Bent Gas Ring - What Should I Check First
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Thread: Bent Gas Ring - What Should I Check First

  1. #1
    Gunco Rookie AlphaBob's Avatar
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    Default Bent Gas Ring - What Should I Check First

    Assembled an AR lower and added a purchased (tested) upper.

    Fired 15 rounds (three sets of 5 each) and after the last round, the bolt jammed about 1/4" into it's rear travel. Extremely odd because it ejected the casing from the 15th round - I wouldn't think that 1/4" would be enought to clear a spent cartridge - it might have been as much as 1/2", but it certainly wasn't more than that.

    More on point, when I finally got it all disassembled, one of the gas rings was bent which is what caused the bolt to jam in the bolt carrier.

    Measured the band* on the bolt and it is 0.527" in diameter. The bore in the bolt carrier is 0.532" in diameter. I don't know much about the AR-15, but I'm guessing that 0.005" clearance is in the range of reason.

    Need advice:

    1) Anybody know where I can find the actual manufacturing specification for the bold and bolt carrier? If one of these two items is out of spec, I'll need to replace it.

    2) Could it just be cheap gas rings? This was the cheapest kit on the market (maybe a poor choice on my part, but I shot all 15 shots within a 1 1/2" diameter pattern at 25 yards free hand - so it can't be that bad - just unreliable!). Has anyone heard of this problem before - I tried to search for "bent gas ring" and only found one marginally related post.

    3) Source for high-quality gas rings?

    Any suggestions / comments would be appreciated.

    Thanks,


    Bob


    *band - the "band" I'm talking about on the bolt is right behind the extractor roll pin hole - the band is the largest diameter on the portion of the bolt that actually goes into the bolt carrier. I'm referred to "front" and "back" in relation to the barrel. So "behind" the extractor roll pin hole means toward the stock.

  2. #2
    jrs
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    B.U.F. (Bald, Ugly, Fat) jrs's Avatar
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    I'd vote for bad gas rings. I had two kits I bought arrive with bad rings. One set jammed as you describe and the other just broke a piece off. After buying and replacing with known good rings both rifles have fired several thousand rounds with no problems.

    Midway has replacement rings.
    DPMS Bolt Gas Ring McFarland 1-Piece AR-15 - MidwayUSA
    jrs
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    "A great civilization is not conquered from without until it has destroyed itself from within.", Will Durant

    "All that is necessary for the triumph of evil is that good men do nothing.", Edmund Burke

  3. #3
    Gunco Addicted for life j427x's Avatar
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    i would replace the rings first. their cheap. then shoot a few rounds with it and see if anything new pops up. if not you should be GTG.

    if the rings come up bent again you got a problem with the bolt or carrier.

    i have built numerous ar/car clones and never ran across this problem after thousands of rounds. what bolt/bolt carrier are you running?

  4. #4
    Gunco Rookie AlphaBob's Avatar
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    Perfect Advice - I didn't know that one-piece gas rings were available - new to the AR-15, wanted to add one to the collection - mostly an AK-47 guy, but each has its place.

    I've ordered the DPMS one-piece gas ring and I'll let you know how it works out.

    After I get everything debugged I'll write up a summary of my build experience - including the name of the kit supplier.

    The reason I wanted to build, instead of purchasing a completed weapon, is that I want to learn how to tweak and debug the AR platform. Also, given that I purchased the cheapest kit on the market, I fully expected to spend some time "dialing it in".

    Throughout the shopping process and purchase the supplier has been extremely easy to work with. Did not contact the supplier about the bent gas ring because I suspected they'd just have me send the entire upper back which would deprive me of the learning experience.

    I'll keep you posted.

    Bob

  5. #5
    Gunco Rookie AlphaBob's Avatar
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    Default Several Hundred Rounds Later - Success! Thanks You!

    DPMS one-piece gas ring solved the problem. Actually, I couldn't wait for the DPMS one-piece to arrive so I first tried a set of Rock River rings from the local shop - they worked great also. Did switch to the DPMS one-piece when it arrived and again, no problems.

    The gun kit came from akpartskits - it was $409, which made it affordable to me. I know that there is an ongoing debate regarding quality and service. For me it doesn't make sense to ask, "Why doesn't my $400 kit work as well as a $600+ kit?"

    Besides the gas ring, I had some trouble fitting the handle to the receiver. It's molded thermoplastic and mine was probably pulled from the mold too quickly so the upper part of the opening where it fits onto the receiver pulled in a little. I fixed the problem by immersing the top part of the handle in near boiling water for 20 seconds before muscling it on.

    The only truly defective part was the mag catch - it would not hold the magazine in place. I thought it was a manufacturing defect with the Stag receiver. I called Stag and they promptly sent me a new mag catch - even though I only bought the receiver from them - GREAT company. Can't say enough good about Stag.

    Overall I enjoyed the building experience, akpartskits offers the lowest price, they are very easy to work with and shipped promptly. I did not try to work any issues back with them, but feel that they would have worked with me to get everything resolved.

    I would purchase from akpartskits again. If it were not for them and their competitive prices, I'd still own a bare receiver and only be dreaming about an AR-15.

    Again, IMHO, if you're going to be frustrated to learn that a $400 kit doesn't work as well out of the box as a $600 kit, they may not be the right company for you. I now know how to work through issues on my AR-15 and feel very comfortable working on it.

    Thanks for the quick advice when I ran into problems!

    AlphaBob

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