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Thread: So, this happened while shooting my newest rifle...five times during one magazine

  1. #11
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    Hard to say but this could also be the result of short stroking, where the bolt lugs don't travel rearward enough to clear the rim, then as the bcg travels forward the bolt carrier catches the rim instead of the bolt. Then the cartridge gets wedged in there with the feed ramps putting the dents in it.

  2. #12
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    I would guess he didn't call BCM and even if he did contact them, it's Friday and we all know no one is going to answer until at least Monday or Tuesday. In addition, though he is using some BCM components, he has clearly assembled this with a non-BCM upper.

    Quote Originally Posted by MegademiC View Post
    Edit. What did BCM say? Call them first, but if you want to troubleshoot yourself:

    Ive seen that from a bent extractor.
    Change the bolt, if fixed, put the old one back in but swap extractors with a different rifle. Or lat the extractor on a flat surface. I suspect a bad extractor spring could also cause this.

    Could be mags. What I think is happening is that the round being fed is getting loose before or during the feeding process.
    In the case a saw, the extractor lost control of the case, it bumped the top round of the mag knocking it loose as the bolt was trying to feed it. The empty case then exited the port.



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  3. #13
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    Personally, Id ditch the HK mag and extractor o ring and go from there.


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  4. #14
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    Man I had no idea these mags were known to be junk, I just went through all of my magazines and found over a dozen.

    I got a bunch on sale a long time ago not knowing they sucked or that replacement parts were non-existent.

    They are now quarantined, thanks for all of your input.

    As for the o-ring around the extractor spring, why is this bad?

    I have installed them in all of my rifles except for my A1 clone.

  5. #15
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    I own a lot of magazines and the numerous HK magazines I own work just as well as the aluminum GI mags. I don't shoot a lot of LC ball out of any magazine but I reload various 556 bullet types/weights and have never had a malf from an HK magazine. 77gr SMK's / TMK's feed flawlessly through HK Magazines into both of my MR556 rifles as well as numerous other 556 rifles.

  6. #16
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    Well, considering I've never had feed failures like this with polymer or aluminum magazines, these are going into the "DO NOT USE" box.

    I'm not going to keep mags in circulation if they work in some of my rifles, but not others.

    I'm going back out this weekend to shoot more of the same ammo with different mags.

  7. #17
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    This is not a BCM rifle, it's a home built gun for all the people telling him to call BCM. OP, check your carrier key, and check your gas block, this could be a gas issue. I have seen this exact thing happen due to short stroking because the carrier key bolts backed off and it became loose. The BCG does not get enough gas, it short strokes and the bolt lugs catch the side of the cartridge as it comes forward, and wedge the cartridge in at an agle and dent the brass. In my case torquing the carrier key screws back down fixed the issue.

  8. #18
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    My novekse loved to do this. The barrel extension "corners" on the inside were very sharp. The round pivots on these as it slides forward into the chamber. If they are too sharp, they did into the case and arrest its movement. You will note significant shaved brass in the pre-chamber area. The magazine feed angle can help or exacerbate this issue.

  9. #19
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    The 3rd Ranger Battalion and Regiment teams nearly lost the 2004 Army Rifle Championships due to the then-new HK mags. A runner from one of their supply rooms saved their butts with a box of GI mags.

  10. #20
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    It’s the HK magazine.

    Went out yesterday and it functioned perfectly using PMAG’s and Okay mags with Magpul followers.

    I tried and could not duplicate the failure with ball ammo and also fed it some HSM 75gr OTM’s, I had one double feed with one of the older Okay magazines.

    I have checked the gas key screws and also looked for leakage around the gas block, I don’t think it is short stroking.

    What threw me off was the fact that the suspect HK mag worked fine in a couple other rifles but in this one I had several failures, I won’t be using HK mags anymore.

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