Loc-tite and gas block

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  • LRRPF52
    Super Moderator
    • Sep 2014
    • 8569

    #16
    Originally posted by Klem View Post
    Have they? First I've heard of it in 30 years ('and years').

    My opinion is that you should use glue sparingly on AR's. If you are worried about a loose seal, get a tighter fitting block that taps on with a hammer or clamps. If it leaks slightly and the system still functions it's probably a blessing that you're not having to cope with that excess pressure at the receiver. If you think glue on blocks improves accuracy ('for some reason') then I have no counter argument for you here. That one is a non sequitur.

    Sorry mate but I have to call it when I see it. I won't lose any sleep if you want to use glue on your block seal or advise others accordingly but the only glue on my guns are gas block screws and sometimes handguard screws.
    AA did testing across a large fleet of rifles, and found that after Loc-titing the gas blocks, accuracy tightened up measurably. It's been addressed here before in detail. My initial guess was some type of resonant harmonics with the block, but it may be about maintaining a consistent gas seal as well. I know smiths that hand-fit them as you describe.

    I like the idea of what Knight's is doing with their Mod 2 gas system, which is a mechanical seal. The benefits to a sealed gas block, and thus less leakage, is a smaller gas port can be used. Smaller ports help reduce erosion, which is a factor in maintaining a consistent gas pressure signature throughout the life of the rifle. A lot of this work has been done for the 16" 7.62x51 NATO carbines, as they have become more requested by end users, after going from 24", to 20" guns in the SASS or DM role.

    Gas porting diameters have been driven by the reality of leakage in the conventional AR gas blocks, and the RDT&E Knight's has done is solid. They have good engineering staff, and the largest collection of Stoner samples in the world to refer to when looking at ways to improve the system. The thing that bothers me about leakage is that it can spiral out on you when looking at consistency, especially as the leaking gas erodes the path of least resistance between the block and journal, as well as the gas tube.

    It also doesn't hurt to have the pressure sealed in the gas block and tube area, and let the BCG deal with it, since there are gas relief ports in the bolt carrier for the expansion chamber to vent when it needs to. I also find the relief port geometry used by the Dutch interesting, when looking at the Dutch ArmaLite AR10's. Compressed fluid dynamics and the geometry of the components can make big differences in how the gas behaves, when looking at laminar flow.
    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

    • NugginFutz
      Chieftain
      • Aug 2013
      • 2622

      #17
      Ok - This is not to recant my stated feelings on the matter, but here is some real world data (with pictures!).

      I recently assembled another table gun, a BHW 5.56 with a 22" Match Bull barrel. Ordinarily, I use clamp on style gas blocks, but due to this build's lightweight hand guard's configuration, I had to go with a lowpro setscrew gas block. I'd decided (this one time) to seal it with loctite because I'd heard good stuff about it here and on other forums. Didn't know what to expect, as I'd not done it before. Last night, I removed the hand guard to gain access to the barrel nut (checking other aspects of the build) and found this.

      Gas blow by from gas tube - NOT gas block.


      Removed block shows absence of gas blow by at gas port.

      The gas was escaping at both ends of the gas block at the tube, which I'd merely pinned in place, without any sealant.

      I reapplied it, as I'd originally done.


      Reinstalled the block...


      I removed the excess, and buffed off the gas residue I'd forgotten to remove while I had the block off.

      So, does it work? I think this would seem to indicate it does. Does it help with accuracy? I can't really say. Next post shows a group from the barrel.
      Last edited by NugginFutz; 12-09-2014, 12:47 AM.
      If it's true that we are here to help others, then what exactly are the others here for?

      Comment

      • NugginFutz
        Chieftain
        • Aug 2013
        • 2622

        #18
        Here is a group it shot over the weekend. The loctite obviously doesn't hurt accuracy.

        Last edited by NugginFutz; 12-09-2014, 12:47 AM.
        If it's true that we are here to help others, then what exactly are the others here for?

        Comment

        • montana
          Chieftain
          • Jun 2011
          • 3209

          #19
          Originally posted by NugginFutz View Post
          Here is a group it shot over the weekend. The loctite obviously doesn't hurt accuracy.

          Nothing beats trial and error. Great summary , thanks for posting.

          Comment

          • jurassic
            Warrior
            • Sep 2014
            • 246

            #20
            Originally posted by NugginFutz View Post
            Ok - This is not to recant my stated feelings on the matter, but here is some real world data (with pictures!).

            I recently assembled another table gun, a BHW 5.56 with a 22" Match Bull barrel. Ordinarily, I use clamp on style gas blocks, but due to this build's lightweight hand guard's configuration, I had to go with a lowpro setscrew gas block. I'd decided (this one time) to seal it with loctite because I'd heard good stuff about it here and on other forums. Didn't know what to expect, as I'd not done it before. Last night, I removed the hand guard to gain access to the barrel nut (checking other aspects of the build) and found this.

            Gas blow by from gas tube - NOT gas block.


            Removed block shows absence of gas blow by at gas port.

