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Thread: A situation I have seen several times:

  1. #1
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    A situation I have seen several times:

    I have seen at least 4 and mebby 5 rifles that came from more than one Smith with shoulders on barrels that weren't perpendicular to the tenon. How can this happen? Seems practically impossible yet it happened. Barrels don't stay tight long !

    Pete

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    Real interesting question Pete I pay allot of attention to that area to insure a proper fit. You can smoke it, use high spot blue or whatever you prefer to use to verify that there is full contact in that area. Our cast bullet compeitive benchrest shooting is quite abit different than most. It is not unusual to have two or more barrels to switch out. All can be screwed on and off without any tools so they are not screwed on real tight. They do have a retaining screw but the fit of the shoulder to the face of the action is very critical for one to achieve. So it makes me wonder is it the shoulder on the barrel or the face of the action that directly relates to what you are experiencing. This is typical of the rifles that we use and this one is the one that I compete with and the matches are shot at 200 yards.


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    Last edited by Louis.J; 02-11-2020 at 04:27 PM.

  3. #3
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    Something is obviously moving, unintentionally, or intentionally. I honestly have no idea why someone would move the part between cutting the shoulder and the threads.

  4. #4
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    Quote Originally Posted by Pete Wass View Post
    I have seen at least 4 and mebby 5 rifles that came from more than one Smith with shoulders on barrels that weren't perpendicular to the tenon. How can this happen? Seems practically impossible yet it happened. Barrels don't stay tight long !

    Pete
    How are you checking shoulder-to-tenon perpendicularity? I can see this going a dozen different ways...

    GsT

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    As do I Gene but it is not something that I have yet knowingly experienced myself but I am extremely interested to why Pete has?
    Last edited by Louis.J; 02-11-2020 at 06:35 PM.

  6. #6
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    Quote Originally Posted by GeneT View Post
    How are you checking shoulder-to-tenon perpendicularity? I can see this going a dozen different ways...

    GsT
    Here's the most likely problem ^^^
    Otherwise, something moved. Or maybe someone else can give me some clarity.

  7. #7
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    Visual gap, as I recall

    Quote Originally Posted by GeneT View Post
    How are you checking shoulder-to-tenon perpendicularity? I can see this going a dozen different ways...

    GsT
    I figured the problem must have been the barrels were either removed from their original setup then cut again or the cut coming back out wasn't enough to clean up the shoulder. Anyway, three different Smiths involved, two from the same one and one each from the other two. Smiths were well known Benchrest Smiths. I had one of the barrels and friends the other three.

    Pete

  8. #8
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    cutting the shoulder and then realign for the chamber ??

  9. #9
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    The thread and the tenon shoulder should always be machined on the same setup.

    The easiest way to check this is to put a light coat of Prussian blue on the face and lightly seat it agains the action face, (assuming it is correct), and check the contact.
    Last edited by jackie schmidt; 02-12-2020 at 09:58 PM.

  10. #10
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    Quote Originally Posted by Pete Wass View Post
    I figured the problem must have been the barrels were either removed from their original setup then cut again or the cut coming back out wasn't enough to clean up the shoulder. Anyway, three different Smiths involved, two from the same one and one each from the other two. Smiths were well known Benchrest Smiths. I had one of the barrels and friends the other three. Pete
    Couple of questions, Pete:

    - How are the barrels being installed?
    - Is there a relief cut ahead of the threads?
    Last edited by Al Nyhus; 02-13-2020 at 07:14 AM.

  11. #11
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    Quote Originally Posted by Al Nyhus View Post
    Couple of questions, Pete:


    - Is there a relief cut ahead of the threads?
    Bingo there you go......

  12. #12
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    I don't recall

    Quote Originally Posted by geo.ulrich View Post
    Bingo there you go......
    but why would a professional do such a thing? I know for sure the one I has wasn't thread bound but don't know about the others.



    Pete

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    This will be a little long. Years ago a H.O.F. shooter was complaining his barrel done by another top br gunsmith was not shooting actually a few. I told him bring it by work I wanted to check something. I set it up blued the face and went in and u'cut the threads without removing any bluing while he watched. He took it home and puts it back on. Then calls me headspace had changed .002 shorter. He showed back up that night with around 12 more barrels that "wouldn't shoot . did the same thing blued up and undercut. when he checked them they had moved between .002---,012 difference in headspace and they started to preform. Two things here where the thread ramps up when pulling tool out AND how much offset there is in threading tool. if you think a centered vee insert is going to make it close enough well it won't. A better question to your question to why a Profesional do this is why not it doesn't hurt a thing and you know its shouldering as it should....
    Last edited by geo.ulrich; 02-13-2020 at 04:26 PM.

  14. #14
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    Even when the action has a tread relief I still under cut the shoulder enough to eliminate any chance of interference between the barrel shoulder junction and the action face. When I used a manual lathe on the last pass turning the tenon I'd plunge in before pulling the tool across the shoulder. It also doesn't hurt to go right back in and shave a few more tenths off. Then you know it's square.

  15. #15
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    I think

    some folks think it looks better to not have a relief cut or they may think the barrel may be set back at some point and the relief cut would weaken extending the thread? Realistically, how many barrels get set back? I have done some but haven't worried about the relief groove. Tenny rate, ill fitting barrels can be prevented.

    Pete

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