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AR-15 Short stroking...? Whats going ON!?

Discussion in 'Rifle Country' started by MoDerN_WarRioR, Dec 16, 2009.

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  1. MoDerN_WarRioR

    MoDerN_WarRioR Member

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    OK I was at the range last weekend out plinking with some of my family and we where all having a ball with my AR! Everything was flawless, not a miss feed or jam, all was good! Well for about the first 120 rounds or so...

    Then my girlfriend went to shoot it and she pulled the trigger and the gun fully cycled just fine! Shot the bullet, extracted the spent cartridge, and re-cocked itself. She went to pull the trigger one more time and *tink* nothing happened except the hammer dropped. I though OK maybe it was a "dud primer" so i extracted it by re-cocking it via the charge handle, it ejected the unspent cartridge and re-chambered the new bullet. It shot again and next shot it didn't shoot!!! Ugh its so frustrating! it did it probably a dozen times...

    So at the range i totally field stripped the gun, lubed up the bolt, the carrier, everything and it seemed to help for a few rounds because i got about 5 shot off and then started misfiring again. I checked the firing pin, its ok. I also totally soaked the buffer spring in solvent and brushed it to remove any carbon and also dumped a ton of oil inside the buffer tube to maybe allow it to flow better...

    I dont know what to do. Do i need a new spring? or what? Please help some one! Thanks so much!!

    -Chris
     
  2. Avenger29

    Avenger29 Member

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    Describe the rifle in more detail, please. Barrel length, gas system (carbine, midlength, rifle), ammunition used, brand of rifle, and what your buffer weight is (i.e, carbine, H, H2, etc), plus if you've recently changed the buffer tube or anything else recently.

    There are a few factors that can make the rifle malf, and the above information should be more helpful in diagnosing the likely cause. Don't fret too much, because this can be solved, but some details would be more helpful.

    Oh, and as posted below, make sure the firing pin channel is clean.
     
  3. Ridgerunner665

    Ridgerunner665 Member

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    Thats not "short stroking"...thats a "failure to fire".

    Inside the bolt...how clean is it??

    Carbon build up on the inside of the bolt around the firing pin hole???
     
  4. Ridgerunner665

    Ridgerunner665 Member

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    just for clarity...


    "Short stroke" = the gun fires and usually (but not always) ejects the spent casing, but because the bolt didn't come all the way back...it fails to pick up the next round from the magazine.

    Common causes = dirty gun and/or using a powder that burns too fast for the bullet weight.


    From the OP's description...this is not his problem.
     
  5. atblis

    atblis Member

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    Improperly staked gas key that is now loose. Doesn't sound like your problem though.
     
  6. Ridgerunner665

    Ridgerunner665 Member

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    Yep...that'll make em short stroke too.
     
  7. MoDerN_WarRioR

    MoDerN_WarRioR Member

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    Well here are some specs. With out tearing through the owners Manual, it is a DPMS sportical. (Which i know alot of people have their opinions about. But has been a great rifle to me.)

    Its all stock no internal mods (only exterior add's)
    - 16" Barrel
    - .223 Cal
    - Was shooting 55gr. PMC Bronze (which ALWAYS shoots flawless in my gun)
    - Bolt is clean after every 200 or so rounds.
    - I did not notice any excess carbon build up around the pin hole.

    Ridgerunner! That is exactly what it seems to be doing. The guy at AZ Tactical explained in detail what a short stroke is and i DO believe that my gun is short stroking because it will pick up the round IF the bolt is completely back, but for some reason right now i BELIEVE it is NOT going completely aft so it isn't picking up the new round.

    Is this sufficient information?

    Thanks!
    - Chris
     
  8. KW

    KW Member

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    If a fresh round is being stripped and the bolt goes back into battery, it's not short stroking. Are the primers on the rounds that didn't fire showing marks from the firing pin similar to spent cases?
     
  9. Ridgerunner665

    Ridgerunner665 Member

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    Ok...you said ..."tink", pulled charging handle and extracted the unspent round.

