Molybdenum disulfide?

[looseprojectile]

Hope I spelled that right.
Some here love it in their lube and some hate it. Some say they would never use it because reduces friction too much. And on and on.
I have used a lot of different powders, nearly all of them maybe.
I have heard that some manufacturers use moly to coat powder as a deterrent to burning or to make it flow better in powder measures.
I have also observed that some loads/powders leave a lot of black fouling or color on the cleaning patch that I don't attribute to leading in the barrel. I also notice that some powders don't seem to have any moly because they aren't black colored.
My questions to those that would not use moly in their guns is. How much is too much? Do you not use the powders that have moly coating on them?
My questions to those that advocate it's use is, how much is too much? Too little?
Do we all benefit from the included moly in powder or do we all suffer from it being there? I am sure that this has been discussed here before though I don't remember coatings on powder as a factor in lubrication being specifically addressed.
Life is good

[Glen]

The black coating on many powders is graphite, not moly. It's added to reduce static electricity and to enhance flow.

[MtGun44]

I don't know the actual cost, but I think MoS2 would be a lot more expensive than
graphite, so less likely to be used in powder. Also, Moly is more shiny gray than black.
Moly is a good extreme pressure lubricant for steel on steel, prevents galling on things
like cams and lifters in internal combustion engines.

I think Glen (as usual) is right on this one.

Bill

[Shiloh]

Graphite as a coating for powder grains is a darkish silvery, shiny gray. it leave a dark streak on my white funnel I use for pouring powders back into containers.

Having never moly coated bullets, I have never seen Molybdenum Disulfide. What does it look like in powder form??

Shiloh

[looseprojectile]

The moly in my can is absoutely shiny black. A friend drops his hot boolits into a running case cleaner/tumbler/vibrator that has moly in the media. This is where I get a lot of my boolits. I then either size and lube or slosh them in LLA. Glen probably knows the straight skinny on this. What would be the difference in using MoS2 and graphite? Inquiring minds being what they are. [empty].
So graphite is acceptable and MoS2 is not? Is it the expense alone? I know it sure makes a mess sometimes.

Life is good

[odoh]

MoS2 based lubes were used in DoD aircraft application. When exposed to humidity like flying thru clouds/precipitation creates sulfuric acid that attacks the host mat'l which in my case was the C130generator drive stub shaft eating away the metal in very short order. Accordingly, I'd never would knowingly use it on/in any of my equipment. FWIW, graphite based lubes were purged from DoD inventory in the late 70's due to being erosive w/some cast iron alloys. The mil spec was canceled and stocks released to disposal.

Additionally, the 220 Swift when first came out in the 1930s, was loaded w/a graphite ball behind the bullet. It developed a rep as a barrel-burner. Eigther the graphite didn't help or it was the cause of short barrel life. I recall someone observing the oil filter on his pontiac appeared unually heavy at changeout so concluded it was filtering out the graphite particals which the Army Engrs maintain was engine block particles and was the reason for it being removed from inventory.

I don't subscribe/use graphited stuff either.

[jhrosier]

I have heard that Tungsten Disufide (WS2) lubes have equal or better properties than MoS2 with none of the disadvantages.
I bought some Tungsten Disufide grease to try to condition a rifle barrel, but have not had a chance to try it yet.

Jack

[Whitespider]

I use the 55-grain moly coated Hornady V-Max in my m77V Swift, H380, CCI 250 Magnum. With that bullet and load, that rifle is the most accurate rifle I own, or have ever owned. I get close to 3900 FPS with extreme velocity spreads under 20 FPS for a 20-round string, standard deviations run in single digits. 20-round, 100-yard groups can be covered with a dime, consistently, a quarter will cover 300-yard groups with room to spare. One windless evening in S. Dakota, and after a single sighting shot and scope adjustment, I nailed two prairie dogs, with two shots, at 710 paces (about 650-yards). I've always cleaned the barrel after fifty rounds and immediately after shooting, regardless of rounds fired. I've never had any corrosion issues.

I don't know how much is too little, or too much, but whatever amount Hornady put on 'em seems just right.

[fredj338]

My biggest issue w/ moly coatings on bullets is you must continue to shoot moly bullets for best accuracy. You can not jump back & forth between jacketed & moly or lead & moly coated lead. For guys that want to wotk up a single load & stay w/ it like WS, moly works great for reducing bbl wear & getting you a little more vel. for equal pressure.

[AZ-Stew]

MoS2 based lubes were used in DoD aircraft application. When exposed to humidity like flying thru clouds/precipitation creates sulfuric acid that attacks the host mat'l which in my case was the C130generator drive stub shaft eating away the metal in very short order. Accordingly, I'd never would knowingly use it on/in any of my equipment.

Interesting. The Navy guided missile launcher (MK-13) I worked on was constantly exposed to salt spray. We had a daily maintenance requirement to wipe down, then re-coat the exposed steel guide rail with a special moly grease. It consisted of what the Navy called General Purpose Grease, STP and MoS2 powder. It was sticky and nasty, but kept the rail well-lubricated and rust-free. It was also capable of jumping an honest 3 feet of space, up wind, if there was any possibility of it attaching itself to a passing sailor's white dress uniform.

Regards,

Stew

[c3d4b2]

I was at a local benchrest shooting goods supplier buying some supplies and asked about molly coated bullets. The gentleman behind the counter said they were not recommending them. He said they tried them in their bench rifles and had problems. When they pulled the barrels they cut them apart and found the barrels were pitted.

