AR-15 Did you use lube on the barrel nut or buffer tube?

[clutch]

My barrel should be arriving fairly soon, I'm wondering if I should install the buffer tube and the barrel nut dry or use an assembly lubricant. What is the current thinking on this? I have a Brownells order ready to send out and will add lube to it if I need some.

Thanks,

Clutch

 

[HOOfan_1]

I used Aeroshell 33MS with molybdenum disulfide on both.

The receiver extension to lower receiver connection is aluminum to aluminum, so might not be ss necessary. But the barrel nut is steel threading on to aluminum. The grease prevents binding.

 

[Walkalong]

I use a tad of anti seize.

 

[wally]

But the barrel nut is steel threading on to aluminum. The grease prevents binding.

If you think you might ever remove the barrel nut, you will likely regret not using grease if you don't.

I just removed a barrel nut from a "second tier" maker that obviously didn't -- ~100 ft-lbs wouldn't budge it, an overnight soak in penetrating oil did nothing, finally after heating it with a propane torch I got it to break loose at about 80 ft-lbs.

 

[atblis]

Just use regular old automotive grease.

 

[otrman]

Absolutely on the barrel nut. Grease the barrel extension, inside the upper receiver where the barrel goes, just a little there. Grease the threads on the receiver and inside the nut. Torque to 30 ft/lbs and loosen 3 times, on the third time do not loosen. If the gas tube lines up with nut you are good. If not, continue torquing until it lines up, do not exceed 80 ft/lbs. If receiver extension is for collapsible stock with castle nut grease the threads on both and on the bottom of the nut where it contacts receiver. If a fixed stock receiver extension I use a little blue locktite, which isn't really necessary.

 

[Averageman]

Always use antisieze, didn't think of grease, but it couldnt hurt.
The idea is to fill the gaps with something that will prevent oxidation from occuring on and between the mating surfaces.
There is nothing more frustrating that taking something apart that has not had this done, when you get to the point where something just has to give, you better back off and come up with another plan as Wally explained.
Shotgun chokes can do the same thing.
Oil Soaks, using a heat gun, a vise and a wrench with a breaker bar, all the while thinking "If they had just used some antisieze."

 

[MistWolf]

The Army manual calls for Aeroshell 33 or equivalent. Don't assemble the threads dry but don't over think it too much. Just stay away from anything with copper (can cause dissimilar metal corrosion) or graphite (can cause embrittlement in aluminum).

Torque the barrel nut into place twice, then torque to 30 ft/lbs the third time. Then torque as needed to align the gas tube without exceeding 80 ft/lbs. If it gets really close at 80, just give a little extra nudge. Ideal torque is about 40 ft/lbs. You can get shims from Geiselle to adjust your final torque

 

[carbine85]

Yes to both areas. You need to use something to prevent gulling. You can use grease or any number of grease lubricants. Old fashion gun grease works fine.

 

[gotigers]

Moly grease on the barrel nut.

Nothing on the buffer threads. Never needed it. Buffers have always come off when I want them to, but not sooner.

It may be bad info, but I have been told that antisieze with copper can be bad for aluminum. So I use Moly grease only. I bought a tube of moly grease from walmart 4 years ago. I still have plenty.

 

[Jason248]

I use moly wheel bearing grease

 

[Arizona_Mike]

I used to use fancy stuff but lately have been using Mobil 1 synthetic bearing grease (Red). I've removed several with no issues.

I'm sure Aeroshell has it's place but I won't be assaulting any beaches in scuba gear any time soon

Mike

PS. Most Moly anti-seize or grease has graphite in the formulation which can cause galvanic corrosion of aluminum.

 

[B!ngo]

I find that the finish on AR-style rifles that produces that sand-in-the-works sound between moving parts to be particularly grating. The sound of the BCG in motion or of racking the charging handle makes a sound that I hardly believe mechanical devices should produce. So when assembling a new gun, you bet I use grease or anti-seize to damp down that feel and ensure that it will resist corrosion and can be removed some time in the future. It just seems 'wrong' to omit it.
B

 

[gotigers]

Bingo: I think the OP is talking about the barrel nut. I have never used grease on anything but the barrel nut. Then it is only moly grease without graphite. It is easy to find. I have never needed to grease other parts. I use CLP lube everything else. After 10's of thousands of rounds, i've never had a part wear out using CLP.

