AR-15 Bolt Carrier Issues

Discussion in 'AR-15 Discussion' started by 2hot2handle, Apr 1, 2018.

  1. 2hot2handle

    2hot2handle Member

    EDIT: I put this in the wrong section. Sorry admin!

    I need some help with an issue I experienced on the range about a month ago.

    I'd like to address the fact that I may be putting a lot of a excess info in this post. This is due to the fact that I don't know what caused this issue and am trying to make sure that I can put in as much info as possible that might help answer this problem.


    You: "Oh my 2Hot, what a lovely rifle you have"

    Me: "Why thank you! She's not perfect, but I do love her so."

    You: "Would you mind telling me more about her?"

    Me: "It would be my pleasure!
    She is a has a Del-ton Bolt Carrier Group
    ACE LTD stock
    Hogue Grip
    BCM Gunfighter Charging handle
    Rock River Lower - Trigger Group unknown
    Brand new PSA 16" Mid-Length 5.56 NATO Nitride 13.5" Lightweight M-lok Upper 1/7"
    Burris Scope P.E.P.R. Mount with a Redfield 3x9 Battlezone Scope."

    You: "Everything looks to be in order. What seems to be the problem?"

    Me: "I used to have a Del-ton 1/9 Bull Barrel Carbine-Length A-2 Upper that worked just fine. However, over Christmas PSA was having a deal on uppers and I decide that I wanted to have an upgrade without an A-2 sight. Not to mention a free-float fore grip for all the goodies I can't afford."

    You: "I've heard of worse decisions, I'm just not sure when. What happened?"

    Me: "After receiving my new upper I decided to go out and break in my new upper. My first and last trip to the range with this beauty started with a break in process."

    IE: 1 round, clean barrel with a swab, brush, swab till clean etc.
    This process continues for 5 rounds.
    Next: 5 rounds, clean barrel with a swab, brush, swab till clean etc.

    (Disclaimer: This is the first time I've attempted a break in process like this for a new rifle. I saw a few articles saying this was something that may improve accuracy & longevity so I figured "what could it hurt?")

    On round 20-ish I decide its time to try out a group at 100 yards.

    Round 24 fails to seat properly in the chamber. I flip on the safety and start to inspect the problem. The round is approximately 50% of the way into the chamber. Numerous attempts are used to extract the round using my charging handle. Negligible success is achieved. I brilliantly thing to myself "maybe try the forward assist" shove on her a few times to no avail. In a desperate (and perhaps quite stupid I'll admit) attempt to free my rifle of its confused brass I slide a cleaning rod down the barrel. The cleaning rod freed the round finally allowing me to use the charging handle to clear the round.

    I seat a new round in the chamber and settle behind the rifle to fire again when a nagging feeling hits me. I should probably check things out to make sure I'm good to go. I separate the upper from the lower and begin my inspection.

    Lower appears to be clear from obstructions & debris.

    Take a peak at the upper with a glance down the barrel and what do I see? A piece of something obstructing my barrel. After another run of my cleaning rod down the barrel what do I get?

    A piece of my own bolt carrier was lodged in my barrel.

    On the mat next to my rifle was the second piece that broke off of my bolt carrier.


    I noticed that the two pieces broken off are on either side of the extractor. I'm not sure how much of that has to do with the issue but I took a few photos of the ammunition I was shooting just to be sure.


    If the photos I took are clear enough you should be able to see some scoring marks on the brass. There doesn't appear to be any bulging of the brass around the neck though.

    Here are a few more photos of the bolt carrier and the inside of the chamber as best as I could manage. I will be taking the rifle to a gunsmith, I was curious if anyone here could help diagnose what the potential pitfalls were though as well.

    I greatly appreciate any help that people can offer. If you feel that more pictures may help with you assessment please let me know and I will do my best to take a satisfactory photo.

