Lets discuss AR-15 gas block installation techniques

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    John_

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    As a non-vetted hobbyist, I just used about ten different tools to disassemble an upper for a barrel swap without damaging anything. I damaged something in the past and learned from it. I'm not being paid to put rifles together, so time isn't money for me. I can take my time and make sure I do things right.

    Relevant to this thread, the gas block set screws were knurled cup point screws installed with Loctite 271. About 15 seconds with a wood burner touching the screw is enough to heat up the threadlocker where it is easy to break the bond. Even though the barrel had seen enough rounds suppressed to heat up the handguard to the point you had to wear a thick glove, the Loctite held strong when cooled. Heating it up is enough to weaken it, but it will still hold enough to prevent vibration. If it's a concern, use Rocksett or the new high temp stuff from Vibratite.

    That was my point earlier Dave. You show just how easy it is to release the Loctite with the wood burner. So what good is the Locktite 271 if your barrel and GB heat up to 400 or 500F from an extended firing session or a firefight? When you need the Locktite to perform (extreme heat and vibration), it fails. Locktite 271 is rated full strength by Henkel to 300F. 300F + would not be hard to reach on a 556 pistol, much less a suppressed 556 pistol.

    I think Rocksett is a better choice. Unless you are assembling an AR knowing full well it's no good for a 30 minute + sustained firefight. Or could become questionable. My Geissele 556 Super Duty pistol has the 2 setscrews and a roll pin installed in the GB/barrel. And those two setscrews have a white paint stripe marking their lack of movement.
     

    DAVE_M

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    That was my point earlier Dave. You show just how easy it is to release the Loctite with the wood burner. So what good is the Locktite 271 if your barrel and GB heat up to 400 or 500F from an extended firing session or a firefight? When you need the Locktite to perform (extreme heat and vibration), it fails. Locktite 271 is rated full strength by Henkel to 300F. 300F + would not be hard to reach on a 556 pistol, much less a suppressed 556 pistol.

    I think Rocksett is a better choice. Unless you are assembling an AR knowing full well it's no good for a 30 minute + sustained firefight. Or could become questionable. My Geissele 556 Super Duty pistol has the 2 setscrews and a roll pin installed in the GB/barrel. And those two setscrews have a white paint stripe marking their lack of movement.

    Threadlocker is just a medium used to fill up the space between male and female threads. It bonds to the substrate to hold on, but it does not create tension. When you tighten a bolt or screw, you are applying torque to create tension. Tension is the actual force holding the fastener in place. We use knurled screws, because the knurling bites into the barrel, sort of like a how a zip tie works. When you apply enough torque to remove them, the knurling itself breaks off. You can see the smooth ring on the end of the screw I removed. Granted, these are tiny set screws and not large fasteners, so the torque needed is minimal. Heat isn't what will cause the screws to back out, but it is a factor overall. Heat will cause the threadlocker to degrade and parts will expand, but it's vibration that will cause the screws to loosen. This is why some choose to pin the gas block, but that's another discussion.

    I've used Loctite 271 with good success. It's what BCM recommends and many other manufacturers do as well. Rocksett and Vibratite both make suitable alternatives if you feel that 271 won't handle the job. FWIW, for the casual shooter sending one round down range every 10-30 seconds, it's not something to be overly concerned with, but if you're building a defensive rifle that will see how volumes of fire, I would definitely go the strongest route on everything I can.

    49852641683_c66a5f6355_z.jpg
     

    John_

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    Henkel has a performance curve graph for 271. @ 300F its bond is 100%, then its performance degrades downward until @ 500 its pretty much nothing. I viewed it on their website yesterday.

    excerpt from their website: Loctite® Threadlocker Red 271™ is designed for the permanent locking and sealing of threaded
    fasteners. The product cures anaerobically, when there is an absence of air between close fitting
    metal surfaces. It protects threads from rust and corrosion and prevents loosening from shock and
    vibration. It is only removable once cured by heating up parts to 450°F (232°C).

    271 docs page: https://www.loctiteproducts.com/en/...cts/specialty/loctite_threadlockerred271.html
     

    DAVE_M

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    Henkel has a performance curve graph for 271. @ 300F its bond is 100%, then its performance degrades downward until @ 500 its pretty much nothing. I viewed it on their website yesterday.

    excerpt from their website: Loctite® Threadlocker Red 271™ is designed for the permanent locking and sealing of threaded
    fasteners. The product cures anaerobically, when there is an absence of air between close fitting
    metal surfaces. It protects threads from rust and corrosion and prevents loosening from shock and
    vibration. It is only removable once cured by heating up parts to 450°F (232°C).

    271 docs page: https://www.loctiteproducts.com/en/...cts/specialty/loctite_threadlockerred271.html

    Yes, I've read it and I'm very familiar with their products. You can use it or not. I have both Rocksett and various Loctite adhesives on my bench.

