Is it difficult to build an AR Upper?

Discussion in 'Rifle Country' started by mf-dif, Oct 17, 2015.

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  1. mf-dif

    mf-dif Member

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    I've finished building my first lower and now moving to the next step of tackling my upper. I prefer building since I find the process fun. In my reading a lot of emphasis being put on torquing the barrel. I'm familiar with using a torque wrench when working on my cars/motorcycles but these guys are making it seem like it's a medical procedure down to the pound or the gun will not work reliably? The gap seems pretty large to allow for a lot of margin error and still be in spec. I've read such quotes as "even experienced gunsmiths can have trouble torquing things right".

    I'm kind of confused about this subject as it technically sounds extremely simple, but the feedback is it is not?
     
  2. Walkalong

    Walkalong Moderator Staff Member

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    I found it to be pretty easy, but I have been doing mechanical stuff all my life.

    Anyone with minimal mechanical skills and common sense could do it.
     
  3. jerkface11

    jerkface11 Member

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    If they have trouble torquing things right they probably aren't an experienced gunsmith. That said the upper isn't that hard to put together. You'll need either a receiver clamp or a barrel vice to do it.
     
  4. briansmithwins

    briansmithwins Member

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    Slightly more difficult than assembling Legos.

    Use the gas tube inserted through the rear of the receiver as a gauge for aligning the barren nut. The gas tube needs to pass though a notch in the nut without binding and the tube needs to be straight. But that's the trickiest part.

    BSW
     
  5. Hookeye

    Hookeye Member

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    There is a torque range for your barrel nut.
    Some guns go together on the lighter side, some the heavier.
    If you are cranking one on the heavy side it's kinda common to end up with a canted front sight base.
    You'll have to knock that back over.
    Good bbl wrench, block for receiver.........and a vice on a sturdy bench.
     
  6. Jackal

    Jackal Member

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    ??? The receiver/barrel index on the barrel extension pin, you cannot cant the front sight by tightening the barrel nut.
     
  7. Zerodefect

    Zerodefect Member

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    Easier than cooking a proper Lasagna.

    Get the Magpul BEV block, the old style upper vise blocks are fine as well.
    Get an Aluminum barrel vise block, for flash hiders.
    Get a barrel nut wrench.

    Get an extra low pro gas block and drill the gas port all the way out from under, to turn it into a tool to line up a drill press for barrel dimpling.

    The rest is cake, er, Lasagna.
     
  8. yugorpk

    yugorpk member

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    Get yourself an upper vise rod that uses the barrels steel star chamber locking lugs to hold the barrel instead of the uppers soft aluminum and you wont have to worry about twisting the receiver locator pin slot or over torquing ( within reason)
     
  9. mf-dif

    mf-dif Member

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    Thanks guys. I dunno why I was thinking it was a big deal. Cant wait to get it going.
     
  10. briansmithwins

    briansmithwins Member

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    The Magpul block that's mentioned uses a steel insert that fits into the barrel extension. It's (and the wrench tool they make) are dead easy to use.

    BSW
     
  11. Onmilo

    Onmilo Member

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    Build enough of them and you won't even bother with the torque wrench any more.
    60 foot pounds is pretty easy to achieve with minimal force if you have quality tools.
     
  12. rcmodel

    rcmodel Member in memoriam

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    +1

    You can torque to the nearest ft\lb.

    But if one of the notches on the barrel nut doesn't line up for the gas tube to go through hole in the upper and hit the gas key dead center?

    You are going to have to loosen or tighten it anyway.

    Alignment with the gas tube hole is more important then what a torque wrench tells you it should be.

    rc
     
  13. rskent

    rskent Member

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    Sure you can. If you make sure the gas tube is centered in the hole in the barrel nut and the receiver (as in lined up well ) it should be OK.
    At that time its also a good idea to check on how the gas tube slides into the bolt carrier. If everything doesn’t line up well, it could rub on
    the side of the hole in the gas key. Can't have that now, can we?

    No doubt.
     
  14. Ibmikey

    Ibmikey Member

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    The Magpul block is a nifty tool just use a carrier (no bolt) with it to lock everything up, best to also have a clam vise for some applications. A good barrel wrench, torque wrench and piece iof gas tube for lining uo the nut to receiver gas tube hole and you are pretty much GTG. Don't rush the build, use anti sieze on barrel nut threads, don't over torque and work where you can chase the pins , springs and detents that occcasionally get launched through out the room. I built a local deputy a 300 BO pistol upper yesterday and test fired it all within about thirty minutes using a stripped receiver.
     
  15. Tirod

    Tirod Member

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    I've assembled AR uppers in vices with jaw blocks to protect the aluminum and a pair of large adjustable pliers.