 

[Tirod]

Pics of the barrel nut corrosion - or it's not happening. Surf "corroded barrel nut" and see what kinds of pics comes up. Nada.

I wouldn't worry too much about corrosion of the nut and upper, the Montagnards are still shooting M16's 45 years after they were given them, and the guns have more furniture issues than corrosion.

There is another issue, too. The barrel extension fits inside the upper and that is also another steel & aluminum contact point. But, nobody much talks about greasing it. If the barrel nut threads are prone to it, then the barrel extension is an even bigger surface area.

Since the greases often mentioned aren't electrically conductive, it goes to any electrical path that has lower resistance having more electron flow. I speculate that the bolt carrier riding inside the upper with both surfaces worn down to base material will have more corrosion than the nut. And shooting it will keep them scoured clean.

"Don't use copper antiseize" on the barrel nut is more folklore than reality. Plenty of cars use antiseize on the lug nuts mounting aluminum rims to the cast iron hubs and brake rotors. After 15 years of some unrelenting harsh conditions, things aren't that bad. Improper installation of the nut onto the stud with a air gun is much more likely.

As noted in depth, use whatever you like, something is better than nothing. I do question any need for a thread locking compound - the teeth on the nut allowing the gas tube to pass thru is the lock. Dump a few mags thru the gun and NO thread locking compound will hold up to it, they ALL break loose with heat. That is why a mechanical lock has to be used in high temp applications - like exhaust bolts. Thread locker fails.

That's why any company that thread locks the barrel nut is one to avoid - if they don't understand that, what else have they done wrong?

 

[Z-Michigan]

I use automotive type grease on the barrel nut. Have used a conventional one and lately a grease intended for boat trailer wheel bearings, on the theory that greater water repellency is more useful than a reduction in friction on a non-moving part. But I think any good grease is fine.

Haven't used anything on barrel extension, but you have me wondering if I should. I won't be disassembling my lowers with staked castle nuts, but the rest I might put a little grease on. (I often assemble and test a lower before staking the nut, and sometimes take a while to get around to the staking.)

 

[Onmilo]

I use Lubriplate on the upper threads and barrel nut threads.
Works fine.
Grease will allow you to put a bit more torque on the threads without galling.

 

[wally]

There is another issue, too. The barrel extension fits inside the upper and that is also another steel & aluminum contact point. But, nobody much talks about greasing it. If the barrel nut threads are prone to it, then the barrel extension is an even bigger surface area.

Red Herring. The barrel extension is a slip fit into the upper, there are relatively minimal forces at the contact surfaces other than the shoulder where the barrel nut holds it in the upper.

I also think you underestimate the contact area of the threads -- significantly more than the cylindrical surface that would cover them.

IMHO the issue the Aeroshell grease addresses is "cold welding" or "sticktion" of the barrel nut thread. Any lube is probably much better than using nothing.


If you don't care about possible disassembly I doubt it matters. But having just been the poor fool who recently disassembled one they forgot to grease, I sure wish they hadn't forgot!

 

[Cesiumsponge]

Copper anti-seize isn't going to cause galvanic corrosion any more than simply having steel touching aluminum with an electrolyte like moisture to establish current flow. A common example of this is the "lasagna cell", where aluminum foil will get pinholes from corrosion where lasagna touches it, if placed in a steel pan.

If you're really worried about this, use a zinc-based anti-seize. Zinc is less noble than aluminum in the electropotential series and will serve as a sacrificial anode.

 

[MistWolf]

..."Don't use copper antiseize" on the barrel nut is more folklore than reality...

It's "Don't use copper anti-seize with aluminum". If you still think it's more folklore than reality, feel free to contact Boeing Aircraft Company and explain it to their engineers. Boeing Technical Data specifically forbids the use of copper based anti-seize on aluminum threads because it can cause dissimilar metal corrosion. This tech data is important enough that it has the force of federal law that regulates aviation.

