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Thread: Still fighting issues.....

  1. #21
    Warrior
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    It looks like your extractor may be too far into the center of the boltface. Are you sure you don't need a 7.62x39 extractor?
    Here are some photos of the group buy Grendel bolt from this site and a 223 bolt face.
    You can see these extractors are farther from the firing pin than yours.
    IMG_0006 (Medium).JPGIMG_0010 (Medium).JPG

    Edit: Just found this on a search.
    https://www.kakindustry.com/ar-15-pa...2x39-extractor

    And this:
    https://www.ar15.com/forums/ar-15/-/121-463164/&page=1
    Last edited by bj139; 11-03-2017 at 08:33 PM.

  2. #22
    I have the 7.62x39 extractor, just tried the 5.56 to see if it made any difference. Still didn't. So I still have 6.5 grendel that I am fighting cycling issues. I feel like its the chamber since the upper portion of the case is scratched/dull from the previous pictures which I feel could cause an issue once things heat up and start constricting.

  3. #23
    Warrior grayfox's Avatar
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    OP, refresh my memory - how many rounds do you have down the pipe?
    If less than 50 give or take, then a sticky chamber could be part of the issue (maybe this idea has already been covered, I'm coming back to the thread here with memory cells erased - lol.) I had sticky/FTE's on a separate grendel-model, until I had cleaned the chamber and sent 50 downrange, pretty much 1 at a time... then things finally smoothed out as it all broke in.
    Chuck Norris doesn't do push-ups, the earth does push-aways.

  4. #24
    Probably 200 rds. Steel and brass, steel fed the best/most reliable. I have never been real aggressive with polishing the chamber, just used flitz polish but with those marking showing up on the brass it makes me think there is more to be polished.

  5. #25
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    I posted photos of brass from a Grendel barrel I had in a thread called "My Striped Grendel".
    The ridges on the brass were very pronounced and it still ejected fine.

    Is it still sometimes ejecting and sometimes not?

  6. #26
    Warrior grayfox's Avatar
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    I went back to look at BJ's pics and your pics of bolt/extractor... and I see what BJ is talking about, it's like the extractor collapses farther in radially towards the pin. Also, and here I'm not totally sure but is the extr a bit too short length-wise? as in, it seems to not extend fwd to the front of the bolt face-pin surface, is that the case? Finally, what about the groove does its bottom align with the bolt face, seems as though it might not match dimensionally there...
    None of my bolts are the 0.125 sort, all 0.136, so I don't have any to personally examine.
    Chuck Norris doesn't do push-ups, the earth does push-aways.

  7. #27
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    I'm pretty sure the 5.56 extractor and the 7.62x39 / 6.5 Grendel have different circumferences. That is why your extractor is ripping the case rim apart.

    Gotta have the right extractor.
    Sticks

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  8. #28
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    How much do you think a gunsmith would charge to diagnose the problem?
    He could check headspace and determine if it is correct.

  9. #29
    Chieftain
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    Quote Originally Posted by 96superflow View Post
    once things heat up and start constricting.
    Things typically don’t constrict when they heat up.
    Knowing everthing isnt as important as knowing where to find it.

    Mark Twain

  10. #30
    Quote Originally Posted by Sticks View Post
    I'm pretty sure the 5.56 extractor and the 7.62x39 / 6.5 Grendel have different circumferences. That is why your extractor is ripping the case rim apart.

    Gotta have the right extractor.
    I have the correct 7.62x39 extractor, did not matter. The 5.56 was swapped in to see if if anything would change.

    Quote Originally Posted by bj139 View Post
    How much do you think a gunsmith would charge to diagnose the problem?
    He could check headspace and determine if it is correct.
    No idea, I looked into purchasing the go, no go gauges myself just haven't done it yet. I haven't heard of any gunsmiths in my area that are decent to help with the issue.

    Quote Originally Posted by grayfox View Post
    I went back to look at BJ's pics and your pics of bolt/extractor... and I see what BJ is talking about, it's like the extractor collapses farther in radially towards the pin. Also, and here I'm not totally sure but is the extr a bit too short length-wise? as in, it seems to not extend fwd to the front of the bolt face-pin surface, is that the case? Finally, what about the groove does its bottom align with the bolt face, seems as though it might not match dimensionally there...
    None of my bolts are the 0.125 sort, all 0.136, so I don't have any to personally examine.
    I'm sorry I was totally unable to gather what you were asking.

    Quote Originally Posted by rabiddawg View Post
    Things typically donít constrict when they heat up.
    I know its difficult to put into words what I mean, and know that is not what happens. It was the best way I could put it into words to how things happen. The first 10 round or so typically extract and eject fine. After that its a crap shoot.


