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Thread: barrel bedding

  1. #11
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    This earlier thread covers the issue, a quick read, especially if you skip through the usual bickering about whose pee pee of knowledge is bigger:

    https://www.m4carbine.net/showthread...rease-accuracy

    tl:dr version:

    pinzgauer: Bill Alexander has indicated in the past that while it is not *needed*, he has seen some benefit in using locktite on the barrel extension for grendels. It reduces some of the harmonics that can cause vertical stringing without having to over torque the barrel nut like some bench shooters do.

    He was very clear that in any single rifle you may not see a benefit. Remember, grendels are normally sub-moa even with carbine rack grade barrels and half MOA is not uncommon with some care and decent ammo. So the grendel crowd is more accuracy oriented. Bill recommends Loctite 243, and it handles the heat in the receiver sections with no problem, yet can still be removed if needed.

    For a typical hard use 5.56 carbine I personally do not believe you would see a benefit.


    rob jensen:
    When assembling an AR for absolute accuracy (stainless barreled varmint, Hipower, 3gun) uppers I use Loctite between the bbl extension and receiver, between the gas block and bbl and on the threads of the muzzle device and use as little torque on the muzzle device as I can.

    bp7178: I actually listed that answer in my first post in this thread, which was Loctite 609, and is a sleeve retainer compound.

    Never had an issue removing a barrel if 609 was applied. You won't be pulling it out by hand though. Warm it with a heat gun and tap it out with a dowel.

    pinzgauer: 243 is medium strength, can be unbolted even on very large bolts with hand tools. Hit it with localized heat (on the barrel you wore out) and it "unlocks". (actually, drops to about 20% of it's strength or less) Note: this is way more heat than you'd see in at the receiver in normal firing, even full auto.

    As to who uses it, and the "trains of thought".... It would be a very broad generalization to believe that anyone who wants an M4C "tier 1 spec" carbines is therefore not concerned with accuracy. I want both if it does not compromise function or reliability.

    I build my grendel carbines using DD, LMT & Colt components with the exception of the Barrel & Bolt, which I source from AA. (And Bill has mentioned they will be releasing a CHF barrel as well).

    Grendels carbines can be very accurate, so it's worth using 243. I shoot SS "Gov profile" (M4 without 203 cuts) and have found them to be very accurate with several ammo combinations. The grendel (and I suspect 6.8) also puts stress on the AR-15 platform that 5.56 will never see. (Bolt thrust & barrel vibration)

    Bill will also tell you that mil-spec receivers & barrel extensions can be sloppy by design due to tolerance stack, so they carefully manage extension to receiver fit to help with accuracy.

    Not something the average 5.56 carbine user shooting cheap M-193 would ever see as an issue, but with inherent Grendel accuracy even with basic Hornady ammo it's worth making the effort.

    I also see a trade off.... I'd probably worry less about the armorer changing barrels than a loose barrel nut stressing the gas tube and causing odd accuracy situation due to different barrel vibration/harmonics. Neither issue are common occurrences, but any armorer can change a 243'd barrel. Harder to deal with loose barrel nut issues away from the bench & tools. So for me it makes sense to err on the conservative side.

    To be clear, I'm not advocating that M4C 5.56 shooters "glue", use random loctite, or even use 243.... just relaying what one very savy Mfg has shared which also aligns with other accuracy oriented mfg's & smiths indicate.

  2. #12
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    Great post 26.

    Appreciate the insight. Good to have a broader perspective on the issue.

    Still, as you mentioned, not worth the worry with it on a 5.56.

  3. #13
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    thanks for finding that. I had issue finding any info on tightening up the receiver to barrel fit.

    Darrin

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