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Thread: BCM 11.5 upper troubleshooting

  1. #1
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    BCM 11.5 upper troubleshooting

    What we're working with:
    BCM 11.5" BFH barrel
    BCM Lo profile gas block
    LMT Enhanced carrier
    Stardard bolt w/ Oring on the extractor spring
    Vltor A5 (as the kit came, H2 buffer?)

    What happened:
    Initial firing of the upper using M855 and M193 had the bolt locking back reliably with a nice 4 o'clock ejection. To further evaluate the upper, the rate of fire was increased to rapid and after 60-70 rounds the first malfunction occurred. The spent casing was 3/4 of the way extracted from the chamber and the next round was partially stripped from the magazine and started to feed. At that time a friend noticed the ejection patter moving more towards the 5-5:30 (and some brass residue on the deflector).

    Seemed like as the rifle got warm the problem reared up. Going back to basics, the mags were loaded with a single round and the rifle still reliably locked to the rear with a single round. However, anytime the mags were loaded up, the problem as noted above occurred almost each time.

    Where should the investigation begin?

  2. #2
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    Lose the O-ring to begin. Make sure you are also lubing it good. I would possibly look at upgrading to the A5H3 buffer but it will run as is.



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  3. #3
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    BCM 11.5 upper troubleshooting

    I would try a regular BCG as well. That would eliminate the enhanced carrier causing issues or not.
    Last edited by steyrman13; 07-05-14 at 18:22.

  4. #4
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    Unless it is defective, it's a non-issue. I run an LMT E-Carrier in my BCM 11.5", 12.5" and 20" without one single issue.


    Quote Originally Posted by steyrman13 View Post
    I would try a regular BCG as well. That would eliminate the enhanced carrier causing issues or not.



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  5. #5
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    Quote Originally Posted by Iraqgunz View Post
    Unless it is defective, it's a non-issue. I run an LMT E-Carrier in my BCM 11.5", 12.5" and 20" without one single issue.
    I agree they will work, but when having problems to lock back or fully extract and pick up the next round it sounds like it may not be getting enough pressure to push the BCG back far enough.
    Using a standard known good BCG could at least narrow it down to the carrier/o-ring issue rather than buffer or has port/gas block.

  6. #6
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    Quote Originally Posted by JustDSM View Post
    Stardard bolt w/ Oring on the extractor spring
    No such animal... Where did the bolt assembly and extractor spring come from? Always start your troubleshooting with the cheapest part first. In this case, the extractor spring and insert. If your using an o-ring and still getting FTE's, it's likely either the spring or the extractor.

  7. #7
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    First thing I'd try is a standard known good M16 carrier and start over.
    Chief Armorer for Elite Shooting Sports in Manassas VA
    Chief Armorer for Corp Arms (FFL 07-08/SOT 02)

  8. #8
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    I had 2 FTE's with my 11.5 BCM on the first 100 rounds (PSA bcg, standard spring, no o-ring). They also happend near 60-80 round mark.

    I then ordered the BCM upgraded extractor upgrade kit (spring, insert and o-ring).

    I installed the upgraded spring w/o the o-ring.

    Next 100 rounds no issues. I know 100 rounds isn't much, but I don't exspect anymore FTE's.

  9. #9
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    I thought this was a BCM bolt. Now that we are talking about PSA that's different. I will still default to the O-ring first. Only because I have THOUSANDS of rounds through my properly built uppers with no problems.



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  10. #10
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    The original just says standard bolt. I was just suggesting using a known good BCG as the quickest test. Some people don't have the skills or tools to take a bolt apart and swap out springs and o rings

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