    You're also missing a key component, which is time. It needs to heat up and stay hot to be removed. If it cools down again, it solidifies once more, although it has lost some strength.
     

    John_

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    I've used Loctite 271 with good success. It's what BCM recommends and many other manufacturers do as well. Rocksett and Vibratite both make suitable alternatives if you feel that 271 won't handle the job. FWIW, for the casual shooter sending one round down range every 10-30 seconds, it's not something to be overly concerned with, but if you're building a defensive rifle that will see how volumes of fire, I would definitely go the strongest route on everything I can.

    Lots of people are enamored with BCM. Sure they may build good rifles (never owned their rifle but did own an upper of theirs) but they do not supply our military with M16s or M4s. Never did to my knowledge. Colt, Daniel Defense, LMT, FN Herstal, Bushmaster (now defunct) but no BCM. What other manufacturers recommend Locktite 271 for the GB setscrews as you mentioned?
     

    thperez1972

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    It doesn’t have to be required but I’m sure there are members on here who are proud to be auto mechanics, armorers, carpenters etc ,who wouldn’t mind being recognized for their skills and offer professional advice. If you are on the internet your info is out there anyhow.


    Sent from my iPhone using Tapatalk Pro

    Yeah...it could be voluntary. I'd do it. I'm pretty good with photoshop. I could create an official unofficial icon for their signature. Someone would have to feel comfortable sharing their credentials/certifications with me to verify.
     

    ozarkpugs

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    That was my point earlier Dave. You show just how easy it is to release the Loctite with the wood burner. So what good is the Locktite 271 if your barrel and GB heat up to 400 or 500F from an extended firing session or a firefight? When you need the Locktite to perform (extreme heat and vibration), it fails. Locktite 271 is rated full strength by Henkel to 300F. 300F + would not be hard to reach on a 556 pistol, much less a suppressed 556 pistol.

    I think Rocksett is a better choice. Unless you are assembling an AR knowing full well it's no good for a 30 minute + sustained firefight. Or could become questionable. My Geissele 556 Super Duty pistol has the 2 setscrews and a roll pin installed in the GB/barrel. And those two setscrews have a white paint stripe marking their lack of movement.
    Did you bother to read the article ? Just recently one of the best barrel providers in the industry and man who designed the 6.8 performance chamber was ridiculed and dismissed as a non profesional for his suggestion to install barrels into loose uppers by chemical shimming just like this barrel maker does . I think it is waste of time for anyone to try to help you. You even argue with the onointed one . You are hung up on vibration loosening up a knurled screw and refuse to grasp the facts given you . If you have a loose block get to measuring . If both parts are within the range of specs it tolerance stacking . Your choice is to swap out one or the other until you find a combination that is tight or put a sealer between them to keep vibration and movement down . We can argue until dooms day about which one so use what you want . The whole temperature thing is Non issue . When things heat up the barrel expands faster than the block and gets really tight . If you left the rail off for quick access and dumped enough mags to heat the barrel to 400° you would have a hard time getting the screw out even if it was not installed with loc-tite and then would have to beat the block off with a hammer . Quit worrying about non issues and quit arguing with people who try to help you . Maybe if you really apply what people who know what they are doing tell you soon you will be saying building uppers are a piece of cake like you said lowers are for you .








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    John_

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    You're also missing a key component, which is time. It needs to heat up and stay hot to be removed. If it cools down again, it solidifies once more, although it has lost some strength.

    Yes, I fully understand that component, and the screw is torqued to the GB. But any form of threadlocker is there to prevent vibration and heat from allowing a fastener to back out, to move whatsoever. And 271 is good to 300F by its manufacturer, and @ 450F its bond has failed. So in my mind if you are building a SHTF weapon, a rock solid no bars weapon your life can depend on, 271 is not a good choice. Rocksett is, or the ceramic Vibratite product. Good to 2000F.

    And I also understand me shooting @ the range is prob little threat to my GB or the 271 locktite. Slow rate of fire schedule. But again for a weapon your life may depend on, extended firing session or combat, or suppressed, 271 is a poor choice imo. And exactly why Geissele pins their GB in addition to the setscrews. I bet the M4s supplied to our military do not rely solely on Loctite 271 on the GB setscrews for GB retention. I don't know for sure on that, just my educated guess. We have any active duty certified US military armorers who are members here?
     

    John_

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    Did you bother to read the article ? Just recently one of the best barrel providers in the industry and man who designed the 6.8 performance chamber was ridiculed and dismissed as a non profesional for his suggestion to install barrels into loose uppers by chemical shimming just like this barrel maker does . I think it is waste of time for anyone to try to help you. You even argue with the onointed one . You are hung up on vibration loosening up a knurled screw and refuse to grasp the facts given you . If you have a loose block get to measuring . If both parts are within the range of specs it tolerance stacking . Your choice is to swap out one or the other until you find a combination that is tight or put a sealer between them to keep vibration and movement down . We can argue until dooms day about which one so use what you want . The whole temperature thing is Non issue . When things heat up the barrel expands faster than the block and gets really tight . If you left the rail off for quick access and dumped enough mags to heat the barrel to 400° you would have a hard time getting the screw out even if it was not installed with loc-tite and then would have to beat the block off with a hammer . Quit worrying about non issues and quit arguing with people who try to help you . Maybe if you really apply what people who know what they are doing tell you soon you will be saying building uppers are a piece of cake like you said lowers are for you .

