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Thread: The 6.5mm Grendel Concept Rifle

  1. #21
    Gunco Samurai Polish Taipan's Avatar
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    Quote Originally Posted by OrdnanceGuy
    Conceptually, the 6.5 Grendel has no dibs on the Galil. Building a Galil costs big bucks. Let's see if a Bulgy AK-74 or a Polish Tantal might be a good start point. But I'm not big on AK versions of M-4's, just my opinion.
    Hmmm 74 sounds ok, but I think the merit of this round is that its great for long distance. Otherwise you might as well use a straight 7.62 X 39 weapon.
    Thats why I was thinking of some sort of DMR configuration.
    However...this would work for me.
    AK milled reciever
    18 inch 74 profile barrel
    Bulgarian Bat wing buttstock
    matching PG & handguards
    side rail mounted 1P21 3x9x42 scope
    ____________
    "The way of the warrior is death, this means choosing death whenever there is a choice between life and death. It means nothing more than this, it means to see things through, being resolved."---Yamamoto Tsunemoto's Hagakure

  2. #22
    Happy Camper hcpookie's Avatar
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    Interesting thread. What exactly is your design goal? Are you talking about a simple "meeper-style" caliber conversion? OR are you talking about a fully-tricked-out "loosely based on an AK" custom one-off build?

    PERSONALLY...

    I would consider a meeper-style conversion more than a "custom one-off" and build it based on the AK-100 style rifle. Galil? Well, there's a lot of good reasons to prefer a Galil but I think I would lean towards the AK-100 tweaks. Think AK-74 with updates. This is more of a personal preference I think as both designs have their good points, and the Galil has a ton of "extras" that would be more work to add to an AK design - night sights, bent charging handle, different rear sight/top cover concept. That said, you COULD add these things to an AK with some work. Night sights being the most work - maybe strip them from a beater Yugo? Not a big fan of the milled receiver - I understand why they did that, and don't see the need for the extra weight. Again, personal preference.

    THAT SAID... let's look ahead 6 months... start with your 6.5 Grendel barrel from any of the custom AR barrel builders. Lathe it down to the proper journal sizes, sleeve the breech if necessary (I have no idea what the chamber diameter is for an AR... need to dig in my safe). OK, you've got you're barrel now. Next, you get a "chopped" AK-74 kit, press off the barrel components, press them onto the AR barrel, and drill for the handguard retainer, barrel pin and cross-pins like any other AK. Put on your choice of receiver and you've got your rifle. It would look almost identical to an AK-74 or AK-101. Put on a (folding) stock of your choice.

    This leads to my only other consideration - magazines. What kind of magazines will properly feed this caliber. I STRONGLY SUSPECT that an un-modified AK-74 mag will work, but I need to surf around for more pictures of the two calibers before I'm convinced. If not, choose standard 5.56x45 caliber mags (like Galil mags) or AK-74 mags with Robarm followers.

    "Done". Trick it out with whatever scope/tri-rail/adapters you care to buy.

    Again, that's all for a "standard caliber conversion". I've given thoughts to this in the past few weeks due to the ominous threat of barrel supply issues we face. I'm pretty sure all of this will be doable, and there may be some minor issues to contend with, such as extractor problems with an AK-74 bolt. No idea on that, need to research cartridge dimensions more.

    hth,
    - Jerry

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  4. #24
    Happy Camper hcpookie's Avatar
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    Well guess what -

    This link:
    http://www.6mmbr.com/gunweek027.html
    states:
    6.5 Grendel Cartridge Specifications
    "Case length is 39mm. Case head diameter is .445". Case capacity is 35.0 grains of water and about 32.5 grains powder. The cartridge was developed to maximize performance in the AR15 platform. In that role, magazine-length loads are limited to 2.255" OAL. However, in single-round loading or in a bolt-action rifle, OAL can be extended with bullets up to 130 grains as far as 2.420". "

    Case head is .445".

    Guess what the 7.62x39 cartridge case head measures? Yep, you guessed it - .445". Therefore, a standard 7.62x39 AK bolt/carrier should work perfectly with this cartridge!

    Do you know what this means? The Yugo kits, the ones with "shot-out bores" are readily suitable for this application... since the barrel will be removed anyway. For that matter, the still-cheap Romy kits could be adapted to this as well.

    Me? I still like the 90-degree gas block setup, so I'd have to get one of those. Just my personal preference vs. the slanted gas block.

    Note OAL - supposedly, the 78gr through 156gr bullets will still fit an AR magazine. There are larger bullets that require longer magazines, and wouldn't be suitable for this application. Wolf is rumored to start making 6.5 later this year.

