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To Loctite or not Loctite

Larry L

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That is the question... 


Hey everyone, new M4 owner here and new to firearms in general.
Recently picked up my M4, and about to install a bunch of stuff on it and wanted some guidance or best practices as to where I should use Loctite, and where I shouldn’t?


I'm installing a mil spec rail from FFT. A trijicon mount on that. An SRO on that.


also an IWC light mount with a surefire light.


Should any/all of these components use Loctite?


Thanks everyone!

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I think I should clarify my response about your SRO screws. THEY should come with a patch of thread lock already on them.

As far as the other items, I don't really have an opinion, however I would offer this small word of caution, if you use thread locker on the new rail screws that go into the receiver I'd reduce the torque to 8-10 inch pounds. You can always tighten if they work loose, but if you overtighten the damage is already done.


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37 minutes ago, Larry L said:

Is it recommended to only use a torque screwdriver when working on these guns so you can see exactly how hard you’re tightening?

Yes. But not all fasteners on the Benelli have known torque specs. The only negative to using thread locker is the need to clean the thread locker off if you need to remove the screw for whatever reason. A Dremel and aside wheel work well, but you have to get creative to hold small screws while cleaning them. I squeeze the screws in a padded vice then rotate them as I work around the diameter of the screws. 

Knowing which thread locker to use is also important. There are different grades of blue and red Loctite. Blue 242 is best for steel to steel components. Blue 243 is best for steel to aluminum components. I use red 272 on things like the receiver extensions. 

You should be using a Loctite primer which is essentially Acetone to clean your screws and the threaded holes they’re going into. This removes oil contaminants that may reduce the effectiveness of the Loctite. 

In other projects I use the green Loctite wicking type for bedding AR15/AR10 barrel to receiver fit after taking up as much barrel slop as possible with shims. 

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Often the torque for a fastener is given. Other times there is no mention of torque or the use of a thread locking compound. If one decides to use thread locker, reduce the given torque by 15-20%. Wet torque reduces the fastener friction, reducing the torque value takes this into account. 

243 is an improved version of 242. It does not require the use of a primer and is less susceptible to weakening from the intrusion of oils and other fluids, AFTER it has cured. It also works better with plated fasteners than 242.

There are charts available that list general torque values for threaded fasteners. When in doubt, check the chart.

Edited by M2_shootr
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