AR 5.56 chambering but not firing

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  • PorP

    Active Member
    Mar 11, 2016
    197
    Im pretty perplexed.

    The gun was running fine then about 2/3 magazine through it would chamber the round but not fire. I would have to pull the charging handle back a few inches to fire and this happened every round after that 2/3 magazine.

    It almost felt like a hammer set issue

    I got home and tried to replicate it by hand charging with different to no pressure on the trigger with no luck, it either reset or set fine. I charged with the empty magazine to see if it was rubbing but no joy there either. I inspected the trigger group and it seems fine.

    I can't figure this out.

    It's a newer style Adams stainless trigger group

    Band new amend2 magazine

    In an AR I've put a few hundred rounds through.

    Any help is greatly appreciated.
     

    GuitarmanNick

    Ultimate Member
    Jan 9, 2017
    2,221
    Laurel
    Sounds like you are getting light primer strikes. I suspect the hammer spring may be too weak in your new trigger group.
     

    PorP

    Active Member
    Mar 11, 2016
    197
    P.s.

    I have a fairly heavy buffer spring in it but ruled that out because it chambered the round.....

    In case my addington is wrong.
     

    PorP

    Active Member
    Mar 11, 2016
    197
    Sounds like you are getting light primer strikes. I suspect the hammer spring may be too weak in your new trigger group.

    Thanks for the reply but not that, after the new round is chamber, the trigger can't be pulled.

    Pulling the charging handle back was to set the trigger, not refire on a struck round

    I should have been more clear

    It's either the hammer is following the bolt or the bolt is not seating,
     

    357Max

    Active Member
    Feb 28, 2019
    211
    Crownsville
    Need more specifics on your rifle. Is it piston or gas?
    Was this trigger a new addition or has it always been in the rifle? What bolt carrier is in it? What safety selector? Have any of these 3 items been changed prior to the problem starting? Also has the buffer tube length, spring, or buffer been changed? If so what was changed?
     

    PorP

    Active Member
    Mar 11, 2016
    197
    Need more specifics on your rifle. Is it piston or gas?
    Was this trigger a new addition or has it always been in the rifle? What bolt carrier is in it? What safety selector? Have any of these 3 items been changed prior to the problem starting? Also has the buffer tube length, spring, or buffer been changed? If so what was changed?

    Good questions!

    Is gas, no parts new beyond magazine.

    Entire upper with BCG was a bear creek 7.5"

    Lower is Anderson, I bought the lower and installed a separately bought complete Adams lower kit to install (including safety and mag release)

    The brace and buffer tube is sba3.
     

    clandestine

    AR-15 Savant
    Oct 13, 2008
    37,031
    Elkton, MD
    I'm betting the gas key is loose or the gas block walked.

    There are way too many checks to accurately figure this out sight unseen though.
     

    PorP

    Active Member
    Mar 11, 2016
    197
    I'm betting the gas key is loose or the gas block walked.

    There are way too many checks to accurately figure this out sight unseen though.

    When I manually reset the trigger it fires fine and loads the next round fine. Just can't pull the trigger again without manually resetting it.

    Maybe that's a gas block issue but I'm not sure I understand how since the BCG needs to travel 1/2 as far to lock the hammer add it does to chamber the round.

    Help in understand the comment would be appreciated.
     

    clandestine

    AR-15 Savant
    Oct 13, 2008
    37,031
    Elkton, MD
    When I manually reset the trigger it fires fine and loads the next round fine. Just can't pull the trigger again without manually resetting it.

    Maybe that's a gas block issue but I'm not sure I understand how since the BCG needs to travel 1/2 as far to lock the hammer add it does to chamber the round.

    Help in understand the comment would be appreciated.

    I didn't catch that part. So your saying the disconnect won't release the hammer or the hammer didn't stay cocked?

    This may be a FCG issue. Are there KNS pins in the FCG?
     

    357Max

    Active Member
    Feb 28, 2019
    211
    Crownsville
    Sorry if someone already asked this, but does it lock bolt carrier back on last round out of empty mag?

    It could have a gas problem but if it's cycling in a new round then it should be cocking the hammer. Seems like a reset issue.

    Does this look like your trigger? Adams arms doesn't list a trigger like this on their site.
    https://www.primaryarms.com/anderson-manufacturing-hammer-and-trigger-kit-am-hammer-trigger-kit

    If that looks like your trigger, then read the reviews in the link. About half describe a similar reset problem.

    Make sure the correct disconnector spring is installed and installed properly. Should be a tapered spring with large end down.

    If the spring is still in their and in correctly then pull the whole trigger group out, put it in a little box, take a Black sharpie, and write junk on the box. Save it though and if you ever take a build or armorers class from Clandestine (Chad) give it to him.

    I'd recommend this one to replace it. For $80.00 bucks you get a lot of juice for the squeeze and it's a really nice squeeze comparable to $200 triggers.

    https://www.larue.com/products/larue-tactical-mbt-2s-trigger/
     

    jrhzn

    Banned
    BANNED!!!
    Aug 17, 2017
    280
    When I manually reset the trigger it fires fine and loads the next round fine. Just can't pull the trigger again without manually resetting it.

    Maybe that's a gas block issue but I'm not sure I understand how since the BCG needs to travel 1/2 as far to lock the hammer add it does to chamber the round.

    Help in understand the comment would be appreciated.

    If you're saying that the only way to operate the rifle is to operate the rifle as a bolt action (pull charging handle, pull triggger, pull charging handle, pull trigger) then somewhere along the DI system there is a failure or blockage. Gas is not getting to the BCG.
     

