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Thread: Success with getting 9" Barrels to run

  1. #21
    XCR Guru Sean K.'s Avatar
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    Re: Success with getting 9" Barrels to run

    Quote Originally Posted by m118sb View Post
    I think I recall saying Terra saying that the #4 setting was identical on all gas dials.
    Ya, they are all .120".....I bumped mine to .140" as Aziator did on his.

    Sean
    "Necessity is the plea for every infringement of human liberty. It is the argument of tyrants; the creed of slaves."-William Pitt the Younger

  2. #22
    XCR Guru Sean K.'s Avatar
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    Re: Success with getting 9" Barrels to run

    Word of caution:

    I broke off the head of my bbl bolt on the 10.5" today upon reassembly. I've taken the bbl off probably a dozen times now. I'd highly recommend anyone taking their bbl off that frequently to go ahead and replace it when you get up around 1/2 dozen times or so.....

    I always just use a standard allen L shaped 1/4" wrench (5.625" long, so over leverage wasn't an issue) and it snapped the head off. The bolt was not defective. My gut feeling in working with a lot of fasteners in the aerospace industry is that over time, the bolt continues to stretch in the threaded portion and eventually, it just snaps. IMO, this was just run of the mill metal fatigue.

    I'm considering going to a set screw instead of the socket head screw next time around (after I drill and easy out or tap the current clusterfuck) as this problem cannot occur with the set screw....though I could conceivably strip the head....but allen head set screws would also act like a self centering pilot hole if that happened.

    Anyone know off hand what the correct length is for the set screw? Anyone know what size allen bit fits this set screw? I'm concerned that you may overtorque the allen wrench itself if it is significantly smaller than the 1/4" wrench used on the socket head screw. Finally, anyone know if the set screw (or the socket head allen screw for that matter) has a special degree chamfer on the end that mates to the bbl or if it's just a standard taper? I'd like to just pick this up at the local hardware store tomorrow as opposed to having to order from Kermit.

    Thanks,
    Sean

    PS. I'm going to post this as a new thread to hopefully get the info on the bolt more quickly.
    "Necessity is the plea for every infringement of human liberty. It is the argument of tyrants; the creed of slaves."-William Pitt the Younger

  3. #23
    Super Moderator Underground's Avatar
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    Re: Success with getting 9" Barrels to run

    I just got my 5.56 barrel back from ADCO today. I sent it off on the 22nd, came back in a week and a half, and that was over Thanksgiving too. 12" heavy barrel, cut to 11", and 6 flutes. You can see the line on the barrel extension where I guess they dipped it to refinish it. Not that it will matter, no one will see that and it wasn't where any of the raw metal was left.

    Very nice job though. The edges at the muzzle end are all clean and chamfered with nice, sharp threads. There are some very faint longitudinal lines left in the flutes, but no chatter marks or anything.





    Attached Thumbnails Attached Thumbnails Success with getting 9" Barrels to run-xcrbblcutdown.jpg   Success with getting 9" Barrels to run-xcrbblcutdown.jpg   Success with getting 9" Barrels to run-xcrbblcutdown.jpg  
    That guy, he said I should be oblong and have my knees removed. But I don't trust him, he plays the banjo.

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  5. #24
    XCR Guru Sean K.'s Avatar
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    Re: Success with getting 9" Barrels to run

    VERY nicely done. ADCO does great work.

    Sean
    "Necessity is the plea for every infringement of human liberty. It is the argument of tyrants; the creed of slaves."-William Pitt the Younger

  6. #25
    Carbineman Rich's Avatar
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    Re: Success with getting 9" Barrels to run

    How much weight did that save?
    I blow things up for a living.

  7. #26
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    Re: Success with getting 9" Barrels to run

    Quote Originally Posted by Rich View Post
    How much weight did that save?
    I don't know, but it's quite noticable when holding the rifle. I don't have a scale so I can't even tell you what it weighs now.



    That guy, he said I should be oblong and have my knees removed. But I don't trust him, he plays the banjo.

  8. #27
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    Re: Success with getting 9" Barrels to run

    Here it is with and without the can. I got the slightly shorter stock with the PDW but I think I've about decided I don't like it. I think I'm going to swap it out with one of my other ones I've "customized".





    Attached Thumbnails Attached Thumbnails Success with getting 9" Barrels to run-snc00124.jpg   Success with getting 9" Barrels to run-snc00122.jpg   Success with getting 9" Barrels to run-snc00124.jpg   Success with getting 9" Barrels to run-snc00122.jpg   Success with getting 9" Barrels to run-snc00124.jpg  

    Success with getting 9" Barrels to run-snc00122.jpg  
    That guy, he said I should be oblong and have my knees removed. But I don't trust him, he plays the banjo.

  9. #28
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    Re: Success with getting 9" Barrels to run

    Got out to shoot the newly chopped 11" 5.56 barrel a little today (full length gas system). Shooting Wolf MC.

    Unsuppressed it ran fine on 4 and 3, not on 2.

    Supressed it ran just fine on S. Feels like shooting a .22LR with the heavy .308 can on there.

    I think we have a winner.



    That guy, he said I should be oblong and have my knees removed. But I don't trust him, he plays the banjo.

  10. #29
    Rifleman dbooksta's Avatar
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    Re: Success with getting 9" Barrels to run

    Quote Originally Posted by Sean K. View Post
    ***EDIT*** These are the specs I was given by RA.
    I tried bugging Alex for a week or two for port specs and never got a reply. I measured the gas dial holes as best I could with drill bits, and given the measurements on my two uppers I'm wondering if there really is a spec followed in manufacturing:

    On my 5.56 11" upper:
    • [li]Port 4 diameter 7/64"[/li]
      [li]Port 3 diameter 4/64"[/li]
      [li]Port 2 diameter almost 4/64" -- practically the same as Port 3. Why bother?[/li]


    On my 7.62x39mm 9" mini upper:
    • [li]Port 4 diameter 7/64"[/li]
      [li]Port 3 diameter just above 5/64"[/li]
      [li]Port 2 diameter just above 4/64"[/li]
      [li]Port 1 diameter 4/64"[/li]


    I can't see any reason to run the ports this small. I intend to drill up my gas plug to aziator's specs. Sounds like I also need to drill out the gas block and barrel to 10/64" for 7.62 and 9/64" for 5.56. If anyone could publish a picture tutorial on removing and drilling these pieces I would greatly appreciate it!

    And RA, if you're paying attention: Put some thought into your gas system! We can always dial it down, but given the trouble people have running on #4 you obviously didn't set a wide enough top-end!

  11. #30
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    Re: Success with getting 9" Barrels to run

    It would be nice if we could get gas plugs with very small pilot holes drilled at each location. The we could drill them out to the desired size. Would be handy for making custom plugs with multiple suppressed settings.



    That guy, he said I should be oblong and have my knees removed. But I don't trust him, he plays the banjo.

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