Broken Bolt Carrier survey | AR15 Forums

Broken Bolt Carrier survey

Discussion in 'AR Talk' started by John A., Mar 4, 2008.

  1. John A.

    John A. Guest

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    With all the talk about which bolt carrier is the best and the extra step in magnetic particle testing and all the other talk about broken bolts and carriers, I'm wanting to start a running thread to find out just how often it happens. And of course if it happens more with certain brands over another.

    If your bolt carrier has broken, let us know and please give an honest estimate of how many rounds were fired and what brand of carrier it was, and if there were other circumstances that may've caused it..ie, bad reload, etc.

    Pictures obviously get extra credit.

    Slightly off topic, but going on record, I own 3 bolts of various manufacture. 1 LMT with about 1500 through it, and 1 unknown that has about 800 through it and is my newest but is identical to the old Colt SP1 cut, and 1 Olympic Arms (which is my oldest and has around ~15K through it).

    Zero breakages.

    Please keep in mind, I'm looking for first hand problems. Not something you read and I'm not looking for offsite links. I want to know if it's happened to you.

    Let the study begin. I'm looking forward to finding out if all this Magnetic Particle stuff is marketing stratagy or a valid concern. Thanks for participating in the survey. Though I expect this is going to be a quiet topic.
     
  2. petey1

    petey1 Guest

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    Do you mean just the bolt itself breaking? I've heard of bolts breaking, but never carriers.
     
  3. John A.

    John A. Guest

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    Bolts or carriers. Even sheared lugs is alright.

    Basically if you've had a breakage anywhere on the assembly, I wanna know the details about it.
     
  4. younggun22

    younggun22 Guest

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    i have:

    1 sendra -8k no breaks
    1 bushmaster - 6k no breaks but a loose gas key ( not properly staked)
    2 LMT - 2k each - no breaks
     
  5. EricCartmann

    EricCartmann Guest

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    No problems with any of mine.. but then again all my rifles are fairly new. Heaviest use one only has 4k rounds through it.
     
  6. Ed Ely

    Ed Ely Guest

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    This thread deserves a sticky in order to
    gather information which should/would/can
    help all we AR affectionatos.

    When it runs a course, a couple of months
    or so, I will then put it back into the regular
    thread flow.

    For the record, I have not had an issue...
    yet.

    Ed
     
  7. John A.

    John A. Guest

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    Thank you Ed.
     
  8. Badshot

    Badshot Guest

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    No issue with BCG's across a total of 8 AR's in 14 years.. can't count the total number of rounds that comes out to, but it's in excess of 100K easily.
     
  9. WTA_Delta

    WTA_Delta Guest

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    Although this is off topic, the military released their test data some time ago, and I am sure many AR "experts" have read this already, but perhaps this will help those that have not:

    http://www.dtic.mil/ndia/2006smallarms/taylor.pdf#search="sopmod"

    You'll need Abode Acrobat Reader:
    Adobe - Adobe Reader Download - All versions

    The power point presentation has some good information on the results from testing, bolt wear is more frequent with the M4 than M16 due to higher pressures due to the shortening of the gas tube. The stress point is obvious in the bolt, where the cam pin is inserted, and that is were the cracks tend to propogate.

    If I remember correctly they even ran some FEM (Finite-Element) Package, which is a CAD (Computer-Assistant Design) like program that allows the user to input load conditions from point forces, shear forces, pressure, and even radiation (heat). And compared FEM results with test data, and found similar conclusion.
     
  10. EricCartmann

    EricCartmann Guest

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    Thanks for the PDF doc. That doc said the breaking point of an M4 bolt was about 10k rounds for a mildly use M4 with short gas system (mild here meaning semi auto firing mostly). I never knew where people got this info from but I heard a lot of reputable people say it so I just assumed it to be true. One guy told me it is about the end life for a Bushmaster bolt, but turns out is true even for Colts. Moral of the story? Keep a spare bolt. :smile:
     
  11. BlackRifleMP

    BlackRifleMP Guest

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    I wonder what the life is then for my POF's and LWRC. I run a POF 16" fluted with M-4 cuts on a registered A-1 lower. That rifle has now had over 12k through it from HSM, Rem, Win, and at least half of the ammo was Wolf poly. The other two guns are on semi lowers and have had over 8k in each of them. I sure hope I haven't ran the life out of them. Bad news is that I don't shoot them as much, ammo is too expensive. Like I have said, I have put my three rifles through HE11 and they still run like they should.
     
