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Thread: Cam-pin wear as a contributor to bolt failure?

  1. #11
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    Quote Originally Posted by markm View Post
    I used to run grease on my cam pins... I never saw that it stopped that wear. I just dry to have the whole area wet with Froglube and don't think about it anymore.
    but this is super slick 0 friction super snake grease
    Last edited by RMiller; 07-03-13 at 11:43.

  2. #12
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    Quote Originally Posted by WS6 View Post
    Has this been shown statistically to matter?
    I doubt it. Bolts generally last three barrels anyway.

    The chromed ones I bought at Camp Perry don't gall, though. They may have been from DPMS. I bought them on Commercial Row.

    If you want to consistently orient a standard cam pin you can use something like an engraving pencil and mark it with an arrow pointing toward the muzzle.

  3. #13
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    Quote Originally Posted by RMiller View Post
    but this super slick 0 friction super snake grease
    Grease works good there. I just got sick of having to lube with two different products.
    "You people have too much time on your hands." - scottryan

  4. #14
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    Quote Originally Posted by markm View Post
    Grease works good there. I just got sick of having to lube with two different products.
    Ya I know.

    My other profession is automotive. Since my work and "gun area" share the same space in my home, I figured why use more products than I have to. Grease and motor oil have been working very well for me. It's crazy smooth when I rack my carbine.

    Besides a dedicated tube of Lucas red and tacky and a qt of royal purple SAE 30 will last forever! And I can use it on my truck in a pinch. What's not to like?

  5. #15
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    I don't have many rounds through my LMT enhanced carrier (+/-800 rds) but I'll be curious to see how it wears compares to my BCM BCG cam pin after a few thousand rounds.

    I would say theoretically it should wear less because of the shallower track.

    -Jax
    Last edited by jaxman7; 07-03-13 at 12:05.


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  6. #16
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    Note to self: pick up some extra cam pins. Some rifles seem to be harder on cam pins than others. Why is that?

  7. #17
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    Quote Originally Posted by WS6 View Post
    I have noticed that cam-pins quickly wear to the point where a fingernail can catch in the wear on the side.
    I think you'll find that cam pin lash is the primary cause of the wear. The TDP spec for the cam pin diameter and the hole in the bolt are nearly the same. To speed production and reduce returns, most manufacturers make the hole in the bolt to big and the pin to small.

    When the pin is too small and the hole to large, the unlocking force isn't lateral to rotation of the bolt and the pin rocks in the bolt hole. This leads to impact between the carrier and cam pin.

    I'm not sure if the ledge that is created is a result of loss of material due to wear or if the carrier is "hammer forging" the area of cam pin that contacts the carrier to a smaller dimension.

  8. #18
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    My bet is that the cam pin has been swaged, and that once the surface area moved increases to support the load, the metal movement stops.

    I also don't see it as a problem. The carrier is harder than sin, it won't swage/change. the cam pin swages until it supports the load, then metal movement stops.

    I toss such-ridged cam pins when they too bad simply because cam pins are cheap, and I can.

    The tolerance stop is more likely a cause of bolt breakage, and the cam pin wear is just a symptom.

  9. #19
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    It would be nice if someone with long-term experience in this could post a pic or two of a cam pin that is in need of replacement. I never really got into logging the number of rounds or anything so it would be helpful to have a visual image of a bad pin.

  10. #20
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    Quote Originally Posted by Doc Glockster View Post
    It would be nice if someone with long-term experience in this could post a pic or two of a cam pin that is in need of replacement. I never really got into logging the number of rounds or anything so it would be helpful to have a visual image of a bad pin.
    I would like to see this as well. I've seen a cam pin with 125 rounds that looks worse than another that has about 1000 rounds.

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