    Thanks for your time and I look forward to your help on this issue.
    Last edited: Apr 1, 2018
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  2. bluez

    bluez Well-Known Member

    First thank you for excellent + complete description of both the problem and your rifles configuration.
    While in this particular failure not strictly necessary it is best practices for anyone who wants a problem diagnosed over internet and sadly too few people do it.. So thank you for that.

    As for your issue: It is not at all that unusual to have a bolt fail in exactly this manner.

    (its not the carrier group failure BTW ....its the bolt not the bolt carrier, at first i sat up in my chair when I read the title...because I never seen the BCG fail before..)

    Some say the proper life expectancy of a bolt and were one should consider replacing it just as preventative maintenance is about 3000-5000 rds.
    I myself feel this is excessive at least in the civilian environment + have not been following this recommendation .. I own a bolt that has had 15,000 rounds on it before i replaced it (still keep it as a reserve).
    But that was an high dollar bolt from LWRC.

    Bolts are among the common failure items in our rifles along with firing pins and extractors and extractor springs.

    I used to carry a repair kit with a spare bolt and a FP for that reason..
    But I dont do that anymore since I recently upgraded all my FPs for hard primer ammo and use mostly higher end bolts.. so the likely hood is now much less and I get to save the weight and complexity of lugging around extra stuff beyond the rifle..

    But when I put on a training event for my group I usually carry an extra FP and a spare bolt with me just in case.. And last time somoene did need my spare bolt (his ejector spring was shot, technically i could have just replaced that as the parts are dirt cheap but I dint want to hassle with it... also his bolt had LOTS of rounds on it maybe above 10,000 so it was time to change it out anyway so I just gave him a brand new one out of my supply chest.)

    Your bolt failure 100% explains your failure to extract and 100% your failure to chamber as parts of it were lodged in the chamber.

    Not sure how many rounds u have on the bolt if its an early failure, no big deal just buy another bolt.
    They are not expensive.

    Usually with a failure to extract one of the first things PPL look at is the ammo used during that incident but Federal White Box is beyond reproach and constitutes the gold standard for 5.56 mm Ammo.( even though.. and I guess I am alone in this Have always been a bit leery of these long bullets used in 77gr match ammo for feeding and mag clearances.. but I am nearly alone in this )
    And besides we know it was the bolt not the ammo.

    I wouldn't bother w/ a gun smith.
    Just replace the bolt and your done.

    Source: Am a certified Armorer for M4/M16/AR15 (even tho i let those skills atrophy for some years now)
    Last edited: Apr 1, 2018
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  3. Triumphman

    Triumphman Well-Known Member

    Good write-up about what you have, but you're missing one important item. What weight Buffer are you using. If you're using a regular carbine buffer, you might want to go up to the H2 or even a H3 buffer weight to help calm the gassing of being overcharged that causes the BCG/bolt from doing a bounce lockup with a too fast of moving BCG. I know going to a midlength barrel helps calm some of the gas issues, but sometimes it's not enough, so you either go with heavier buffer(s), spring, OR adjustable gas block to better help calm over gassing when a manufacturer might over-size a barrel gas hole to make sure the BCG gets enough gas for when using cheap/dirty/weak ammos that a lot of people use and plink with. Just something to think about and look into. So if you do have a oversize gas barrel hole, using Nato 5.56 ammos just enhance the BCG's over gassing which causes one to break bolt lugs, having excessive bolt bounce and bolt lugs slamming the chamber side of the barrel extension lockup lugs upon firing.

    Also, as what Bluez has mentioned, where the lugs broke off is the weakest point of a bolt and worth getting some spares, but in order to fix the problem, you need to eliminate what caused the problem to start with and which gives the best bang for the buck and in this case I'd think about going with an adjustable gas block for best gassing control for use with any ammos you so choose.
    towboater and bluez like this.
  4. bluez

    bluez Well-Known Member

    its true he could be over gassed.. which puts extra stress on the bolt face.... but could be just a flawed bolt from the factory.

