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  1. #41
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    Mar 2012
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    Quote Originally Posted by baker View Post
    The 77gr TMK showed less drop on the chart in the middle of the thread.
    It also is delivering a lot less energy on target. The 123-grain Hornady SST they are using has proven to be a very effective killer on multiple
    kinds of game. I do not know if the 77 TMK has any record of performance on meat.
    I have never really considered an AR pistol as something I would have a use for but after seeing Doc's setup I think I will reconsider that idea.

  2. #42
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    Nov 2010
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    South-Central Idaho
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    Quote Originally Posted by baker View Post
    The 77gr TMK showed less drop on the chart in the middle of the thread.
    The point of this project was to achieve the maximum amount of reach and terminal energy in the smallest package. I think this 12.5" Grendel pistol build may be the sweet spot for portability, reach and power. I'm interested to see what the recoil and blast are like. If they aren't deal breakers for quick follow up shots, I think this really could be pretty close to a do all mini carbine.
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  3. #43
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    Jan 2012
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    Quote Originally Posted by baker View Post
    The 77gr TMK showed less drop on the chart in the middle of the thread.
    Drop is the easiest thing to compensate for, so it's less important than wind drift and accuracy for long distance shooting. Unfortunately, it's also one of the first numbers a lot of inexperienced shooters look at.

    I'll post more later on the Grendel vs 5.56 ballistics in this short barrel project, but in short - the 12.5" Grendel drops more but drifts less in the wind and hits harder than even a 16" 5.56. The trade-off is a little more recoil, especially in a 5-6 lb SBR or pistol, but it's not bad at all and the blast is about the same as short 5.56 or maybe not even as bad in my very subjective opinion.

  4. #44
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    Nov 2010
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    I think the thing that has been the leading driver in my interest in this build has been that the role of the AR pistol has really changed in my mind.

    The Glock PDW has completely taken over the role of the AR for indoor work as far as I'm concerned.

    So the AR pistol, being relegated to outdoor duty, is now competing for space with the carbine. It must do something better than the carbine does or be dismissed completely. What it does better is portability and concealability.

    The thread on the scoped AR pistol really opened my eyes to the advantages of having a portable and concealable tool that could readily engage targets at ranges further than 100 yards. The Grendel seemed a great choice. Terminal energy is much better than 5.56 and range is much better than 300 blackout for about the same ammo weight.

    The way I look at it, if you're using a red dot and shooting within 100 yards, the differences between a 5.56, 300 blackout and 6.5 Grendel on a bad guy will be pretty minimal. But, if you're willing to have a slightly stronger optic on board, the Grendel really starts to shine. Additionally, if you add a suppressor, the 12.5" Grendel still outperforms the 5.56 or 300 BLK 16" carbines and is quieter with the same length.
    Last edited by DogDoc; 05-21-2017 at 07:42 PM.
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  5. #45
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    May 2008
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    Made it to Free America
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    What optic are you thinking about?

  6. #46
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    Quote Originally Posted by EDELWEISS View Post
    What optic are you thinking about?
    Speaking for myself - any optic that's appropriate on a Recce works here too, something with a milling reticle and turrets. Since it's a smaller package, I'm leaning towards a lighter weight optic and will probably end up with another Mark AR 3-9x.

  7. #47
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    Nov 2010
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    Quote Originally Posted by Yondering View Post
    Speaking for myself - any optic that's appropriate on a Recce works here too, something with a milling reticle and turrets. Since it's a smaller package, I'm leaning towards a lighter weight optic and will probably end up with another Mark AR 3-9x.
    I have a 1.5-4 Leupold for it but am strongly considering a Mark AR 3-9 as well.

    Doc
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  8. #48
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    As promised, here's some ballistic info from these short 6.5 Grendel barrels.

    First, for those who aren't familiar with the Grendel, here's a visual, with large frame AR10 rounds on the left and small frame AR15 rounds on the right.
    Left to right: 308, 6.5 Creedmoor on the 308 mag. 6.5 Grendel, 6.8 SPC, 5.56 on the AR15 mag.


    As you can see in the pic, the Grendel uses a short fat case (derived from 7.62x39) for decent powder capacity while making room in the magazine for long streamlined 6.5/.264 cal bullets of higher b.c. than the 5.56 can use. It uses the same bullets as the 6.5 Creedmoor, but in a smaller case and at lower velocity.

    When I machined these two short Grendel barrels, I left mine at 14" long and cut DogDoc's to 12.5", so I could compare velocity. Both were cut with the same chamber reamer, from the same barrel blanks, and fired on the same lower. Here's what I found:

    Wolf Military Classic 100gr FMJ
    14" - 2415 fps
    12.5" - 2320 fps

    123 A-Max handload
    14" - 2440 fps
    12.5" - 2360 fps

    120gr SMK handload
    14" - 2410 fps
    12.5" 2360 fps

    So velocity difference between the two is 50-100 fps, or worth about 25-50 yards. Not a big difference IMO, so I've cut mine down to 12.5" now as well; it just makes sense.

    Since the point of this excercise is to provide Recce capability in a smaller package, here's a comparison of the 12.5" Grendel to my 75gr 5.56 precision Recce load. I used 1,000 ft density altitude; these numbers will change for different altitudes but the comparison is still valid.



    Note the power of the Grendel in comparison to the 5.56, even from the shorter barrel. By 700 yards, it's retaining double the power of the 5.56.
    The Grendel is a slower round, and drops more at distance than the faster 5.56, but makes up for it with less wind drift, more power, and longer range before it goes trans-sonic which affects accuracy.
    Last edited by Yondering; 05-22-2017 at 04:45 PM.

  9. #49
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    Interesting. I agree with the decision to go down to 12.5". That should be a spectacularly long range rifle for such a short barrel. I remain more intrigued by the Creedmor than the Grendel, but I can see a role for both.


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  10. #50
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    Quote Originally Posted by LawDog View Post
    Interesting. I agree with the decision to go down to 12.5". That should be a spectacularly long range rifle for such a short barrel. I remain more intrigued by the Creedmor than the Grendel, but I can see a role for both.


    Sent from my iPad using Tapatalk
    And why I have both as well. :) I don't think either one replaces the other, they fit different roles despite being the same bore diameter. The Creedmoor is unquestionably the better long range cartridge; the little Grendel in this case at least is a way to meet or exceed 5.56 recce capability in a smaller package. I have to give credit to DogDoc for bringing up this idea here; already owning a Creedmoor I've never been real excited about the Grendel in longer AR15 barrels as it's traditionally used, but this project was a little more outside the box and makes a lot more sense than I would have thought before looking into it.
    Last edited by Yondering; 05-25-2017 at 12:45 AM.

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