  12. John A.

    John A. Guest

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    Thanks for posting guys. That's one of my points about hearing all the mumbo jumbo about needing upgraded this or upgrade that to be a reliable rifle.

    Moral of the story, buy it, enjoy it, shoot the dickens out of it, and don't sweat as much if you don't have the newest internet must have gadget. Some of them cause more problems than the benefits gained in my honest opinion.

    As you can see from the guys who've particiapted in the survey so far have fired many tens of thousands of rounds with no breakages, there's a lot to be learned there if you think about it a minute.

    I'm not saying that a gun should never be upgraded or maintained, but just because something isn't upgraded or on top of the chart, doesn't make it totally inferior or ineffective either.
     
  13. SVThuh

    SVThuh Guest

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    I think for 99.9% of the guys out there that upgrade their BC components do so for the wrong reasons. If one wants to add extra heft to the BCG by swapping the SA BC for a FA BC for any number of reasons, then that is another story. To increase dwell time, to slow things down, whatever the case may be, the people that actually need this mod to make their rifles more reliable are VERY FEW and FAR BETWEEN the ones that do it just to be "Tacti-cool"
     
  14. mpak87

    mpak87 Guest

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    I pulled this smart one a few weeks ago, shooting a bad handload (not mine, and trust me, I have learned my lesson) through my lefty Stag AR.

    We think that there was either a double charge or bad powder (potentially both.) The shell stuck in the chamber, and the gas blew back through the bolt carrier, blowing the bottom out. The gas vented out through the magazine. It blew all of the cartriges, follower, spring and base plate out on to the ground, and had enough energy to launch the magazine body after it. The upper receiver is bulged, the bolt carrier split on the bottom and cracked on the top, and the extractor is bent back. I have yet to get the shell out of the chamber, but it ruptured in there.

    In this pic, you can see the front end of the carrier. Note the crack along the top edge below the gas key.
    [​IMG]

    Close up of the pic above
    [​IMG]

    Upper receiver, note the bulge below the ejection port.
    [​IMG]

    The bent extractor, and the chunk of the case rim that was ripped out.
    [​IMG]

    View of the star chamber and stuck case
    [​IMG]

    From what I could see, the lower appeared to be intact. When I'm able to afford it, I'm going to build a new upper. If anyone has a better idea of what happened, I would like to hear it. I am also wondering if my barrel would be reusable. If there are any other pictures that would be useful I'll try to take them.
     
  15. EricCartmann

    EricCartmann Guest

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    nasty!
     
  16. -CH-

    -CH- Guest

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    OUCH! sorry to see that :(
     
  17. Perchjerk

    Perchjerk Guest

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    Friend had same problem! thanks for post!
     
  18. Ajcrash

    Ajcrash Guest

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    I've got no issues to report with well over 2k (I don't really count though so it may be higher) rounds through my Stag, and about 500 through my DPMS upper. I do however, keep a spare LMT bolt and firing pin in my AR case though.
     
  19. chad_quixote

    chad_quixote Guest

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    ive got about grand to 1500 in my rr with no malfunctions of any kind so far
     
  20. nikon777

    nikon777 Guest

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    So basically somebody got their feelings hurt by "the chart" it seems. I'm not sure how or why this became a sticky.

    People like to feel good about their purchase, you inform them that their pick may not be the best, they then tend to become defensive. Put whatever parts you like in your AR. However don't try and prove why certain parts aren't necessary.

    All guns are used differently. Sure, the person plinking at the range WILL tend to have many rounds on a cheap bolt/BC. However, going through a rifle class on a hot summer day, and dumping a thousand rounds in a day or two is another story. Not to mention sustained fire and heating the bbl extensively. All these things come into play.
     

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