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Unique Gas System Length on AR10

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  • redse7en

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    I say unique but I could just be ignorant, hence I am here asking those who might know. I got a hold of a Frankenstein AR10 with an unknown (unmarked) 16" barrel. Noticed the gas tube was slightly warped so I went to replace it. At first glance it looked to be a standard 11-3/4" mid length tube, but a closer look put it at 12-1/4". Thought that was a little strange but I changed it out with the true mid length thinking it was a mistake. Sure enough the mid length isn't long enough, barely protruding beyond the gas tube channel in the upper. An intermediate length tube at 13-3/4" would be way too long. The tube looks like it could have been special made for the rifle. Wondering what others might have to say about it??
     

    SAWMAN

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    Sounds like a 16" bbl with rifle gas to me. Got a DPMS set up like that. Shoots great,low recoil. (lower gas port pressure) --- SAWMAN
     
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    FrommerStop

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    I say unique but I could just be ignorant, hence I am here asking those who might know. I got a hold of a Frankenstein AR10 with an unknown (unmarked) 16" barrel. Noticed the gas tube was slightly warped so I went to replace it. At first glance it looked to be a standard 11-3/4" mid length tube, but a closer look put it at 12-1/4". Thought that was a little strange but I changed it out with the true mid length thinking it was a mistake. Sure enough the mid length isn't long enough, barely protruding beyond the gas tube channel in the upper. An intermediate length tube at 13-3/4" would be way too long. The tube looks like it could have been special made for the rifle. Wondering what others might have to say about it??

    Is it possible to cut off the intermediate 13-3/4 tube back to 12-1/4 if you are not happy with what you got?
    By the way you did not say if the wrapped tube was working or not? If it works why mess with it.
     

    redse7en

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    No SAWMAN...a normal length rifle tube (15-1/8") would result in 4" of gas tube in the upper receiver. This gas tube is cut to 12-1/4" and fits at that length.
     

    redse7en

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    Is it possible to cut off the intermediate 13-3/4 tube back to 12-1/4 if you are not happy with what you got?
    By the way you did not say if the wrapped tube was working or not? If it works why mess with it.

    It's having some cycling issues...not ejecting. It would be possible to cut an intermediate to a proper length. My thing is why? Why make a one of a kind barrel that doesn't adhere to any of the accepted norms? There's nothing special about this rifle other than the fact it has a gas system that falls between a mid length and intermediate. I just found it odd.
     

    FrommerStop

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    It's having some cycling issues...not ejecting. It would be possible to cut an intermediate to a proper length. My thing is why? Why make a one of a kind barrel that doesn't adhere to any of the accepted norms? There's nothing special about this rifle other than the fact it has a gas system that falls between a mid length and intermediate. I just found it odd.

    Is the tube showing any indications that gas flow is restricted or that it is leaking. If it is warped is there any binding within the gas key on the bolt carrier.
    Inkedgas key AR_LI.jpg
     

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    redse7en

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    Is the tube showing any indications that gas flow is restricted or that it is leaking. If it is warped is there any binding within the gas key on the bolt carrier.
    View attachment 74088

    Oh yeah...there were signs of leaking at both the gas block and the key end of the gas tube. Both ends were blackened pretty good. I also noticed that the "flare" normally present on the key end of the gas tube was absent, completely. An indication that the tube was either cut to length or made "special" without it. I take the latter because the bends in the tube were also way more pronounced and in slightly different positions when comparing end to end from the gas block end with both a mid-length and rifle length tube from Spike's.
     

    FrommerStop

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    I am learning ARs now and the gas tube is an interesting topic.

    Here is an outfit that specializes in after market gas tubes. It is good reading.
    https://www.wingtactical.com/gas-tubes/
    I see that this can be a complicated subject. It maybe that the barrel nut is not properly aligned with gas tube for example.
    barrel nut gas tube alignment..jpg
     

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    FrommerStop

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    That was a lot of words to say "use the right length gas tube and install it properly".
    That is like saying make it so, but if you do not know, a few more words are needed.

    It appears that the person or people that originally put the AR in question together did not do it right. The gas tube is custom since it is not a standard length and the gun does not cycle showing a problem somewhere with the gas system being one place to start with. But it could that the gas port is too small, problem with the buffer or as simple as the rings are not right. I once install rings with the ring gap lined up and not staggered, gun did not cycle. I once assembled an AR stock buffer screw that was too long and it would not cycle. There are a lot of things that if you do not know will prevent your AR from functioning.
    None this knowledge is something you are born with and you have to learn it from somewhere.

    Gas rings on bolt
    ar rings.jpg
     

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    FrommerStop

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    There's also ways to say things succinctly.

    That is most easily done when you fully understand a subject. On ARs If you are like me and do not fully understand, it is almost impossible to be succinct. On the other hand people that are highly familiar with a detailed subject get bored and impatient when what seem like trivial details are gone through and I can be quite guilty of that myself.

    A very difficult thing that teachers must learn is not to assume basic knowledge on the part of their students. Just because it is obvious to you, one often assumes basic understanding where it does not exist. I have run into that in trying teach someone how to aim the iron sights on a pistol where the most basic understanding was not there even after a classroom lecture on sight picture, but this was easily corrected once the instructor figured out what the misunderstanding was.
     

    Little Jack

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    That is most easily done when you fully understand a subject. On ARs If you are like me and do not fully understand, it is almost impossible to be succinct. On the other hand people that are highly familiar with a detailed subject get bored and impatient when what seem like trivial details are gone through and I can be quite guilty of that myself.

    A very difficult thing that teachers must learn is not to assume basic knowledge on the part of their students. Just because it is obvious to you, one often assumes basic understanding where it does not exist. I have run into that in trying teach someone how to aim the iron sights on a pistol where the most basic understanding was not there even after a classroom lecture on sight picture, but this was easily corrected once the instructor figured out what the misunderstanding was.

    I've been a teacher/instructor for the last 12 years. I'm familiar with imparting knowledge and the various techniques involved and also understand different people respond to different techniques.

    The article tried way too hard and took a simple concept and talked in circles.
     

    War-Buff

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    I've been a teacher/instructor for the last 12 years. I'm familiar with imparting knowledge and the various techniques involved and also understand different people respond to different techniques.

    The article tried way too hard and took a simple concept and talked in circles.

    You mean you didn't like Mr. Gas block and Mrs. Gas key? :suspicious:
     
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