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Thread: Please help me diagnose this junk!

  1. #31
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    Quote Originally Posted by sinlessorrow View Post
    So what about ammo can cause it when the extractor is fine? As in my case, I had a stovepipe and was trying to feed a new round.
    Conditions where Ammo can cause stovepipes from short stroking
    1) Under powered
    2) sticking in chamber

    Ammo can cause stovepipes due to poor extraction because extractor cannot get a good purchase due to-
    1) Rim diameter being too large or too small
    2) Rim is too thick or too thin
    3) Rim groove is too shallow

    Conditions where ammo can cause stovepipes because the case does not set back against bolt face and does not fully compress ejector-
    1) Rim diameter is too large or too small
    2) Rim thickness is too thin
    3) Ammo headspace is short combined with underpressure load.
    -Usually this means ejection is also weak

    It's rare that case rims are so out of spec they cause problems by themselves. Usually, they are only enough on the high side or low side of the tolerance to exacerbate a slight problem on a rifle that normally functions fine with good ammo.

    The plunger type ejector of the AR applies constant pressure to the rim of the case. As soon as the case mouth clears the forward edge of the ejection port, it begins to eject. In the case of this rifle, either the ejection is weak, or the extractor is holding the case too tightly.

    If this problem were due to overgassing, that is the BCG velocity was too high and closing on the case before it could eject, the BCG velocity would also be too high for proper feeding. This rifle does not appear to have feed problems.

    I do not have a PSA Dissy, but a PSA middy carbine with a SS barrel and a standard rate action spring. When testing heavier buffers, short stroking occurred
    Last edited by MistWolf; 09-22-12 at 12:38.
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  2. #32
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    Though they make the barrels I believe that tha gas ports are specified by the end user and in some cases the ports are not pre-drilled.

    Quote Originally Posted by vicious_cb View Post
    What kind of barrel is it? Because I doubt an FN HF barrel would have those kinds of issues.



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  3. #33
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    A 16" shouldn't probably exceed. 078 pr so AFAIK.

    Quote Originally Posted by Clint View Post
    You don't really need calipers, just a set of drill bits.

    Measuring the barrel gas port size

    We're interested in finding if the port is in the range of .063" to .093"



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  4. #34
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    Quote Originally Posted by Iraqgunz View Post
    A 16" shouldn't probably exceed. 078 pr so AFAIK.
    Exactly.

    This barrel is a 16" car, so port should be at the bottom of the range.


    My money is on .093", the standard size for rifle hand guards.
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  5. #35
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    Gentlemen, If I might...
    Years ago, I had a 16" "XM" from a place in Texas called "Old Sarge". Original Palmetto billet receiver. This was before anyone was making any kind of lower. Even before E.A. and Olympic were available. (I know, dang it, I'm old! So At ease with any comments. Thank You.)
    Anyhow, I had the same problem. Fail to extract malfunction quite often. And we checked everything there was to check. Clue was the brass would show an extractor divot and pull-over. Ah! we (Good friend helping me) thought the rifle was over gassed. Pulled FSH and checked gas port. I don't recall the port size but I do remember it was OK for a carbine. Seems like it was bigger than a standard 20" but only some. Well within todays standard. It was pushing a lot of gas for it's size, we knew. You should have seen it in the dark. Almost as much exhaust port flash, as muzzle flash. but what was driving us crazy is the fact that it would just do the fail to extract malfunction when it wanted to. No clue as to when or why it would malf. Being young and not having the correct measuring tools at the time, the Guys at "Old Sarge" said to send in the barrel and they would look at it. That was a good group back then, they always took care of the customer.
    Anyway, I got the barrel back and 2 things "Old Sarge" guys told me; 1. It was not one of their barrels and 2. The chamber was out of spec! The chamber dimension was out of round! Now this was long before the 5.56/.223 prob had reared it's head, and what was happening was this: Upon cartridge ignition and primary pressurization, the brass case would swell and obturate into the out of spec chamber dimension. Upon gas bleed off with bullet exit and bolt exhuastion, the brass case would relax it's chamber dimenision and be extracted out of the chamber by bolt funtion, But in this rifle's case, the out of std dimension in the chamber was enough to keep the brass from extracting! Just like a seized case. What drove us crazy was a person could clear the jammed 2nd feed round, drop the bolt on the case in the chamber, and then just extract it normally. Maddening, it was. But we fixed it after that. Quality barrel and the rifle was up and running for years, with NP from then on. That taught me a lot about sub par parts, and I have been somewhat anal about parts not being TDP after that.
    Might be something to look at, maybe? Out of dimension chamber perhaps? Just a thought. Good luck.
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  6. #36
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    To the OP, try another buffer spring.
    Last edited by DatDamnAzn; 09-21-12 at 20:34.

  7. #37
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    Take the BCG out and hook a case under the extractor then compress the ejector, the opposite motion of ejection until the case is in full contact with the bolt face. Now let the ejector push the case away from the bolt face, slowly, you are feeling for binding. The case should move freely under the effects of the extractor and ejector. If the extractor grips the case tightly it won't release and will retain the case in the action. If the ejector fails to push the case the extractor will hold the case which will not clear the action. A too tight extractor can be remedied with a little abrasive paste on a case and a little elbow grease, twisting the rim and paste under the extractor. A sticking ejector can sometimes be freed by soaking the boltface in lube and working the ejector in and out, in and out.
    Last edited by Suwannee Tim; 09-21-12 at 20:15.

  8. #38
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    Quote Originally Posted by nickdrak View Post

    When I initially got the gun I checked the extractor and the claw was chipped and rounded off.
    This gets my vote for the primary problem. Try a well made extractor. I would also try a H3.

    ETA: Was this extractor already replaced? It is unclear in the thread.
    Last edited by P2000; 09-21-12 at 21:43.

  9. #39
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    Quote Originally Posted by Iraqgunz View Post
    A 16" shouldn't probably exceed. 078 pr so AFAIK.
    really? .078? I know colt 6920's run .062"
    Quote Originally Posted by C4IGrant View Post
    Colt builds War Horses, not show ponies.
    Quote Originally Posted by Iraqgunz View Post
    This is 2012. The world is going to end this December and people are still trying to debate the merits of piece of shit, cost cutting crap AR's. Really?

  10. #40
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    Nick, check the bolt face recess and make sure it's not too small. Just hook a bunch of ctgs under the extractor with the bolt out and see if any are tight if you can't measure it, but better to measure of course. I'll have to check the print but I think it's supposed to be .380 to .385. I did have one that was like .376 which is actually smaller than the max rim diameter, so some cases were sticking in it real bad and would not eject.

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