Sticky Stuff (Thread Locker)
Thread locker must be used carefully and strategically. If you don’t know what not to use it on, don’t use it at all. Please PLEASE read the Lock and Lube page before you apply any type of thread locker to any part of your AR.
We do not recommend “bedding” your barrel extension with thread locker or “retaining compound” (i.e. Loctite 620), especially if you don’t know what you are doing (we’ve seen armorers ruin upper receivers by attempting this).
We recommend two types of thread locker for the AR.
R: Required
r: Recommended
O: Optional
Hardening Thread Locker: Rocksett/Rocksett Muzzle Adhesive (R)
The only type of hardening thread locker you should use on the AR for locking threads is Flexbar Rocksett. It is a ceramic cement that is heat resistant up to 1,102°C (2,015°F). For reference, Loctite 243 (blue) is resistant up to 150°C (302°F); Loctite 272 (red) is resistant up to 232°C (450°F). Rocksett can be used everywhere on the AR, including all the places where Loctite would turn to dust.
Note that Rocksett and Rocksett Muzzle Adhesive are the same product. Rocksett Muzzle Adhesive comes in smaller 1 oz bottle versus the larger 2 or 4 oz bottle for the Rocksett-labeled product. 1 ounce will last for many applications, so this is probably more than enough for most folks.
Non-Hardening Thread Locker: Vibra-Tite VC3 Threadmate (R)
For all the places you shouldn’t use hardening thread locker but need some added assurance, we use Vibra-Tite VC3 Threadmate. VC3 is like liquid rubber that cures to a flexible coating. There is no risk of damaging threads and no need to heat the compound to loosen a screw. We use VC3 on handguard screws. It can also be used for pistol grip screw and sight/scope mount screws.
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