barrel nut question

Discussion in 'AR-15 Discussion' started by string1946, Feb 7, 2014.

  1. string1946

    string1946 New Member

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    As I have mentioned several times, I am in the process of building a rifle and this is my first upper build. I have everything but the barrel which should be here within the month I hope. The way I understood the correct way to install the barrel was to use anti-seize compound on the threads and to tighten the barrel nut to 30 ft/lbs and then loosen it up and retighten it and repeat that 3 times to allow the barrel to seat correctly. Then to tighten to 35 ft/lbs before going just a little bit farther to align the gas tube holes. The forearm I have is a YHM customable 12" and the instructions say to just tighten the barrel nut hand tight and them enough farther to align the gas tube holes. They don't mention any anti-seize compound or anything else and skip the tighten/loosen thing. I read on another forum that someone questioned them on that and they said it wasn't necessary unless your using a steel barrel nut and their's is aluminum. This is going to be a target rifle so I'm not planning on taking it into battle so the aluminum doesn't bother me. I plan to do it the way I planned to begin with but was just wondering. Is the anti-seize compound not necessary because the barrel nut and receiver are both aluminum and not dissimilar metals? Is the tighten/loosen thing still a good idea?
     
  2. JonM

    JonM Moderator

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    Tightening and loosening is only needed once. Its not really needed at all but it does help seat the barrel.

    Proper torque is between 30-60ft lbs. Set the wrench to 30 tighten it. Then set it to 60 and align a hole. Proper alignment may not be achievable in such cases its ok to take a dremel and remove a tooth from the nut.

    I use anti sieze on all barrel installs regardless of metals. A small tube is like a couple bucks. I take a qtip get some compound and wipe in a line across the threads of the nut. If you over do it, it makes a godsawful mess.

    When you are instlling a barrel do not use a upper reciever vice block use a barrel vice block made from hard wood. Upper reciever blocks will damage the upper when your torquing in foot pounds.
     

  3. SSGN_Doc

    SSGN_Doc Well-Known Member

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    I have that same handguard on one of my rifles. I stil used the anti-seize greese, and still torqued it and released, and retorqued, three times before seating. I think my final torque ended up being about 45 Ft/lbs to get the holes to line up. Haven't had any problems, and been shooting the rifle for over five years now with that handguard.
     
  4. string1946

    string1946 New Member

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    Thanks for the advice. I have anti seize at my bench and planned to use anyway and the tighten/loosen thing couldn't hurt so why not. I will have to check on the wooden barrel vice block. I have a upper receiver block but not one of those. I would guess it would have match the contour of the barrel.

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  5. SSGN_Doc

    SSGN_Doc Well-Known Member

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    It doesn't have to match contour exactly. I have an aluminum barrel vice block. I use a couple thicknesses of bicycle innertube that have been glued together on either side and lay them in the barrel channels before tightening the vice.
     
  6. string1946

    string1946 New Member

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    I have been reading a little about them and how make one. Pretty much two hardwood blocks drilled either 1/16 to 1/32 less than barrel OD. My drill press should make that pretty easy. Also some use friction tape and some rosin to help with the grip. Guess I need to find a video of one being used.

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  7. JonM

    JonM Moderator

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    i would go half the diameter of the barrel. rosin really helps. i degrease the section to be clamped.
     
  8. string1946

    string1946 New Member

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    Makes sense to me. The barrel is .936 at the gas block. Sounds like 1/2" would be about right. Also what I read said to squeeze the crap out of it. You won't hurt the barrel as the wood gives way before you hurt the barrel. Just squeeze till you hear wood cracking. Sounds a little excessive to me.

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  9. JonM

    JonM Moderator

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    That's correct. You can't hurt it with wood blocks. They will come apart long before anything happens to the barrel.

    When I was getting the wife's savage apart the first time I had it cranked with enough force to withstand 150+ftlbs of torque. Savage waaaaaaaay over tightened that nut. When I got the gun torqued correctly it went from 5moa to .25moa. I eventually had to cut the nut off.

    Oak is a great wood for blocks. If the barrel is inline with the grain its probably going to split the wood.
     
