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Thread: Intermediate length gas system

  1. #41
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    Just been busy with TBAC, etc, not a lot of time left over for forums. I actually found this thread searching for data on Intermediate gas.
    Last edited by Zak Smith; 11-16-20 at 20:21.

  2. #42
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    My first built upper had an 18" White Oak Armory SPR SS barrel with the Intermediate gas port. I don't remember the length of the TROY Ind rail used. It was smooth like a 20" rifle. IIRC it had a Spike's T-2 buffer weight and factory carbine spring.
    A varmint hunter wanted it more than me so I sold it and bought BCM.
    Looking now on WOA website the 18" SPR is only offered in Mid or Rifle length gas now.
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  3. #43
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    What do you guys think is the “optimal” buffer/spring for a 16” intermediate barrel with 55 gr 223 ammo?

    Thanks

    Nick

  4. #44
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    Quote Originally Posted by Nick S View Post
    What do you guys think is the “optimal” buffer/spring for a 16” intermediate barrel with 55 gr 223 ammo?

    Thanks

    Nick
    H2 w/ Colt or Sprinco spring
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    Rifle w/ Sprinco green or Colt spring
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  5. #45
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    Quote Originally Posted by Nick S View Post
    What do you guys think is the “optimal” buffer/spring for a 16” intermediate barrel with 55 gr 223 ammo?

    Thanks

    Nick

    To me the whole point of a longer gas tube/less dwell time is to be able to use a lighter reciprocating mass in the BCG-buffer, or not have to use heavier than standard carbine parts to get reliable function. At least that was the original intent, but it seems like anymore, people want to tune the gun to run with heavy springs and buffers. Which is just chasing your own tail and molesting the whole point of the longer gas tube.
    Last edited by 17K; 12-11-20 at 14:55.

  6. #46
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    Intermediate length gas system

    Someone stop the necro
    Last edited by Mercs; 12-11-20 at 15:57.

  7. #47
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    I got a Noveske Intermediate gas 18" and cut it to 14.2". With a non-adjustable gas block and a small suppressor (Dominus-K-SR), it operated with a JP LMOS (steel) and a normal SCS, up to a JP FMOS with 2 tungsten weights on the SCS.

    Using a Y/M NM carrier and a stock SCS as baseline, the FMOS+2T config is 1.31 ounces heavier, and the LMOS is 2.68 ounces lighter.

    By "operated" I mean it would feed and fire semi-auto without malfunction and it would lock back on an empty new PMAG, and have reasonable if not vigorous ejection.

    FWIW, when an adjustable gas block is in play, or the gas can be permanently or temporarily moderated, my strategy is to use the lightest reciprocating mass possible, my baseline for reliable operation being a JP LMOS (steel) and a stock SCS (3 steel weights, roughly equivalent to a carbine buffer), and then dial up the gas from zero until it operates reliably. I will shortly be experimenting with reducing mass further than a stock SCS by replacing one or more steel masses with delrin or aluminum. A JP VMOS can be run without any weights and in that configuration is 0.38 ounces lighter than a JP FMOS.

    Ages ago I used the original aluminum JP BC and it was so light it was unreliable when dirty. I don't have one anymore but I believe they weigh about 3.7 ounces.

    Unless there is a countervailing factor (such as an accuracy impact or unlocking too early), less reciprocating mass is better as long as the BCG retains enough momentum (even when dirty) to strip the next round and operate the action, and go back into battery reliably, and assuming you can adjust its cycle time via gas adjustment.

  8. #48
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    Quote Originally Posted by 17K View Post
    To me the whole point of a longer gas tube/less dwell time is to be able to use a lighter reciprocating mass in the BCG-buffer, or not have to use heavier than standard carbine parts to get reliable function. At least that was the original intent, but it seems like anymore, people want to tune the gun to run with heavy springs and buffers. Which is just chasing your own tail and molesting the whole point of the longer gas tube.
    The whole point of using a longer gas system is to tap into the gas where pressure is lower to
    1) get a softer gas pulse
    2) have a more forgiving tolerance for the gas port diameter
    3) wider span of operation

    Experimenting with an adjustable gas block (using 5.56 ammo), I found that the minimum gas setting for a carbine, H and H2 buffer was the same. The only difference was that recoil was sharpest with the carbine buffer and softest with the H2.

    A carbine buffer may be the most common buffer (especially with "economy" brand ARs) but it isn't the standard weight buffer. The H2 is. The H2 buffer is what Colt uses in M4s delivered to the government. The other standard buffer is the rifle buffer which has more weight than the H2.

    To properly tune an AR to run with a carbine weight or lighter buffer, the powder charge in the ammo will need to be reduced.

    But if 5.56 ammo is to be used, the right buffers are H2, A5H2 or Rifle
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  9. #49
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    Quote Originally Posted by MistWolf View Post
    A carbine buffer may be the most common buffer (especially with "economy" brand ARs) but it isn't the standard weight buffer. The H2 is. The H2 buffer is what Colt uses in M4s delivered to the government..
    If I remember right, the H2 did not become standard in the M4a1 until the change to the heavier “SOCOM” barrel was made.

  10. #50
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    Quote Originally Posted by 1168 View Post
    If I remember right, the H2 did not become standard in the M4a1 until the change to the heavier “SOCOM” barrel was made.

    You are correct. H buffer is in M4, H2 in M4A1, H2 or H3 in MK18.

    That guy is just repeating internet mantra and doesn’t understand what the buffer is for and what the gas system does.

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