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Thread: Fitting a bolt to a barrel

  1. #61
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    Patrick,

    But if it is over, why couldn't a competent machinist bump back the shoulder and the very end of the barrel to effectively shorten the chamber and move the bolt in by the same amount.

    I realize I'm probably not using the correct terms for the 2 faces I'm referring to, but I think you probably know what I mean.

    I never even thought of messing with it if it was under. I assumed that was the SOL scenario.

    Not sure what the 'stupid' comment was about. The barrel was machined in the first place. If it was machined in a way that's sub-optimal, and it can be modified, why not? I'm not talking about doing it in a garage with a belt sander. This would not be for a general purpose gun either.

  2. #62
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    To bring back a chamber that is over-length, it would take a skilled machinist, a big precise lathe, and a bit of luck.

    (and the following is just an explanation, not a prescription you should follow.)

    You'd have to remove the barrel from teh upper, remove teh front sight assembly (probably) and then unscrew the barrel extension.

    Then, the machinist would have to trim forward the shoulder against which the barrel extension stops. (Remove material towards the muzzle) Also, he'd have to trim forward the back end of the barrel/chamber, and replicated the multiple angles that it is machined to.

    And he'd have to do this in exactly in turn of the barrel threads. Anything else, and your gas port ends up tilted (and your front sight) to one side or the other. then, screw the barrel extension back on, and re-assemble the rifle.

    All this essentially moves the entire barrel back a thread, so you can then re-cut the chamber forward (it will be under-headspaced by then) to the correct dimension.

    The luck part? You'd have to hope that all this doesn't shove the barrel back so far the gas tube now binds inside the key, not having enogh room in its extended-back location. Your handguards will also be a really tight fit, since the barrel has been scrunched back a thread.

    The cost of all this will likely be an appreciable fraction of the cost of a new barrel.
    Last edited by patrick sweeney; 04-01-13 at 10:30.

  3. #63
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    Quote Originally Posted by Ty_B View Post
    The barrel was machined in the first place.
    The gas port is drilled after TDC is determined by where the barrel extension ends up after being installed. Cutting the shoulder the barrel extension stops on would move the gas port from TDC.

  4. #64
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    Quote Originally Posted by Todd.K View Post
    The gas port is drilled after TDC is determined by where the barrel extension ends up after being installed. Cutting the shoulder the barrel extension stops on would move the gas port from TDC.
    Gotcha. That's what I was missing - the alignment of the gas port. Thanks to you and Patrick for the information.

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