To Bed, or Not to Bed the Gas Block? That is the Question.....

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  • Bizzo24
    Unwashed
    • Jul 2017
    • 14

    To Bed, or Not to Bed the Gas Block? That is the Question.....

    Gentleman (And any Ladies on the forum), I have a build Question for you.

    I've been reading through various threads where folks have had variations to this question, but I'm not sure I found what I'm looking for as it pertains to me personally. Sorry if this is just another repeat question.

    So, I built a 6.5 Grendel using a JP Rifles 18" Barrel Kit and I assembled it into a Wilson Combat Receiver Set. I had bed the barrel and I attached the 2-Piece JP adjustable gas black to the barrel. I took it to the range to tune the gas block and could not get the bolt to hold open on an empty magazine. Now I've done a ton of trouble shooting.....that I won't post here......But ultimately I disassembled the rifle (For Armor-tuff coating at WC....different story altogether). And now I am ready to reassemble the rifle.

    On the first assembly, I attached the 2-piece gas block and torqued to spec. Nothing more. shot less than 20 rounds. Upon removal, there was carbon dust (very minor) on the entire inside flat side of the gas block, and a minimal amount on the outside edge of the gas block on the barrel. First thought was that I was leaking. I called JP and they stated there should be no need to bed the gas block. Can you guys tell me if his minimal amount of build up is normal? or should I consider bedding the block? If bedding the block.....is there a good trick as to do it properly and not get the bedding material into the gas port? I used Permatex gasket sealer to bed the barrel and it worked very well and reasonably simple to remove.

    Thanks for the knowledge!
  • Slappy
    Warrior
    • Feb 2014
    • 711

    #2
    I have never had a leak in or around a gas block so you have something going on there it sounds like. A 2 piece gas block I would not use. That is just me though. Just more that can have room for error and more to mess with. If it is leaking it would seem to me that you might have one side not so straight or both pieces no so straight??, maybe bent or something while it was being made? Ask for a different one and see what happens then. That is my half cent worth. BANG BANG!!

    Comment

    • Bizzo24
      Unwashed
      • Jul 2017
      • 14

      #3
      Thanks for the Feedback Slappy.

      I thought it was a bit odd myself. a 2-piece system was not my first choice, but it came with the barrel kit I ordered so I used it.
      I recently disassembled the whole thing and rebuilt it yesterday. I'm about to post pics under the Picture Thread.....
      I took time to re-measure the gas port distances on the barrel and match them to the gas block. I also found that JP' DFUs do state that using a Loctite type of agent to bed the gas block can be done. And I made sure to torque the 6 torx screws to proper spec. (I did last time as well, but sometimes double checking your work is worth the extra effort). This time I did decide to bed the gas block.....but I used it very sparingly. but after final clamping I think it came out well. Now I have to get it to the range and see how it does. But I'm confident all is well. I'll put some rounds through it and let everyone know how it goes.

      Comment

      • Sticks
        Chieftain
        • Dec 2016
        • 1922

        #4
        Another member here used bees wax to plug the gas port hole when bedding, then a hair dryer or heat gun to melt the wax out. Kind of academic now.

        2 piece block will react the way scope rings do. You have to very gradually tighten all the screws in a left/right pattern until you reach the torque required, or they will start to walk on you. Best if you put witness marks on the top block and barrel to make sure the top half at least stays in alignment.
        Sticks

        Catchy sig line here.

        Comment

        • Slappy
          Warrior
          • Feb 2014
          • 711

          #5
          Originally posted by Bizzo24 View Post
          Thanks for the Feedback Slappy.

          I thought it was a bit odd myself. a 2-piece system was not my first choice, but it came with the barrel kit I ordered so I used it.
          I recently disassembled the whole thing and rebuilt it yesterday. I'm about to post pics under the Picture Thread.....
          I took time to re-measure the gas port distances on the barrel and match them to the gas block. I also found that JP' DFUs do state that using a Loctite type of agent to bed the gas block can be done. And I made sure to torque the 6 torx screws to proper spec. (I did last time as well, but sometimes double checking your work is worth the extra effort). This time I did decide to bed the gas block.....but I used it very sparingly. but after final clamping I think it came out well. Now I have to get it to the range and see how it does. But I'm confident all is well. I'll put some rounds through it and let everyone know how it goes.
          Never did get back to posting . Sounds like you have an idea, with the bedding of the block. A lot of folks here bed the gas block and use a couple different things to do so. Blue Loctite should work. Hope it works out. BANG BANG!!

