.204 Ruger AR bbl question

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  • Unclered
    Bloodstained
    • Sep 2016
    • 29

    .204 Ruger AR bbl question

    Greetings from Manchester Mi, I purchased a 24" hvy ss barreled upper in 204. I always lap a new bbl. As I looked down the pipe I saw a burr. I mean .004 of .005 around the gas port. And the hole seemed to be BIG. I mean 1/8 inch or more. So out to the shop I go, patch the bbl out,& begin to lap it. OH OH, big resistance on that spot. I sent it back. They send me the same upper back, w/ a note cleaned out burr w/ a cleaning rod. Nope. same "feel" same .200" gas port mistake. They claim the 204 hole is .006 bigger than the 5.56 hole. None of my 8 ARs have a visually big gas port hole or a definite sticky spot while running a cleaning rod down it. School me on this 204 gas port. Thanks, Red
    Last edited by LRRPF52; 11-09-2017, 06:13 PM. Reason: Clarified chambering
    "It's a long shot with a limb in the way but it beats suckin' pond water"- Jed Clampit 1964
  • grayfox
    Chieftain
    • Jan 2017
    • 4295

    #2
    Which manufacturer for the barrel is this. And is the ss treated, cerakote, QPQ/Nitrided... or?
    That will help the horde in discussing (I'm not a barrel expert myself).
    "Down the floor, out the door, Go Brandon Go!!!!!"

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    • VASCAR2
      Chieftain
      • Mar 2011
      • 6218

      #3
      Originally posted by Unclered View Post
      Greetings from Manchester Mi, I purchased a 24" hvy ss barreled upper in 204. I always lap a new bbl. As I looked down the pipe I saw a burr. I mean .004 of .005 around the gas port. And the hole seemed to be BIG. I mean 1/8 inch or more. So out to the shop I go, patch the bbl out,& begin to lap it. OH OH, big resistance on that spot. I sent it back. They send me the same upper back, w/ a note cleaned out burr w/ a cleaning rod. Nope. same "feel" same .200" gas port mistake. They claim the 204 hole is .006 bigger than the 5.56 hole. None of my 8 ARs have a visually big gas port hole or a definite sticky spot while running a cleaning rod down it. School me on this 204 gas port. Thanks, Red

      I found this info on AR.15.com where Tony from Tromix posted this info on 20 caliber rifles. From my reading improper port location and port size cause significant issues with 20 caliber AR-15’s. I guess because of the different pressure characteristics mid length gas system is preferable on 20” 204 Ruger AR-15 barrels. On 24” barrels I believe most are running rifle length gas system.



      “ I just found my notes when I was making small bore barrels 10 - 15 years ago.

      204 Ruger 24" barrel, rifle gas, .101" port.
      20 Vartarg 18" barrel, mid-length gas, .081" port
      17 Remington 24" barrel, rifle gas, .078" port
      17 Remington 20" barrel, rifle gas, .089" port
      17 Mach 4 24" barrel, rifle gas, .110" port

      Based on the above data, if I were to take a guess on port size for the OP's barrel, it should be about .076", unsuppressed.

      On a 20" 204 Ruger, you would have to run a mid-length gas system. It would be nearly impossible to flow enough gas through any size gas port, to get it to run with a rifle length gas system. “

      Tony




      Here is a link to the thread on AR-15.com.

      Firearm Discussion and Resources from AR-15, AK-47, Handguns and more! Buy, Sell, and Trade your Firearms and Gear.

      Comment

      • Unclered
        Bloodstained
        • Sep 2016
        • 29

        #4
        thank you, interesting.
        "It's a long shot with a limb in the way but it beats suckin' pond water"- Jed Clampit 1964

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