    I'm not interested in any thing you have to say. You keep repeating the same ignorance over and over. You advocate sealing a gas block with liberal application of blue Locktite and you got that from your hero builder on his website. Genius.

    And this is a discussion not an argument with Dave. You don't even know the difference, lol. Why don't you go change a water pump or something?

    Edit: You are going to be my first "ignore member" winner in 7 years here. Congrats, and adios.
     
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    DAVE_M

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    Lots of people are enamored with BCM. Sure they may build good rifles (never owned their rifle but did own an upper of theirs) but they do not supply our military with M16s or M4s. Never did to my knowledge. Colt, Daniel Defense, LMT, FN Herstal, Bushmaster (now defunct) but no BCM. What other manufacturers recommend Locktite 271 for the GB setscrews as you mentioned?

    First I would like to clarify that just, because a manufacturer may have supplied the US Military with a product does not mean it is indicative of the quality you will receive as a consumer.

    Bravo Company Mfg has supplied rifles to US Military units, but they are not the Colt rifles you see being carried by the infantry. Not everyone in the US Military is running around with a 20" M16.

    Bravo Company USA, Inc.
    Your M4 Super Store. AR-15, M16, M4 Specialists

    Bravo Company started in the garage of a veteran United States Marine in Hartland Wisconsin, shortly after Operation Iraqi Freedom in 2003.

    Founded to support the needs of Private Security Professionals working in theaters where durable mil-spec components for their weapon systems were not readily available, BCM (Bravo Company MFG, Inc.) builds professional grade weaponry manufactured, reinforced and tested to meet the unforgiving needs of professional Soldiers, Law Enforcement and responsible citizens in some of the most high threat environments in the world.

    Engineered and built as lifesaving equipment with industry leading mechanical quality control, BCM lifesaving tools serve US Military Special Operations Units, Department of Homeland Security, responsible American citizens and other government agencies at home and around the world.

    Please consider us for your next purchase.

    Si Vis Pacem Para Bellum
    "If You Wish For Peace; Prepare For War"

    Bravo Company makes good products. I don't have a simple complaint about anything they make. Are they the best? No, not even close, but they have a solid product and stand by it. That being said, BCM was just one example that I could think of off the top of my head. Companies like LMT have their own proprietary gas blocks that are pinned. FN and Daniel Defense have pinned gas blocks. If I recall what Mike said, SOLGW uses Loctite 271 with a dimpled barrel and set screw gas block. I also believe SIONICS installs their low profile gas blocks with Loctite 271. Trajectory Arms recommends it and I believe Modern Armory does as well. If you don't want to use Loctite 271, then don't. Use Rocksett or Vibratite's High Temp stuff. Rocksett is better than Loctite 271, but that doesn't necessarily mean you "need" Rocksett. It is highly dependent on what you're doing with the rifle.

    This is exactly why I don't get into brands and what they have done in the past. Daniel Defense has supplied rifles for the US Military, but I wouldn't touch a current production rifle with a ten foot pole.
     

    DAVE_M

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    Yes, I fully understand that component, and the screw is torqued to the GB. But any form of threadlocker is there to prevent vibration and heat from allowing a fastener to back out, to move whatsoever. And 271 is good to 300F by its manufacturer, and @ 450F its bond has failed. So in my mind if you are building a SHTF weapon, a rock solid no bars weapon your life can depend on, 271 is not a good choice. Rocksett is, or the ceramic Vibratite product. Good to 2000F.

    And I also understand me shooting @ the range is prob little threat to my GB or the 271 locktite. Slow rate of fire schedule. But again for a weapon your life may depend on, extended firing session or combat, or suppressed, 271 is a poor choice imo. And exactly why Geissele pins their GB in addition to the setscrews. I bet the M4s supplied to our military do not rely solely on Loctite 271 on the GB setscrews for GB retention. I don't know for sure on that, just my educated guess. We have any active duty certified US military armorers who are members here?

    Loctite 271 can be a good choice for a rifle you need to depend on. There are rifles in use by various LE Agencies that have gas blocks installed with Loctite 271 and they are still running well after thousands of rounds down range. Don't get hung up on threadlockers. The screw will do its job if installed properly. Threadlocker is just there for vibration. Just an FYI, you can stick a bit in the screw and give it a whack to break Rocksett. It's not indestructible. You should also read up on the performance specifications for each when it indicates fastener size. Outside of the firearms industry, you probably won't see many people using Loctite 271 on set screws lol.
     
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