Troubleshoot: BCG stuck in battery

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  • Mindreader1
    Bloodstained
    • Sep 2016
    • 69

    Troubleshoot: BCG stuck in battery

    So I just finished my first ever AR build, a lightweight Grendel with JP 18', JP Adj. Block, JP Bolt and RCA BC. I tested out my build for the first time, but for some reason after every shot the BCG becomes stuck in the feed ramp and had to be pried open with an allen wrench. I was using the Hornady Black ELD from Academy. Could anyone help me with this issue? The set screws for both the gas block and the adjustable gas key had been backed out from the closed position so I don't think they were the cause. Once I pry the BCG open and pull the CH the casing is ejected. Any advice would be highly appreciated!
  • Sticks
    Chieftain
    • Dec 2016
    • 1922

    #2
    Post the lot number on the ammo. Also do a COAL measurement on an unfired round.

    Unlikely, but measure the bolt overall length, and bolt face depth to see if it is a .125 or .136.

    With the gas block in position (your post reads like you tried to move it) - remove the BCG and look to see if your gas tube is centered inside the receiver, and you have the correct end of the gas tube in the receiver. Inspect your gas key on the BCG to see if there are nicks or deep markings on it.

    And stop prying open your action. Google "AR15 Malfunction Clearing", and "AR15 Mortaring" and learn how to do it. Two handed pull on the charging handle first, then Mortar if you still can't get it to release.
    Sticks

    Catchy sig line here.

    Comment

    • A5BLASTER
      Chieftain
      • Mar 2015
      • 6192

      #3
      First question is the gas block tight against the shoulder on the barrel?

      If it isn't then your cutting most of the gas port off with the gas block body .

      If it's set properly open the gas block to wide open then work down from there.

      If your bcg is moving back when you fire a round but won't completely unlock you are very undergassed and you need to fix the glass issue.

      Comment

      • Mindreader1
        Bloodstained
        • Sep 2016
        • 69

        #4
        The gas tube came pre inserted with the gas block from JP so not likely for that to be screwed up? Which ammo should I use instead?
        Originally posted by Sticks View Post
        Post the lot number on the ammo. Also do a COAL measurement on an unfired round.

        Unlikely, but measure the bolt overall length, and bolt face depth to see if it is a .125 or .136.

        With the gas block in position (your post reads like you tried to move it) - remove the BCG and look to see if your gas tube is centered inside the receiver, and you have the correct end of the gas tube in the receiver. Inspect your gas key on the BCG to see if there are nicks or deep markings on it.

        And stop prying open your action. Google "AR15 Malfunction Clearing", and "AR15 Mortaring" and learn how to do it. Two handed pull on the charging handle first, then Mortar if you still can't get it to release.

        Comment

        • explorecaves
          Warrior
          • Sep 2014
          • 284

          #5
          Is the gas tube bent? Can happen in shipping....

          Comment

          • A5BLASTER
            Chieftain
            • Mar 2015
            • 6192

            #6
            My JP 18 inch barrel did the same as yours when I first put it together the cause was the gas was cutt off to much and the bcg wasn't completely unlocking.

            Check the gas block is a line properly and open it up to a lil more then half are go to full open and work down from there.

            Comment

            • Mindreader1
              Bloodstained
              • Sep 2016
              • 69

              #7
              Ah good to know you someone else had trouble! I did turn the screw very loose (as loose as possible before the set screw comes out completely and it still had that issue. Same thing with the gas key. When looking down the charging handle I don't see any vents. The problem is my kmr rail is so tight against the barrel and receiver that it's next to impossible to remove the part without hammering it and risk damage.
              Originally posted by A5BLASTER View Post
              My JP 18 inch barrel did the same as yours when I first put it together the cause was the gas was cutt off to much and the bcg wasn't completely unlocking.

              Check the gas block is a line properly and open it up to a lil more then half are go to full open and work down from there.

              Comment

              • A5BLASTER
                Chieftain
                • Mar 2015
                • 6192

                #8
                What do you mean by ( gas key).

                Or you useing a adjustable bcg with a adjustable gas block?

                If not and you meant you lossed the screws in the gas key for some reason that could be a problem I think, if it's a normal bcg with a fixed gas key I don't think you should be lossing the screws that hold it on to the bcg.

                Might sound kind of dumb but I want to ask are you adjusting the gas with the screw that's on the right side of the gas block are the screw that's in the front face of the gas block?

                Also a note of info, JP barrel's are spec's to have the gas block tight against the shoulder area on the barrel, no gap.

                Comment

                • Mindreader1
                  Bloodstained
                  • Sep 2016
                  • 69

                  #9
                  Good question. I'm actually running a Rubber City Bolt carrier with an adjustable gas key - hence loosening the set screw in the gas key. As for the gas block I'm referring to lessening the set screw on the right side of the gun not in front of it. Im running a KMR so I had to dremel through part of the HG to get to the screw but it's nevertheless loosened.
                  Originally posted by A5BLASTER View Post
                  What do you mean by ( gas key).

                  Or you useing a adjustable bcg with a adjustable gas block?

                  If not and you meant you lossed the screws in the gas key for some reason that could be a problem I think, if it's a normal bcg with a fixed gas key I don't think you should be lossing the screws that hold it on to the bcg.

                  Might sound kind of dumb but I want to ask are you adjusting the gas with the screw that's on the right side of the gas block are the screw that's in the front face of the gas block?

                  Also a note of info, JP barrel's are spec's to have the gas block tight against the shoulder area on the barrel, no gap.

                  Comment

                  • m796rider
                    Warrior
                    • Jul 2011
                    • 398

                    #10
                    You're using an adjustable gas block AND an adjustable gas key? I'd go with one or the other, but not both... You're introducing way too many variables, IMHO.

                    Comment

                    • Mindreader1
                      Bloodstained
                      • Sep 2016
                      • 69

                      #11
                      Yeah it was silly of me in hindsight. Don't wanna just replace the bcg again though. Anything else I can do?
                      Originally posted by m796rider View Post
                      You're using an adjustable gas block AND an adjustable gas key? I'd go with one or the other, but not both... You're introducing way too many variables, IMHO.

                      Comment

                      • VASCAR2
                        Chieftain
                        • Mar 2011
                        • 6218

                        #12
                        I would close the adjustable gas Bolt Carrier as much as possible and treat it like a non adjustable BC and adjust the gas block on the barrel.

                        Comment

                        • Mindreader1
                          Bloodstained
                          • Sep 2016
                          • 69

                          #13
                          Originally posted by VASCAR2 View Post
                          I would close the adjustable gas Bolt Carrier as much as possible and treat it like a non adjustable BC and adjust the gas block on the barrel.
                          Cool as in turn the gas key screw all the way in and then back out a turn?

                          Comment

                          • A5BLASTER
                            Chieftain
                            • Mar 2015
                            • 6192

                            #14
                            VASCAR2, If you close the adjustable gas key as much as possible wouldn't that be the same as useing a adjustable gas block to turn off the gas to the bcg.

                            I will admit I'm not totally sure how a adjustable gas key bcg works compared to a adjustable gas block.

                            I would think you would need to open the adjustable gas key to full power to allow it to work like a normal bcg would and then use the adjustable gas block to tame the gas down.

                            Comment

                            • Mindreader1
                              Bloodstained
                              • Sep 2016
                              • 69

                              #15
                              Here are some pix



                              Comment

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