    Right now nothing in his description leads me to think he is overgassed (tho its certainly possible).

    Overgassing a big thing when 16 inch barrels with carbine gas systems were much more common and the heavier buffer (and other mods to the tune like heavier full auto BCG or stiffer buffer spring) were all the rage and rightfully so..

    but he has a midlenght gas..

    My suggestion would be he can shoot (after he puts in a new bolt) and have someone check his ejection patterns to readily determine how the carbine is tuned.

  5. 2hot2handle

    2hot2handle Member

    First I would like to thank everyone for their prompt and helpful responses. It's a definite relief to hear that this isn't something that is terribly uncommon.

    First I'd like to express my embarrassment at calling the bolt by the wrong name haha. Secondly that Bolt has seen a few thousand rounds, so I don't suppose that I should be too surprised that it pooped out. I like the idea of carrying around a few spare parts, something I definitely need to add to the range bag.

    Do you think I need to worry about the piece of bolt lodged in the barrel doing any damage to the rifling etc? I just don't want to start slinging lead if there may be potential issues in that region.

    I'm very interested in diagnosing any issues that may be remaining so as to prevent this from happening in the future. I have to be honest and state that I don't know what weight my buffer I am using. There weren't any discernible markings on the buffer, I took a picture any way in hopes that someone may be able to identify it.


    Thanks for this info! I'll be sure to have a buddy come along and maybe we can learn a thing or two after I get a new bolt & potentially buffer.
    towboater and bluez like this.
  6. bluez

    bluez Well-Known Member

    1) I would not bother to buy a new buffer unless your ejection patterns indicate your gun is overgassed. It can be a good solution but only when applied to the right condition.

    2) I get your concern about the bolt component having scratched something. We do not know for sure if it got outside the chamber though, yes? I am not completely clear on that. You do know for certain it was in chamber at one point. A scratch in the chamber is not much to worry about at all.
    A scratch in barrel can be somewhat deleterious but my feeling is the rifle will still be mnore accurate than most shooters... ..the most deleterious scratches u can get are to the barrels crown and it seems pretty clear like thats not the case.
    (BTW take care when cleaning accuracy oriented rifles not to damage crown, which is the ring on end of barrel where bullet exits)

    3) As Triumphman correctly pointed out since you went from a rifle upper to a 16 inch upper and shooting it on the same lower w/o any changes to the buffer + spring,... tuning issues may indeed exist (tho not likely to cause a bolt to fail right away).
    Important thing is to shoot the rifle and look at the pattern.. everything else you need (or need not) do will spring from that.

    I generally consider a 3 o clock to 4 o' clock perfect and a 4:30 to 2 o clock within acceptable tolerance..I generally dont bother making any changes to the guns tune unless it gets out of that range (assuming there is no short stroking and the like going on)
    Last edited: Apr 1, 2018
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  7. 2hot2handle

    2hot2handle Member

    Alrighty, sounds like I'll wait on that till after replacing the bolt and firing a few rounds.

    I should have made this more clear in the original post. One of the broken pieces of bolt was most definitely down the barrel, not just in the chamber. Thus my concern for safety.
    If it's just a matter of accuracy due to a scratch then I won't be overly concerned.

    Great info on the barrel crown. I don't know if I've heard that before.

    The original upper was a 16" Del-ton bull barrel 1/9 with a Carbine-length system.
    The new is a 16" PSA 1/7 with a Mid-length system.
    Sorry if that wasn't clarified before.

    Thanks again for all the info. This has been more helpful than I was even hoping for.
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  8. bluez

    bluez Well-Known Member

    - No need to worry about safety at this point, even if bolt pieces got inside barrel.
    - When you said "bull barrel" I assumed 20 inch barrel in your original confioguration.. :)
  9. MistWolf

    MistWolf Member

    If your buffer has no markings, it's a carbine weight buffer and far too light. At the very least, it should be replaced with an H buffer. An H2 buffer would be preferable.

