When checking bolt-lug face surface % with a sharpie...

Discussion in 'Gunsmithing' started by Ingwe, May 23, 2019.


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  1. Ingwe

    Ingwe Well-Known Member

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    How much pressure do you exert on the bolt face?? I read that some just chamber an empty case, while others exert pressure with a dowel inserted in barrel....what do you guys do?

    What percentage contact of the lug-face is considered to be good/adequate??

    Thanks!;)
     
  2. shortgrass

    shortgrass Well-Known Member

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    We don't lap lugs with the barrel installed. What action do you want to lap?
     
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  3. therifleman556

    therifleman556 Well-Known Member

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    I think he's simply checking contact and wants to know how much is enough.
     
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  4. shortgrass

    shortgrass Well-Known Member

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    Ummmmm. May be. Using the pressure of the main spring is a no-no.
     
  5. therifleman556

    therifleman556 Well-Known Member

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    If all we're doing is checking contact, take a fired case with a thickness or two of scotch tape on the case head and chamber it. Just work the bolt up and down a few times, that should be enough to give you an idea.
     
  6. DSheetz

    DSheetz Well-Known Member

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    Ok that tells us how to check the lugs now for how much contact do you want?
     
  7. javman

    javman Well-Known Member

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    IRC you want at least 80% contact.
     
  8. DSheetz

    DSheetz Well-Known Member

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    Thank You
     
  9. Ingwe

    Ingwe Well-Known Member

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    I tried it too with a sharpie on the lug faces and a spent case in the chamber....no tape.

    My best guess is that I have give or take, 90% on one lug and 50% on the other.

    My rifle shoots sub 1/2 MOA all day long, so I don’t intend on “fixing” it;)
     
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  10. DSheetz

    DSheetz Well-Known Member

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    I have never had a custom action and haven't had any trued I have had some re-barreled I have looked at the bolt lugs after use and noticed that for the most part they showed close to the same wear patterns on both of the lugs . If both lugs are exerting pressure what does it change if one is at 50% and one is at 80% to have them changed to 80% on both of the lugs ? I'm here to try to learn . So I ask questions on other peoples questions not to be rude and butt in but because that is when they come to mind
     
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  11. javman

    javman Well-Known Member

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    Nothing wrong with uneven wear if your getting good accuracy like ingwe for example. But it has to do with the bolt and barrel being truly squared along with the receiver and making sure everything is nice and snug to get the best accuracy out a rifle. I've had a few with less than 80% contact but equal wear on both lugs and they shot outstanding groups, but at that point if "it ain't broke" why fix it, I leave it alone.
     
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  12. Ingwe

    Ingwe Well-Known Member

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    I should mention that I tried it several times with various results using case only no tape

    I bet it I used tape it would be more consistent
     
  13. shortgrass

    shortgrass Well-Known Member

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    Lapping, after the barrel has been installed, may create a longer headspace dimension. If headspace is still in spec after lapping, no problem. If not,?????
     
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  14. shortgrass

    shortgrass Well-Known Member

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    OK,, the lugs are lapped and now we have exceptable contact on both. Now, what about the bolt face? Is it uniform and 90* to the centerline?
     
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