AR Barrel Nut Torque - Nut won't line up...

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  • BenL

    John Galt Speaking.
    I'm installing a barrel and have tried two different barrel nuts. The gas tube doesn't line up at 30 ft/lbs and even at 80 ft/lbs, it still doesn't quite line up. Can I go up to 90 ft/lbs, or do I have to use shims?
     

    clandestine

    AR-15 Savant
    Oct 13, 2008
    37,031
    Elkton, MD
    Beyond shearing the Barrel Nut or Upper Receiver Threads, its possible to twist the Upper which will result in not being able to get on paper or getting the Upper on a Lower. It usually take much more than 80ft/lbs to do that damage though. over 100 will usually be the starting point.

    It either causes the barrel timing pin to widen the notch in the Upper which will cause the Barrel to not index properly or cause misfeeds due to the ramps, or depending on how the upper is secured it can twist the rail on the Upper.

    I have seen many twisted AR uppers
     

    Atlasarmory

    Ultimate Member
    MDS Supporter
    Mar 2, 2009
    3,359
    Glen Burnie
    Would doing the math on the tpi on the receiver and removing the appropriate amount off the receiver threads be able to correct this or would that mess with the head space. Or are shims a better option ?
     

    iH8DemLibz

    When All Else Fails.
    Apr 1, 2013
    25,396
    Libtardistan
    Try torqueing and releasing and torqueing and releasing.

    I've been able to gain that little extra bit of rotation by doing this 5 or 6 or more times.

    If you haven't done so, lube the hell out of every load bearing point each time prior to retorqueing.

    JMOOO
     

    clandestine

    AR-15 Savant
    Oct 13, 2008
    37,031
    Elkton, MD
    Try torqueing and releasing and torqueing and releasing.

    I've been able to gain that little extra bit of rotation by doing this 5 or 6 or more times.

    If you haven't done so, lube the hell out of every load bearing point each time prior to retorqueing.

    JMOOO

    This is what I do. Pretty solid method.
     

    Sticky

    Beware of Dog
    MDS Supporter
    Mar 16, 2013
    4,501
    AA Co
    What kind of barrel nut? Can you just take a lug off the nut with a dremel to allow clearance for the gas tube? I did this on a pistol build, works fine.. ;)
     

    EMS Burnout

    Member
    Oct 10, 2012
    95
    Baltimore County
    Beyond shearing the Barrel Nut or Upper Receiver Threads, its possible to twist the Upper which will result in not being able to get on paper or getting the Upper on a Lower. It usually take much more than 80ft/lbs to do that damage though. over 100 will usually be the starting point.

    It either causes the barrel timing pin to widen the notch in the Upper which will cause the Barrel to not index properly or cause misfeeds due to the ramps, or depending on how the upper is secured it can twist the rail on the Upper.

    I have seen many twisted AR uppers

    Thank you for the information. I had this problem in the past and just decided to us a different rail. But always wondered.
     

    BenL

    John Galt Speaking.
    What barrel nut? Factory?

    It's a factory Colt barrel nut. I'm using a 5 pin wrench and a Craftsman torque wrench and double-checking with a Wheeler torque wrench. The upper is being held with Spike's Block Worx; it works better then the Wheeler block. I'm using Mobil 1 Synthetic Grease on the threads.

    I also tried the Stag barrel nut that was on it, which lined up the exact same way (but the metal seems softer; the holes changed shape slightly at ~75 ft/lbs; the looked more like waves than "U"s.)

    What do you think of shims?
    Would I be better off having the face of the upper shaved 1/1000"?
    Should I try sanding the finish off of the face of the receiver with a fine grit paper?
    Will this effect barrel extension enough to really matter?
    What do you think my best approach is?
     

    BenL

    John Galt Speaking.
    Try torqueing and releasing and torqueing and releasing.

    I've been able to gain that little extra bit of rotation by doing this 5 or 6 or more times.

    If you haven't done so, lube the hell out of every load bearing point each time prior to retorqueing.

    JMOOO

    Tried that; gained a little rotation, but not enough for proper timing. At 80 ft/lbs, it's *almost* there. 90 would probably do it, but that's outside spec.
     

    BenL

    John Galt Speaking.
    What nut/rail system??

    Colt barrel nut with a Fortis forerail. This is a home defense rifle that I use for classes, occasionally.

    My Stag factory M-4 profile barrel was shot out, so I'm replacing it with a Noveske 16" Recon barrel. This also required replacing the rail (the old rail was a 7" carbine rail.) My stag was never very accurate (It was my very first AR; has ~18K rounds through it. It was never better than a 2-3 MoA gun, no matter what the ammo). Turns out, the factory-installed barrel nut was only finger-tight. :sad20:
     

    BenL

    John Galt Speaking.
    What kind of barrel nut? Can you just take a lug off the nut with a dremel to allow clearance for the gas tube? I did this on a pistol build, works fine.. ;)

    The Fortis REV rail relies on the 3 and 9 o'clock lugs to maintain it's timing. If they're not lined up properly, the forerail will be off timing. If I were using a Noveske forerail, I could get away with that because its proprietary nut's timing doesn't effect the gas tube alignment. Plus, I'd rather it be done properly. It would bug me, otherwise.
     

    Sticky

    Beware of Dog
    MDS Supporter
    Mar 16, 2013
    4,501
    AA Co
    The Fortis REV rail relies on the 3 and 9 o'clock lugs to maintain it's timing. If they're not lined up properly, the forerail will be off timing. If I were using a Noveske forerail, I could get away with that because its proprietary nut's timing doesn't effect the gas tube alignment. Plus, I'd rather it be done properly. It would bug me, otherwise.
    Okay, understand... when the nut is properly indexed for the rail is there a tooth on the standard barrel nut that interferes with the gas tube?
     

    clandestine

    AR-15 Savant
    Oct 13, 2008
    37,031
    Elkton, MD
    I have the same issues with MI barrel nuts. If the teeth are warped you shod replace the nut.

    I often lap the upper receiver face and this helps sometimes.

    I say order a new nut and some Barrel shims. Try the torque and loosen technique and only use the shims if necessary.
     

    aquaman

    Ultimate Member
    Sep 21, 2008
    7,499
    Belcamp, MD
    I have the same issues with MI barrel nuts. If the teeth are warped you shod replace the nut.

    I often lap the upper receiver face and this helps sometimes.

    I say order a new nut and some Barrel shims. Try the torque and loosen technique and only use the shims if necessary.

    sounds like a '2nd rate' solution:innocent0:D
     

    BenL

    John Galt Speaking.
    I have the same issues with MI barrel nuts. If the teeth are warped you shod replace the nut.

    I often lap the upper receiver face and this helps sometimes.

    I say order a new nut and some Barrel shims. Try the torque and loosen technique and only use the shims if necessary.

    Thanks, Chad. Will do. :thumbsup:
    (The Colt barrel nut is the replacement for the warped Stag nut.)
     

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