  10. Ibmikey

    Ibmikey Active Member

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    Jon, You have me a bit perplexed, block the barrel and torque the nut against an unsupported upper receiver? It would seem to me the steel nut upon contacting the aluminum receiver would transfer the torque and the index pin would be the only thing to keep the receiver from turning. I hope I am not confusing everyone, using a clam shell vise supports the receiver, the barrel does not need support, torque is then applied to a solid point. I have installed/removed 100 + barrels with a receiver vise without incident but never contemplated leaving the receiver just hanging. Get my brain back on track expanding your method as I am always looking for "a better mousetrap".
     
  11. purehavoc

    purehavoc New Member

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    I use boelube instead of antisieze, its made by Boeing . It is a dry lube that I mainly use at my drill press . Its all personal choice so long as it keeps the aluminum from seizing it will work
     
  12. string1946

    string1946 New Member

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    I figured the blocks would need to be drilled across the grain. Thanks.



    I also would be interested in your response. I was wondering the same thing. As this is my first go at this I was going to wait till had everything on hand so I could see it then maybe ask that question.



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  13. JonM

    JonM Moderator

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    the index pin is going to see torque. thats not an issue. the issue is crushing the reciever side walls or bending them, depending on the upper block used, which are not durable for lateral stresses. thats why you want to use barrel blocks for barrel and muzzle device installs. crunching an upper is no bueno.



    with properly made parts its a non issue. some uppers are kinda sloppy where the index notch is. thats why a quality upper is more important than the lower.
     
    Last edited: Feb 8, 2014
  14. Ibmikey

    Ibmikey Active Member

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    I have never heard of an upper being crushed with the use of a good receiver block, mine supports the entire receiver and is locked it's full length with the vise. Sometimes there is considerable torque on the nut, transmitted to the receiver. The index pin would be difficult, but not unheard of, to break however your method may rip the notch in the receiver. Since I have not used or even know of others who use your method I can only speculate on results. I was trained by the M-16 rebuild unit at an air base at a time when one of my police duties was running the firearms training and repair for a good sized PD. I built a pile of M-16's before the unit gave me their okey-dokey.
    But "works for me" has been one of my life's mottos, so if "it works for you" go for it.
     
  15. JonM

    JonM Moderator

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    All I can do is relay info on how I was taught by depot level armorers in the us army early 90's.

    Correct procedure is detailed in TM9-1005-249-23P free online copy https://archive.org/details/ArmyTechnicalManualforM16Rifle-Tm9-1005-249-23p

    If you have an ar15 HIGHLY recommend getting a copy in printed format for the workbench. Been working on these things for over two decades and I still refer to that manual.

    Read it judge for yourself do what ya will.
     
    Last edited: Feb 8, 2014
  16. Ibmikey

    Ibmikey Active Member

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    Jon, Thanks for the reference, I learned on M1 Thompson's and Garand's so you can date me accordingly but always willing to learn better ways if available. This exchange is why I like this forum as a different opinion is not desired on some others. :)
     
  17. JonM

    JonM Moderator

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    The procedure for those is to clamp the reciever and twist the reciever onto the barrel. The ar15 is the only rifle I know of that no clamping force is used on the reciever to mount a barrel.
     
  18. string1946

    string1946 New Member

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    I would like to thank both of you adding to this thread and contributing to my on going education. That one of the reasons I'm here.


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    Last edited: Feb 9, 2014
  19. BRL

    BRL Member

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    I've done a few barrel/free float tube installs through the years and I like to use anti-seize compound on the receiver/barrel nut threads and not blue Loctite because aluminum tends to gall when torqued and I would like to have the option of being able to remove the assembly at some point in the future without snapping something off. :eek:

    Haven't had a barrel fall off yet either! :D

    [​IMG]
     
  20. string1946

    string1946 New Member

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    Thanks for the advice. I plan to use anti-seize on the barrel nut to receiver threads, a little grease on the forearm to barrel nut threads and jam nut. Blue Loctite on the forearm end cap and gas block set screws. I know heat degrades Loctite but this rifle is for punching holes in paper so I don't anticipate doing a full magazine dump.

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