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Thread: 6mm Grendel Group Design Project

  1. #41
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    Quote Originally Posted by StoneHendge View Post
    Well there could be a lucky soul out there if they haven't spent all of their Black Friday money yet. Looks like McGowen actually has a 24" 6mm Grrrr in stock and ready to ship

    http://mcgowenbarrel.com/shop/ar15-6...4-polished-ss/

    Just let me know how it shoots while I wait for mine. And if you're a lurker, create an account lol

    Edit: wtf? Clicked link after posting to confirm it worked - looks like it has 1/2" muzzle threads?
    That's fine, I'd be chopping it to 18" anyway. But it is tempting.

  2. #42
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    Quote Originally Posted by CavityBackBullets View Post
    Lets just agree to disagree since I shoot them all. Do you?
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    You have an extensive working experience with 6mm wildcats between the 2 cases?

    This one is pretty basic math.

    We want to be able to shoot ogive lengths that can't be loaded into a 6.8 case without cutting down the case length significantly.

    Grendel case is a neck-size operation and done without losing capacity.

    Measure the magazine well limitations, then the bullets we want to be able to shoot.

    Basic addition. The room isn't there for a 6.8 wildcat case to shoot 105s and 107s unless you cut the case down so far, reducing case capacity and velocity as a result.

    6 PDK, 6mm Hagar, 6 DTI, 6x6.8, 6mm SPC, etc all don't have the ability to load 105s and 107s to mag length.

    I just measured a 105gr Nosler RDF in a 6.8 case without moving the shoulder.

    2.440" COL. AR15 magazine well is 2.395".

    105gr Nosler RDF already drops into 6mm AR and 6mm AR Turbo.

    This shouldn't be too hard to figure out.
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  3. #43
    Quote Originally Posted by LRRPF52 View Post
    __________________________________________________ ______________________________________
    You have an extensive working experience with 6mm wildcats between the 2 cases?

    This one is pretty basic math.

    We want to be able to shoot ogive lengths that can't be loaded into a 6.8 case without cutting down the case length significantly.

    Grendel case is a neck-size operation and done without losing capacity.

    Measure the magazine well limitations, then the bullets we want to be able to shoot.

    Basic addition. The room isn't there for a 6.8 wildcat case to shoot 105s and 107s unless you cut the case down so far, reducing case capacity and velocity as a result.

    6 PDK, 6mm Hagar, 6 DTI, 6x6.8, 6mm SPC, etc all don't have the ability to load 105s and 107s to mag length.

    I just measured a 105gr Nosler RDF in a 6.8 case without moving the shoulder.

    2.440" COL. AR15 magazine well is 2.395".

    105gr Nosler RDF already drops into 6mm AR and 6mm AR Turbo.

    This shouldn't be too hard to figure out.
    Actually it can shoot 105's with enough case capacity.
    How its accomplished though I cannot reveal.

  4. #44
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    Quote Originally Posted by CavityBackBullets View Post
    Actually it can shoot 105's with enough case capacity.
    How its accomplished though I cannot reveal.
    Claims like this stretch credibilty.

    At some point one will need to disclose any “secret sauce” and demonstrate the perfomance claims are valid within acceltable pressure limits.
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  5. #45
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    Quote Originally Posted by StoneHendge View Post
    Well there could be a lucky soul out there if they haven't spent all of their Black Friday money yet. Looks like McGowen actually has a 24" 6mm Grrrr in stock and ready to ship

    http://mcgowenbarrel.com/shop/ar15-6...4-polished-ss/

    Just let me know how it shoots while I wait for mine. And if you're a lurker, create an account lol

    Edit: wtf? Clicked link after posting to confirm it worked - looks like it has 1/2" muzzle threads?
    There is a bigger selection of .223 muzzle devices with 1/2"-28 threads.
    Clearances would have to be checked between bullet diameter and ID of muzzle device.
    I know you know this but I am only posting this in case there are others that try it. Maybe you have more ideas.

