Guide to Thread Locking Compounds

Over the years, one of the things I have found that I cannot do without is a good thread locking compound. Whether it is a 1911, Glock, or M4, I find that there is always something that can and will work itself loose on a weapon system.

Here are the compounds I keep on hand both in the shop and inside my range bag, and what I use them for.

Loctite 242 (Blue)

This is what I end up using most. It is best for applications where you want screws to stay put, but may need to loosen them for periodic maintenance. I use Loctite 242 on all sorts of screws that need to stay in place, but not permanently. These include screws for 1911 grips, M4 rail mounts, light mounts, optic mounts, sling mounts, etc., I also use this for sight screws for the rear sight on pistols. Remember that a properly fitted sight should fit snugly and the screw should not be the primary source of tension in the dovetail. 

Some optic or light mounts are secured via a thumb screw, and I always hit these with a bit of 242 as well. If this doesn't secure it, you may have to try 271 to hold them in place.

Loctite 638

I started using Loctite 638 Retaining Compound at the suggestion of my good friend Hilton Yam, who had discovered it was far more robust than Loctite 271 (Red) or Black MAX for permanent application. I recommend using this compound for permanent or semi-permanent installations of parts, such as final installs of 1911 front sights or plunger tubes. Some rifle manufacturers use it for permanent installations of gas blocks on M4 type rifles. Since using this compound on plunger tubes, I have yet to have one come loose (with proper staking, of course.)

Loctite 271 (Red)

There are still some good uses for 271, where you want something more robust than 242 yet less permanent than 638. Examples of this might be 1911 grip screw bushings (you don't want those coming out every time you unscrew your grip screws) or some stubborn roll pins that just keep wanting to wander out.

While appropriate thread locking compound is good insurance, I still hit all critical screws with a paint pen to make witness marks. This will make it easy to tell if any screws begin to back out.

Do you have any handy uses for Loctite that you'd like to share? Hit me up and let me know!

Tim Lau

10-8 Consulting, LLC