I'm probably looking too far into this, but I've been reading up on barrel nut grease vs anti seize containing graphite.  It would seem that graphite COULD cause corrosion between the aluminum upper and the steel barrel nut.  I built a few rifles with rails that used aluminum barrel nuts and used anti seize.  I've since started using aeroshell.  Would it be worth it to tear down the rifles I've built and replace the anti seize with aeroshell or since it's an aluminum receiver on aluminum barrel nut will there be no chance of corrosion?

No. Tear them down to install shiny new rails.

Shoot them and don't worry about it.

Leave it.

Copy, thanks.

Hey Tig!

I think we should name the bunny "Barrel Nut Bunny"

If anything happens like that you will only know it if you try to take the barrel nut off. It will be "seized," and pretty much permanently attached to the upper. If you're just wanting to change the handguard at that point you'll need to find one that works with that barrel nut.
If it's because you shot the barrel out, just call it a loss, toss it, and move on.

In all honesty (and as a former "Aeroshell evangelist"), most people have the wrong idea about what the grease is there for in the first place, so they make poor decisions about what they use, and sometimes that can be a problem.

The grease is NOT an "anti-seize" agent.  It is an assembly grease.  Its purpose is to ensure that the barrel nut slides smoothly across all of the threads of the upper which in turn is important to getting a consistent grip between the nut and the upper.  And that grip, in turn, controls the clamping force applied between the barrel nut and the barrel flange against the upper's face.  And a good bit of that force comes from actually stretching the upper (microscopically).

But if you did not use grease, or used something other than a grease that meets MIL-G-21164 specs (which Aeroshell 33MS (now called Aeroshell 64, by the way*)), it's unlikely you have caused any problems.

There are tons of people claiming that "Brand X must use super thread locker on their barrel nuts because it took me and Bubba on a 6' cheater bar to get that sucker off!!!"  And they're wrong**.  People make this claim (often) because they assume that they shouldn't have to use more than 80 ft-lbs of torque to remove a barrel nut.  Force needed to remove a torqued fastener often has little to nothing to do with the torque originally applied to install it.

*This specific kind of grease, meeting the specs it does, is generically called "Grease 64" throughout the aviation industry, and in military use.  Royco has always called their MIL-G-21164 grease "Grease 64", and I think it's probably related to the spec number (but I could be wrong).

**There's evidence that some builders have used a variety of materials on their barrel nuts.  And some DO use LocTite in assembling barrels to uppers, but generally NOT on the barrel nut threads.  Over time, some assembly agents could cook away, dry up, or otherwise become sticky.  But a heat gun or a carefully used torch usually takes care of that.

I use a grease that meets the mil-spec.
It is readily available and the price is reasonable enough.
Presumably the aviation industry is knowledgeable about the potential issues when aluminum is involved.
However many posts of the use of other products without issues makes it seem likely there is a lot of tolerance in what can be used in this application.

I use high temp wheel bearing grease that I have laying around, purchased in the 80's but now you don't repack wheel bearings on newer cars anymore,
Probably enough to build several hundred more uppers with some left over.

I have some Honda branded moly grease that I plan to use for the barrel nut on my next build. So far it’s worked great on everything from the final drive splines on my BMW motorcycle to the sear surface in my AR triggers (makes them smooth as silk).

If you must get Lok-Tite brand copper antisieze in the jar thing. No graphite in it

moly di-sulfide grease  for CV joints

Molybdenum disulfide

Why no graphite is saturated in an grease / oil mixture?

Some people think that graphite could contribute to galvanic corrosion, but as you indicate, it's hard to do that when your graphite is completely surrounded by grease.

My issue with graphite is that it is cheap, and often cheaper greases use graphite to make up for poor grease base choices.  Moly grease is usually about as affordable as graphite-bearing grease.  There's also some speculation that graphite can clump, even in good grease bases, which makes it less consistent than moly.

Finally, the absence of graphite in a MSDS listing does NOT guarantee that the product has none.  Graphite is considered a non-hazardous substance, and is sometimes (legally) omitted from MSDSs.

Have to say that this stuff is kind of magic. Haven't tried it as barrel grease, but best high temp lube I've used. For work applications I transitioned from using this to lube roller bearings vs graphite, and there is no comparison in terms of long term stability. Messy af but does the job with fewer maintenance intervals.

Huh?