    The "torque" spec issue is overblown - it only needs about 30 foot pounds, which isn't much. The point of the 85 foot pound spec is that going over increases the risk of STRIPPING THE THREADS on the upper, It's a number to AVOID, not achieve. And due to the various locations of the nut teeth, all you are really trying to do is get it over 30 pounds and lined up to pass the gas tube. That is all.

    Despite all the noise on the AR assembly channel, you do NOT torque it TO 85 pounds. It's a range of at least 30 to a maximum of 85 - for your protection (and ours as taxpayers to keep some kids in the Army from twisting off the nose.) Just get the teeth lined up so the gas tube goes thru and done.

    It definitely isn't rocket science - not even techy car level. Fancy tools and expensive grease and all sorts of warnings aren't really needed except one - don't strip the threads.

    And when you tighten or take off a muzzle brake, you have to clamp the barrel itself, NOT THE UPPER, or you could definitely twist the barrel pin right out of the nose or even screw off the barrel extension. Both are unrecoverable - major fails. Always clamp the barrel when doing muzzle device work.
     
  16. WNTFW

    WNTFW Member

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    The only thing I don't see addressed is anti-seize or whatever you decide to use on the threads. Research that and again you will find arguments.

    I am in the group that say in needs to be tight enough and align. No need to get any tighter after that. If you want to look over the fit of barrel to receiver that makes sense. After a certain point I think locking down the front sight post offers a bigger gain to accuracy.
     
  17. Shawn Dodson

    Shawn Dodson Member

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    Buy yourself a package of barrel nut shims (about $5 for three plus shipping) so you can complete your build if your barrel nut doesn't line up. Bison Armory has a video on YouTube that's helpful if you have to use a shim.

    The torque spec exists for a reason. Same with the anti-seize - use it as the torque value is based on "lubricated" threads, not dry threads.

    After performing the 3x torque procedure at minimum torque value, and the barrel nut doesn't align, I inspect the barrel nut alignment to determine if I need to apply greater torque or if I need to shim. In my experience a shim (or two) is required if the notch is just past the gas tube hole on the upper. When this happens applying max torque will not turn the barrel nut enough to align with the next notch.

    If the barrel nut looks like I need to turn it just a little more to get the notch to align then set the torque wrench to the max torque value and tighten the barrel nut until it either aligns or I reach max torque. If I reach max torque and the barrel nut doesn't align then I install a shim or two.

    Be sure to install your combination wrench on the torque wrench at a right angle otherwise you'll apply more torque to the barrel nut than indicated on the torque wrench.

    Good luck with your build! :)
     
  18. mavracer

    mavracer Member

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    Yes that will be extremely difficult they're like tater chips you won't stop with one lol
     
  19. barnbwt

    barnbwt member

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    "I dunno why I was thinking it was a big deal."
    That's because a lot of people are idiots and also on youtube/etc. Lot of really bad instruction out for...just about anything :p

    So, there're actually people shooting for 85ft-lbs on aluminum threads? Wow. We really need to bring back shop class, so these poor folks can get a clue early on in life. 85ft-lbs is like lug-nut levels of torque (and they ain't aluminum ;)). I sure these same folks are also twisting guns in the process, having 'secured' the upper by clamping the lower in a bench vise :uhoh:. Some people just can't/shouldn't use tools.

    TCB
     
  20. SlimeDog

    SlimeDog Member

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  21. Shawn Dodson

    Shawn Dodson Member

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    The upper torque limit is 80 ft/lbs, as specified in the Caution on page 0015-17 of the tech manual.
     
  22. Onmilo

    Onmilo Member

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    80 foot pounds is Maximum and at that you will be crunch fitting the barrel nut into the front receiver wall.
    The 60 foot pounds I referenced is more than enough to hold everything together when using anti seize grease on the threads.
    40 foot pounds will hold everything together if you didn't use grease which you should to prevent galling the receiver threads.
     
  23. henschman

    henschman Member

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    Meh. I've put a couple barrel nuts on that wouldn't align within the specified torque values. I went over 80 ft./lbs. to get them to line up and haven't had any issues with those rifles.
     
  24. gotigers

    gotigers Member

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    Easy. Novice understanding of torque, vise blocks, barrel blocks for the flash hider and correct grease on the barrel nut threads and you are good to go.

    Edit: It is good to have a spare barrel nut. Rarely, one will not clock properly. Always buy American AR parts. The chinese junk at gun shows can ruin your day.
     
  25. Onmilo

    Onmilo Member

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    I haven't had the chance to handle or play with one of the Chinese or Iranian made M16 clones but I'm willing, sight unseen, to bet cash money that neither weapon had a barrel nut that is torqued anywhere near approaching 80 foot pounds...
     
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