Loc-tite and gas block

[cst]

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?

[jurassic]

I believe I used Loctite 620, or 609 which is designed to hold bearings, etc. at high temperature. I can see the gas tube going into the gas block through my handguard, no leaks or carbon anywhere on the gas block and barrel.


Loctite ® 609™ Retaining Compound, Cylindrical bonding


Loctite ® 609™ is a low viscosity, rapid-curing anaerobic adhesive that augments the strength of press fit assemblies or slip fit assemblies up to 0.005"in diameter. Adds up to 3,000 psi holding power. Recommended for parts that will need subsequent dismantling, i.e., retention of bearings onto shafts and into housings.
Technical Data:
Typical applications: Augment press fits
Viscosity: 125cP
Cure Time: Fixture - 10 minutes Full - 24 hours
Max gap fill: 0.12mm
Temperature resistance: 150°C
Shear strength: 15.8 /mm2

Loctite ® 620™ Retaining Compound, Cylindrical bonding, High temperature


Loctite® 620™ is a high temperature (450°F), high viscosity liquid retaining compound for cylindrical bonding .Provides a shear strength of over 3,800 psi on steel. Locks and secures metal cylindrical assemblies up to 0.015" diametral clearance. Prevents metal fretting and corrosion, Stops leakages. Typical applications
include locating pins in radiator assemblies, sleeves into pump housings and bearings in auto transmissions.

Technical Data:
Typical applications: High temperature
Viscosity: 8,500cP
Cure Time: Fixture - 30 minutes Full - 24 hours
Max gap fill: 0.38 mm
Temperature resistance: 232°C
Shear strength: 26N/mm2

[NugginFutz]

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.

[PrecisionFirearms]

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!

[Klem]

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.

[LRRPF52]

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.

[Klem]

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.

[cst]

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.

[jurassic]

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)

[olde sarge]

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.

[Desmo900]

Won't the 500 to 600 Deg F. of the gas block just melt the LockTite? Isn't this one of the reasons the Gas Key bolts are staked?

[Bwild97]

It would take several mag dumps on full auto to get the GB to 500°F , so no the the lock tight will not melt under normal target\plinking type of fire.

Again the gas keys are staked for full auto fire, to keep them in place under the rapid and violent cycling of the carrier.