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I built this AR and it failed. AR15 scientist help much appreciated!!!

Discussion in 'Rifle Country' started by Mohave-Tec, Jun 29, 2013.

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  1. Mohave-Tec

    Mohave-Tec Member

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    I finished building my first AR 15 yesterday. Here it is in its earliest carnation.

    [​IMG]

    So even though it was 100 degrees at 8:30 this morning at 4000 feet elevation I wanted to at least get out and run the barrel in. Now I've put together numerous bolt guns before and I'm a pretty handy mechanic but my experience this morning was dismal. I couldn't get off 2 rounds before a failure occurred. In the desert I wasn't able to make any determinations as to what was going on but back here at home after cleaning up the gun I am seeing some issues. Please give me a hand if you can?!

    I hand load. I've developed 2 loads for other 223 rifles I have (KelTec SU16C and a Savage Axis 223) so I started out with the simpler hand load for those guns to run the new barrel in. The load on the middle is that load. It is a Remington 55gr Power-Lokt over 24.5 gr H335 with a COL of 2.182 to mimic the factory load sold at Wal Mart. The load on the left is a 60gr VMax over 25gr of Varget with a COL of 2.250. On the far right is one of the many Power-Lokt rounds I killed in my upped receiver this morning on its way to cambering. The next picture sounds one of these rounds nearly folded over.

    [​IMG]

    I know next to nothing about ARs but I know other rifles. It looks as if I am having fail-to-eject issues then I'm slamming a new round into the back of the still chambered but spent case in front of it. What is doing this? I have a couple suspicions but would love to hear your opinions.

    The rifle is currently a Frankengun. I got it in my head a couple weeks ago I wanted to build an AR and though I want a certain quality, I was obliged to pick up what I could in some cases if I wanted to get this thing built in a month. Some of the hardware I believe might be to blames. Here it goes.

    In this picture you see an fairly well made AR Stoner 18 inch mid gassed Wylde chambed barrel over extended into a slick sided DPMS upper. First thing that bugs me is the feed ramp alignments. Not only is the barrel's feed ramps further into the receiver than the receiver's feed ramps but clearly the right feed ramp aligns but the left ramp does not. I think both the depth and alignment issues are making my rather short reloads bounce and making it difficult for them to chamber. What do you think might happen here?

    [​IMG]

    Also, with the 18 inch mid gassed barrel I have an adjustable gas block on it but the adjustment is wide open as I cannot tell the relationship between the gas port and the jet (set screw) that regulates gas flow in the block. This and the buffer weight is 2.9 ounces when I'm thinking something much heavier might help with this gas/barrel configuration? Maybe?

    Lastly, and what scares me the most is that it is a BCM BCG that is failing to eject the spent cases from the chamber. Why would this be?

    I'd appreciate any help I can get on this. Since I am in "very hungry nube learning mode" I am going to cross post this thread in another forum to see how much I can learn about all this.
    Thanks again.

    Oh, by the way, this rifle is majorly accurate and the most repeatable off shoulder 200 yard COM I have ever shot......f I can keep it shooting.
     
  2. Omaha-BeenGlockin

    Omaha-BeenGlockin Member

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    Soak your bolt/carrier with Break Free----work it into the extractor---then slap it back into the gun wet and see how she runs.
     
  3. taliv

    taliv Moderator

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    Is the round coming out of the chamber and staying in the action? Or not even making it out of the chamber?

    If you're picking up another live round then you've got plenty o gas. My guess is chek your extractor and ejector
     
  4. readyeddy

    readyeddy Member

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    Shoot a box of factory ammo to make sure it's not your reloads.
     
  5. Mohave-Tec

    Mohave-Tec Member

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    Omaha, I will do that. I kinda had a similar idea already. I was going to shoot a couple rounds, clean the gun, shoot a couple more rounds then run 70 or 80 rounds through it just to limber up the gun then clean it to the core and re-lube accordingly when I got home. Other than run 80 rounds through it I did just that. I have a BCM BCG and it scares me I'd need to be looking at the BCG at all but I actually wouldn't know what a properly running BCG is supposed to feel like since this s the only BCG I've ever handled.
     
  6. Mohave-Tec

    Mohave-Tec Member

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    taliv, I do figure I have plenty of gas. Part of me thinks I may be over-gassed. Anyway, more often then not the spent rounds is never being picked up and is staying in the chamber. Again, a second reference to what is supposed to be the best quality part in this rifle. Hmmmmm.....
     
  7. Mohave-Tec

    Mohave-Tec Member

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    reddyeddy. I haven't owned a box of factory ammo in 5 years. LOL. But I will pick some up and I do think I know what you are getting at. When I was in the desert this morning I was beating myself up for not bringing some of the VMAX rounds with me which are built to more traditional 223 dimensions and are not blunt nosed.

    Several goods thoughts here already everybody. I will try all these things right away but I won't be going back into the desert until next weekend. It's supposed to be 118* here tomorrow.
     
  8. taliv

    taliv Moderator

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    sounds like an extractor problem or maybe yes overgassing, but that's a little unlikely with an 18" mid-length.

    try a heavier buffer. make sure your extractor has a lot of tension. you shouldn't be able to move it easily with finger pressure. i'm assuming you didn't take it apart and futz with it alread. but try the little black oring that probably came in the package with it.
     