  6. #46
    Warrior StoneHendge's Avatar
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    Quote Originally Posted by bj139 View Post
    There is a bigger selection of .223 muzzle devices with 1/2"-28 threads.
    Clearances would have to be checked between bullet diameter and ID of muzzle device.
    I know you know this but I am only posting this in case there are others that try it. Maybe you have more ideas.
    My guess is that whoever made the barrel screwed up. Seems like an odd caliber and configuration for a custom manufacturer to make for stock. I’m sure they’d cut and rethread it for someone who asks. I did have a good visualization of Bugs Bunny handing a rifle with a muzzle device that’s too narrow to Yosemite Sam.
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  7. #47
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    A2 flash hider would work just fine. Just look at the muzzle of your 5.56.
    There is plenty of clearance. 0.01" additional each side of center.
    Last edited by bj139; 12-04-2017 at 05:35 PM.

  8. #48
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    Why the .243" and not a .257" ?

    In the quest for MV and BC, what are we loosing in hunting capability? Are sectional densities equal in 6mm and 6.5mm?

    I thought the 6.5 Grendel already provided the optimal balance between target shooting and hunting performance.

  9. #49
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    Quote Originally Posted by Bwild97 View Post
    Why the .243" and not a .257" ?

    In the quest for MV and BC, what are we loosing in hunting capability? Are sectional densities equal in 6mm and 6.5mm?

    I thought the 6.5 Grendel already provided the optimal balance between target shooting and hunting performance.
    That was my original question as well.

    The 6.5mm (.264") is midway between the beloved 30 cals for us old timers and the newbies 5.56mm.

    It is just the ideal compromise.

    Target shooters are looking for the last tiny advantage so the 6mm has value to them.

  10. #50
    Warrior StoneHendge's Avatar
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    Quote Originally Posted by bj139 View Post
    Just look at the muzzle of your 5.56.
    Lol - my "new" 20" target 556 (ie, life after 22 Nosler) has a VG6 Epsilon on it - has about as much muzzle movement and recoil as a 22lr.

    But for target, 6mm offers more than a "last tiny advantage." I'm pretty confident that my 26" 6mm Grrr barrel arriving today (yay!) will have ballistics nipping at the heels of what I do with 130's in my 6.5 S'more. To put it in perspective, I was having a lot of fun with a buddy yesterday shooting 1k in winds that ranged from the high teens to the high 20s. Drop and 20 mph wind drift were 24' and 8.5' with me S'more while drop and 20 mph wind drift were 29' and 11' in my 22" 6.5 Grendel shooting 123 gr Scenars. The S'more got more first shot hits, while follow up shots were faster with the Grendel due to lower recoil. That didn't equate into more second shot hits with the Grendel since it is more susceptible to wind speed fluctuation. But with 6mm Grrr, you would have the S'more 1st shot hit percentage combined with even lower recoil than 6.5 Grrr. At one point when I was on the Grendel, the wind got into the high 20s and my horizontal hold was 5 mils on a 16" (half mil) target - over 15' of wind drift. Was kind of crazy to dial the scope back to zero at the end of the day and take a look at what the crosshairs were actually pointing at with a 9.1 mil vertical and 5 mil horizontal hold

    Bwild, I don't know if anyone even makes a .257 match target bullet. My interest in 6mm Grrrr is solely on the basis of target shooting, with the caveat that I consider p-dogs to be exploding targets.
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  11. #51
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    I think most of us here only have a pipe dream of shooting at 1000 yds. As in precision match grade pipe.

    My home range only has 100 yds maximum, so I am resigned to the pursuit of sub MOA groups.

    Isn't the last tiny bit your difference of 1 foot in hold left between 6mm and 6.5mm?

    Just like the last tiny bit of shooting a 0.4 MOA group vs. a 0.6 MOA group.

