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Posted: 1/27/2015 5:18:38 PM EDT
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I'm getting ready to put a rifle together for the first time and was wondering if there are any specific things I should or should not put Loctite on and what type of Loctite I should use.
I know they recommend some on the castle nut, but what about the barrel nut (I'm using a BCM Keymod FF tube) or the Flash suppressor (YHM Phantom). I don't want anything coming loose on me. Not sure how Loctite handles heat. Thanks in advance for the input. Nick |
| Rocksette for gas block screws if you have them, it's a very high temp thread locker. Blue loctite is medium strength and become soft around 400*f, good for optic mount screws. Red or blur loctite can be softened by heating the screw with the tip of a soldering gun. High pressure grease for the barrel nut, I stake the castle nut...sometimes. I've never had a castle nut come loose when torqued to 40lFtLbs. With Loctite less is more.. |
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Hi,
The castle nut doesn't really need it. Loctite can be used instead of staking. Myself, I just stake it. The barrel nut (female thread) doesn't really need anything. The upper receiver barrel nut threads (male threads) should get a little lubrication during assembly for proper thread engagement. Moly grease is what you should use on the receiver threads. The muzzle device doesn't need any Loctite, just lube the male threads, and time/torque correctly. The blue Loctite is standard strength and the red is high strength (might take heat to get red off). A standard build, does not include Loctite. It's generally for accessories, or bolt on items. There are lubricants and sealers used during assembly but Loctite is not one of them that I know of. -W ETA: To properly lube male threads, you fill the valleys of the threads with lubricant, without any puddles. drips. globs, or excess. -W |
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Quoted:
Put away the LocTite until after you get the rifle completed. DO NOT use it on your barrel or barrel nut. There are actually some very good reasons to use Loctite on the barrel. I've increased the accuracy of several ARs by loctiting between the barrel extension and upper receiver. If the barrel slides into the receiver by hand without having to heat the receiver, then there is a small gap between the receiver extension and upper. As you fire, vibration and/or heating can cause the barrel to move around in that gap slightly and degrade accuracy. Filling in the gap with Loctite prevents that movement. One rifle in particular would shoot groups 1/2" wide @100 yards, but they were usually about 2" tall. After Loctiting the barrel into the receiver and the barrel nut threads and reassembling, the groups shrank to 1/2x1/2". I used blue Loctite so I can remove the barrel nut and barrel in the future if I so desire. Rocksett is good stuff, but you should assume whatever you use it on is a permanent installation. I've used it on gas blocks, and stripped the screw heads even though I applied heat with a MAPP gas torch while trying to loosen them. |
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Quoted:
There are actually some very good reasons to use Loctite on the barrel. I've increased the accuracy of several ARs by loctiting between the barrel extension and upper receiver. If the barrel slides into the receiver by hand without having to heat the receiver, then there is a small gap between the receiver extension and upper. As you fire, vibration and/or heating can cause the barrel to move around in that gap slightly and degrade accuracy. Filling in the gap with Loctite prevents that movement. One rifle in particular would shoot groups 1/2" wide @100 yards, but they were usually about 2" tall. After Loctiting the barrel into the receiver and the barrel nut threads and reassembling, the groups shrank to 1/2x1/2". I used blue Loctite so I can remove the barrel nut and barrel in the future if I so desire. Rocksett is good stuff, but you should assume whatever you use it on is a permanent installation. I've used it on gas blocks, and stripped the screw heads even though I applied heat with a MAPP gas torch while trying to loosen them. Quoted:
Quoted:
Put away the LocTite until after you get the rifle completed. DO NOT use it on your barrel or barrel nut. There are actually some very good reasons to use Loctite on the barrel. I've increased the accuracy of several ARs by loctiting between the barrel extension and upper receiver. If the barrel slides into the receiver by hand without having to heat the receiver, then there is a small gap between the receiver extension and upper. As you fire, vibration and/or heating can cause the barrel to move around in that gap slightly and degrade accuracy. Filling in the gap with Loctite prevents that movement. One rifle in particular would shoot groups 1/2" wide @100 yards, but they were usually about 2" tall. After Loctiting the barrel into the receiver and the barrel nut threads and reassembling, the groups shrank to 1/2x1/2". I used blue Loctite so I can remove the barrel nut and barrel in the future if I so desire. Rocksett is good stuff, but you should assume whatever you use it on is a permanent installation. I've used it on gas blocks, and stripped the screw heads even though I applied heat with a MAPP gas torch while trying to loosen them. |
