Lock and Lube: Using Thread Locker and Lubricant on an AR
Thread Locker (Lock)
Short Story: In many cases, you don’t need thread locker on the AR platform.
There is a pretty significant debate raging on regarding the use of thread locker (Loctite®, etc.) in an AR build. Thread locker is great, when it is used appropriately. It can do a lot of damage when it is not.
We will make this simple: don’t use thread locker on your AR if you don’t know where not to.
Rule #1: If you properly torque everything that needs to be torqued and stake everything that needs to be staked, you probably don’t need thread locker. Thread locker is not an acceptable alternative to appropriate torquing or staking.
Rule #2: Never use thread locker where steel meets aluminum. Steel is hard. Aluminum is not. If you ever have to separate the two, you will likely damage the aluminum threads.
Rule #3: Don’t use standard thread locker in high heat areas. Most thread locker will turn to dust. If a high heat component calls for thread locker, use a high heat product like Flexbar Rocksett or Flexbar Rocksett Muzzle Adhesive.
Where (Not) To Use Thread Locker
People want to use thread locker in all the wrong places. Here is a rundown on the parts and our advice for each:
- Castle Nut: The castle nut must be torqued and staked properly. See Rule #1. The castle nut is steel. The receiver extension is aluminum. See Rule #2. Absolutely DO NOT use thread locker to secure the castle nut.
- Pistol Grip Screw: The grip screw should be tightened properly with a lock washer (as applicable). See Rule #1. The grip screw is steel. The lower receiver is aluminum. See Rule #2. Absolutely DO NOT use a hardening thread locker to secure the pistol grip screw. non-hardening, elastomeric thread compound (e.g. Vibra-Tite VC3) may be used in lieu of a lock washer.
- Gas Key Screws: The gas key screws must be staked. See Rule #1. The gas key experiences very high heat. See Rule #3. Do not use thread locker to secure the gas key screws.
- Barrel Nut: The barrel nut must be torqued properly. See Rule #1. Some barrel nuts are steel (the M4E1 Enhanced Upper has a steel barrel nut). The upper receiver is aluminum. See Rule #2. Absolutely DO NOT use thread locker to secure the barrel nut.
- Gas Block Set Screws1: The gas block set screws must be torqued properly. See Rule #1. The gas block is a high heat component. See Rule #3. Even when torqued appropriately, the heat cycling of the gas block and set screws can cause the screws to loosen. As such, gas block set screws can be secured with a high heat thread locker like Flexbar Rocksett or Flexbar Rocksett Muzzle Adhesive. DO NOT use Loctite here.
- Muzzle Device2: The muzzle device must be torqued properly. See Rule #1. The muzzle device is a high heat component and special thread locker is required for these conditions2. See Rule #3. Some muzzle devices need grease; others can benefit from thread locker. Check out our Muzzle Devices article for additional guidance. If the manufacturer of your muzzle device calls for thread locker, use an extreme heat thread locker like Flexbar Rocksett Muzzle Adhesive, which is heat resistant up to 2,015°F.
- Handguard Screws3: Handguard screws must be torqued properly. See Rule #1. However, it may be acceptable3 to use a non-permanent thread locker (i.e. Locktite® Blue 242) or non-hardening, elastomeric thread compound (i.e. Vibra-Tite VC3) on these screws (DO NOT use permanent thread locker; i.e. Locktite® Red 271). Before you use thread locker on your handguard screws, always consult the handguard manufacturer’s instructions (if they don’t mention it, contact them first). Use of a hardening thread locker may void the warranty.
1: The barrel should be dimpled for un-pinned gas blocks (i.e. those secured with set screws).
2: You can also pin/weld the muzzle device to the barrel for a permanent installation.
3: The Aero Precision Enhanced handguard that we use in our firearms and build recommendations uses 8 little screws to hold the handguard onto the receive lug or barrel nut. They can come loose and disappear if you do not torque them properly. We DO NOT recommend using a hardening thread locker (Loctite, Rocksett, etc.) for the Aero Precision Enhanced handguard screws; the screws are steel and the upper receiver (or BAR barrel nut if using a threaded upper) is aluminum, so it does not pass Rule #2. We have confirmed with Aero Precision that THEY DO NOT RECOMMEND THE USE OF THREAD LOCKER (we read this as “you’re on your own if you do”). For the Enhanced upper receiver (unthreaded) version, you will be screwing into the upper receiver, so you really don’t want to do this wrong. That said, we use Vibra-Tite VC3, a non-hardening compound, to add additional assurance to our handguard screws.
