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I've read a hundred topics on this and none have the same answer. What should one put on the threads when mounting a barrel? Heard moly grease, anti-sieze, oil, even one that used lard. Yes, lard. Gonna put the Grendel together tomorrow and could use an honest answer from people whose opinions I trust.

tbirdman74 wrote:I've read a hundred topics on this and none have the same answer. What should one put on the threads when mounting a barrel? Heard moly grease, anti-sieze, oil, even one that used lard. Yes, lard. Gonna put the Grendel together tomorrow and could use an honest answer from people whose opinions I trust.

Opinions are like butt holes. Everyone has one.

I've used several different greases. Dow Corning MoS2 "metal assembly paste". Jet Lube Kopr-Coat, which is a grease with copper powder suspended in it. Even Silicon Dielectric Grease. They all worked fine however, for an anodized aluminum nut that rides on a rough, parkerized steel barrel lip and mates with rough anodized aluminum receiver threads, the Kopr-Kote was the most slippery. I could send you some if you want to wait a couple of days for it to arrive. The silicone dielectric grease is a close second though. The MoS2 grease did better with SS or blued steel nuts being screwed onto SS or blued steel receiver threads. Read smooth surfaces.

PM me if you want some Kopr-Kote.

Hoot

Thanks Hoot, I got a jug or two of that laying around, that's kinda what I planned on using, but thought I'd ask. I dry fit all parts this evening, and things are looking good, except a troy alpha rail does not fit a dpms slick side upper. Have to trim the little nub that stops it from turning.

For those of you who don't have the "exotic" materials lying around, I use Permatex Anti Seize Lubricant, which I got at my local mom and pop hardware store. It may also be available at a big box or from an auto parts store. It is commonly used on spark plugs to keep them from seizing, galling, or causing corrosion in the engine block due to the dissimilar metals. It will take the high temperatures, which the barrel nut / barrel will see.

Jim in Houston wrote:For those of you who don't have the "exotic" materials lying around, I use Permatex Anti Seize Lubricant, which I got at my local mom and pop hardware store. It may also be available at a big box or from an auto parts store. It is commonly used on spark plugs to keep them from seizing, galling, or causing corrosion in the engine block due to the dissimilar metals. It will take the high temperatures, which the barrel nut / barrel will see.

You sir are a very smart man. I use the same and it is my preference.

I'll try not to be too long winded, but my mind is coming back after getting my butt royally kicked by the flu.

For those who do not know, I am a forensic engineer/materials engineer and I do some firearms design as a consultant as well. Anyway, aluminum and steel have some corrosion potential, and, threads are cut on different machines, with different tools at different amounts of wear. We also "know" that 35-85 ft-lbs of torque is "specified." I use the aforementioned Permatex anti-seize. I coat the first 4 or 5 threads of both the barrel nut and the receiver AFTER the barrel is inserted and indexed. Run the barrel nut on and torque to just past hand tight, remove. With either brake parts cleaner or acetone on a soft cloth, wipe away any excess off the barrel and shoulder of the nut. Then re-torque to about 35 foot pounds, loosen and repeat. Torque to 45 ft'pounds, loosen and repeat. Now you have one or two more torques to go. If you need a hole lined up for the gas tube, you have some constraints. As long as you can get to at least 50 ft-lbs, with this method, you will typically be able to have the best accuracy for normal shooting. If you anticipate high rates of fire and need CB to HB drift minimized, consider trying to get to at least 75 ft-lbs of torque. This method will typically give you about 1/2 hole space more on a nut for the same torque just slapping it on. BTW, I do the same for muzzle devices.

When you use anti-sieze and the three torques/release, you burnish the threads a little, knock off some high points and increase the clamping force w.r.t. the torque levels while also greatly reducing the corrosion potential. I have also seen a reduction in CB vs. heated bore POI shifts using this method. My current match rifle was torqued to 95 ft=lbs, has 5K on it and shoots 0.5 MOA with the tester 10x scope on it even after 30 round mag dumps!

So, got the Grendel put together, and the wife surprised me with an ATN Night Arrow 4. This is gonna be way too much fun.

Beautiful!

Nice looking setup!

MarkCO - great post on how to put the barrel on the upper receiver. Had I only known before I slapped the Permatex on, screwed on the barrel nut, and torqued it until the gas tube holes were in alignment. Next time . . . I will probably forget where I saw this post.

No worries. I saw Hoot linked it in the Information Depository, so it should be easy to find.