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Thread: Misfire central...Check out the dents on this brass

  1. #11
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    Quote Originally Posted by AKDoug View Post
    The swipes on the base of the brass, combined with the dents mid-length down the brass from the brass deflector, are both signs of over pressure.

    How does it perform with other ammo?
    Well, now that I think of it I also fired some Winchester M193 and had the same result. I don't have any standard .223, because I train with what I will deploy the rifle with. I do remember reading that some early runs of E3's had trouble cycling some .223 because they were tuned and tested with 556. It has me wondering if what they did to help rectify that situation is now showing some over pressure issues with some 556? I don't want to get ahead of the curve...I honestly have no clue what the issue really is which is why I posted.

  2. #12
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    It seems to me like your BCG is cycling too fast which is why the cases are getting dented - they're hitting the back of the ejection port or the base of the deflector. In the case of a stovepipe, they're bouncing back into the ejection port where the bolt closes on them. I wouldn't say its because of overpressure per se - I've seen a lot of factory ammo show mild ejector swipes: IMI M855, PPU M193, various LC heasdstamps, etc. Too much gas drive is a better explanation I think, although too much gas drive could be a function of overpressure. The gas port could be a little big or the action spring could be weak/short.

    What they would do is open the gas port which, yes, could contribute to the issue if that's what was done.

    Quote Originally Posted by O3SKILL View Post
    I do remember reading that some early runs of E3's had trouble cycling some .223 because they were tuned and tested with 556. It has me wondering if what they did to help rectify that situation is now showing some over pressure issues with some 556?
    Have you spoken to anyone at KAC? Maybe F2S can help you out.
    Last edited by Eric D.; 09-18-13 at 02:45.
    B.A.S. Mechanical Engineering Technology

  3. #13
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    It's over gassed, bolt cycles to fast not giving enough time for ejector to kick the brass. The dents left on the brass are from slamming into the brass deflector and are to strong.

  4. #14
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    Quote Originally Posted by O3SKILL View Post
    Factory new Rifle, cleaned, well lubed, gas key tight/staked, gas block tight/straight/pinned, barrel, barrel nut and rail all appears to be properly installed and tight. Took it to the range for a BZO, fired around 35-40rds, accuracy compared to my norm was disappointing, overall extraction was pretty weak with intermittent FTE's, stovepipes, one double feed. Ammo was 2011 Winchester RANGER M855 (all of my other 556 AR's love it), mags used were known good magazines both USGI and PMAGS. I've never experienced any problems with a AR-15 like this before. Always used high quality weapons, parts etc and good quality ammo and mags. Looking at the brass it seems that there is something in the chamber that is denting/gouging into the brass and causing the extraction problems. The flash is drowning, but there are also scratches down the length of the brass on the same side as the dents and some gouging on the case rim from the extractor having to work hard.

    What do you malfunction guru's think is going on. Chamber out of spec?







    Normal marks but extreme dents.
    The lengthways scratches comes from the round being drug over the barrel extension lugs. The dent as big as it is comes from an over-gassed rifle slamming them into the rear of the ejection port.
    If those dents have a sharp line they are hitting the rear of the port. If rounded they come from the shell deflector. I think the gas port in the barrel is too large. Try an adjustable gas block to cut back on some of the gas.
    AR15performance
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    The 6.8 is the best choice for hunting deer and hogs with an AR15.

  5. #15
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    Quote Originally Posted by constructor View Post
    Normal marks but extreme dents.
    The lengthways scratches comes from the round being drug over the barrel extension lugs. The dent as big as it is comes from an over-gassed rifle slamming them into the rear of the ejection port.
    If those dents have a sharp line they are hitting the rear of the port. If rounded they come from the shell deflector. I think the gas port in the barrel is too large. Try an adjustable gas block to cut back on some of the gas.
    This is good information to know. As an armorer I have been able to make rifles work, but I am still learning the technical aspect of being over/under gassed.
    Train 2 Win

  6. #16
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    I should have expanded a little.
    A weak or sticking ejector and or overly strong extractor could cause larger than normal dents in the cases too but with other symptoms like poor accuracy and sticking cases the "over-gas" alarm is ringing pretty loud.
    AR15performance
    TRUMP 2020
    The 6.8 is the best choice for hunting deer and hogs with an AR15.

  7. #17
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    Thanks to all that responded. Some great info and it makes total sense to me now as to what is actually occurring.

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