  5. #25
    Gunco Samurai Polish Taipan's Avatar
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    Do you think the 100 series platform really is the way to go for a DMR? Maybe 100 series but keep the 18" barrel? Wouldn't the milled reciever lend itself to better accuracy? Or would the RPK trunnion of the Yugo do just as well?
    I do know that the Grendel in the AR platform does not use completely stock magazines. They have a different follower and I think I read here somewhere that the flutes on the inside have been removed. Might be interesting to pick up a couple boxes of ammo and see how they fit in a 74 mag.
    ____________
    "The way of the warrior is death, this means choosing death whenever there is a choice between life and death. It means nothing more than this, it means to see things through, being resolved."---Yamamoto Tsunemoto's Hagakure

  6. #26
    Gunco Regular pupwag's Avatar
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    Any thoughts on lug strength,bolt mass or recoil springs?How much do they monkey with on the AR platform?Seems like a sporty cartridge.The imagination gears grind.
    It's only metal, it's not magic.

  7. #27
    Gunco Samurai Polish Taipan's Avatar
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    Quote Originally Posted by pupwag
    Any thoughts on lug strength,bolt mass or recoil springs?How much do they monkey with on the AR platform?Seems like a sporty cartridge.The imagination gears grind.
    I don't think any of those things are anything to worry about. Alexander Arms uses a standard 7.62 AR bolt for both the Grendel and the Beowulf .50cal. It seems to work for them.

    I've been thnking about it most of the day and I have to say a Grendelized 100 series AK sounds as cool as the Galil idea. It may just be the perfect assault weapon. Great for 0 to 600 yards. I know its probably capable of longer ranges but I'm being conservative about its effective range. Combined with a Kobra and a 1P21 scope for different styles of shooting I don't see what else you would need.

    The only think to settle is the milled vs stamped question....which would offer better accuracy? I know I've brought that up in another thread long ago but not sure what the outcome was.
    ____________
    "The way of the warrior is death, this means choosing death whenever there is a choice between life and death. It means nothing more than this, it means to see things through, being resolved."---Yamamoto Tsunemoto's Hagakure

  8. #28
    Gunco Regular OrdnanceGuy's Avatar
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    Exclamation The mag.

    Quote Originally Posted by Polish Taipan
    ... I do know that the Grendel in the AR platform does not use completely stock magazines. They have a different follower and I think I read here somewhere that the flutes on the inside have been removed. Might be interesting to pick up a couple boxes of ammo and see how they fit in a 74 mag.
    Originally, for the 6.8 SPC Rem, the M-16 mags were used. The fatter cartridges were not at an optimum position in the mag, but it worked with reduced capacity. Dedicated mags were then produced for the 6.8. The mags were externally sized to fit in an AR magwell. The inside cartridge position was given more width (side to side) by making the mag side grooves (inward ridges) shallower.

    The 6.5 Grendel's parent case is the 7.62x39. It is "blown out". Taper is lessened. Don't know where the shoulder was moved to, which does not matter for this mag discussion. OAL will fit in the confines of AK mags, 7.62, 5.45, and 5.56.

    With the head the same size as the 7.62x39, the mag will hold the 6.5. BUT the straighter taper will not like the sharp curve of the AK-47 mag. This will cause problems, in my estimation.

    On the opposite end, the 5.56 AK mags are narrow on the inside. The 6.5 will sit almost (watch this word) as though the rounds were in a single stack mag. The banana curve is much straighter.

    So this leaves me thinking that the AK-74 5.45 mag is the better start point. BTW, I have modded a 74 mag to shoot 5.56 with success. All 31 rounds (yes, 31) feed without a hitch. The mag's overall banana curve is not too bad, and can take the 6.5 straighter taper. The inside width (side to side) could stand a little more space to give optimum case to case positioning. Depending on how much taper there is, it "might" prefer a Robinson-type follower (the case "bump" might be tweaked in size).

    I have lots of 7.62x39 cases, but I can't fireform them (no Grendel chamber). Does anyone have 6.5 Grendel cases, even steel ones, to play around with?

  9. #29
    Gunco Regular OrdnanceGuy's Avatar
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    Quote Originally Posted by pupwag
    Any thoughts on lug strength,bolt mass or recoil springs?How much do they monkey with on the AR platform?Seems like a sporty cartridge.The imagination gears grind.
    Within a reasonable range, adjustments/tweaking of the gas bleed hole size and the recoil spring strength, could handle the differences. Best not to fool with the bolt mass.

  10. #30
    Gunco Samurai Polish Taipan's Avatar
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    Here that VEPR with the free floated barrel in the FAL handguard.
    Belongs to a guy that goes by Hilljack.
    ____________
    "The way of the warrior is death, this means choosing death whenever there is a choice between life and death. It means nothing more than this, it means to see things through, being resolved."---Yamamoto Tsunemoto's Hagakure

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