  12. #52
    Super Moderator LRRPF52's Avatar
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    Quote Originally Posted by Bwild97 View Post
    Why the .243" and not a .257" ?

    In the quest for MV and BC, what are we loosing in hunting capability? Are sectional densities equal in 6mm and 6.5mm?

    I thought the 6.5 Grendel already provided the optimal balance between target shooting and hunting performance.
    Good to see you again!

    If we're limited to the AR15 magazine well dimensions, then .257" is really close to 6.5mm, suffers from a lot of the same challenges, but I'm a big fan of the .257 bore.

    It has been neglected when it comes to bullet selection, but I really think is a great balancing point if we could get bullet manufacturers to support it.

    I think this will actually happen moving forward, as Hornady has already done some work on the .257 Creedmoor. .257 Creedmoor was featured in a recent Handloader Magazine as well.

    For competitive shooters in long range matches, most people want a .550 to .6 or higher G1, .275 to .3 + G7 bullet. That's easier to do in .257 and keep the recoil down than it is in 6.5mm (140gr + cup and core).

    In a 6mm, that usually puts you in the 105gr + weight category.

    It could be done in .257 with a 123gr - 130gr, but would be quite long for the AR15.
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  13. #53
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    Quote Originally Posted by Bwild97 View Post
    Why the .243" and not a .257" ?

    In the quest for MV and BC, what are we loosing in hunting capability? Are sectional densities equal in 6mm and 6.5mm?

    I thought the 6.5 Grendel already provided the optimal balance between target shooting and hunting performance.
    Best way to answer is to look at the .243 Win. It has a fine reputation but folks don’t normally hunt elk and larger with it.

    The 25-06 is occasionally used for elk because we can get 110 ton120 gr hunting bullets for it.

    Trying to bridge the gap between 6 and 6.5 mm, however, feels more like an exercise for the sake “completeness” rather than wgenerating a new capability.

    This is especially true now that one can get 110-115 gr 6 mm and be able to accurately shoot them with proper twist barrels.
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  14. #54
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    People complain about lighter bullets having less ringability on steel targets.

    Doesn't the 6mm give up ringability for the sake of better ballistics?

  15. #55
    Quote Originally Posted by bj139 View Post
    The 6.5mm (.264") is midway between the beloved 30 cals for us old timers and the newbies 5.56mm. It is just the ideal compromise. Target shooters are looking for the last tiny advantage so the 6mm has value to them.
    This.

    14 years ago, I would have been fine if they had first presented us with a .25 or .27 Grendel, but, heck, then again why not .26? .26 cal exactly splits the difference between .22 and .30. The intermediate of intermediate cartridges! Supreme efficiency balancing bullet mass, ballistics, and recoil.

    I consider the 6.5 Grendel the best assault rifle cartridge possible within the confines of the AR platform, given high-capacity, double-stack magazines with a max 2.230 COL. This is why I love it.

    It is also the best multi-role hunting cartridge in that platform.

    It is also very good for informal target shooting, but technically and competitively speaking, is edged out in both drop and drift by a 6mm in the same case. (Or, as I've proposed above, a case stretched from 38.6mm to 40.4mm.)

    So the 6.5 Grendel is a fantastic AR hunting round that can also be used for target shooting.

    My proposed 6mmAR Turbo Stretched is a fantastic AR target round that can also be used for hunting.

    Now, if we could get some of the newer hybrid, optimized ogives on long-range friendly 6.5mm 115-123 grain HPBTs, I think we could give 6mms a run for their money. Every time the major bullet makers come out with a "new" 6.5mm bullet with the same old fat, lazy tangent ogive (hello, Hornady 123gr ELD-M), I'm like, "Nooooo!!! Just put the Berger 140 Hybrid nose or Sierra 150 SMK nose on a 6.5mm 115gr and let us have a bit more velocity from the smaller Grendel case with a super sleek ogive. Why can't they just do it right the first time? It's so simple."
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