    If its short stroking...there won't be an unspent round in the chamber.

    The gun has to fire...not go "tink" ;)

    If it don't fire...there is no way for it to pick up the next round.


    Something is getting lost in translation here...
     
  10. Mags

    Mags Member

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    Check for debris in your buffer tube assembly if the bolt isn't going all the way back.
     
  11. MoDerN_WarRioR

    MoDerN_WarRioR Member

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    No KW the primers where not hit. Infact i would eject the misfired cartridge, reload it and re-cock the gun and it would shoot.
     
  12. Mags

    Mags Member

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    Sounds more like a failure to go to battery to me, if the primers are not being struck. Could be a weak or broke hammer spring as well.
     
  13. MoDerN_WarRioR

    MoDerN_WarRioR Member

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    Ridgerunner your right i think i did word it wrong. i would pull the charging handle back which pulled the bolt completly aft and you are right, No sell extracted. :) My bad! only when it fires, i get a spent shell extracted. Other wise the chanber IS empty.
     
  14. Ridgerunner665

    Ridgerunner665 Member

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    Its a firing pin obstruction of some kind...or a hammer obstruction.

    Are there any primer parts in the hammer? (No...I have NEVER fired cheap hot loaded 5.56 ammo that didn't have crimped primers...LOL)
     
  15. MoDerN_WarRioR

    MoDerN_WarRioR Member

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    If it where a broke hammer spring should'nt it stop firing all together? Possible it is weak.
     
  16. KW

    KW Member

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    Ok, so you pull the charging handle after it didn't fire and find no round in the chamber? Is the bolt definitely closing all the way? You may want to verify it is with the forward assist. Typically with a short stroke the bolt hangs over the top of the mag and it's obvious something is wrong. It sounds like you just aren't getting a round stripped off of the mag sometimes which may be a mag issue, or a mag catch issue.
     
  17. Mags

    Mags Member

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    No it may not stop fring all together depending on how it is broke/worn.
     
  18. MoDerN_WarRioR

    MoDerN_WarRioR Member

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    Primer parts in the hammer? like peices that would obstruct the strike?
     
  19. Ridgerunner665

    Ridgerunner665 Member

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    OK...it is short stroking then.

    Could be ammo, loose gas key, obstruction in buffer tube, remote possibility of an obstructed gas tube...what did we leave out???

    Its late...I'm forgetful when its late.
     
  20. Ridgerunner665

    Ridgerunner665 Member

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    And yes...primer junk (and sometimes the whole spent primer even) can and will make its way into the hammer and stop the rifle dead in its tracks.
     
  21. MoDerN_WarRioR

    MoDerN_WarRioR Member

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    Those options have all come to mind for me too runner. I will inspect everything from the hammer up to the pin including the bolt. Even if i have to buy a high speed camera to view the bolt's progress. if its moving back far enough or not.

    Thanks for your help! Get some sleep. i need too also. LoL
     
  22. MoDerN_WarRioR

    MoDerN_WarRioR Member

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    Alight guys, i will strip it apart tomorrow again and look over all the areas people have brought up! Thanks for your help everyone!

    Ill let you know if i get to the root of this.

    If anyone has any more ideas i will check back frequently so post up! thanks!
     
  23. KW

    KW Member

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    Well you don't need a high speed camera - just fire some rounds with an empty mag inserted. If the bolt locks back on the empty mag every time it isn't short stroking.
     
  24. Uncle Mike

    Uncle Mike Member

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    Mud dobber nest in works!

    Take apart, clean really good, examine for stuff that's NOT supposed to be there and is there, and for stuff that's supposed to be there and is not there, re-assemble, lube, shoot! lol

    More than likely some bad ammo....how are the feed lips of your mag(s), did it do it with all your mags?
     
  25. Bobarino

    Bobarino member

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    did you change or modify the gas block by chance? if so, the hole in the barrel and the hole in the gas block may not be aligned properly? gas rings at 120° to each other? gas tube and gas key mating correctly?

    Bobby
     
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