strange problem with new build

Discussion in 'AR-15 Discussion' started by Nathantc, Oct 7, 2011.

  1. Nathantc

    Nathantc New Member

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    OK I have tried milspec gi mags, they work fine, and magpul """30rd""" mags work fine.

    This odd issue I am having is only with magpul """20rd"""mags, they will not activate the last round bolt hold open. I have 10 gi mags they all work, 4 30rd pmags they all work, but the 4 20rd pmags I have will not hold the bolt open.

    Maybe some one can shed some light on this

    With the 20rd mags I have to smack the bolt release very hard to get it to let go, also with the mag inserted on a closed bolt if I pull the charging handle back and use the bolt hold open manually it is very hard to move and make a loud click when it breaks free.

    the 20rd mags work just fine in my bull barrel ASA AR-15, just fyi

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  2. fsted2a

    fsted2a Active Member

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    Could be a batch of magazines with bad followers.
     

  3. Nathantc

    Nathantc New Member

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    they work fine in my other ar15, they also work just fine in my buddies other 3 ar15's, we actually just got done testing that.

    it seem like the bolt catch is binding, but only with these mags.

    its not that big of a deal being as i will only be useing 30rders in this one but i cant help but want to know whats going on
     
  4. fsted2a

    fsted2a Active Member

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    Try swapping out uppers between your AR's to see if the problem is in your upper or lower. You can use the charging handle to similate firing for this purpose. My bet is it is in the lower. If so, try a micrometer or caliper on the mag well to see if you can find where the dimensions are different. If the magwell is binding, you can usually take a file to the spot that is binding and cure the problem if you don't take too much material off. If it is in the upper, which is less likely, it probably is in the extractor.
     
  5. Nathantc

    Nathantc New Member

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    its the lower for sure, i just dont see what the differnce is between the 20 and 30rd mags
     
  6. Quentin

    Quentin New Member

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    Seems like the bolt catch lever would be high on the list of culprits. I'd compare it closely against on in the other lowers that work with 20rders.

    If that's it, it's a cheap fix so probably a good idea to replace it since both types of mags are important.
     
  7. Blackbeard1718

    Blackbeard1718 New Member

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    Hmmm! I use nothing but the PMAG 20-Rounders with the same Black Follower, and haven't had any problems..... Knock-On-Wood!

    I have an RRA Tac Op 2, and the Mags Load/Eject just fine.

    Best of Luck!

    Cheers!

    BB
     
  8. Nathantc

    Nathantc New Member

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    i dont think its the mags, though i cant see why the 30rd mags work and the 20 dont.

    the 20rd mags i have work in many other lowers, just not this one.:confused:
     
  9. fsted2a

    fsted2a Active Member

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    Have you taken a caliper or micrometer and measured the 20 rd mags? Sometimes a batch from an otherwise reputable manufacturer can be off a little. Doesn't take much. Just going by process of elimination. Stands to reason that if other mags work fine, and the 20 rounds don't, you might want to check the measurements. It doesn't take but a thousanths to mean the difference between working fine, and causing problems. If a GI issue works good, it probably is the mags. Even the best have some lemons.
     
  10. AlphaKoncepts

    AlphaKoncepts Member

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    Download each mag by one? I have a batch of magpul mags where I can load 31 rounds. If I do the mag will not latch into place. This is fairly common with the gen 2 Pmags.