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Thread: Installing USGI barrel nut to specific torque/shaving any impeding teeth: problem?

  1. #21
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    I was just thinking of lapping after re-reading this thread.

    It would accomplish changing the barrel nut alignment, if alignment was a problem.

    So in this case, try the barrel nut installation as-is.

    If alignment doesn't happen within the target torque value, remove the barrel and lap the front of the reciever slightly and try again.

    The other obvious solution is to try another barrel nut if the first one doesn't line up.

    Quote Originally Posted by Surf View Post

    - I prefer lapping vs. shims if such an instance is required. It is my belief that lapping may also have a minute benefit of potentially truing the shoulder on the barrel opening of the receiver whereas a shim may have the slightest potential to have the opposite effect. Nitpicking but just my preference. I will also add that there is rarely times that this is ever necessary.
    Quote Originally Posted by ScottsBad View Post
    Hi, I'm not trying to hijack this thread, but I saw lapping mentioned as a possible solution to barrel nut alignment issues. I've been looking at a lapping tool on Brownell's because I'm not happy with the torque range I'm getting with a NSR barrel nut. Either way I turn the nut the range is either too high or too low (Noveske barrel and upper).

    Would it make sense to lap the upper slightly to adjust the torque? From what I read above this sounds like a viable option. I've never liked the idea of a shim of any kind.

    Also, do you know of a place where I can read about the proper procedure for lapping the receiver, since I've never attempted to do this before? Any help would be appreciated thank you.
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  2. #22
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    Quote Originally Posted by ScottsBad View Post
    Hi, I'm not trying to hijack this thread, but I saw lapping mentioned as a possible solution to barrel nut alignment issues. I've been looking at a lapping tool on Brownell's because I'm not happy with the torque range I'm getting with a NSR barrel nut. Either way I turn the nut the range is either too high or too low (Noveske barrel and upper).

    Would it make sense to lap the upper slightly to adjust the torque? From what I read above this sounds like a viable option. I've never liked the idea of a shim of any kind.

    Also, do you know of a place where I can read about the proper procedure for lapping the receiver, since I've never attempted to do this before? Any help would be appreciated thank you.
    That was a great post by Surf. I just assembled my new patrol upper using that exact lapping jig from Brownells. It comes with excellent written instructions...just make sure to use a thin film of grease on the main shaft of the jig that rides in the upper. I used some Aeroshell #7 with a Slip 2000 EWL floater to get it to turn freely and without chatter inside my BCM upper. Some jeweler's rouge or other lapping compound (preferably a non-embedding compound unless you really enjoy detail cleaning) goes on the portion that sits against the receiver face. Just spin slowly and with even pressure until about 80% of the anodizing on the receiver face is removed.

    I was easily able to make my torque window when installing using a GI barrel nut and I only needed 4 windage clicks on my MBUS gen-2 rear sight to get the 18" RA Mountain Series barrel zeroed and verified at range (50m/200m zero). I've never had to use so little windage on a rear sight before. The front sight only needed 2 full turns from how it came from Magpul. Very easy.
    "That thing looks about as enjoyable as a bowl of exploding dicks." - Magic_Salad0892

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  3. #23
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    I will admit to doing a grind move on the tooth of a barrel nut early in my assembly career. Only did it once and it totally bit me in the backside as the Troy Alpha rail I later tried to install actually won't work if the barrel nut isn't installed correctly (teeth aligned to allow the gas tube to pass freely). I'd suspect it is probably not a problem for certain applications, but a definite no-no for the Troy Alpha rail mounting system.

  4. #24
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    Quote Originally Posted by BufordTJustice View Post
    That was a great post by Surf. I just assembled my new patrol upper using that exact lapping jig from Brownells. It comes with excellent written instructions...just make sure to use a thin film of grease on the main shaft of the jig that rides in the upper. I used some Aeroshell #7 with a Slip 2000 EWL floater to get it to turn freely and without chatter inside my BCM upper. Some jeweler's rouge or other lapping compound (preferably a non-embedding compound unless you really enjoy detail cleaning) goes on the portion that sits against the receiver face. Just spin slowly and with even pressure until about 80% of the anodizing on the receiver face is removed.

    I was easily able to make my torque window when installing using a GI barrel nut and I only needed 4 windage clicks on my MBUS gen-2 rear sight to get the 18" RA Mountain Series barrel zeroed and verified at range (50m/200m zero). I've never had to use so little windage on a rear sight before. The front sight only needed 2 full turns from how it came from Magpul. Very easy.
    Thanks, that is very very good info. I move forward with that. I'm thinking now about how to get even pressure on the lapping tool, but I'm guessing that if the tolerances are tight enough through the receiver this shouldn't be a problem. I've got some AeroShell 33, damn slippery stuff, and I'll try that first.

    I may lap other builds if it works out well.

    Good info thanks a lot!
    Last edited by ScottsBad; 01-08-14 at 16:03.

  5. #25
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    Quote Originally Posted by ScottsBad View Post
    Thanks, that is very very good info. I move forward with that. I'm thinking now about how to get even pressure on the lapping tool, but I'm guessing that if the tolerances are tight enough through the receiver this shouldn't be a problem. I've got some AeroShell 33, damn slippery stuff, and I'll try that first.

    I may lap other builds if it works out well.

    Good info thanks a lot!
    33 will work just as well.

    The shaft of the tool provides a very tight fit in the bolt raceway. Just be smart with the hand drill. You'll be able feel when it's out of square to the receiver face. Just go slow on the RPM s. If you have a high torque setting, use that.

    Sent from my SPH-D710 using Tapatalk
    "That thing looks about as enjoyable as a bowl of exploding dicks." - Magic_Salad0892

    "The body cannot go where the mind has not already been."

  6. #26
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    Doesn't take much, either.
    Duane Liptak, Jr.
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    This is a personal account linked to a personal e-mail. Company affiliation and titles are provided purely for transparency requirements of the host site. Although factual company information may be shared through this account, any opinions expressed are solely those of the account holder, and not necessarily those of Magpul Industries or subsidiaries.

  7. #27
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    Quote Originally Posted by SPQR476 View Post
    Doesn't take much, either.
    Very true. Don't go buck wild, ScottsBad.
    "That thing looks about as enjoyable as a bowl of exploding dicks." - Magic_Salad0892

    "The body cannot go where the mind has not already been."

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