New Build with thread lube questions

AR/M4 AR General Discussion
1

Howdy all,

I am in the middle of doing my first AR pattern assembly now that I have finally gotten my hands on a 18’ Criterion barrel.
I have done a search but I could not find what I am looking for.

I am putting on a MI free float tube and I am wondering if I should put moly lube on top of the barrel nut, where the tube contacts the nut?

Also wondering if I should put lube on the threads for the JM Brake, that I have on order

Lastly, I am using the MI low profile gas block that has three set screws. What value should the screws be torqued too?

In addition I am using the VC-3 thread compound that was included with the gas block, does anyone have any experience with this as opposed to blue thread lock.

Thanks…

2

Have you bothered to ask the manufacturers of the above components???

3

redacted

4

AeroShell 33 MS is the “milspec” assembly grease if you want the right stuff. IIRC it is moly grease.

5

That is what I have.

6

Vibra Tite (VC3) will work fine, alought I prefer red Loctite 262. Set screws about 30-40 inch pounds.

7

The gas block gets too hot for blue loctite. The manufacturer says the flashpoint is “>200F”. In my experience it vaporizes around 250F or so.

Use the red high temp loctite as others have said. I have no experience with VC-3.

8

On the MI free-float tube, MI’s suggested method is to take the blue sealant provided (Loctite I presume) and coat the outside of the barrel nut with it, slide the tube over the nut and tighten the two clamp screws.

This is for the SS Gen2 tube, btw. Other models may require different methods.

9

I probably should have been more specific. The “regular” blue loctite (242) is the one with the lower flash point. There is a different version of blue loctite (246) that is designed for higher temps. I would assume that is what MI supplies.

Regardless, you want to use the high temp red loctite (272?) on gas block screws.

10

Bingo. Use liberally on barrel threads, but NOT in between the barrel nut and the rail. Ever.

I use MS33 on muzzle device threads to prevent galling and because it is very high temp (so you can actually get it off if you later decide to do so).

The screws can be torqued to between 20 and 40 inch pounds if the gas block is properly heat treated STEEL. I don’t mess with aluminum GB’s, so if it’s aluminum, good luck.

As others have said, Red high-temp (450 degree) Loctite or Red (450 degree) high temp Permatex thread locker should be used on gas blocks. But it’s pretty damn permanent. If you don’t want permanent, try Resbond TS Blue (it is high temp stable but low/medium strength). It’s considerably more expensive than either Loctite or Permatex, but you can take the thing off with hand tools. You can find Resbond on eBay. It basically does for small fasteners what some think Rocksett will do (Rocksett is NOT designed for small fasteners like GB screws).