          Comment

          • LRRPF52
            Super Moderator
            • Sep 2014
            • 8569

            #6
            The JP 2-piece system does not need to be bedded, but I personally just do it anyway.

            Most importantly, is the gas block correctly aligned with the gas port. Simply seating the gas block to the shoulder often results in a choked port, which will short-stroke the action on you due to lack of sufficient gas volume and rate within the optimum window of time.

            Failure to lock on empty has also been seen with some of the ASC and CProducts magazines that have too much play between the follower and inside of the magazine body, to the point that the tail of the follower will not activate your bolt catch. Weak spring strength in the magazine can also cause this problem.

            It's usually gas though. Since the JP barrel uses RLGS, the port pressure is much lower than a MLGS, so any failure to secure the gas port in the circuit correctly will result in short-stroking. The JP 18" barrel and gas block is good kit, one of the top brands on the market. The guns handle much differently than a rack-grade AR.
            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

            • dega37
              Bloodstained
              • Nov 2014
              • 87

              #7
              LRRPF52, what are you bedding the gas block with?

              Comment

              • LRRPF52
                Super Moderator
                • Sep 2014
                • 8569

                #8
                Red Loc-tite 271

                Bill A. said that in testing across large samples of rifles, 50% of them would shoot out of the gate, and the others wouldn't. After bedding the gas blocks, those rifles would shoot like the others.

                Old technique used by AR15 smiths looking for as much accuracy as possible.

                A machinist can press fit or thermo-fit the gas block too.
                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

                • Bigs28
                  Chieftain
                  • Feb 2016
                  • 1786

                  #9
                  How do you keep the loctite out of the gas port? Or does the first shot just clear it out?

                  Comment

                  • Sticks
                    Chieftain
                    • Dec 2016
                    • 1922

                    #10
                    Another member here used bees wax to plug the gas port, and a hair dryer or heat gun on low to melt it out after.
                    Sticks

                    Catchy sig line here.

                    Comment

                    • LRRPF52
                      Super Moderator
                      • Sep 2014
                      • 8569

                      #11
                      Originally posted by Bigs28 View Post
                      How do you keep the loctite out of the gas port? Or does the first shot just clear it out?
                      I make a ring around the gas block journal with a space for the gas port, so that when the gas block slips over the journal, it doesn't drag any Loc-tite into the port.

                      It's anaerobic anyway, so pretty hard to clog it up, but I don't get it in the port.
                      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

                      • Dave_H
                        Unwashed
                        • Jun 2017
                        • 24

                        #12
                        FWIW, I just bought a JP clamp-on adjustable gas block this week. The instructions that came with it said to use Loctite 609 to bed the gas block. 609 is a green retaining compound. I personally think that LRRPF52's recommendation of Loctite 271, or just about any other good Loctite or Permatex thead locker or retaining compound that a guy has on the shelf, would work just fine, but JP did recommend the 609 compound.

                        I also wondered about how to keep the bedding compound out of the gas port.
                        Last edited by Dave_H; 08-13-2017, 04:00 AM.

                        Comment

                        • rasp65
                          Warrior
                          • Mar 2011
                          • 660

                          #13
                          I usually hit it with compressed air down the muzzle and let the self cleaning nature of the gas block take over.

                          Comment

                          • LRRPF52
                            Super Moderator
                            • Sep 2014
                            • 8569

                            #14
                            Originally posted by Dave_H View Post
                            FWIW, I just bought a JP clamp-on adjustable gas block this week. The instructions that came with it said to use Loctite 609 to bed the gas block. 609 is a green retaining compound. I personally think that LRRPF52's recommendation of Loctite 271, or just about any other good Loctite or Permatex thead locker or retaining compound that a guy has on the shelf, would work just fine, but JP did recommend the 609 compound.

                            I also wondered about how to keep the bedding compound out of the gas port.
                            Thanks for the info.

                            The reason I use Loc-tite 272 is the temp tolerance of 450˚F. There can be a lot of heat sink at the gas block. For removal, a heat gun is fine, no open flame needed.
                            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

                            • bj139
                              Chieftain
                              • Mar 2017
                              • 1968

                              #15
                              I doubt any bedding compound in the port could withstand the 10,000 or so psi at the first shot.

                              Comment

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