    If your AR is overgassed, an H or H2 buffer will help, but won't solve the problem. The only way to solve the problem is to restrict the gas flow with either a smaller gas port, or adjustable gas block. A smaller gas port can be achieved by using a barrel with the right diameter gas port or fitting the gas block with a micro port from Black River Tactical.

    Another solution is to use an adjustable gas block. One of the best is the SLR. It has click adjustment, holds up well to heavy use and if any does go wrong, SLR has great customer service.

    BRT is planning to release an adjustable gas tube that should be more affordable than the SLR adjustable gas block. Have not tried it yet, but it should work as well as an adjustable gas block.

    Get a new bolt. Your AR will be fine. If you're worried about headspace, get a new barrel the same time.
  10. Henry Stevens

    Henry Stevens Member

    If this BCG is Del-ton, then I would call Del-ton and get their opinion. These guys are very helpful and their products have a good reputation.
    bluez likes this.
  11. fsted2a

    fsted2a Well-Known Member

    I have never had or seen a malfunction that could be traced back to the buffer, although it is possible. Really cheap buffers can and do last a million rounds or more. Most likely the blame for this malfunction was the bolt or firing pin.
  12. Sniper03

    Sniper03 Supporting Member Supporter

    2 HOT
    The problem is AMMUNITION! If you look at the Primers I definitely see and issue with over pressure. IMO you should not shoot any more of the ammunition. Check the LOT # on the box if you have more left! "DONT SHOOT IT"! "Two things can cause this pressure. 1. Improperly loaded / faulty ammunition 2. A Bullet Recessing in the Case while being loaded in the Chamber.
    The pressure can break the Locking Lugs off the Bolt. The reason you could not load or eject the round was because a piece of the Bolt Lugs was wedged either in the chamber and against the casing or jammed up in the Barrel Extension Lugs. I received a call two weeks ago from a law enforcement agency who they were having issues with ejecting casings from their rifles and finally two rifles blew up. Why they kept shooting I do not know when they experienced these problems. And the bolts were severely damaged. I asked them if the Rifles were frequently checked for Head Space and Throat Erosion regularly per maintenance inspection. They said the keep an eye on the Throat Erosion on the rifles. And the other rifles having the same problem as the ones who blew up had passed a throat erosion test! Bottom line they were shooting Federal Ammunition as well. So you may have some of that same ammunition. Federal Full Metal Jacket ammunition? The reason I instructed them about the Head Space is, once head space has been checked on an AR you never have to check it again unless you change a Bolt or change a Barrel. Because the Throat will erode to the point of needing a new barrel before the head space dimensions ever changes! SO diagnosis! IMO AMMUNITION! Not the Rifle!;)
    In closing Federal Technical in Minnesota is aware of the agencies issue and is doing a review. Of course you know they think it possibly the rifle. But with all of their rifles doing it! NO WAY! It is the ammunition!
    Last edited: Aug 21, 2018
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  13. bluez

    bluez Well-Known Member

    Sniper: Wow I did not know that Federal White box was having issues? They are not cheap.. they sure have a reputation for being hot ammo but was unaware that batches of bad white box were floating out there. Just validates my use of economy ammo once more ;)
    locutus likes this.
  14. Sniper03

    Sniper03 Supporting Member Supporter

    Sorry to say it has also happened with Winchester White Box and American Eagle in the recent past. And I am a Federal and Hornady guy! But with the human element involved and the fact that the manufacturers are running ammunition 24-7 probably contributes to the issue! Out of every ten rounds of ammunition 5 of the 10 rounds produced is going to our military and to also to our allies military. 4 of the 10 are going to Law Enforcement. And 1 round of the 10 is going to the commercial market!;) So IMO it seems that in some cases quality control is possibly fairly lenient to meet production?

    Last edited: Aug 23, 2018