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Quoted: There are actually some very good reasons to use Loctite on the barrel. I've increased the accuracy of several ARs by loctiting between the barrel extension and upper receiver. If the barrel slides into the receiver by hand without having to heat the receiver, then there is a small gap between the receiver extension and upper. As you fire, vibration and/or heating can cause the barrel to move around in that gap slightly and degrade accuracy. Filling in the gap with Loctite prevents that movement. One rifle in particular would shoot groups 1/2" wide @100 yards, but they were usually about 2" tall. After Loctiting the barrel into the receiver and the barrel nut threads and reassembling, the groups shrank to 1/2x1/2". I used blue Loctite so I can remove the barrel nut and barrel in the future if I so desire. Rocksett is good stuff, but you should assume whatever you use it on is a permanent installation. I've used it on gas blocks, and stripped the screw heads even though I applied heat with a MAPP gas torch while trying to loosen them. Quoted: Quoted: Put away the LocTite until after you get the rifle completed. DO NOT use it on your barrel or barrel nut. There are actually some very good reasons to use Loctite on the barrel. I've increased the accuracy of several ARs by loctiting between the barrel extension and upper receiver. If the barrel slides into the receiver by hand without having to heat the receiver, then there is a small gap between the receiver extension and upper. As you fire, vibration and/or heating can cause the barrel to move around in that gap slightly and degrade accuracy. Filling in the gap with Loctite prevents that movement. One rifle in particular would shoot groups 1/2" wide @100 yards, but they were usually about 2" tall. After Loctiting the barrel into the receiver and the barrel nut threads and reassembling, the groups shrank to 1/2x1/2". I used blue Loctite so I can remove the barrel nut and barrel in the future if I so desire. Rocksett is good stuff, but you should assume whatever you use it on is a permanent installation. I've used it on gas blocks, and stripped the screw heads even though I applied heat with a MAPP gas torch while trying to loosen them. I personally would never Loctite or Rocksett a barrel, barrel nut, barrel extension into or onto a receiver, moly grease is sufficient for me.
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Quoted:
Could have been barrel torque? Could have been simply filling a space that moly grease would have filled. Or maybe it did. I wasn't there and I don't know. The last sentence is the key thought here. The whole point of loctiting the barrel extension is to fill any gaps between the extension and receiver, so the barrel doesn't move around in the receiver due to the heat and vibration of firing.Think of it as similar to bedding an action in a stock--trying to use any kind of grease would be ridiculous. Loctite is much more solid than moly grease, even at high temps. In the example I cited, the only thing that changed was the addition of the loctite. I put the same barrel into the original upper receiver, and torqued the barrel nut to a similar torque value. It's about an apples-to-apples of a comparison as you can get, and group size changed from a 2"x1/2" rectangle to a 1/2" circle. |
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Quoted:
any need to put the "press fit" Loctite on the gas block pin, or are those pretty much never coming out on their own? If you're referring to the pins used to secure A2-style sight posts, they're generally enough of a pain in the ass to remove without any loctite. The roll pins used to secure the gas tube to the gas block don't need it, either. |
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Quoted:
The last sentence is the key thought here. The whole point of loctiting the barrel extension is to fill any gaps between the extension and receiver, so the barrel doesn't move around in the receiver due to the heat and vibration of firing.Think of it as similar to bedding an action in a stock--trying to use any kind of grease would be ridiculous. Loctite is much more solid than moly grease, even at high temps. In the example I cited, the only thing that changed was the addition of the loctite. I put the same barrel into the original upper receiver, and torqued the barrel nut to a similar torque value. It's about an apples-to-apples of a comparison as you can get, and group size changed from a 2"x1/2" rectangle to a 1/2" circle. Quoted:
Quoted:
Could have been barrel torque? Could have been simply filling a space that moly grease would have filled. Or maybe it did. I wasn't there and I don't know. The last sentence is the key thought here. The whole point of loctiting the barrel extension is to fill any gaps between the extension and receiver, so the barrel doesn't move around in the receiver due to the heat and vibration of firing.Think of it as similar to bedding an action in a stock--trying to use any kind of grease would be ridiculous. Loctite is much more solid than moly grease, even at high temps. In the example I cited, the only thing that changed was the addition of the loctite. I put the same barrel into the original upper receiver, and torqued the barrel nut to a similar torque value. It's about an apples-to-apples of a comparison as you can get, and group size changed from a 2"x1/2" rectangle to a 1/2" circle. +1 for a little thread locker on the barrel extension to upper receiver fit. I have just used blue, haven't tried red. |
