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Barrel and gas system lengths

blksno

blksno

OG
Full Member
Minuteman
    • Mar 15, 2009
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    #1
    So I've got a pair of AR10s and I use that term on purpose.
    One is an Armalite AR10 that was originally a 300 SAUM. I rebarreled it to a 6.5 PRC with a 24" barrel and a +2 gas system. I've just about got it dialed in to cycle perfect...but the Armalite mags are dog-spit and I think I'm gonna end up having to 3d print a self leveling follower for their Gen2 pattern mags.
    The 2nd is a Matrix upper lower set that is still the Armalite pattern, but takes SR25 mags...that one is a 22" 6.5 Creed with a +2 gas system. Pmags don't work 100% but so far ACS mags have been doing great. Seems to be tuned and feeding/cycling but with both systems...I'm thinking I should have just made them 16 or 18? from the jump.

    Has anyone ever taken a barrel with a +1 or +2 gas system and shortened the barrel down to 16 or 18"??
    I assume this is going to drastically reduce the gas and potentially start short stroking, but with the buffer, springs and gas block I have...I assume getting it tuned to run suppressed again would be fairly easy.

    Really thinking I should have gown shorter.


    20241231_193120.jpg
     
    Last edited:
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    #6
    Check mag catch height on that Matrix set. I had a set that it was a few hundredths high and causing ftf malfunctions. The fix was filing down the top of the catch.
     
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    #7
    Jsp556 said:
    Check mag catch height on that Matrix set. I had a set that it was a few hundredths high and causing ftf malfunctions. The fix was filing down the top of the catch.
    Click to expand...
    If anything, mine is low, causing rounds from a pmag to slam face first into the front of the barrel extension, below the feed ramp.

    Doesn't happen with ASC
     
    #8
    blksno said:
    Has anyone ever taken a barrel with a +1 or +2 gas system and shortened the barrel down to 16 or 18"??
    Click to expand...

    Not a direct answer to your question, but as a data point for reference, I've got a 17" RLGS+1 in 5.56 that works great and ran with no issues out of the box.
    Obviously that's small frame and lower pressures but in my mind that says theoretically a much higher pressured cartridge could run an 18" RLGS+2 with the same amount of dwell time.
     
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    #9
    Do both rifles currently function correctly without a suppressor, and now you intend on running them 100% suppressed with an Ultra 9? If so, you should be able to shorten the barrel an amount to have the same equivalent dwell, giving you the same function. Running both suppressed and unsuppressed will be a bit more challenging. Also, I don't think that a +2 gas system is possible on a 16" barrel.
     
    #11
    TonyTheTiger said:
    If I remember correctly, a 16" RLGS has 2.5-2.75" of dwell time, so it may be technically possible to do, but yeah, not likely a realistic thing.
    Click to expand...
    I was thinking of the physical dimension between the shoulder of the gas journal and the shoulder of the muzzle tenon on a +2 16". I believe that it would be less than 1", and even the ultra short single set screw gas blocks might not work. Of course, he wouldn't have to chop it at exactly 16", but the actual gas block/AGB length and adjustment mechanism access would have to be considered.
     
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    #12
    msgriff said:
    Do both rifles currently function correctly without a suppressor, and now you intend on running them 100% suppressed with an Ultra 9? If so, you should be able to shorten the barrel an amount to have the same equivalent dwell, giving you the same function. Running both suppressed and unsuppressed will be a bit more challenging. Also, I don't think that a +2 gas system is possible on a 16" barrel.
    Click to expand...
    I built and tested them without...but they whole purpose was to shoot them suppressed. Currently, they function 97% both ways (very minor magazine issues), but once they are tuned and running...they will be 100% suppressed.

    I just have a feeling that 18" will work just fine
     
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