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Thread: Loose Barrel Extension Help

  1. #41
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    I got in some barrels made and I had one of the extensions unscrew. I asked the maker how that could happen - as the drawing I provided said 150 ft-lbs of torque. He said "Oh, I never use that much torque - makes the gun less accurate."

    So he decided on his own to disregard my drawing and make it "his way."

    That is one problem with the concept of gunsmiths - they know so much they tend to do things their way rather than to follow the drawing. For this reason I now work with general machinists and provide fully defined drawings.

    So for example, I would be horrified to send a gun to a gunsmith and say "Please thread this barrel 1/2-28." This is because, rather than follow a drawing, they will ask for the mating device and just make them fit, but then the threads may be oversized and won't be interchangeable with all standard parts later.

    Instead, I would do a complete drawing, and have a machinist thread it - and they will use a thread micrometer or thread wires to verify that it matches the drawing.

    As far as a barrel vise vs a receiver fixture - today I removed a flash suppressor from a 9 inch barrel with an 8 inch rail. I had to use a receiver fixture. It should not be a problem, as muzzle devices are typically 30 ft-lbs of torque, and the barrel extension should need 5x that in order to unscrew. The pin, if made properly and actually tempered, should not shear.

  2. #42
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    The pin doesn't go into the threads. It goes into the extension. It's an indexing pin for the upper receiver, not a locking pin for the barrel.

  3. #43
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    So who was the original manufacturer?

    Did they send you an all new barrel assembly?

    If not, why would you shoot it, or worse yet let your girlfriend shoot it?
    Quote Originally Posted by scottryan View Post
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    They are illigetimate weapons that have no real purpose other than to attract retards to the gun community.

  4. #44
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    Quote Originally Posted by polymorpheous View Post
    So who was the original manufacturer?

    Did they send you an all new barrel assembly?

    If not, why would you shoot it, or worse yet let your girlfriend shoot it?
    ...ummmm, because it was re-torqued to the proper specification? ...

  5. #45
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    Quote Originally Posted by wrench View Post
    ...ummmm, because it was re-torqued to the proper specification? ...
    You obviously don't understand what is going on here.
    .
    Typically when a manufacturer assembles an AR15 barrel they torque on the receiver extension to spec, and then drill the gas port. The barrel and extension will only be in alignment at that exact torque and that exact position. You can't just torque a loose extension back onto a barrel at the proper torque spec and have it align.

    Since the barrel extension wasn't properly torqued to begin with it will never line up at the proper torque.

  6. #46
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    If everything lined after the alleged re-torque I bet there is some Loctite at work here.

  7. #47
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    I guess someone could have gotten lucky and the stars and moon were aligned just right. But, I know how often that really happens.

    Quote Originally Posted by DBR View Post
    If everything lined after the alleged re-torque I bet there is some Loctite at work here.



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  8. #48
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    LOL, that's funny. I'm a manufacturer of barrels, guy. I know how they're built. I have a pile of them that just came back from being Melonite treated. Would you like to see them?

    Hell, half the guys commenting on here thought that the barrel extension pin protrudes into the barrel itself.

    The thing is, if it was torqued before it was drilled in the first place, then it should just about time right back up to the same place, when it's re-torqued.

    And even if it ended up not being properly timed, assuming this barrel wasn't chrome lined, it's very possible that they could have machined the barrel shoulder down to re-time it, and then recut the chamber.

    The barrel's not just disposable because some self-appointed "gunsmith" managed to dick around and unscrew the barrel extension...


  9. #49
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    When I had a barrel maker fix one that I complained about, he said that he went through about 200 barrel extensions to find one which lined up.

  10. #50
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    Quote Originally Posted by rsilvers View Post
    When I had a barrel maker fix one that I complained about, he said that he went through about 200 barrel extensions to find one which lined up.
    That's one way to do it... Seems like a WHOLE LOT of work, to avoid 45 min of work on the lathe though.

    After trying about 50 extensions or so, I think I'd just send you a new barrel... Maybe he had a slow day at the shop. Or maybe he just felt like punishing one of his employees...

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