    I am fixing to be using a 9 oz buffer for my work sbr/suppressed rifle, and may try that buffer in my gun to see if it could be buffer related.

  11. #31
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    Does the rim of a cartridge fit into the boltface when it is out of the bolt carrier?
    Maybe you could pull straight back on a cartridge when holding it into the boltface.
    It should not slip out.
    The extractor groove may not be wide enough or may be below the boltface slightly.

  12. #32
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    It would appear to me that the extractor is levered to far onto the bolt face. The bevel on the extractor is supposed to almost even with the ringed bevel on the bolt.

  13. #33
    96superflow, You mentioned that the extractor tension was lower on your x39 bolt before changing the extractor. Have you tried assembling it with the original extractor and spring/o-ring from the .223 bolt?
    If the extractor springs are weakening (even more) after heating up that could definitely be your problem. However, your testing method of swapping the entire extractor introduces an entirely different problem of having an extractor that isn't tuned for the proper cartridge.

    Put the original extractor in with a new spring/o-ring and test again to rule out low extractor tension as your issue. Also, removing the o-ring would only exacerbate this particular issue
    .

  14. #34
    Quote Originally Posted by ALshooter View Post
    96superflow, You mentioned that the extractor tension was lower on your x39 bolt before changing the extractor. Have you tried assembling it with the original extractor and spring/o-ring from the .223 bolt?
    If the extractor springs are weakening (even more) after heating up that could definitely be your problem. However, your testing method of swapping the entire extractor introduces an entirely different problem of having an extractor that isn't tuned for the proper cartridge.

    Put the original extractor in with a new spring/o-ring and test again to rule out low extractor tension as your issue. Also, removing the o-ring would only exacerbate this particular issue
    .
    I will definitely give this a shot. At this point I am willing to try almost anything.

  15. #35
    Bloodstained
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    by the looks of the rim of the cases and how far the extractor is in towards firing pin, I would also say extractor is not the right one...

  16. #36
    Bloodstained
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    did you take the extractor off and see how it fit the base of the brass ?

  17. #37
    I am certainly no expert in this area however I had this same issue when I built mine. I brought the rifle to my custom barrel maker and he polished the sharp edges off the extractor. Every shell extracted perfectly after that.

  18. #38
    Super Moderator LRRPF52's Avatar
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    Quote Originally Posted by 96superflow View Post
    I have the 7.62x39 extractor, just tried the 5.56 to see if it made any difference. Still didn't. So I still have 6.5 grendel that I am fighting cycling issues. I feel like its the chamber since the upper portion of the case is scratched/dull from the previous pictures which I feel could cause an issue once things heat up and start constricting.
    With MLGS 18" barrels, if the port size is too large, you'll get too much gas into the expansion chamber inside the carrier quickly, which will cause the carrier to begin moving earlier and faster than the optimum window for the gun.

    The brass will still be purchased to the chamber walls under obturation, and it will play tug-of-war with the extractor. The extractor often loses that battle, slips off the case rim, leaving the empty case in the chamber.

    You also have a tighter .295" neck with .264 LBC-AR and imitation chambers based off of Les Baer's chamber, which may or may not be held to Les Baer's spec. BHW told me that they hold strictly to the .264 LBC-AR chamber, but they are at the mercy of the reamer maker unless they measure reamers with optical comparator.

    Anyway, a tighter neck isn't going to help with a MLGS 18" barrel that is ported too large, and even adjustable gas will barely keep it managed sometimes unless you buffer it heavily as well.

    After reading over the thread again and looking at the extractor lip rips in your rim, I think most experienced AR15 trouble-shooters would lean towards your cyclic rate being clocked way too fast.
    Last edited by LRRPF52; 11-18-2017 at 03:47 AM.
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  19. #39
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    Quote Originally Posted by Jakegsxr11 View Post
    I am certainly no expert in this area however I had this same issue when I built mine. I brought the rifle to my custom barrel maker and he polished the sharp edges off the extractor. Every shell extracted perfectly after that.
    I like Johnny's Reloading Bench videos on youtube and he did a series on reloading for his Grendel. He also had problems with the extractor; he was getting inconsistent ejection and it was marking up the rim of the brass. He ground off the sharp edges with a Dremel and it cured the problems.
    I think it was the third video in the series: https://www.youtube.com/watch?v=kMrM...lh4cjTRb-JJmto

  20. #40
    Warrior grayfox's Avatar
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    The situation described by LRRPF52 was what I ran into with my LBC, an 18-er. I tried smoothing the extractor maybe it helped a little... But the real fix was using the Spikes ST2 and the JP polished spring to slow it down and now it runs really well. Don't have an AGB so that's what I had to do.
    Chuck Norris doesn't do push-ups, the earth does push-aways.

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