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Quoted: The last sentence is the key thought here. The whole point of loctiting the barrel extension is to fill any gaps between the extension and receiver, so the barrel doesn't move around in the receiver due to the heat and vibration of firing.Think of it as similar to bedding an action in a stock--trying to use any kind of grease would be ridiculous. Loctite is much more solid than moly grease, even at high temps. In the example I cited, the only thing that changed was the addition of the loctite. I put the same barrel into the original upper receiver, and torqued the barrel nut to a similar torque value. It's about an apples-to-apples of a comparison as you can get, and group size changed from a 2"x1/2" rectangle to a 1/2" circle. Quoted: Quoted: Could have been barrel torque? Could have been simply filling a space that moly grease would have filled. Or maybe it did. I wasn't there and I don't know. The last sentence is the key thought here. The whole point of loctiting the barrel extension is to fill any gaps between the extension and receiver, so the barrel doesn't move around in the receiver due to the heat and vibration of firing.Think of it as similar to bedding an action in a stock--trying to use any kind of grease would be ridiculous. Loctite is much more solid than moly grease, even at high temps. In the example I cited, the only thing that changed was the addition of the loctite. I put the same barrel into the original upper receiver, and torqued the barrel nut to a similar torque value. It's about an apples-to-apples of a comparison as you can get, and group size changed from a 2"x1/2" rectangle to a 1/2" circle. |
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Quoted:
+1 for a little thread locker on the barrel extension to upper receiver fit. I have just used blue, haven't tried red. Quoted:
Quoted:
Quoted:
Could have been barrel torque? Could have been simply filling a space that moly grease would have filled. Or maybe it did. I wasn't there and I don't know. The last sentence is the key thought here. The whole point of loctiting the barrel extension is to fill any gaps between the extension and receiver, so the barrel doesn't move around in the receiver due to the heat and vibration of firing.Think of it as similar to bedding an action in a stock--trying to use any kind of grease would be ridiculous. Loctite is much more solid than moly grease, even at high temps. In the example I cited, the only thing that changed was the addition of the loctite. I put the same barrel into the original upper receiver, and torqued the barrel nut to a similar torque value. It's about an apples-to-apples of a comparison as you can get, and group size changed from a 2"x1/2" rectangle to a 1/2" circle. +1 for a little thread locker on the barrel extension to upper receiver fit. I have just used blue, haven't tried red. If the barrel fits sloppy in the upper, either the upper's bore or the barrel extension is a little off in diameter. In-spec parts should fit smoothly, and a quality barrel might need a little grease - and a lot of attention to alignment - to slide into the upper. But if you feel it is too loose, "bedding" is a band aid fix. I have seen plenty of people post that they "got their gun more accurate" by using LocTite on their barrel extension, but I haven't seen a lot of "before/after" comparisons to demonstrate that accuracy improvement. In order to factually say "it was more accurate," you'd have to build the upper, do a careful test of the accuracy potential of that upper, then take it apart and rebuild it with the LocTite, then completely redo the accuracy testing. Subjective assessments may make a builder feel good about an upper, but it's hard data that actually proves things. |
| I've had problems with rocksett coming loose on both gas block set screws and flash hiders. I switched to blue loctite and never had a problem with them after that. If your barrel nut is aluminum, you can use a small amount of blue loctite. This was in the instructions for the Knights rails. But if your barrel nut is steel, you should use a Milspec Moly grease to prevent the steel threads from galling the aluminum. I would not use loctite on the receiver extension tube castle nut. Even the low strength pink loctite will require too much torque to break the nut loose. You may end up with the index lug on the end plate breaking through the slot in the tube and destroying the threads before the loctite breaks loose (ask me how I know). You can use just a small drop in the receiver threads but make sure none gets on the castle nut threads. Also do not put loctite in the gas tube or you may not be able to remove it from the gas block again, even with heat. Using blue loctite on the barrel extension into the receiver is ok and not hard to remove, it holds up to heat just fine but I've not seen any accuracy benefit to it in that application. The only place to use red loctite is on the screws for the carrier key, my BCM key screws came with red thread locker on them and it was much stronger than the staking. It's easy to break just staking when removing the key but with loctite it will usually strip the head of the screw out even after using heat. The key had to be cut off to replace. |
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