapulas at about 40m. Frankly, that didn't look much different from my Tikka T3 shot at 70m on a 240lb sow with 308 Winny 165gr Federal Trophy Bonded Tip (a TBBC with a boat tail and ballistic tip). Effects on the animal were the same; a quick dirt nap and some squiggling in place.... which quickly ended.

    Granted I'm not equating the two calibers. Not hardly (I just spent serious coin building my own AR10). But the effects I'm seeing from the 70gr GMX are slightly better than with the 55gr Superformance GMX and the 62gr TBBC (neither of which would I hesitate to use for hunting or SD/HD). The farm I used to hunt at mistook my hogs for hogs my buddy shot with his Romanian AKM clone using 7.62x39 Wolf soft point and Hornady soft point on more than one occasion while they got started dressing the carcasses from the truck beds.

    The guides who occasionally came out to hunt/spot with me commented that, when fired from my 11.5" suppressed SBR, the 70gr GMX created an audible "thump"/thwack that made them think it was a 7.62 AK round or a 6.8. Purely anecdotal. But they are all seasoned guides and not prone to praise. More like merciless mockery on a constant basis.


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    Last edited by BufordTJustice; 11-26-18 at 12:46.
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    Quote Originally Posted by Ironman8 View Post
    Good stuff Buford. Thanks for adding some data points for everyone to consider.

    Not sure if you remember but I did a similar test with a few different types of rounds about 5-6 years ago. If you want me to, I can link it for everyone’s benefit. Your call.
    I vaguely remember. Please link.


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    Quote Originally Posted by WS6 View Post
    Velocity IS a wounding mechanism at 1800+. It contributes greatly to secondary projectiles as well. As a matter of fact, this doe (shot with 70gr gmx by me at 78m) had secondary projectiles all through the top 3" of her lungs from her spinal column. Further, expanded bullet shape, etc. Does matter. A large flat meplat will destroy tissue more than a rounded one. Especially at the latter portion of the wound tract. My ra556b at 27m (pix on harddrive, not phone) produced significantly less damage than my 70gr gmx at 23m, from a shorter (14.5 vs 16.1) barrel on the exit side. Very interesting about bullet shape, weight, etc.. the wounds look like they cam from different caliber weapons, and you can see the value of retaining velocity through the target. Lots of blood trail on the 70gmx, none really on ra556b.

    Attachment 54678
    Attachment 54679
    Definitely yes to bullet shape but no to velocity.Thats one thing I see written over and over in these papers about velocity and energy not being a wounding factor in and of themselves. I believe Fackler et al did tests where they shot steel BBs at ~4000 fps into pigs and gel and it did not significantly increase wound severity. My understanding is that velocity and kinetic energy only matter in the sense that they provide the bullet with the ability to do work ie. fragment, expand, penetrate. How that bullet uses that energy depends on the design, construction and shape of the bullet. A good bullet design will harness that energy to properly expand while still penetrate deeply enough. Poor bullet designs waste that energy by simply passing through the target. The 1800+fps, I believe has to do with the threshold to produce a significant temporary cavity ie handgun bullets move too slow to produce a TC and as I mention before, I have become increasingly underwhelmed by TC as a wounding mechanism.

    One thing I hear from hunters often enough is that copper solids like TSX seem to "hit harder" on meat than other hunting rounds. I suspect that has to do more with how that bullet violently changes its shape as it traverses through tissue early in its upset.
    Last edited by vicious_cb; 11-26-18 at 14:08.

  6. #26
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    Quote Originally Posted by vicious_cb View Post
    Definitely yes to bullet shape but no to velocity.Thats one thing I see written over and over in these papers about velocity and energy not being a wounding factor in and of themselves. I believe Fackler et al did tests where they shot steel BBs at ~4000 fps into pigs and gel and it did not significantly increase wound severity. My understanding is that velocity and kinetic energy only matter in the sense that they provide the bullet with the ability to do work ie. fragment, expand, penetrate. How that bullet uses that energy depends on the design, construction and shape of the bullet. A good bullet design will harness that energy to properly expand while still penetrate deeply enough. Poor bullet designs waste that energy by simply passing through the target. The 1800+fps, I believe has to do with the threshold to produce a significant temporary cavity ie handgun bullets move too slow to produce a TC and as I mention before, I have become increasingly underwhelmed by TC as a wounding mechanism.

    One thing I hear from hunters often enough is that copper solids like TSX seem to "hit harder" on meat than other hunting rounds. I suspect that has to do more with how that bullet violently changes its shape as it traverses through tissue early in its upset.
    Shoot an animal with a federal DP 1oz 12ga hardened flat nose slug. Shoot it with a 5.56 bonded or monometal. Look at the lungs from both. You'll change your mind.

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    Quote Originally Posted by WS6 View Post
    Shoot an animal with a federal DP 1oz 12ga hardened flat nose slug. Shoot it with a 5.56 bonded or monometal. Look at the lungs from both. You'll change your mind.
    Im open to the idea if theres sufficient evidence. If you're telling me a 70gr GMX is blowing out lungs vs a 12g slug then Id like to understand the mechanism behind that.

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    Quote Originally Posted by vicious_cb View Post
    Im open to the idea if theres sufficient evidence. If you're telling me a 70gr GMX is blowing out lungs vs a 12g slug then Id like to understand the mechanism behind that.
    The lung lobes hit by a 5.56 expanding round turn out looking more or less like the aftermath of a nosebleed blown into the toilet. Several inches around the bullet path. The lungs i hit with a 12g DP federal flat nose slug looked healthy right up to the cookie cutter 3/4" hole in them. I prefer to damage stuff more. I feel, looking at tissues hit with both low and high velocity bullets with flattish meplats, that velocities in the 2000s are far superior.

    But seriously...go do it yourself! Nothing beats doing. Internet forums and he said she said pale in comparison to holding that tissue yourself...and the venison YOU get to eat
    Last edited by WS6; 11-26-18 at 23:07.

  9. #29
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    Quote Originally Posted by WS6 View Post
    The lung lobes hit by a 5.56 expanding round turn out looking more or less like the aftermath of a nosebleed blown into the toilet. Several inches around the bullet path. The lungs i hit with a 12g DP federal flat nose slug looked healthy right up to the cookie cutter 3/4" hole in them. I prefer to damage stuff more. I feel, looking at tissues hit with both low and high velocity bullets with flattish meplats, that velocities in the 2000s are far superior.

    But seriously...go do it yourself! Nothing beats doing. Internet forums and he said she said pale in comparison to holding that tissue yourself...and the venison YOU get to eat
    My experiences mirror yours.


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