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Thread: Failure to Feed; Was Failure to extract

  1. #1
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    Failure to Feed; Was Failure to extract

    I built a new upper for suppressed use using the Sionics 11.5” reduced gas port barrel. I function tested today unsuppressed (suppressor still in NFA jail) running a BCM bolt with LMT E-Carrier and Vltor A5 RE, Sprinco green spring and A5H2 buffer. Test was run on a Seekins forged lower with 2500+ rounds run. First 40 rounds through went with no issue. GECO 223 55gr FMJ was fired on approximate 2 second intervals.

    Next, I ran some basic movement drills shooting at a much faster pace. IMI 556 55gr FMJ, Wolf Gold 223 55gr FMJ and American Eagle 223 55gr FMJ were used in various Gen 2 and Gen 3, 30 round pmags that have run hundreds of rounds with out issue.

    About four to five mags into these drills, as the gun got hot, I started to get failure to extract malfunctions. The first failure to extract was with IMI 556, the remainder of the malfunctions were with the AE 223 rounds.

    I was anticipating possible short stroking/failure to lock, but this malfunction doesn’t appear to be that. I changed out the BCM/LMT BCG to a BCM built BCG with several hundred rounds run and the malfunction appeared to go away, however, I was out of the AE ammo after running 20 rounds. Wolf Gold and GECO ran with out issue using the BCM BCG. The ejection pattern with both BCG's was consistent and about 4 o'clock.

    Outside air temperature was 87 degrees.

    Need some advice on what changes to make to isolate the issue. I don’t think there is a gas flow issue at the gas block, as the barrel is pre-drilled and a BCM low profile gas block with set screws was used and appears to be installed properly. Similar situation with the gas tube.

    Thank you.

    Nightchief

    Attachment 45146Attachment 45147Attachment 45148Attachment 45149
    Last edited by nightchief; 04-24-17 at 22:25.

  2. #2
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    I think there have been a few threads here about some BCM bolts have extraction/ejection issues. I cannot guarantee that is the issue, but it's the cheapest place to start.

    My RGP upper also uses the LMT E-Carrier, Vltor A5H4 and green Sprinco and I have no issues.



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  3. #3
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    Quote Originally Posted by Iraqgunz View Post
    I think there have been a few threads here about some BCM bolts have extraction/ejection issues. I cannot guarantee that is the issue, but it's the cheapest place to start.

    My RGP upper also uses the LMT E-Carrier, Vltor A5H4 and green Sprinco and I have no issues.
    Reading the most recent thread I could find regarding failure to extract/eject, there was some discussion about the O ring use with the bolt's supplied spring and insert. I left the O ring out of my bolt before starting the function testing as I thought that would be better. Do you think this is an extractor issue or an ejector issue?

  4. #4
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    There are more, but they aren't titled BCM which is why they won't just pop up. I hate doing internet diagnosis because some little detail is always left out (like the guy who was using a Magpul BAD lever) which was causing issues and it wasn't revealed for quite a while.

    The easy way to troubleshoot is to have spare parts on hand that YOU KNOW WORK.

    For example- in your issue we have no idea how many rounds on that bolt (is it new or used, etc..). Magazines are supposed to be working fine. So if it were me, I would get another set of mags to rule it out.

    If that doesn't solve the problem I would jump to the bolt and use another that you know works. If it solves the issue, then you start to look at the two items which can cause problems. Extractor/spring and ejector. Both of them are fairly easy to replace and cost less than $10.00.

    Quote Originally Posted by nightchief View Post
    Reading the most recent thread I could find regarding failure to extract/eject, there was some discussion about the O ring use with the bolt's supplied spring and insert. I left the O ring out of my bolt before starting the function testing as I thought that would be better. Do you think this is an extractor issue or an ejector issue?



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  5. #5
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    Failure to extract

    Its a new BCM bolt. I checked the extractor spring, and it does not have the extra power type, so I have replaced the spring with a Sprinco extra power spring. No BAD levers in use. I have several spare parts that are vetted, so if the spring change doesn't solve the issue, I'll start looking for other options. I'm pretty confident its not a mag issue, as I had the FTE's on three different mags, and none have ever given me an issue. I'll check them over for cracked feed lips or a cracked spine.

    Will update after trying out the new spring.

    Quote Originally Posted by Iraqgunz View Post
    There are more, but they aren't titled BCM which is why they won't just pop up. I hate doing internet diagnosis because some little detail is always left out (like the guy who was using a Magpul BAD lever) which was causing issues and it wasn't revealed for quite a while.

    The easy way to troubleshoot is to have spare parts on hand that YOU KNOW WORK.

    For example- in your issue we have no idea how many rounds on that bolt (is it new or used, etc..). Magazines are supposed to be working fine. So if it were me, I would get another set of mags to rule it out.

    If that doesn't solve the problem I would jump to the bolt and use another that you know works. If it solves the issue, then you start to look at the two items which can cause problems. Extractor/spring and ejector. Both of them are fairly easy to replace and cost less than $10.00.
    Last edited by nightchief; 04-24-17 at 20:35.

  6. #6
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    Failure to Feed...cartridge slamming into feed ramp

    I updated the title as I appear to have fixed the extraction problem by replacing the extractor spring. Today I fired 200ish rounds of various types along with four different kinds of magazines. I shot PMC Bronze, GECO 223, American Eagle 223 and IMI m193 5.56 to test the extractor issue. I used Magpul Gen 2 and Gen 3 Pmags of known good service, as well as some D&H and one Lancer mag, also of know good service. Good service meaning I have shot several hundred rounds of various types from these mags without issue. The combination of DH metal mags, with IMI M193 5.56 cartidges resulted in multiple failures to feed...

    Attachment 45256Attachment 45257

    PMC Bronze, AE 223 and GECO all fed okay thru the DH and Lancer mags. The IMI M193 fed without issue from the Gen 2 and Gen 3 Pmags. I changed out bolt carrier groups, again using one of know good service (over 1000 rounds without issue) and the FTF from the DH mag with IMI 556 still occurred.

    I detected no issue with the feed ramps in the upper...

    Attachment 45258

    or the feed lips on the DH mag...

    Attachment 45259Attachment 45260

    Is this simply a bad combination of ammo in magazine? If not, what other possibilities causing this issue...I need some help isolating this problem.

    Thank you,

    NC

  7. #7
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    Attached is an additional pix of the M193 cartridge measured with a caliper.

    Attachment 45263

  8. #8
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    2.254'' is fine. Those rounds with setback are scary. Setback can cause an over-pressure situation.

    If it only happens with the DH mags, I'd get rid of them. One reason why I like the Magpul gen M3 mags is that they hold the round more nose up than any other mag I've seen (Lancers, various GI, older Magpul ect).

    I'd like to hear other's input as well.

  9. #9
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    At this point I would use the power of reasonable deduction. If that ammo works in other mags and not the D&H, I would probably relegate them to training or range use until it's sorted out.



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  10. #10
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    Quote Originally Posted by Iraqgunz View Post
    At this point I would use the power of reasonable deduction. If that ammo works in other mags and not the D&H, I would probably relegate them to training or range use until it's sorted out.
    The mags or the ammo? Or both? I'm also concerned something is awry with the upper...anything to look for on the upper that could cause this?

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