  9. HOOfan_1

    HOOfan_1 Member

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    Umm...nevermind I was wrong about he feed ramps...Those are M4 feed ramps on both the barrel extension and the receiver
     
  10. gotigers

    gotigers Member

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    When it does eject, where do the spent casings land? 3 o'clock, 4 o'clock, etc?
     
  11. Mohave-Tec

    Mohave-Tec Member

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    taliv, I am unable to move the extractor with my fingers or fingernail but I can push it out a little with a screwdriver. I don't remember anything about an O-ring. I don't see one. What is this about?
    Oh, and I haven't taken the BCG apart or messed with it in any way.
     
  12. Walkalong

    Walkalong Moderator

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    The feed ramps do not look like they line up well and that the barrel ramp is higher than the upper receiver ramp. This is an easy check with a fine dental pick etc. Run it up the ramp and see if it hangs at the junction.
     
  13. Mohave-Tec

    Mohave-Tec Member

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    gotigers, very interesting question. In my shop when I pull the charging handle back, loaded rounds will eject at 5 0'clock. When I was in the desert this morning I had a couple guys beside me watch the ejection pattern and the spent rounds would eject at 2 o'clock. And for this purpose I would remind everybody that this is a slick side anf there is no deflector behind the ejection port.
     
  14. itsa pain

    itsa pain member

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    I think looking at the adjustable gas system itself and alignment with the hole in the barrel. maybe the adjustment is stripped out part fell out etc. extractor problems I have seen which made me think overgassing had to have the extactor spring trimmed
     
  15. Mohave-Tec

    Mohave-Tec Member

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    Walkalong, I know it does. You are correct. This is why I put the photograph in in the first place. The depth and alignment are not in sync. Along with ejection issues, I suspect feeding issues as well but the barrel staking pin had no play between it anf the receiver and this is how everything settled.
     
  16. Walkalong

    Walkalong Moderator

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    Yea, it's a matter of tolerances.

    You will need to do some work on the barrel ramps, or find a receiver that matches the barrel or vice versa, which would be expensive. Me? I would make the barrel you have match that nice receiver.
     
  17. jdh

    jdh Member

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    First look at the extractor and see if there are any obvious defects like missing chips.
    With the bolt in hand take a piece of brass, Not a loaded cartridge, and push it into the bolt, straight in, you will have to work against the ejector spring.
    Does the extractor snap over the cartridge rim?
    If it does, does it hold the rim?
    If it does pull straight out on the case. Does the extractor let go easily or hang on to the case rim?
     
  18. Krusty783

    Krusty783 Member

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    You have a pmag, so that's probably not the issue.

    It sounds like the gun is short-stroking/failing to feed? I didn't see a clear description of the malfunction.

    - Are you sure the gas block is aligned correctly? A small misalignment can make a big difference.

    - Get some commercial brass ammo. If you're gonna hand load for your rifle, start with rounds that are closer to 5.56 NATO Spec, which is higher pressure than .223 and makes a difference in some rifles.

    - There should have been a small black o-ring ("donut") that came with the BCG. It goes over the extractor spring to provide some extra strength for extracting on over-gassed systems.
     
    Last edited: Jun 29, 2013
  19. mtrmn

    mtrmn Member

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    Does the extractor tear a chunk out of the rim?

    Given a choice, I get upper receivers that have no feed ramps so I can match the receiver to the barrel myself.
     
  20. 45_auto

    45_auto Member

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    Take the extractor out of the bolt and make sure it's assembled correctly. I went and checked on 4 different AR15's, and on every one of them I can easily pull the forward end of the extractor out (like it has to do to snap over the case rim) 1/16" to 1/8" with the tip of my finger reaching through the ejection port. I'm a pretty puny guy, I doubt if my fingers are that much stronger than yours!
     
  21. Mohave-Tec

    Mohave-Tec Member

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    walkalong, the receiver was $86, the barrel was $260. HAhahahaa
     
  22. Mohave-Tec

    Mohave-Tec Member

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    jhd, I never played with a bolt to actually know what was going on in there but in your little test I think I learned everything there is to know about bolts (not really) and everything seems to work just fine. with some work the case drops right in. The extractor snaps tight over the cartridge rim and holds on to it when I pull staright out bu flips it readily when I let go.
     
  23. Mohave-Tec

    Mohave-Tec Member

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    Krusty, I don't have a great description of the issue. This is almost the first time I've fired an AR and I left the range after a few minutes in discust. : )
    I just took the gas block off. I'm very well aligned on the tube.
    I don't see an oring anywhere. I'm going to run up to a gun store in a minute and take the bolt group with me.
     
  24. Mohave-Tec

    Mohave-Tec Member

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    mtrmn, this sounds like a fine idea. I could easily machine the ramps.
    For your question, no, the extractor isn't doing any damage to the cartridge rim.
     
  25. Walkalong

    Walkalong Moderator

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    Yep, but if you work on the aluminum receiver you will get down below the hardened surface to bare soft aluminum. The barrel is the way to go. FMJ is rough on soft aluminum. :)
     
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