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  1. #11
    Newbie

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    I never had the problem of aligning the nut to gas tube. I did use the Brownells lapping tool on a couple of builds and was surprised that the face of the upper receiver where the barrel seats is not very flat. You basically apply a little valve grinding compound to the receiver face and then spin the lapping tool and check. Grind until you get a uniform silver color and you are done.

  2. #12
    Newbie

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    Hi all. Not bragging here but I've spent the last five years building AR15s, using every single brand of handguard on the market. From Cheap to Ultimate AR high dollar stuff. Shims were rarely needed, but when they were usually 4-5 max did the job. I agree that lapping is a good idea, but it was rarely done/needed in a production environment. And here is some food for thought.....if you can get at least a good 35-40 ft.lbs on the nut, with the gas tube going through the barrel nut, you're good to go. Here's why. The gas tube essentially acts as a locking key for the nut. It won't allow the barrel nut to unscrew and loosen up. Have done tons of uppers that fell into this circumstance, and to my knowledge, all of them are still out there slinging lead with aplomb.
    In times of universal deceit, telling the truth becomes an act of rebellion. (George Orwell)

  3. #13
    ESSAYONS

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    Quote Originally Posted by redbaron8 View Post
    Hi all. Not bragging here but I've spent the last five years building AR15s, using every single brand of handguard on the market. From Cheap to Ultimate AR high dollar stuff. Shims were rarely needed, but when they were usually 4-5 max did the job. I agree that lapping is a good idea, but it was rarely done/needed in a production environment. And here is some food for thought.....if you can get at least a good 35-40 ft.lbs on the nut, with the gas tube going through the barrel nut, you're good to go. Here's why. The gas tube essentially acts as a locking key for the nut. It won't allow the barrel nut to unscrew and loosen up. Have done tons of uppers that fell into this circumstance, and to my knowledge, all of them are still out there slinging lead with aplomb.
    With the barrel nut the OP is referring to, that is the challenge. A lot of barrel nuts have 20 or so places for the gas tube to fit. That means the most you should have to tighten it once you hit the minimum 30 ft-lbs of torque is 18 degrees. If you start lining it up at 30 ft-lbs, you're almost assured to have it indexed before you hit the 80 ft-lb upper torque limit. (I realize these values are not agreed upon by everyone but they are a widely accepted guideline.)

    The Aero Precision BAR barrel nut, on the other hand, has 4 indexing points. More torque won't get you from right past one to the next one. Shims or lapping will almost always be necessary. The instructions even have a math test to help you figure out what shims may work.



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    Last edited by thperez1972; June 5th, 2019 at 11:50 AM.

  4. #14
    Marksman

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    I had a stretch 16" barrel that shot like shit. Changed mounts for scope ect. Ended up calling Stretch and they said lap upper. Fixed all my issues. So now I lap everything to be safe

    Sent from my SM-G965U using Tapatalk

  5. #15
    Newbie

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    I lapp every reciver I use. No matter how much they cost. Not only does it help with getting things torqued. But it makes everything nice and square when the bolt is locking and unlocking.

    I only run grendel rifles and doing this above I have never broke a bolt or extractor.

    A simple trick to trimming a barrel nut. Don't use a barrel nut that the gas tube has too go through. Much more simpler and no chance the tube will touch the barrel nut and cause binding issues with the bcg and wreck your accuracy.

    I also follow the balanced torque theory. You can Google that and read up on it. I have seen a real improvement in my consistent group tightness since useing this practice.

  6. #16
    All or nothing

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    I’ve had to drill alternate gas tube pathways thru barrel nuts at times. Mostly on the off brand or chinese rail kits. Even had to enlarge a few holes on some of the aluminum multi hole nuts because the gas tube wouldn’t pass thru. Without the press and vise I have I prolly wouldn’t attempt it tho. I have used shims but I’d rather drill where it will work.
    I’m the guy people bring their screw ups to apparently. I’ve not once let someone walk away without the fix, but it’s a chore sometimes. I beg people to do some research and look for rails that use hardware that works, like steel low profile barrel nuts that the gas tube doesn’t pass thru or that use a mil spec nut. Hopefully the demand will create a standard! Stranger things have happened.
    So, research and spend wisely. It may save you a lot of time and dollars down the road. Personally I’d rather spend the extra time and money on shit that works than buying twice or spending a day trying to make shit work.
    Contrary to popular belief, a head shot is not necessarily a guaranteed kill shot....but it sure does take the fight out of 'em.

    and if one in every 100,000,000 M&M's contained enough cyanide to kill a person, the Mars candy company would be forced by public outcry to correct it———
    Bangswitch

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