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Thread: PMAGs not locking bolt open...figured out why

  1. #21
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    Fchen17213 the channel in which your bolt release sits in maybe worn or cut to wide, a thin small waster placed on the left side around the roll pin will straiten the release as it maybe slouched over do to excessive gap. You may be able to find a tiny washer or e clip at a hardware store. I done this on several out of spec Sharps Rifle Company lowers and they work great now.
    Last edited by WAR FACE; 09-19-11 at 22:52.

  2. #22
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    Finally got around to getting some pictures. There is not much play at all in the bolt catch as far as wobble and it makes good contact with both followers. I wiggled and jiggled as much as the stop would move and there's no way it can slip off the follower. You can see that on the follower with the shallower stop channel that the front of the follower isn't coming up as far as the other.

    From the front:


    Shallow channel follower


    Deep channel follower


    From the rear:


    Shallow channel follower


    Deep channel follower

  3. #23
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    Is that a BAD lever? is it possible it could have anything to do with it? I've heard about them exerting a slight pressure, which in my mind would exacerbate any issue there might be. If this were my rifle I'd try removing that just to see what happened.

    I'm just a 90% lurker ar noob though, so take anything I say with a grain of salt. I just wanted to throw that out there.
    Last edited by erratic; 09-20-11 at 23:01.

  4. #24
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    I've heard the same stories. But I played with it for a good half hour tonight and just don't see how it could possibly cause any issues. I just don't see how it has enough mass to it to cause any ill effects. I inserted the empty mag, pushed the follower down and let it rise back up, there was no hesitation of the mag catch to move. And when shooting my finger stays firmly on the trigger and I haven't been wearing gloves so there is no chance of me riding the bad lever.

  5. #25
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    Take that contraption off, install Colt bolt catch.



    If you still have issues I will swap you lowers with something that works (minus that BAD contraption).

  6. #26
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    Next time I go out I will see if I can get one mag to fail consistently, like I said, this issue is intermittent. If I can get one to do it I will remove the BAD lever and try again, as that is an easy check. I'm not about to start blaming the lower and the LPK for the issue when I see no issues with them but can point out a distinct difference in follower design. The followers with the shallower channel would not be exerting as much force on the mag catch because they are not trying to push it up as far. I wish I had access to a force gauge to verify this.

  7. #27
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    I believe that Belmont's advice will be your best course of action. Replacing your current bolt catch with a Colt bolt catch will help alleviate any issues you have. Either way, feel free to call our customer service line to have your magazines replaced. I know you emailed them but considering the amount of email traffic they receive I would suggest you call instead.

    I hope this helps.
    Product Manager at Magpul Industries

    This is a personal account linked to a personal e-mail. Company affiliation and titles are provided purely for transparency requirements of the host site. Although factual company information may be shared through this account, any opinions expressed are solely those of the account holder, and not necessarily those of Magpul Industries or subsidiaries.

  8. #28
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    I appreciate the advice. I'm just curious, how would the Colt bolt catch differ from the one currently on my rifle?

  9. #29
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    Colt is actually held to the TDP. The difference could be in the bar that makes contact with the follower or the width of the section that mounts into the lower. Any dimensional difference in any of the areas can potentially cause a problem. The worst we have seen is DPMS but without having your particular catch to compare to a Colt I could not say with certainty what the actual difference is.
    Product Manager at Magpul Industries

    This is a personal account linked to a personal e-mail. Company affiliation and titles are provided purely for transparency requirements of the host site. Although factual company information may be shared through this account, any opinions expressed are solely those of the account holder, and not necessarily those of Magpul Industries or subsidiaries.

  10. #30
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    What make is your receiver? It may be your receiver and not the magazines....

    Parts manufactured at different times can have slight variations in size, so there is a + and - size that is considered to be within spec.
    Colt rifles are held to a very tight standard, as are the other parts they put in their rifle. The parts all come together and are supposed to work together.

    When you get a receiver from one maker, and parts from another, very slight manufacturing tollerances (the + and - sizes) can come into play and cause performance issues.

    I have an early PWA receiver that either has the magazine well broached slightly forward from the bolt catch channel OR the bolt catch channel is slightly rearward from the magazine well.

    That PWA receiver works 100% every day with USGI magazines, but when PMags hit the market, the bolt catch would fail to lock open. Another PWA receiver does not have this trouble and it works well with every magazine I have tried.

    Upon digging into the measurements of the troubled receiver/bolt catch,,,the catch was just barely able to miss the rear of PMag followers. Looking at the PMag magazine body and also at the USGI magazine body, you will find the USGI body offers slightly more depth to allow the magazine follower to hit the bolt catch. The thinner USGI magazine body construction allows this.

    I tried many bolt catches but none would measure long enough to be pushed reliably by the PMag magazine follower in my troubled receiver. I just bit the bullet and altered a Colt 9mm bolt catch to fit the receiver, allowing a longer "finger" to get pushed up by the follower.

    So, in my case, it was only run USGI magazines in that rifle OR modify the bolt catch to ensure reliability. This is a training rifle, so no problem in leaning on this fix- if it fails, not sweat. It has been working well and showing no signs of failure for some time now.

    Here is a link to TOS where I posted pictures regarding the fix for my rifle. http://www.ar15.com/forums/t_3_66/47...0________.html


    The altered 9mm bolt catch.
    Last edited by a308garand; 09-21-11 at 22:49.

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