            The gas was escaping at both ends of the gas block at the tube, which I'd merely pinned in place, without any sealant.

            I reapplied it, as I'd originally done.


            Reinstalled the block...


            I removed the excess, and buffed off the gas residue I'd forgotten to remove while I had the block off.

            So, does it work? I think this would seem to indicate it does. Does it help with accuracy? I can't really say. Next post shows a group from the barrel.
            I saw the same thing when I removed my handguard to clean the rifle. That is why I used loctite on the tube and not the gas block itself. Also wouldn't a leak free gas system give you more consistent pressure and velocity, helping with consistency? I'm pretty sure I read about the green loctite from something posted by Bill on this forum.

            Why didn't you remove and loctite the gas tube since that's where you have the leak?

            Comment

            • cst
              Warrior
              • Jan 2014
              • 239

              #21
              Has anyone checked what the locktite seal looks like after long term testing? How much is left...? I figure with prolonged shooting under all the heat and blow out pressure...u will have an eventual leak?

              I took apart my m4 yesterday..plenty of leaks but there was so much hard carbon build up on the block as well as the gas tube (I couldn't remove the tube)......is it conceivable it will seal itself over time?

              Comment

              • jurassic
                Warrior
                • Sep 2014
                • 246

                #22

                Comment

                • NugginFutz
                  Chieftain
                  • Aug 2013
                  • 2622

                  #23
                  Originally posted by jurassic View Post
                  I saw the same thing when I removed my handguard to clean the rifle. That is why I used loctite on the tube and not the gas block itself. Also wouldn't a leak free gas system give you more consistent pressure and velocity, helping with consistency? I'm pretty sure I read about the green loctite from something posted by Bill on this forum.

                  Why didn't you remove and loctite the gas tube since that's where you have the leak?
                  All true. Loctite green? Didn't have it. Choice was Blue or Red. I cut the Blue wire. Remember - this was a simple experiment, and I didn't want to cement anything in place. Red seemed too ominous.

                  Why didn't I pull the tube and seal it? In all candor, I couldn't be bothered. I was looking into a different issue at the time, and this was low priority. I've run plenty of systems without sealing the gas tubes, but never ran a setscrew gas block. My previous focus was on that, and that alone.

                  I'd like to convince myself that I left the gas tube alone so that I could determine if the carbon would eventually seal the leaks without help but, as I mentioned, I just didn't worry over it. No - wait! That's it... I'm conducting a longer term test on carbon build up. That's it. Carbon build up test.
                  If it's true that we are here to help others, then what exactly are the others here for?

                  Comment

                  • PrecisionFirearms
                    Warrior
                    • Apr 2011
                    • 767

                    #24
                    We use Red or Blue Locktite on gas blocks. YES we have tested and found Locktite does help with accuracy. Has to do with Barrel harmonics or bolt unlock dwell times due to more consistent gas pressure. Either way we do it on all precision rifle builds. In over 8000 upper builds, we have not had one report of a set screw gas block coming loose. Why not when it costs so little and no negatives in doing it?

                    Just had a customer email me his group. 3 shots measuring .3 inches but done at 300 yards. Says it will do it every time he does his job. Tongue in cheek: It has the gas block Locktited!
                    "Precision - The Pinnacle of Perfection."

                    Comment

                    • Klem
                      Chieftain
                      • Aug 2013
                      • 3509

                      #25
                      Originally posted by PrecisionFirearms View Post
                      We use Red or Blue Locktite on gas blocks. YES we have tested and found Locktite does help with accuracy. Has to do with Barrel harmonics or bolt unlock dwell times due to more consistent gas pressure. Either way we do it on all precision rifle builds. In over 8000 upper builds, we have not had one report of a set screw gas block coming loose. Why not when it costs so little and no negatives in doing it?

                      Just had a customer email me his group. 3 shots measuring .3 inches but done at 300 yards. Says it will do it every time he does his job. Tongue in cheek: It has the gas block Locktited!
                      Why not glue the gas block?
                      1. Because it's a hassle pull apart whenever you ever want to change parts.
                      2. Because most systems are overgassed anyway.

                      Is it more accurate?
                      Needs proper testing, so far I see anecdotal evidence from precision firearms with an aleady good barrel and everything else tickety boo. It is convenient to point to a glued block as the reason for its accuracy but let's face it, it's probably a good barrel, good shooter, good optics, good ammo and good weather conditions. What would solve this debate is to convincingly isolate the block as the variable that caused the group to be better than it otherwise would.
                      Harmonics? Hmmmm (see above)
                      Dwell time. In a system with short lengths beyond the block and/or internal ballistics with steep time/pressure curves (i.e. low pressure after the block) like an SBR...Sure, you need all the dwell time you can get (or you could just get a heavy-duty extractor spring and/or those expensive 'D Fender's. In other guns, maximizing the pressure during dwell time is not an issue. And in some there can even be too much dwell time so an unglued block might help.

