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Thread: Formerly reliable BCM 11.5" upper has sudden issues PART II

  1. #11
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    2015 ish.

  2. #12
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    If you can feel it cycle slower with one BCG it is probably a gas issue.

    Check the rings and the carrier key bolts.

  3. #13
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    I don’t want to drift this thread to far off, but I have had two new complete BCG’s from the same company that have had their carrier cam pin paths machined slightly out of spec where the pin *very noticeably dragged on the upper much more than normal when pulling back on the CH. I will just say brand wise they are a top tier and don’t get any better. I Put in a new BCM BCG and different brand than previous, and the excessive drag was gone. I also tried the other cam pin in the BCM bolt carrier and again, no drag. So to me it shows that any company can produce stuff out of spec and that gets by their QC program from time to time.
    Last edited by Biggy; 12-20-18 at 00:52.

  4. #14
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    Way late to the thread here...but if I had enough rounds through my AR to wear out the gas tube...I just just "rebuild it" all. New tube, new gas rings, new extractor and new springs. These parts are super cheap. :-) Sorry. I know that prob didn't help. :-)

  5. #15
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    Quote Originally Posted by TomPenguin5145 View Post
    Way late to the thread here...but if I had enough rounds through my AR to wear out the gas tube...I just just "rebuild it" all. New tube, new gas rings, new extractor and new springs. These parts are super cheap. :-) Sorry. I know that prob didn't help. :-)
    Gas tubes can wear prematurely for other reasons. Key misalignment could cause this. And I have had middy gas tube tips wear out in hundreds of rounds. Someone else here experienced the same. The outer diameter wore down and let lots of gas leak out into the rail area. Replaced it, and the gun came back to life.
    "You people have too much time on your hands." - scottryan

  6. #16
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    Quote Originally Posted by markm View Post
    Gas tubes can wear prematurely for other reasons. Key misalignment could cause this. And I have had middy gas tube tips wear out in hundreds of rounds. Someone else here experienced the same. The outer diameter wore down and let lots of gas leak out into the rail area. Replaced it, and the gun came back to life.
    Do I need to consider the type of stainless steel they're made from? I've never heard anyone make a distinction between manufacturers of gas tubes.

  7. #17
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    There are only a couple actual manufacturers of gas tubes that I know of.

  8. #18
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    After installing a new gas tube verify alignment. This is done by removing the bolt from the carrier and inserting the carrier into the upper receiver. It should close smoothly without catching or dragging on the gas tube. If there is a stumble or an audible tick, adjust the gas tube until the tick is gone.
    Proper Planing Prevents Piss Poor Performance.......

  9. #19
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    Quote Originally Posted by 1911-A1 View Post
    Do I need to consider the type of stainless steel they're made from? I've never heard anyone make a distinction between manufacturers of gas tubes.
    No. Like Todd.K said, I've read they're mostly made by the same companies. For what ever reason, there appeared to be some crappy mid length tubes.
    "You people have too much time on your hands." - scottryan

  10. #20
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    Quote Originally Posted by TomPenguin5145 View Post
    Way late to the thread here...but if I had enough rounds through my AR to wear out the gas tube...I just just "rebuild it" all. New tube, new gas rings, new extractor and new springs. These parts are super cheap. :-) Sorry. I know that prob didn't help. :-)
    I tend to agree. A lot of folks live some distance from where they shoot, and many have to pay range fees, that plus the gas money kind of leans me toward making sure I solve the problem versus multiple range trips or rebuilding a part at the range.

    Especially since, based on the OP's description, it is an issue confined to one BCG.

    Check the key for leakage, make sure there is nothing obstructing the gas passage, use the gravity method to check the gas rings. Someplace during this process you should have looked at the extractor, if not, do so now, make sure it isn't chipped and is clean.

    Then, here is my hillbilly way of checking ejectors: BCG placed horizontal in the padded vise, carrier key up, bolt extended. Take an empty case snap the rim under the extractor and press it firmly against the ejector - I use my thumbnail to hol it in place. Then I stand to the side,slide my thumb nail off the case and let it fling. With the bolt fully extended I find the cases generally hit the shop floor about five feet away. I 'developed' this method after reading an article on ejector tuning for service-rifle shooters and decided to try it out.

    I think that mostly you'll find that if anything the ejector is slowed by being cruddy, not the spring sacking out. Generally a disassembly and cleaning will put you back in action. The OEM spring is pretty stout for the job - I've cut up to four coils off an ejector spring and had it still function - don't do this on anything but a rifle shot strictly for fun or competition.

    All that being said, unless you want to get something that has been fondled by a Volcano Virgin, you can buy a bolt rebuild kit for under $20.00.
    Patriotism means to stand by the country. It does not mean to stand by the President... - Theodore Roosevelt, Lincoln and Free Speech, Metropolitan Magazine, Volume 47, Number 6, May 1918.

    Every Communist must grasp the truth. Political power grows out of the barrel of a gun. Our principle is that the Party commands the gun, and the gun must never be allowed to command the Party Mao Zedong, 6 November, 1938 - speech to the Communist Patry of China's sixth Central Committee

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