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Thread: Intermittent Failure to Extract on Colt LW Carbine

  1. #1
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    Intermittent Failure to Extract on Colt LW Carbine

    Long time reader, first time poster...great site, gentlemen.

    I've done the search feature and have read around 10 threads dealing with similar issues.

    What I have...and not completely Colt:

    Colt upper w/ DD LW HF 16" barrel (carbine gas)
    BCM guts (BCM BCG + CH)
    Colt Lower (all factory + H2 buffer)

    This build is new and a backup to an identical build. Upper was assembled by Specialized Armament. Factory springs in all components and well lubed with SLIP EWL.

    The problem:

    First range session, 100 rounds and no issues; sight in and function check. Second range session and one FTE spent casing at round 70; extractor tore the rim off. Popped out easily with cleaning rod. Did single round mag test to check pressure and got 10 consecutive solid lockbacks. Cleaned the weapon, cleaned chamber thoroughly and hand polished the chamber with a cotton chamber brush and a little Flitz to smooth out any roughness.

    Back to range (third trip), made it through 140 rounds, FTE; extractor tore the rim off. Shooting was consistent with some rapid fire (doing some drills) and the upper was plenty hot.

    Ammo used is Aguila 55 grain .223 and I've got a few thousand rounds of this on my identical build with no issues. Aguila tends to run on the hot side for .223.

    I'm thinking the issue may be a tight chamber, but would like to know what some of experts here think before I contact Mr. Elmore and he yells at me for not using a Colt barrel and Colt BCG.

    Thank you for the help, gentlemen.
    Last edited by Slimcakes; 01-12-14 at 18:07.

  2. #2
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    I'm actually surprised Ken put this upper together since he generally frowns upon non Colt components.



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  3. #3
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    Maybe not enough dwell? (Case still swollen when extraction is happening). You try any different buffers?

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    Quote Originally Posted by Leaveammoforme View Post
    Maybe not enough dwell? (Case still swollen when extraction is happening). You try any different buffers?
    So it could be possibly over gassed...bolt cycling to fast? I was thinking that was possible, but last I read on here, out of spec DD barrels were a thing of many years ago and gas ports are .062-.063. H3?

    IG, yes, Ken has put together two uppers like this for me, and the other runs great.
    Last edited by Slimcakes; 01-13-14 at 12:40.

  5. #5
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    First thing I would do is try different ammo regardless. I'm assuming all components were new? Ripping the extractor rim off concerns me.



    Owner/Instructor at Semper Paratus Arms

    Facebook: https://www.facebook.com/SemperParatusArms/

    Semper Paratus Arms AR15 Armorer Course http://www.semperparatusarms.com/cou...-registration/

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    Master Armorer/R&D at SIONICS Weapon Systems- http://sionicsweaponsystems.com

  6. #6
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    Quote Originally Posted by Iraqgunz View Post
    I'm assuming all components were new? Ripping the extractor rim off concerns me.
    Yes, all components are new.

    On the Aguila, I initially bought a case of the stuff for my other carbine (identical one) and it ran wonderfully, going 300+ rounds with no cleanings and no issues. That led to me buying a shit ton of it (good deal) and still have plenty on hand. Probably be a week before I work up another ammo order and receive it.

    ETA: Here's another detail and it skipped my mind. When I first put things together, lower to upper with bcg, I hand cycled a few rounds for function and the bolt was stuck briefly and took some force to rip it open (one hand). I chucked it up to being new and fresh, but now with these recent FTEs...tight chamber.
    Last edited by Slimcakes; 01-12-14 at 20:49.

  7. #7
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    Quote Originally Posted by Slimcakes View Post
    Long time reader, first time poster...great site, gentlemen.

    I've done the search feature and have read around 10 threads dealing with similar issues.

    What I have...and not completely Colt:

    Colt upper w/ DD LW HF 16" barrel (carbine gas)
    BCM guts (BCM BCG + CH)
    Colt Lower (all factory + H2 buffer)

    This build is new and a backup to an identical build. Upper was assembled by Specialized Armament.

    How did you convince him to build you an upper with non Colt parts?
    "Not every thing on Earth requires an aftermarket upgrade." demigod/markm

  8. #8
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    Quote Originally Posted by scottryan View Post
    How did you convince him to build you an upper with non Colt parts?
    I wanted a DD hammer forged barrel with a Colt upper, so I just sent an email and asked. I sent the barrel and got it mated to a Colt upper in the shop.

    BCM guts and Colt lower were purchased elsewhere via some LE discounts I get.

  9. #9
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    What do the rims on your fired cases look like?
    My brother saw Deliverance and bought a Bow. I saw Deliverance and bought an AR-15.

  10. #10
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    Quote Originally Posted by Heavy Metal View Post
    What do the rims on your fired cases look like?
    I've consulted this chart/picture:

    http://www.ar15barrels.com/prod/operation.shtml

    None of the cases look 'that' tore up and I inspected many at the range.

    On the two case that FTE'd, there is just a chunk missing from the rim where the extractor grabbed it and some vertical lines/wear marks running the length of the case.

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