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Thread: Tex's First Grendel Build - 18" Piston SPR

  1. #1
    Warrior
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    Tex's First Grendel Build - 18" Piston SPR

    Yeah, I posted some photos in the Group Buy section, but this thing deserves more air time...

    Upper:
    LAR Grizzly OPS-4 Ambi Side Charge Upper Receiver
    Heavy, slab-sided LAR satin NiB-coated Bolt Carrier
    18" Grendel-logo Faxon Barrel via BFT's recent group buy
    Gen II Grendel-logo Bolt from the BFT's recent group buy
    Superlative Arms Mid-length Short-Stroke Piston Kit
    Omega Carbon Fiber 12" hand-guard with all rails removed (material removed for piston kit)
    Lightweight no-name comp/brake/adapter

    Lower:
    Aero Precision STS Lower Receiver
    RRA 2-Stage NM trigger
    CMMG Lower Parts Kit
    Stark One one-piece grip w/integrated Swivel Mount (Flex Seal applied)
    Magpul MOE A1 Rifle Stock

    Optic:
    Hi-Lux CMR8 1-8x26mm FFP
    Aero Precision Ultra-light mount

    Total Weight
    8 lbs 11.05 oz

    Balance
    Center of Gravity is center of the mag well.

    GrenRight2 (Custom).jpg
    GrenLeft2 (Custom).jpg
    GrendelVert2 (Small).jpg
    ARweight (Small).jpg

  2. #2
    Warrior
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    It looks really nice. Why piston?

  3. #3
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    Quote Originally Posted by bj139 View Post
    It looks really nice. Why piston?
    Thanks.

    Had the ambi-side upper just sitting there after removing a heavy 6.8 barrel I sold to a friend. The side chargers are very cool, but DI gas puffs into your face thru the left side slit, even with a bolt filling the handle hole ("exhaust port"). Piston solves that problem.

    Plus, I was curious to see how light and balanced I could make it with a piston. I had a piston on a 6.8. It bucked like wild AK and made a loud "TINK" sound when fired. This system is a different model and I had to do a bit of customization to get it to work with a side charger carrier. Really looking forward to getting it out on the range.

  4. #4
    Warrior
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    I have an AR with ambi side charging receiver on my 20" group buy barrel.
    I only shot it once and did not notice any gas coming out the left side.
    Maybe it did.

  5. #5
    Warrior
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    She’s purdy!

  6. #6
    Chieftain NugginFutz's Avatar
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    Nicely done. It looks like an exceptional selection of components, with a good weight and balance, to boot.

    Shoot / show / tell!
    Last edited by NugginFutz; 01-15-2018 at 04:42 PM.
    When you earnestly believe you can compensate for a lack of skill by doubling your efforts, there's no end to what you can't do. ~ Larry Kersten

  7. #7
    Warrior
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    Quote Originally Posted by bj139 View Post
    I have an AR with ambi side charging receiver on my 20" group buy barrel.
    I only shot it once and did not notice any gas coming out the left side.
    Maybe it did.
    Not a problem with the 65?
    What sort of eye protection were you wearing? I wear normal eyeglasses to shoot. My eyes felt like a gravel pit after 20 rounds last time I was out with that upper DI.
    My carrier has no bolt exhaust holes on the left and only one on the right... Maybe better gas relief on the right would help. What's your bolt carrier look like?

  8. #8
    Warrior
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    TN - very nicely done and well thought out. Impressive weight and balance. Have you punched any paper as yet?

  9. #9
    Warrior
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    Quote Originally Posted by just_john View Post
    TN - very nicely done and well thought out. Impressive weight and balance. Have you punched any paper as yet?
    Thanks and no. I haven't been able to get away to shoot it, yet.
    Got everything packed and ready to go, though. Just gotta set aside the time.

  10. #10
    Warrior
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    What a nice rifle!

  11. #11
    Bloodstained
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    Nice setup, I like it. That was the first time I heard of the piston system for an AR before too.

  12. #12
    Warrior
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    Quote Originally Posted by Crusty View Post
    What a nice rifle!
    Quote Originally Posted by earlwb View Post
    Nice setup, I like it. That was the first time I heard of the piston system for an AR before too.
    Thanks.

    SIG, LWRC and Ruger all make piston AR-15s. They're generally front heavy and often not too accurate. This Superlative Arms bolt-on kit is ultra-lite so the weight penalty is minimal and the center of gravity didn't suffer.

    Really excited about it. May not shoot it for another week or more, though. As you can imagine, the suspense is absolutely killing me.

  13. #13
    Warrior shooter545's Avatar
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    Good looking stick! We built a buddy of mine an 18" 6.5G using the Superlative Arms piston system. Shoot really nice. In for the range report.

  14. #14
    I have the same piston kit on my AR15 but Iíll think Iím sticking with DI for my Grendel build.

    How do you like the 1-8x Hi-lux, do you find the reticle useful for hold overs? Ranging seems simple with the chokes.

  15. #15
    Bloodstained
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    Just got my superlative arms carbine clamp on piston kit saving it for the 12.7 group buy kit. I have a 24" DI gun and it gets way too dirty with a suppressor on it so that's why I chose the piston kit.

  16. #16
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    Quote Originally Posted by ToeheadAR View Post
    I have the same piston kit on my AR15 but Iíll think Iím sticking with DI for my Grendel build.

    How do you like the 1-8x Hi-lux, do you find the reticle useful for hold overs? Ranging seems simple with the chokes.
    Remains to be seen how I like the piston kit on this build. Was cool on a 6.8 SPC, but loud on the left-side charger BCG.

    This CMR8 was great on the 6.8. I have the older model with a green combat-style reticle, so ranging works best if there's a human standing next to the target. Holdovers work, but ya gotta dope sheet your ammo. I had to do a refresher every trip out. Overall, I like the scope.

  17. #17
    Nice rifle, what bolt catch is that?

  18. #18
    Warrior
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    Quote Originally Posted by Andrew74 View Post
    Nice rifle, what bolt catch is that?
    Thanks.
    LAR.
    That part came on the left side or dual side-chargers because a release pad would hit a left side charging handle.
    Side chargers need no side release pad.
    It looks like it's just a standard release mechanism with the pad machined off.
    Last edited by Tex Nomex; 02-14-2018 at 02:39 AM. Reason: clarity

  19. #19
    Unwashed
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    Very sleek looking rifle! Nicely thought out build!

  20. #20
    Warrior
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    Quote Originally Posted by Tex Nomex View Post
    Not a problem with the 65?
    What sort of eye protection were you wearing? I wear normal eyeglasses to shoot. My eyes felt like a gravel pit after 20 rounds last time I was out with that upper DI.
    My carrier has no bolt exhaust holes on the left and only one on the right... Maybe better gas relief on the right would help. What's your bolt carrier look like?
    I just wear normal eyeglasses sometimes no glasses and I don't notice anything hitting me in the eyes.
    I never tried to figure out where the gas goes.

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