BA 12.5 barrel port size...

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  • Schrambo
    Warrior
    • Oct 2016
    • 224

    BA 12.5 barrel port size...

    Built a 6.5G BA 12.5 upper with the usual components, Vltor Mur 1A Upper, GB Bolt, Vltor GB(non-adjustable), WMD carrier, and Chandler handguard...

    Short stoking with full power loads over 2 trips to the range... Pulled the GB and the port was .055" using a drill bit... Drilled it out (my first time) to .073", and everything is running great...

    It's accurate and I'm happy, but has anyone else seen a small gas port on 12.5" BA barrels?
  • just_john
    Chieftain
    • Sep 2012
    • 1565

    #2
    My 12.5 will be here next week. WIll measure and inform. Thanks for the tip.

    Comment

    • LRRPF52
      Super Moderator
      • Sep 2014
      • 8569

      #3
      .055" would work with some cans that generate a lot of accumulation, but sounds a bit small for CLGS Grendel, even with 12.5".

      It would work better on a 5.56 NATO since bore space is less, but Grendel allows a lot of venting/pressure release for the bore space.
      NRA Basic, Pistol, Rifle, Shotgun, RSO

      CCW, CQM, DM, Long Range Rifle Instructor

      6.5 Grendel Reloading Handbooks & chamber brushes can be found here:

      www.AR15buildbox.com

      Comment

      • irishpride114
        Unwashed
        • Nov 2017
        • 2

        #4
        Originally posted by Schrambo View Post
        Built a 6.5G BA 12.5 upper with the usual components, Vltor Mur 1A Upper, GB Bolt, Vltor GB(non-adjustable), WMD carrier, and Chandler handguard...

        Short stoking with full power loads over 2 trips to the range... Pulled the GB and the port was .055" using a drill bit... Drilled it out (my first time) to .073", and everything is running great...

        It's accurate and I'm happy, but has anyone else seen a small gas port on 12.5" BA barrels?
        I just my 12.5" BA barrel in and the gas port measures 0.063. What size drill bit did you use to drill yours out? Where did you gets yours from? Did you just a cordless drill, wood dowel rod, and some oil?

        Comment

        • Sticks
          Chieftain
          • Dec 2016
          • 1922

          #5
          You need a #49 bit. Drill press, V block, and a depth stopper. If you have none of the above, find a gunsmith.
          Sticks

          Catchy sig line here.

          Comment

          • Leadslinger
            Unwashed
            • May 2017
            • 12

            #6
            This was asked in the BA industry forum on ar15.com. BA stated that they purposely did this as they believe people would be shooting this barrel length suppressed and said a carbine buffer was recommended.

            Comment

            • Schrambo
              Warrior
              • Oct 2016
              • 224

              #7
              Originally posted by irishpride114 View Post
              I just my 12.5" BA barrel in and the gas port measures 0.063. What size drill bit did you use to drill yours out? Where did you gets yours from? Did you just a cordless drill, wood dowel rod, and some oil?
              Barrel clamp, .073 bit, drill press set short, wood dowel rod just in case, and oil... Added an adjustable gas block to tune it for my suppressor... Carbine buffer and spring works great now...
              Last edited by Schrambo; 03-14-2018, 03:21 AM.

              Comment

              • wideglidejoe
                Bloodstained
                • Dec 2014
                • 82

                #8
                I have a new, recently purchased BA 12.5" Gr barrel. I've put a few rounds thru it, it's ejecting empties OK, but not loading a new round. All indications are that its under-gassed. Yesterday I called the BA tech line, and was told that my barrel port should be .0595". Today I pulled the gas block and gas tube off, the barrel port is .0550" using calipers, I don't have drill bits to get any more accurate than that.

                I'm using the BA gas block and gas tube which has a roll pin hole that lines up with the slot/notch in the barrel and two set screws. The residue stain on the barrel indicates that the barrel port was centered in the gas block port.

                Sounds like I need to open up my barrel gas port.

                Edit; I'm running standard carbine buffer and spring.

                Comment

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