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Thread: 13.7 issue

  1. #1
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    13.7 issue

    Just put a new upper together. 13.7 stainless mid gas barrel, kit came with a bcg & gas block/tube. Using a H buffer & carbine spring. Went to do a quick zero, locked bolt back, inserted mag, hit bolt release, round did not fully chamber. Pulled out mag, round then chambered completely. Fired mag until empty & got lock back, put in fresh mag, hit the bolt release & the same sequence happened. Ammo was steel case brown bear. Mags were usgi loaded to 28 rounds. This happened with & without a suppressor on. Any thoughts? Thank you

  2. #2
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    I’d try some brass case ammo. See if problem continues, or disappears.
    I would guess a chamber issue if brass case ammo chokes as you describe with steelcase.
    A true "Gun Guy" (or gal) should have familiarity and a modicum of proficiency with most all firearms platforms.

  3. #3
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    So it won't feed steel case ammo from a USGI mag and bolt lock.

    Could be a friction issue of too much drag or not enough spring.

    Inspect the feed ramps for any potential hangups.

    Narrow down variables.

    Try slingshotting the charging handle vs using bolt release.

    Try 10 rounds loaded vs 28.

    Try brass ammo vs steel case.

    Try a PMAG.

    Try a new spring.
    Black River Tactical
    BRT OPTIMUM Hammer Forged Chrome Lined Barrels - 11.5", 12.5", 14.5", 16"
    BRT EZTUNE Preset Gas Tubes - PISTOL, CAR, MID, RIFLE
    BRT Bolt Carrier Groups M4A1, M16 CHROME
    BRT Covert Comps 5.56, 6X, 7.62

  4. #4
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    Quote Originally Posted by Clint View Post
    Inspect the feed ramps for any potential hangups.
    See if they’ll grab a q-Tip. Particularly the right side one, if the top round in your mag is on the right.
    RLTW

    Former Action Guy
    Disclosure: I am affiliated PRN with a tactical training center, but I speak only for myself. I have no idea what we sell, other than CLP and training. I receive no income from sale of hard goods.

  5. #5
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    In addition to the suggestions already in the thread, make sure that the BCG is sufficiently lubricated. This is even more important for a new build.
    “You have made us for yourself, O Lord, and our heart is restless until it rests in you.” -Augustine

  6. #6
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    I have encountered this quite a few times with a new build, especially if using brand new g.i. mags. I think it’s just a friction issue as everything is all brand new.

    One thing I have found, and one of the reasons why I exclusively use them, is that you can change nothing but the mag and it will feed with a Pmag.

  7. #7
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    Quote Originally Posted by 17K View Post
    I have encountered this quite a few times with a new build, especially if using brand new g.i. mags. I think it’s just a friction issue as everything is all brand new.

    One thing I have found, and one of the reasons why I exclusively use them, is that you can change nothing but the mag and it will feed with a Pmag.
    Funny you should mention that. I actually had some problems today with some metal mags if unknown manufacture. Some barely held 30, some only held 29 (damaged lips implied, but not really looked at). With my full-time suppressor host and its heavy-ish spring, I had trouble getting the first round to strip without the push-jerk inertia trick. The BCG was clean-ish and lubed.

    There may be something to be said for the top round having a little space, and PMags do that, for sure. I never have trouble with my own GI mag collection, though.
    RLTW

    Former Action Guy
    Disclosure: I am affiliated PRN with a tactical training center, but I speak only for myself. I have no idea what we sell, other than CLP and training. I receive no income from sale of hard goods.

  8. #8
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    Agreed, the top round of 30 certainly needs room to push the stack down as it pivots.

    The OP was downloaded to 28, so probably not that issue in this case.

    Quote Originally Posted by 1168 View Post
    Funny you should mention that. I actually had some problems today with some metal mags if unknown manufacture. Some barely held 30, some only held 29 (damaged lips implied, but not really looked at). With my full-time suppressor host and its heavy-ish spring, I had trouble getting the first round to strip without the push-jerk inertia trick. The BCG was clean-ish and lubed.

    There may be something to be said for the top round having a little space, and PMags do that, for sure. I never have trouble with my own GI mag collection, though.

    PMAGS certainly feed rounds higher and with less friction.

    Yes, this can eliminate feed issues in many cases.

    Quote Originally Posted by 17K View Post
    I have encountered this quite a few times with a new build, especially if using brand new g.i. mags. I think it’s just a friction issue as everything is all brand new.

    One thing I have found, and one of the reasons why I exclusively use them, is that you can change nothing but the mag and it will feed with a Pmag.
    Black River Tactical
    BRT OPTIMUM Hammer Forged Chrome Lined Barrels - 11.5", 12.5", 14.5", 16"
    BRT EZTUNE Preset Gas Tubes - PISTOL, CAR, MID, RIFLE
    BRT Bolt Carrier Groups M4A1, M16 CHROME
    BRT Covert Comps 5.56, 6X, 7.62

  9. #9
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    Cleaned barrel & chamber. Put it on a lower with an A5 system. Problem went away. Shot steel & brass from usgi & pmags fully loaded. Thanks

  10. #10
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    What mags where you using?

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