Bedding an AR?

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  • realtreehunter
    Bloodstained
    • Feb 2016
    • 36

    Bedding an AR?

    I have only built 1 AR rifle but I am wanting to build another. My first was a 9.5" 300aac that I'm not really expecting to shoot farther than about 100yds so I just bought parts and put them together. This time I would like to build a Grendel with somewhere between an 18" and 22" barrel. I would like to be able to use this rifle to shoot some of these little bitty groups I see some of you guys shooting so I started looking at tools to face the upper, AGBs, muzzle breaks, and just anything to make this future build smooth shooting and accurate. Then I started noticing on this site, guys talking about bedding the barrel to the upper receiver with blue loc-tite. What is the theory behind this? Does the barrel nut not hold the barrel in place well enough? How do you do this, just put some around the barrel extension before sliding it in the face of the receiver? I have also seen guys talking about bedding the gas block with blue loc-tite. Again, how do you do this, a few strings around the barrel being careful not to get any in the gas port? I can see where this may help seal off any gas leaks but does it help with accuracy? I have stayed in the Holiday Express but I guess I went to sleep to early.
  • A5BLASTER
    Chieftain
    • Mar 2015
    • 6192

    #2
    I can help some on your questions sir.

    I beded my barrel to my receiver and yes all you do is put the lock tite on the barrel extention, put barrel in tighten down barrel nut and then wipe the extra lock tite from the barrel extention inside the receiver.

    I also beded the gas block and gastube. It helps with gas leaks and from what I was told makes the rifle easyer to set with a adjustable gas block.

    Put blue lock tite around gas tube where it goes in to the gas block and put red lock tite around the gas port in barrel in a semi circle, leaving a gap on the muzzle side of gas port so you dont push any in to the gas port when installing gas block.

    I used a jp split yoke adjustable gas block so I was able to put a full ring of red lock tite around gas port but this type of gas block is not a have to have other gas blocks will work I just choose this one because I like the design and anything made by JP.

    Hope this info helps sir and that you can understand it. Others will be along shortly with more advice and knowledge then me.

    Comment

    • realtreehunter
      Bloodstained
      • Feb 2016
      • 36

      #3
      Your explanation is clear and makes very good sense. Thank you. The locktite on around the parts on the gas block makes very good sense as for stopping gas leaks. I still have to wonder the purpose of the locktite on the barrel extension.

      Comment

      • A5BLASTER
        Chieftain
        • Mar 2015
        • 6192

        #4
        Sorry forgot to add that part in there lol.

        What I was told is when You have a barrel to reciver fit that is lose as in you can wiggle the barrel by hand when its in the reciver (before you install barrel nut of caurse ) that applying blue locktite to the barrel extention will fill that foid when you install and tighten down the barrel nut giveing it less chance to flex when a shot is made. And increse accuracy.

        I have seen it work first hand with the first grendel upper I had, I also had to lapp the reciver face on that upper as well and that seem to help the groups as well.

        What people told me is true the most important things for accuracy in the AR is barrel and trigger and lots of trigger time.I have seen these lil things we are talking about help out as well.

        So I did them on my new upper.

        Comment

        • A5BLASTER
          Chieftain
          • Mar 2015
          • 6192

          #5
          What I have learned is for the best accuracy potential from a barrel and upper reciver is you want a barrel and upper reciver that you have to freeze the barrel and heat the upper in the oven to beable to install the barrel and upper together. That way when the barrel warms and the upper cools the upper shrinkes and the barrel will swell and they will have the tightest fit possible.

          Comment

          • ricsmall
            Warrior
            • Sep 2014
            • 987

            #6
            The theory i believe in loc titing these parts is to reduce flex to some point, but more importantly is regulating the vibrations(harmonics) between these parts. The loctite does take up extra space, but think of it as trying to combine three major components and making them act as one component.

            Richard
            Member since 2011, data lost in last hack attack

            Comment

            • Klem
              Chieftain
              • Aug 2013
              • 3507

              #7
              I don't use glue on my guns, except for the gas block screws.

              I don't know if I would get noticeably better groups if I did but I doubt it.

              My rationale is that I don't need to seal the gas block because I need the gas that might be escaping. I have too much gas as it is and so I regulate it.

              If you source a quality upper there should be no play in the barrel/upper fit. If there was I would use glue. As it is I use Castrol high pressure/high temp moly grease and pay attention to barrel nut torqueing.

              Some people are passionate about the use of glue so in deference to them I say...each to their own.

              Comment

              • LRRPF52
                Super Moderator
                • Sep 2014
                • 8569

                #8
                I've been bedding my precision guns for years now after hearing that AA does it, and several other accuracy smiths do it.

                When I was down at Steel Safari last month in New Mexico, I had the pleasure of being able to talk with JP for about 2 hours every night, for 3 nights straight.

                I did a lot of asking, and tried to shut my pie hole so my ears would be open.

                He had told me many years ago that he thermo-fits barrels into their billet uppers, which were undersized.

                In this latest sit-down, he said that in order to deal with the variation in anodizing thickness, they also use a steel shim in sheet form when bedding the barrels.

                Bill A. said in fleet testing, 50% of the guns shot well regardless, but the other 50% clearly benefited from bedding, so I just do it as a norm so it isn't a question.

                I use Red Loc-tite on the gas block as well, not Blue, since the temps there can get pretty hot, to the point that Blue will release.

                Hope this helps.
                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

                • realtreehunter
                  Bloodstained
                  • Feb 2016
                  • 36

                  #9
                  Thanks for the explanations guys. You have taught me something new. I would never expect a boltgun to shoot little bitty groups without bedding, not saying it isn't possible, but I would never have considered bedding an AR. To be honest until I started reading on this forum I wouldn't have known what to bed much less how. This will definitely be a consideration on my Grendel once I get a good go at it. Does anyone know of any negative side effects?

                  Comment

                  • LRRPF52
                    Super Moderator
                    • Sep 2014
                    • 8569

                    #10
                    You just have to heat the gas block when you want to remove it, using hot air gun, not open flame. Do it until the Red Loc-tite releases, which will be evident with smoke and smell.

                    I have never had to heat the upper to get Blue Loc-tite to release the barrel extension.

                    I just tap it with the Delrin receiver insert and the barrel pops right out.
                    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

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