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Thread: barrle Nut loctite

  1. #21
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    If this is your first assembly (or your XXXth), it may be wise to have an extra barrel-nut assembly handy. Perhaps even from a different vendor. This way if it just does not line up, or something goes "wrong", you can start clean.
    Have 2 of everything plus a back-up has often made my day go by with a smile instead of a frown.....
    Per Ardua ad Astra.
    STS - gone but not forgotten.

  2. #22
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    The "pre-torqueing" of the barrel nut is to help mate the threads to each other to get more contact area and a more secure final assembly. It should be done with the moly grease and a torque wrench to 30 foot pounds. The grease is necessary to get acccurate torque readings and to prevent galling.

    When the final tightening is done then you can go higher up to 80 foot pounds to get the notch aligned.

    Galling involves the cold welding of one material to another where particles of one material are actually torn from and adher to the other material when they rub together under load.

    Galvanic corrosion occurs when there is transfer or conversion of a material when it is in contact with another material with a different electrical potential.

  3. #23
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    Quote Originally Posted by Iraqgunz View Post
    I'm sure that sounds good in theory, but I have been using for close to 4 years and it has yet to cause an issue. I have used it on my personal weapons as well. YMMV
    With respect, I would like to point out Boeing Tech Manuals prohibits the use of copper based anti-seize on aluminum threads on their aircraft as galvanic action may occur. I share this only to clarify why I posted the warning. I do not dispute your experience. I have installed exactly 1 AR barrel. If you haven't had a problem yet, I don't think you will
    INSIDE PLAN OF BOX
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    2. MATCH SCRATCHES ON MATCH-BOX
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  4. #24
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    Quote Originally Posted by MistWolf View Post
    Boeing Tech Manuals
    More here

    I wonder if this a factor in the selector detent wear some have seen?

  5. #25
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    Quote Originally Posted by MistWolf View Post
    With respect, I would like to point out Boeing Tech Manuals prohibits the use of copper based anti-seize on aluminum threads on their aircraft as galvanic action may occur. I share this only to clarify why I posted the warning. I do not dispute your experience. I have installed exactly 1 AR barrel. If you haven't had a problem yet, I don't think you will
    Copper, graphite and even moly can cause galvanic corrosion. Fortunately, we're dealing with an anodized aluminum receiver and nice smooth high carbon or even stainless steel, sandwiched together with a generous schmear of grease.

    See: "Effect of molybdenum disulfide on electrochemical corrosion of metals": http://www.springerlink.com/content/n17r4hvq646j0g43/

    I generally march to NASA-TM-584, which does not forbid copper but does warn against graphite. Note that TM-584 references MIL-STD-889, specifically for dissimilar metals.

    If you think aluminum-steel interfaces are bad, you ain't seen nothing. Be glad few gun parts are made from titanium.
    Oh no, not another lube thread! Read this first: Lubrication 101.

  6. #26
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    Quote Originally Posted by rickp View Post
    Thanks guys.

    Where can I get the grease?

    Rick,
    I have a small jar of it. A little goes a LOOng way. I will gladly share with you.
    Colt AR-15/M-16 Armorer, GLock Armorer, HK USP Armorer
    Firearms Instructor

  7. #27
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    Quote Originally Posted by Iraqgunz View Post
    I'm sure that sounds good in theory, but I have been using for close to 4 years and it has yet to cause an issue. I have used it on my personal weapons as well. YMMV
    Same. I use Loctite C5 copper anti-seize, same stuff Glock was using on newly assembled guns (recently the color of the anti-seize in new Glocks has changed, dunno if Loctite changed or Glock switched to something else).

  8. #28
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    Quote Originally Posted by bananaman View Post
    Thanks for the apparently time-traveling responses that actually appear to precede my first post (weird).

    Now that the no loctite answer is unanimous, a related question:

    What is the deal with 2 or 3 "pre torques" for the barrel nut? I've read others recommend it too but just never heard of it being done on any other machines (aircraft, auto engines, etc). I'm not a mechanic by trade or training, just an interested amateur wanting to build the best rifle I can.
    It is very common in automotive engines. Intake manifolds, cylinder heads and such. You do that to keep even pressure all around when multiple fasteners are present.

    Sent from my MB860

  9. #29
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    Quote Originally Posted by bananaman View Post
    Now that the no loctite answer is unanimous...
    Actually; let me add just a tidbit of information here. There are two schools to what compound to use on the threads: anti-seize or loctite. Anti-seize would be the Mil Spec way to go; and also the way to go for anyone who will put a lot of bullets through the barrel and who will (most likely) end up replacing the barrel once or twice before the lower passes on to greener pastures.

    On the other hand we have the bench rest shooters et al who are more worried about accuracy; these guys will loctite their barrels for that one gnat's hair of added accuracy. They don't care if the barrel is stuck for life; because they will never fire enough bullets through it to lose accuracy (or, if they do; they are willing to risk the upper).

    What is the deal with 2 or 3 "pre torques" for the barrel nut?
    Glen D. Zediker mentions that in his book "The Competitive AR-15 Builder's Guide"; it is to even out any imperfections in the receiver threads and/or barrel nut. You do not go full torque on the "pre-torques" though; only on the last one. The pre-torques would only be tight enough that you are not leaning into it to tighten it further; only "hand tight".

    Hope that helps share some light.

  10. #30
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    Quote Originally Posted by kartoffel View Post
    Copper, graphite and even moly can cause galvanic corrosion. Fortunately, we're dealing with an anodized aluminum receiver and nice smooth high carbon or even stainless steel, sandwiched together with a generous schmear of grease.

    See: "Effect of molybdenum disulfide on electrochemical corrosion of metals": http://www.springerlink.com/content/n17r4hvq646j0g43/

    I generally march to NASA-TM-584, which does not forbid copper but does warn against graphite. Note that TM-584 references MIL-STD-889, specifically for dissimilar metals.

    If you think aluminum-steel interfaces are bad, you ain't seen nothing. Be glad few gun parts are made from titanium.
    Ask SpaceX about Galvanic Corrosion at Kwaj and the 1st Falcon flight.
    My brother saw Deliverance and bought a Bow. I saw Deliverance and bought an AR-15.

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