It is also forbidden to mark any aviation parts with a graphite pencil because it will cause embrittlement and a stress riser and the parts will crack along the pencil mark, something I've witnessed first hand.

Maybe copper anti-seize has never caused a problem when used to assemble the aluminum parts of an AR. I've talked to a couple of long time AR armorers who have never experienced any trouble using it. However, copper and aluminum causes a dielectric reaction and it's the aluminum that gets eaten away, not the copper. It's not folklore, it's basic science and I prefer to use science to my advantage, not thumb my nose at it

 

[Cesiumsponge]

A more complete picture here is needed as the discuscion is incomplete(I work in aerospace, not as an engineer, including work for Boeing) Dielectrics are electrical insulators, not conductors. Oddly enough, anodized aluminum is an oxide layer, and aluminum oxide is actually a very good electrical insulator.

Copper itself will only cause galvanic corrosion if it's strictly in an aluminum-aluminum interface. By introducing copper, you turn aluminum into an anode.

If you're attaching steel to aluminum, you've already created a galvanic cell with dissimilar metals. The same physics are at play, absent even copper. This can be seen in daily life with zinc coated nails or flashing. Zinc is consumed as the anode before steel is attacked. Anyone who has worked on old cars or motorcycles can attest to steel bolts seizing in aluminum castings because of this (real, but slow) effect. There's a bunch of powdery aluminum oxide that has corroded in the threads.

In a steel-aluminum interface with copper anti-seize, copper is more noble than aluminum but less noble than steel. Copper doesn't actually facilitate or advance the rate of corrosion. The addition of copper, which lies between the two in nobility, is irrelevant as aluminum will be consumed first, regardless. I mentioned earlier that aluminum oxide (the coating grown by agonizing) is an insulator electrically, so if you scratch through an anodized surface (about 2-3 thou deep) corrossion will happen faster. If you don't, the mechanical interface is fairly sound.

In an aluminum-aluminum interface, zinc anti-seize is used since aluminum is more noble, so zinc is consumed. In a steel-aluminum interface, you want something less noble than aluminum to preserve the aluminum. A product like Jetlube zinc dust petrolatum which conforms to MIL-CID-A-A-59313 is suitable for aluminum-aluminum interfaces or any interface where you want the paste to be sacrificial.

http://en.m.wikipedia.org/wiki/Galvanic_series

 

[Walkalong]

Anyone who has worked on old cars or motorcycles can attest to steel bolts seizing in aluminum castings

Oh yea. (Motorcycles)

Very interesting info.

 

[Arizona_Mike]

http://en.m.wikipedia.org/wiki/Galvanic_series

But in the link you posted, Cu is more cathodic than either aluminum or steel. I think the issue with graphite is that it is so noble, even more than precious metals.

Mike

 

[clutch]

I googled around and found someone repackaging Aeroshell 33MS on ebay. I ordered 5 bucks worth from him. I'll go with it.

I do expect that I will screw on another barrel some day when this one degrades from just enough shooting.

Thank you for the responses.

 

[Cesiumsponge]

My mistake. I am used to dealing with stainless steels at work. My previous post should be reworded then with genetic carbon steels to reflect the error. In that case, with steel and aluminum interfaces, copper still wouldn't do anything as aluminum would still be anodic in the presence of an electrolyte. There is probably more real world practices/info on this with maritime and naval sources since you generally don't encounter salt water in general aviation, certainly not to the degree of boats and ships, or even bridges and dock structures, where galvanic corrosion is a more serious and accelerated issue

It's also worth mentioning the same practice takes place in electrical system prep. For electrical aluminum-aluminum or aluminum-copper mechanical joints, you use a zinc-based compound in a petroleum base, basically zinc anti-seize. It prevents oxidation by isolating the surfaces from air and the zinc corrodes before the joints. One such product that I have on hand is called Burndy Penetrox A. MSDS shows its just zinc and petrolatum jelly. Pretty important when you can have hundreds or thousands of amps through the circuit and want to avoid resistive heating which can become a disastrous failure point.