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Thread: Odd 10.5 SBR issues

  1. #11
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    Check the Ejector and also what extractor spring do you have? I would skip the O-ring and get some Colt Gold springs.

    Quote Originally Posted by Jmacken37 View Post
    Hope I don't come across as a dick, but this is exactly why an 11.5" barrel is really the right way to go with a SBR/MG/Pistol. The only 10" gun I've had work perfectly was the HK416.
    My DD Mk18 ran amazingly even though it was overgassed.

    Quote Originally Posted by bigredneck61088 View Post
    99% sure they were both live rounds, the failure to extract from the chamber seemed to have went away since the gas port was opened, just now sometimes fail to eject from the receiver


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    Do you happen to know the gas port size?
    Last edited by sinlessorrow; 09-07-13 at 02:02.
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  2. #12
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    First thing's first. Terminology, terminology, terminology. Now that we have that out of the way.

    1. Double Feed- two live rounds occupy same place same time. This is magazine related.

    2. Failure to Extract/Failure to Feed- Spent casing has remained in chamber and live round feeds into it. This is more than likely the extractor/extractor spring.

    3. Spent casing in chamber/Stovepipe- This is a failure of the ejector. If the ejector feels mushy or there is little resistance then you need a new spring.

    I would try and ascertain the port size. If it is conservative then you will probably need to run 5.56 only, not .223. I believe that the port size on the Crane uppers are around .071-.073. As a comparison many of the 10.5's I have seen were closer to .080-.082.

    A few years back Paul from BCM explained why they don't do the 10.5". They will run but they are definitely more finicky. 11.5" gives you something like 40% more dwell time over the 10.5".

    I would get magazines that you know for a fact are 100% reliable. I would then lube the BCG correctly and then I would run several mags of 5.56 ammo (M193 or M855). Then you need to observe and document the malfunctions to narrow it down.

    You should be able to run an H2 buffer in that set up.



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  3. #13
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    Quote Originally Posted by sinlessorrow View Post
    Check the Ejector and also what extractor spring do you have? I would skip the O-ring and get some Colt Gold springs.


    My DD Mk18 ran amazingly even though it was overgassed.


    Do you happen to know the gas port size?
    Stock centurion arms m16 BCG, no ejector/extractor upgrades

    No, It was under gassed i believe from centurion and would short stroke/fail to lock even with a carbine buffer. I inquired the size of the port before and after them opening it, and never received a reply with sizes. I They stated they would open it up a bit to fix the issue, and it did. I read somewhere else that factory 10.5 centurions measure .062 but unsure whether truth or not.
    Last edited by bigredneck61088; 09-07-13 at 06:56.

  4. #14
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    Quote Originally Posted by Iraqgunz View Post
    First thing's first. Terminology, terminology, terminology. Now that we have that out of the way.

    1. Double Feed- two live rounds occupy same place same time. This is magazine related.

    2. Failure to Extract/Failure to Feed- Spent casing has remained in chamber and live round feeds into it. This is more than likely the extractor/extractor spring.

    3. Spent casing in chamber/Stovepipe- This is a failure of the ejector. If the ejector feels mushy or there is little resistance then you need a new spring.

    I would try and ascertain the port size. If it is conservative then you will probably need to run 5.56 only, not .223. I believe that the port size on the Crane uppers are around .071-.073. As a comparison many of the 10.5's I have seen were closer to .080-.082.

    A few years back Paul from BCM explained why they don't do the 10.5". They will run but they are definitely more finicky. 11.5" gives you something like 40% more dwell time over the 10.5".

    I would get magazines that you know for a fact are 100% reliable. I would then lube the BCG correctly and then I would run several mags of 5.56 ammo (M193 or M855). Then you need to observe and document the malfunctions to narrow it down.

    You should be able to run an H2 buffer in that set up.
    Just to clarify, before opening it up, the gun would fail to extract from the chamber. Now the gun fails to eject from the ejection port, and causes a jam on top of the bolt with an attempt to clear.

    I was never able to get an exact port size from centurion through email, as I asked just so i could reference it in later posts, as it is a big topic with the short guns. I heard .062 stock from other users, but that is hearsay until I know for sure.

    Hypothetically assuming, say the double feed is indeed from the magazines, would it be safe to say it is an extraction/ejection issue? Or do you think more is going on? I have a hard time getting past a new bcg already needing parts, but that's why I posted here for the pros. I do plan on going back and taking better notes while shooting, just wanted to pick some brains for the time being until i made it there.

    Thanks!
    Last edited by bigredneck61088; 09-07-13 at 07:18.

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    Quote Originally Posted by Jmacken37 View Post
    Hope I don't come across as a dick, but this is exactly why an 11.5" barrel is really the right way to go with a SBR/MG/Pistol. The only 10" gun I've had work perfectly was the HK416.
    My 10.5 inch LMT has given me exactly two failures to feed in roughly 5k rounds. And the FTFs were due to it being overly dirty from suppressed use.

    10.5s can be very reliable, but I agree they can be more finicky than an 11.5.

    N of 1 and not a scientific sample, I know.
    Last edited by JoshNC; 09-07-13 at 11:08.

  6. #16
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    If you want a fresh set of eyes to look at it send me a PM. I'm the SBR Whisperer as someone once called me.
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  7. #17
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    Quote Originally Posted by bigredneck61088 View Post
    ...Hypothetically assuming, say the double feed is indeed from the magazines, would it be safe to say it is an extraction/ejection issue?...
    A double feed is NOT an extractor/ejector issue. It is strictly a mag issue. A double feed occurs when the mag pops out two live rounds when the bolt tries to chamber the next round.

    It sounds like your current issue is a failure to eject. The spent case is extracted from the chamber but is not ejected and the unejected empty jams the action when it tries to strip the next round from the mag and chamber it and causes the rifle to malfunction. In this instance, there will be a spent round and a live round jamming up the works
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  8. #18
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    Quote Originally Posted by Jmacken37 View Post
    Hope I don't come across as a dick, but this is exactly why an 11.5" barrel is really the right way to go with a SBR/MG/Pistol. The only 10" gun I've had work perfectly was the HK416.
    His barrel length is not the issue. I also have a DD MK-18 that runs like a sowing machine. Double feeds are almost exclusively mag related. I've used an H & H2 buffer with a normal carbine spring, and with a Springco Blue enhanced buffer spring to increase lock time and slow the cyclic rate, with no extractor or lock back issues. Stuck cases or stove pipes are extractor or ejector issues. That makes me think he needs either a 5 coil spring with a black insert or O ring, but not both, and test or replace the ejector.
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  9. #19
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    Re: Odd 10.5 SBR issues

    Quote Originally Posted by MistWolf View Post
    A double feed is NOT an extractor/ejector issue. It is strictly a mag issue. A double feed occurs when the mag pops out two live rounds when the bolt tries to chamber the next round.

    It sounds like your current issue is a failure to eject. The spent case is extracted from the chamber but is not ejected and the unejected empty jams the action when it tries to strip the next round from the mag and chamber it and causes the rifle to malfunction. In this instance, there will be a spent round and a live round jamming up the works
    Sorry to not be clear, assuming the double feed is from the magazines, is it safe to say the bcg/ejector/extractor is causing the ejection issues? And the upper is not the culprit at this point?



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  10. #20
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    Re: Odd 10.5 SBR issues

    So this is an unscientific test, but compared to a factory lmt m16 bcg, and a factory armalite ar15 bcg, the spring on the ejector seems slightly weaker on my centurion bcg, anyway to test this for sure? I never ran the gun the second time after being shipped back with a different bcg.... Dumb question but can I buy an upgraded ejector spring only?

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