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Thread: Bolt Lug Tolerance/Spec

  1. #11
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    Re: Bolt Lug Tolerance/Spec

    Quote Originally Posted by RMiller View Post
    In the past 2 weeks I've never heard of so many headspace and tight lug issues on AR15's. It's everywhere and enough that its strange.

    The one common theme is a no-name (claimed to to mil-spec) obviously not mil spec bolt. Just an observation.
    Just to be clear, my issue was not a fault of any of the bolts tested.

  2. #12
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    This bolt needs to be guaged in a barrel too. It may be that the bolt face is cut too shallow.
    "You people have too much time on your hands." - scottryan

  3. #13
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    Quote Originally Posted by mtdawg169 View Post
    Just to be clear, my issue was not a fault of any of the bolts tested.
    It's not just on the interwebs.

    I'm even having friends that have come to me in the past couple weeks with the same issues. My BCM bolt would resolve the issue. It just strikes me as weird or maybe its a big coincidence.
    Last edited by RMiller; 07-16-13 at 11:03.

  4. #14
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    Quote Originally Posted by RMiller View Post
    It's not just on the interwebs.

    I'm even having friends that have come to me in the past couple weeks with the same issues. My BCM bolt would resolve the issue. It just strikes me as weird or maybe its a big coincidence.
    Not coincidence.

    I could see this coming months ago. In a rush to bring any and everything to market, this kind of thing was inevitable.
    "You people have too much time on your hands." - scottryan

  5. #15
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    On my Colt bolt, all the lugs were about 0.100" x 0.278" x 0.177".

    The overall width of the bolt was 0.739" measured at adjacent lugs. Obviously the extractor side would measure different. Overall length is 2.800".

    Bolt has a couple of thousand on it.

    I don't know what the big secret is in not listing the brand. I'd want to keep other guys from buying crap, and these things tend to run in batches.
    Last edited by bp7178; 07-16-13 at 12:16.

  6. #16
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    The Daniel Defense bolt (came with the gun, works fine) measures 0.102" across the lug, and 0.275 by the length of it. This is compared to 0.98" and 0.280", respectively, of the offending bolt.

  7. #17
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    I suspect it's not a lug problem, the lugs don't have that snug of a fit with the barrel extension. It could be an issue with the cam pin hole as to its position. Without comparing the suspect part with a known good one, its hard to say.

  8. #18
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    Quote Originally Posted by bp7178 View Post
    On my Colt bolt, all the lugs were about 0.100" x 0.278" x 0.177".

    The overall width of the bolt was 0.739" measured at adjacent lugs. Obviously the extractor side would measure different. Overall length is 2.800".

    Bolt has a couple of thousand on it.

    I don't know what the big secret is in not listing the brand. I'd want to keep other guys from buying crap, and these things tend to run in batches.
    The rules here are to contact the company first. I have now done that.

    Rubber City Armory originally, upon hearing my issue (but no measurements) stated that while they would do whatever I wanted (refund, swap out, etc.), I might be best to "just write them off", and that perhaps I and others like me were "picky", as most of these types of returns "work just fine" in their guns. I was informed that AK-47's have a lot of slop and can work with a lot of gunk in them and that I may be better served to consider one.

    Upon hearing the measurements of 0.280", they agreed that this was a little off and seemed more inclined to my way of thinking.

    I had agreed to send in the bolt for a swap...

    ...but after a good hard work-out this AM, and thinking about the things that have transpired, I decided against returning the bolt for a new one as I had discussed on the phone.

    The carrier is nice, and I'll keep it. Bolt can go in the trash. I would rather run a known quantity from BCM or Daniel Defense, as I have literally never before encountered a bolt out of spec to the point that it caused administrative unloading of the weapon to require goodly effort. (Feeling like trying to extract brass-case after shooting a lot of steel). Chamber is not the issue as my other bolts work fine, including one of the previous one's from RCA. Their products seem to be "all over the map" when it comes to machining, and I'd just rather not.

  9. #19
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    Re: Bolt Lug Tolerance/Spec

    Quote Originally Posted by markm View Post
    This bolt needs to be guaged in a barrel too. It may be that the bolt face is cut too shallow.
    Interesting idea. I hadn't thought of that.

  10. #20
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    The rule about contacting the company has nothing to do with disclosing their name. It's to keep someone from bad mouthing a shop without giving them the chance to rectify the problem.

    Again, I really doubt this is a lug dimension issue. They just don't fit that tightly. I really suspect this has more to do with how the bolt is timed, ie its not in its fully unlocked position when it should be.

    As for the bolt face idea, is this only when ammunition is present? Or does it do it when retracting on an empty chamber?

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