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Lubrication (Lube)
Short Story: The AR platform needs the right lubricant in the right places in the right amounts.
Lubrication is critical to your AR platform. Under-lubrication will result in excess friction and corrosion, and can cause premature wear and failure of moving components. Over-lubrication is also not the best thing for your AR (though much better than under-lubrication), as lube can attract dust and hot gas can carbonize the lubricant if it ends up in the wrong place, resulting in fouling and reduced performance.
Grease
Grease can make the torquing process easier and more reliable by lubricating threads. It is also a long-term solution for mitigating wear and corrosion and will prevent seizing (which will make disassembly much easier). However, it doesn’t belong everywhere.
In our opinion, the only parts of your AR that should be receive straight grease are the following, during installation:
- Barrel nut threads: lubricates threads to allow proper torquing; prevents galling between dissimilar metals.
- Barrel extension: lubricates threads to allow proper torquing; prevents galling between dissimilar metals.
- Muzzle threads for any muzzle device that uses a crush washer or lock nut: lubricates threads to allow proper torquing.
- Receiver extension threads: lubricates threads to allow proper torquing; prevents galling between dissimilar metals (castle nut).
For most applications, we recommend AeroShell 64/33MS or MIL-COMM TW25B. A small container will cost you between $10 and $20 and will last you a very long time.
For high heat applications (e.g. muzzle threads), we recommend DuPont Molykote G anti-seize grease. AeroShell 64 has a service temperature up to 121°C (250°F). Molykote G-Rapid Plus paste has a service temperature up to 450°C (842°F), which is much more appropriate for the conditions at the muzzle.
Do not use straight grease on any moving parts (unless instructed to by a component manufacturer; even then, be wary). Grease can get very thick in the cold, and this can cause cycling issues.
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Wet Lube
Aside from the few exceptions noted, everything else gets wet lube.
For a general purpose lubricant (including for long term storage), we use light weight synthetic motor oil (we use Mobil 1 0W20 or 0W30). Synthetic motor oils have been designed in the harshest racing environments; they have been developed and refined over the course of decades, through billions of dollars of research, and with more real-world evidence than any firearm-specific lubricant. Some synthetic motor oils are formulated specifically for racing, with beneficial additives (e.g. zinc and phosphorus) that further reduce friction. There is no reason to think the firearm has more stringent general lubrication requirements than Formula 1 and NASCAR racecars. This is why we use synthetic motor oil as a base lubricant for our guns.
We use a custom mix of synthetic motor oil (we use Mobil 1 0W20) and synthetic bearing grease (we use Mobil 1 synthetic grease) in some high wear parts of the gun (e.g. bolt body, cam pin). You can experiment with the ratio, but generally a 1:5 ratio (grease to oil by weight; i.e. 1/6 grease) is an good all around mix. We use a dedicated immersion blender to homogenize the suspension. Whatever ratio you use, this mix can be diluted with additional oil to reduce sticking, if working in a colder environment.
For lubricating a gun that is used regularly, you can use a Clean Lubricate and Protect (CLP) product. Specifically, we like Clenzoil CLP, because its the best lubricant for the AR (refer to THIS VIDEO for objective performance testing). Break Free CLP and Slip 2000 EWL are also great choices. The only thing to bear in mind is that these lubricants are very thin. This means that your gun will spit CLP everywhere so you you will have to apply more often and if you are storing for extended periods, the lubricant will not stay where you want it to stay. For these scenarios requiring your lubricant to stay put, go with synthetic motor oil or a blend of oil and grease, as described above.
Wet lube is your friend, when the right lube is used appropriately. We have run ARs VERY wet with no issues (other than oil spatter on our shooting mats).
You should NOT lube anything in the direct path of hot gas. Do not lubricate inside the gas key (gas tube insertion point on top of the bolt carrier). We DO NOT recommend that you squirt lube in the 3 little holes in the right side of your bolt carrier…these are gas vents (i.e. “out holes”; not “in holes”). Absolutely do not lubricate the bolt behind the gas rings. These are HOT places for lube. Hot gas will carbonize the lube, and carbon will foul up the bolt/gas key and impact performance. Gas rings do not need lubricant; they are consumable metal gaskets. We know some will argue just the opposite, without a rational argument. Believe what you want.
If you are using a drop-in cassette-style trigger, do not lubricate the trigger unless the manufacturer requires you to do so. This is especially true for intricate assemblies like the Triggertech Diamond trigger. Remember that lubricant attracts dust and grit and this can impede delicate and precision assemblies.
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For Detailed Instructions on Lubrication