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AR Pistol Issue

Discussion in 'Maintenance & Gunsmithing' started by cascadianliberty2012, Jan 7, 2016.

  1. cascadianliberty2012

    cascadianliberty2012 DPR Portland Well-Known Member

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    I set up a 10.5" AR pistol recently (5.56/.223) as an 80% build (this is not my first 80%), with a factory upper and upon testing it, I got about 20 rounds through it before I started getting light primer strikes (light enough to see a faint mark, but not strong enough to even hear any click of the trigger/hammer) with every round the gun would chamber. It shoots the first shot that I manually chamber with the charging handle or bolt release, but every subsequent shot has the aforementioned issue. Here are the things I've tried:
    - Complete de-lubing and light lubing.
    - Different BCG.
    - Holding the bolt catch release down while shooting (this was an issue on a previous build that necessitated the slight filing-down of the catch).
    - Using the forward-assist button.
    - Different types of ammo.
    ^^^All of these have had ZERO effect on the issue in question. Again, if I manually cycle the BCG, that round will fire without issue. So, overall, when it cycles, it will successfully load a new round and eject the old one, but the new chambered round will receive a light primer strike and will not be set off.

    Has anyone encountered a similar issue? From those I've talked with already it sounds like either a hammer/hammer spring issue or a gas issue. How do I go about troubleshooting this more?
     
  2. Velzey

    Velzey Estacada, Oregon Gunsmith Gunsmith Bronze Vendor Bronze Supporter

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    I have had brand new hammer springs fail within one magazine! So I would start there.
     
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  3. cascadianliberty2012

    cascadianliberty2012 DPR Portland Well-Known Member

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    Would the failure be obvious? I'll check that now...
     
  4. cascadianliberty2012

    cascadianliberty2012 DPR Portland Well-Known Member

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    This one is a mil-spec, from a CMMG lower parts kit.
     
  5. Velzey

    Velzey Estacada, Oregon Gunsmith Gunsmith Bronze Vendor Bronze Supporter

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    The failure is obvious.. The hammer isn't hitting the primer hard enough, if it's the spring.

    Remove a bullet from a primed case, chamber it. Close the bolt by hand and use the forward assist if it has one to help close the bolt all the way. Pull the trigger.
     
  6. Medic!

    Medic! What just happened? Has eagle eyes. But cant remember what he saw. Bronze Supporter

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    I'm with Velzey. A spring problem should be ruled out.

    Three coil 3.5lb spring? Or four coil 5lb spring?
    Is the spring installed correctly?

    Edit: Also It may help to go read the ''Dent on primer'' thread in this same section.
     
    Last edited: Jan 7, 2016
  7. cascadianliberty2012

    cascadianliberty2012 DPR Portland Well-Known Member

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    That's how it's looking. It doesn't appear cracked or anything.
     
  8. Medic!

    Medic! What just happened? Has eagle eyes. But cant remember what he saw. Bronze Supporter

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    When you pull the trigger but it doesn't fire. Use the forward assist to see if you can move the carrier forward slightly. In other words find out if the bolt carrier is all the way into battery?

    Also what kind of buffer spring?
    Titanium firing pin?
     
  9. Dyjital

    Dyjital Albany, Ore Flavorite Member Bronze Supporter

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    Nah nah nah...

    You all are wrong.;););););););) Ease up, don't get mad.

    Floating firing pin. You know what that does...

    Then how about the gas block and barrel not aligned properly now. ???

    Seriously, that's what it sounds like to me.

    I'm sure I'm missing some key piece of evidence that's keeping me from agreeing with you guys. Read the OP five times and that's what it sounds like is happening.


    See:
    https://www.northwestfirearms.com/threads/dent-on-primer.180276/
     
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  10. Medic!

    Medic! What just happened? Has eagle eyes. But cant remember what he saw. Bronze Supporter

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    If the primer has a small mark then it should be going into battery.
    You said there is no click when you pull the trigger?

    That sounds like the trigger is not resetting?

    So. With the gun made safe. And the hammer dropped. Pull and hold the trigger.
    Use the charging handle to pull the carrier back and supposedly cock the hammer.
    All the time holding back the trigger.
    Let the bolt go forward. When the bolt is forward back in battery. Let off the trigger.
    You should hear an audible click.
    Then pull the trigger. You should here the hammer fall.

    Do this five or so times to make sure the hammer catches wile the trigger is pulled.
    Just as it would have to do when you shoot your second or subsequent shots.
     
    cascadianliberty2012 and Velzey like this.
  11. cascadianliberty2012

    cascadianliberty2012 DPR Portland Well-Known Member

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    I tried the forward assist, nothing.

    I also tried a different BCG, the one from my carbine that I know is functioning, again, the same issue.

    Pistol buffer spring, if that's what you're getting at?
     
  12. Medic!

    Medic! What just happened? Has eagle eyes. But cant remember what he saw. Bronze Supporter

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    Well. Did you check to see if the trigger reset like I posted?

    Edit: In my later post.
     
    Last edited: Jan 7, 2016
  13. cascadianliberty2012

    cascadianliberty2012 DPR Portland Well-Known Member

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    Interesting, something is off, get this: I did exactly what you said and when I let off the trigger... nothing, however then I grabbed the trigger and pushed it forward slightly then I heard the click! So what does this sound like to you? The trigger position is off or something shifted? This was an experimental build for me with a cheap plastic lower that I was given and "finished" with a Dremel. So maybe something is screwed up or needs modding. Thoughts?

    Great test by the way, we've definitely isolated where the issue is.
     
  14. Medic!

    Medic! What just happened? Has eagle eyes. But cant remember what he saw. Bronze Supporter

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    Look down on your trigger group with the upper off the gun.
    Cock the hammer with your thumb wile holding the trigger. Then let off the trigger and see if the disconector lets go of the hammer and hands contron over to the trigger sear?
    It sounds like the hook on the disconector is not letting go of the hammer when you let go of the trigger.

    Easiest thing? A bad trigger disconector. Or some smoothing.

    Or the pin holes not drilled in the wright place?
    I.E. Bad trigger geometry.

    If it was a trigger/hammer sear not catching when the disconector handed the hammer off to the trigger sear. You would hear the hammer drop when you let off the trigger in my earlier test.
     
    Last edited: Jan 7, 2016
  15. cascadianliberty2012

    cascadianliberty2012 DPR Portland Well-Known Member

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    I feel confident in the drill holes.

    How do I check the disconnector?

    So you're saying that it isn't the trigger/hammer sear not catching, so that's ok?
     
  16. etrain16

    etrain16 Oregon Bronze Supporter Bronze Supporter

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    Just watching this thread as a lurker and novice AR builder. So, as I'm hoping to learn from others, how about some photos showing some of the stuff being discussed???

    :s0122:


    ;)
     
  17. Medic!

    Medic! What just happened? Has eagle eyes. But cant remember what he saw. Bronze Supporter

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    It's in the post you quoted.

    The part right after ''Look down on your trigger group with the upper off your gun''.

    It may not have been there when you first read it. I went back and edited it. :D
     
  18. cascadianliberty2012

    cascadianliberty2012 DPR Portland Well-Known Member

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    As good as my phone's camera is, it is HORRIBLE at focusing on anything sort of close to it... I tried.
     
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  19. cascadianliberty2012

    cascadianliberty2012 DPR Portland Well-Known Member

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    Yup, that wasn't there. I'll check once I'm done watching Obama's town hall nonsense. It's a disaster for him btw.
     
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  20. v0lcom13sn0w

    v0lcom13sn0w Keizer, or Well-Known Member

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    add me to the list of thinking its a spring issue