                      Knights supply a little bottle of Rockset with their muzzle breaks. Very nice of them but to be realistic it's not in the manufacturers interests that their part ever comes loose. And why would anyone want to replace a Knights brake with another manufacturers break anyway?! Or, a PF block with someone else's?

                      Take pause guys, I am just playing Devil's advocate here. Does gluing your block really tighten the groups? Or is it just another affectation from aficionado's who like to tinker with every aspect of the platform? Searching for the Holy Grail of accuracy from something that is after all, an AR15.
                      Last edited by Klem; 12-12-2014, 01:40 AM.

                      Comment

                      • LRRPF52
                        Super Moderator
                        • Sep 2014
                        • 8569

                        #26
                        When I had this conversation with Bill A., he said 50% of the rifles exceeded his expectations off the bat, while the other half didn't, even when they were all assembled with the same components. We're talking 20" and longer guns. After some head scratching and research, he decided to try the Red Loc-tite on the blocks, and all of a sudden they tightened up to sub-MOA.

                        This was across a large enough fleet sample to be conclusive for him at least. I know Les Baer Red Loc-tite's the crap out of his guns, and they are very accurate as well.

                        To get the blocks off, I just apply heat with a heat gun, not open flame, and can smell when the compound goes liquid. I insulate the barrel, use a lot of thick tape and leather, then pound the block off with a large brass piece and a hammer.
                        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

                        • Klem
                          Chieftain
                          • Aug 2013
                          • 3509

                          #27
                          Originally posted by LRRPF52 View Post
                          When I had this conversation with Bill A., he said 50% of the rifles exceeded his expectations off the bat, while the other half didn't, even when they were all assembled with the same components. We're talking 20" and longer guns. After some head scratching and research, he decided to try the Red Loc-tite on the blocks, and all of a sudden they tightened up to sub-MOA.

                          This was across a large enough fleet sample to be conclusive for him at least. I know Les Baer Red Loc-tite's the crap out of his guns, and they are very accurate as well.

                          To get the blocks off, I just apply heat with a heat gun, not open flame, and can smell when the compound goes liquid. I insulate the barrel, use a lot of thick tape and leather, then pound the block off with a large brass piece and a hammer.

                          How many rifles are we talking about? You are talking in percentages which implies a subset of 100 or more. As you know any sample size of less than 100 is communicated by the actual number to avoid unreasonable assumptions (e.g. 'one out of two guns tested' instead of '50% of the guns tested').

                          If true and statistically valid this is an extraordinary revelation with industry-wide implications. If half of all (long barreled) AR's can have the accuracy noticeably improved by something as simple as gluing the block. All gun assemblers will be doing it and it will become common knowledge on AR forums.

                          That said, I will leave the glue in the drawer until it is more than just anecdotal.

                          Comment

                          • cst
                            Warrior
                            • Jan 2014
                            • 239

                            #28
                            Bottom line. ....if it shoots good without it..don't touch it.....if it sucks...can't hurt to try it....


                            But I can't believe a setup that is shooting really poorly will suddenly shrink to sub moa just from glue. ....there will be bigger inherent problems that need to be addressed.

                            Comment

                            • jurassic
                              Warrior
                              • Sep 2014
                              • 246

                              #29
                              Originally posted by NugginFutz View Post
                              All true. Loctite green? Didn't have it. Choice was Blue or Red. I cut the Blue wire. Remember - this was a simple experiment, and I didn't want to cement anything in place. Red seemed too ominous.

                              Why didn't I pull the tube and seal it? In all candor, I couldn't be bothered. I was looking into a different issue at the time, and this was low priority. I've run plenty of systems without sealing the gas tubes, but never ran a setscrew gas block. My previous focus was on that, and that alone.

                              I'd like to convince myself that I left the gas tube alone so that I could determine if the carbon would eventually seal the leaks without help but, as I mentioned, I just didn't worry over it. No - wait! That's it... I'm conducting a longer term test on carbon build up. That's it. Carbon build up test.
                              I was taking apart and experimenting with 2 different guns for no good reason until I sold them and built a rifle with a Lilja barrel, it has not been apart since. If I can get my hands on a cut rifled barrel I can afford I'll do the same thing, build it right and leave it alone.

                              Mega upper (barrel fits very snuggly in this upper)
                              Lilja 17" AR740 profile, wasp profile behind gas block)
                              Young NM bolt carrier
                              PF bolt
                              Geissele Super gas block
                              Timney Trigger
                              Spikes LPK
                              Aero Precision lower (I really don't like it, but I will not take apart again!)
                              BCM carbine buffer tube and spring, H2 buffer
                              ALG Defense EMR M-LOK handguard (I believe this helps, they include shims and wrench extension to get the barrel torque perfect)
                              Last edited by jurassic; 12-12-2014, 11:54 AM. Reason: update

                              Comment

                              • olde sarge
                                Warrior
                                • May 2014
                                • 247

                                #30
                                Mark (PF), do you dimple the barrels before adding the gas block? Trying to decide if it is needed or not on my PF barrel.

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