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Thread: Best way to hold upper while TQ barrel nut?

  1. #11
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    I have always clamped the receiver in a bench vice. I use a block of wood on either side, and obviously clamp the flat lower surface and the picatinny rail top, with the upper on its side. I have never had an issue with this, although I've never had anything horribly seized, either.

    The downside is that you can't have an optic mounted, so if you have a scope that's a pain to remove, and want to swap muzzle devices, this wouldn't work so well.

  2. #12
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    I hold the upper (in a "clamshell" type of holder) when tightening barrel nuts.

    I hold the barrel (with a Reaction Rod type of holder) when tightening muzzle devices.

    Joe Mamma
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  3. #13
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    Quote Originally Posted by Joelski View Post
    Has anybody actually seen this happen with their own eyes, or is this theoretical hogwash?
    If it were theoretical hogwash there wouldn't be so many pictures to prove it.

  4. #14
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    Quote Originally Posted by 556Cliff View Post
    If it were theoretical hogwash there wouldn't be so many pictures to prove it.
    So, you've seen it happen?

    Somebody made an interesting observation; the magic word was "seized". It makes sense that a properly torqued barrel would possibly require higher torque to loosen, however wouldn't it occur to apply heat before brute force, considering the different expansion rates of the metals involved? It seems like the majority of those failures might have been easily prevented...

  5. #15
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    I agree with that. Years of wrenching on motorcycles and cars and bicycles have given me a decent feel for "enough force" for a given fastener size. If it doesn't come off with what feels like a reasonable pull, it's time for heat, and maybe penetrating oil.

  6. #16
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    Quote Originally Posted by Joelski View Post
    So, you've seen it happen?

    Somebody made an interesting observation; the magic word was "seized". It makes sense that a properly torqued barrel would possibly require higher torque to loosen, however wouldn't it occur to apply heat before brute force, considering the different expansion rates of the metals involved? It seems like the majority of those failures might have been easily prevented...
    There was a picture here not two weeks ago of a sheared pin. Also I believe Iraqgunz said he had 1(one) shear upon dis-assembly of a highly over torqued nut.

    It's pretty well known that it can happen.

  7. #17
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    I'm having a hard time visualizing how a clamped receiver would prevent the pin from shearing with a seized barrel nut compared to a reaction rod. Either way the force is going through the pin.

  8. #18
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    Subscribed for comments.
    when life closes doors on you, blow them off the hinges.

  9. #19
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    Quote Originally Posted by Joelski View Post
    So, you've seen it happen?

    Somebody made an interesting observation; the magic word was "seized". It makes sense that a properly torqued barrel would possibly require higher torque to loosen, however wouldn't it occur to apply heat before brute force, considering the different expansion rates of the metals involved? It seems like the majority of those failures might have been easily prevented...
    I have not seen it happen in person but I have seen it posted about more than enough times to believe it really happens. It does happen mostly with stuck barrel nuts but it has on occasion happened on assembly as well.

  10. #20
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    Let's assume seized means that the threads of the receiver are fused to the threads of the barrel nut such that any applied torque to the nut creates a tendency for the entire receiver to rotate. With an unsupported receiver that rotation is largely opposed only by the indexing pin (some opposition is created by friction between the receiver face and barrel extension shoulder). With a supported receiver most of the rotational opposition is taken by the supporting fixture. With a supported receiver the only force directed through the pin is the result of the rotational tendency created by friction between the barrel nut and the barrel extension shoulder.

    Quote Originally Posted by bigwagon View Post
    I'm having a hard time visualizing how a clamped receiver would prevent the pin from shearing with a seized barrel nut compared to a reaction rod. Either way the force is going through the pin.
    Also, no one should assume that the aluminum part in an system of mating parts will automatically be the part to fail simply because it is the weaker material (7075 T6 actually has a higher tensile strength than many low alloy, low carbon steels in the annealed condition). You need to look at actual stress developed in each part.
    Last edited by Eric D.; 01-04-16 at 17:53.
    B.A.S. Mechanical Engineering Technology

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