    PorP

    Active Member
    Mar 11, 2016
    197
    I didn't catch that part. So your saying the disconnect won't release the hammer or the hammer didn't stay cocked?

    This may be a FCG issue. Are there KNS pins in the FCG?

    On you first question, that's what im saying. And it loads the next round fine. I'm not sure, there wasnt enough light for my old man eyes to see inside the carrier cut out to see what position the hammer was in.

    I'm also at believing it's a FCG issue, it's just word to me I cannot replicate it manually.

    Im not sure the acronym KNS but the are anti- roll pins holding the FCG in place.
     

    PorP

    Active Member
    Mar 11, 2016
    197
    If you're saying that the only way to operate the rifle is to operate the rifle as a bolt action (pull charging handle, pull triggger, pull charging handle, pull trigger) then somewhere along the DI system there is a failure or blockage. Gas is not getting to the BCG.

    For clarity....

    I pull the trigger. The round is fired, spent case ejected, new round is chambered.

    At this point the trigger will not travel.

    When I said im pulling the charging handle, I'm only pulling it fast enough to set the trigger but not fast enough to eject the round.
     

    PorP

    Active Member
    Mar 11, 2016
    197
    Sorry if someone already asked this, but does it lock bolt carrier back on last round out of empty mag?

    It could have a gas problem but if it's cycling in a new round then it should be cocking the hammer. Seems like a reset issue.

    Does this look like your trigger? Adams arms doesn't list a trigger like this on their site.
    https://www.primaryarms.com/anderson-manufacturing-hammer-and-trigger-kit-am-hammer-trigger-kit

    If that looks like your trigger, then read the reviews in the link. About half describe a similar reset problem.

    Make sure the correct disconnector spring is installed and installed properly. Should be a tapered spring with large end down.

    If the spring is still in their and in correctly then pull the whole trigger group out, put it in a little box, take a Black sharpie, and write junk on the box. Save it though and if you ever take a build or armorers class from Clandestine (Chad) give it to him.

    I'd recommend this one to replace it. For $80.00 bucks you get a lot of juice for the squeeze and it's a really nice squeeze comparable to $200 triggers.

    https://www.larue.com/products/larue-tactical-mbt-2s-trigger/

    357, no one asked and the answer is that it locked just fine on the empty mag. Thanks for the link. I'll dig into it.

    Like I just replied to clandestine with, I had narrowed down to the trigger group but not being able to replicate it when manually cycling the gun confused me.

    I will also look into the FCG you recommended.

    Thanks greatly!
     

    3paul10

    Ultimate Member
    MDS Supporter
    Mar 6, 2012
    4,879
    Western Maryland
    I'll get in on this....anti-rotation pins suck, the pins are supposed to rotate, this may be one issue....if I read all this correctly the trigger will not reset after a round is fired....it may also be a bad trigger spring. As said already, it's really tough to diagnose a problem with out a) shooting the gun and b) having the gun in your hands and going thru a check list of possible problems, etc.....
     

    3paul10

    Ultimate Member
    MDS Supporter
    Mar 6, 2012
    4,879
    Western Maryland
    ...my apologies is asked, is this a factory gun or a home built gun? I have found that Anderson trigger springs are garbage and I won't use them, just an example..
     

    clandestine

    AR-15 Savant
    Oct 13, 2008
    37,031
    Elkton, MD
    On you first question, that's what im saying. And it loads the next round fine. I'm not sure, there wasnt enough light for my old man eyes to see inside the carrier cut out to see what position the hammer was in.

    I'm also at believing it's a FCG issue, it's just word to me I cannot replicate it manually.

    Im not sure the acronym KNS but the are anti- roll pins holding the FCG in place.

    Anti Rotation Pins can cause this issue. They prevent rotation. Rotation is part of the design.

    This is a long video, but watch it. It addresses a proper FCG Install.


    https://youtu.be/zviir5N8Q-c
     

    calicojack

    American Sporting Rifle
    MDS Supporter
    May 29, 2018
    5,348
    Cuba on the Chesapeake
    PopP, does a simple trigger functions check pass?

    From https://www.opticsplanet.com/howto/how-to-clean-ar15-inspection-and-function-check.html

    1. Make sure the rifle is clear.
    2. Place the selector switch on fire and squeeze and hold down the trigger. You should hear the hammer striking the firing pin.
    3. While still holding the trigger, pull the charging handle fully to the rear and let go to reset the hammer.
    4. Release the trigger. You should hear a mechanical click. This is the disconnector releasing the hammer onto the trigger. If you do not hear a click, or the hammer completely falls onto the firing pin,
    you have a worn disconnector, hammer, or trigger and they need to be replaced.
    5. Place the selector switch on safe and try to pull the trigger. The hammer should not fall. If it does there is a problem with your selector switch and/or trigger.
     

    PorP

    Active Member
    Mar 11, 2016
    197
    I'll get in on this....anti-rotation pins suck, the pins are supposed to rotate, this may be one issue....if I read all this correctly the trigger will not reset after a round is fired....it may also be a bad trigger spring. As said already, it's really tough to diagnose a problem with out a) shooting the gun and b) having the gun in your hands and going thru a check list of possible problems, etc.....

    I have no opinion on the anti-roll pins, I can only tell you why I used them.... right wrong or indifferent.

    My first AR build after a few thousand rounds started firing on the trigger pull and would fire again on trigger release.

    I read that this issue was due to the trigger group pins walking. I installed the anti-- roll pins and it fixed the issue. I've used them in every build since.

    Again, not disputing your comment, only telling you how I got to using them.
     

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