Did some digging around and came up with the following

(from www.shootingsoftware.com/ftp/molytech.txt)

(3) Q - I have heard that moly is corrosive. Is this true?

A - Any moly is corrosive if it does not contain an inhibitor to
neutralize the naturally occurring acidic quality of the moly. Dry
moly is particularly bad as it is chemically impossible to add an
inhibitor to dry moly. Even the most highly refined and pure moly will
contain (among other compounds/elements) some Sulfur and Sulfur
Dioxide (SO2). When the Sulfur or Sulfur Dioxide is exposed to the
humidity in air, it combines with water vapor to form Sulfuric Acid
(H2SO4) which then immediately attacks any metal. The higher the
humidity the more acid is formed and the more corrosion which takes
place. One cannot detect this corrosion by simple examination as it
takes place between the moly crystal and the substrate and is hidden
by the moly crystal covering it. Corrosion can only be seen by first
removing all moly thereby exposing the corrosion to view. Those who
fire bullets coated with dry moly will have little corrosion as long
as firing is being done as the heat from firing drives off the
moisture. However, as soon as a firing session stops and the weapon
cools down, water vapor will begin to be absorbed by the moly and
corrosion begins. And, the longer between firing sessions, the more
corrosion which will take place. The corrosive properties of
uninhibited or dry moly have been well documented by military testing
as far back as 1968.


Also......

Title: The Corrosion of Steel in Contact with Molybdenum Disulfide
(this article was originally circulated as Technical Report TR 65-219)

Author: Dr. E. Kay, Royal Aircraft Establishment, Farnborough, Hants,
UK.

Printed: June 1, 1968

Excerpted Quotations:

"SUMMARY"

" The corrosion of steel surfaces in contact with Molybdenum Disulfide
(MoS2) has posed the question whether the process is induced by the
lubricant. The present investigation shows that MoS2 can accelerate the
attack of steel at high humidity and that the milled material is much
more corrosive than the unmilled product. The addition of a suitable
inhibitor is effective in suppressing corrosion."

"CONCLUSIONS"

"(1) The corrosion of steel at high humidity is accelerated by contact
with MoS2.

(2) Milled MoS2 and synthetic MoS2 are much more corrosive than the
unmilled natural product.

(3) Boron Nitride, WS2 and graphite also induce corrosion but to a
less marked degree.

(4) Under the conditions of test, corrosion can be prevented by the
addition of a small quantity of corrosion inhibitor."


And an anouther refererance



Coefficients of friction also increased with higher humidity with thick bonded films where metallic contact was improbable. For the case of lubrication by mans of unbended MoS2 powder, wear increased as humidity was increased, and increased metallic contact and corrosion occurred. Steel specimens were corroded by acids formed on contact of moisture with MoS2.


Sorry, the link is no longer working


FRICTION AND WEAR INVESTIGATION OF MOLYBDENUM DISULFIDE I – EFFECT OF MOISTURE
(http://http://64.233.167.104/search?q=cache:oiguDrw4meYJ:naca.larc.nasa.gov/digidoc/report/tn/55/NACA-TN-3055.PDF+The+Corrosion+of+Steel+in+Contact+with+Mo lybdenum+Disulfide+-grease+-oil&hl=en)

[AZ-Stew]

The addition of a suitable
inhibitor is effective in suppressing corrosion.

I will assume the GP grease and STP in our moly grease acted as the "inhibitor", since the moly grease did not promote corrosion, but rather protected the bare steel guide rail from it, as well as providing lubrication for the passage of missiles. There's no question about it being a moly grease. That's what was marked on the 5 gal. bucket it came in.

I've used it for sprue plate lube for 30 years, as well, and never had any rust.

Regards,

Stew

[c3d4b2]

Stew,

Moly in grease is a different situation than pure moly disulphide. The grease and oil prevent moisture from getting to the metal and the Moly. The concern with the moly is the sulfide reacts with water to form sulfuric acid that will etch the metal. The second concern is the galvanic corrosion cell that can be established with two dissimilar metals are brought into contact. In this case the steel will corrode to protect the moly.

[WildmanJack]

Crap!! I have been using Molly Disulfide sold by Lyman for quite a while, (it's the super fine Moly that I apply in a vibratory tumbler with ceramic media), only in my .45 Colt winchester. Now u guys have me worried!! I live in South WEst Florida, and keep my guns in a safe with a heat strip and the house is A/c'd but what happens between the house and the range when the gun is int he car??? I can't believe the Lyman would sell something that wwould be caustic to a barrell, but it sure seems that way..
Jack

[Big Boomer]

Do the facts about moly forbid the addition of this lubricant to one's bullet lube?
Seems I saw some sticks of Lyman moly lube one time. Would moly being added to a lube prevent the above mentioned liabilities? 'Tuck

[Glen]

Concerning the so-called corrosive properties of MoS2 listed above, let me add this to the discussion --

First off, there is no SO2 (which is indeed corrosive, and oh, by the way, when SO2 combines with water it does NOT form sulfuric acid, whoever wrote this originally failed freshman chemistry). Plain and simple the firing of a shot with nitrocellulose powders takes place under REDUCING conditions, NOT oxidizing conditions (for anybody who doubts this, balance the chemical equation). Therefore none of the S in the MoS2 can be oxidized to SO2. Oh yeah, and by the way, MoS2 is thermally stable to well above 3000 degrees and does not break down -- that's why it's used as a high-temperature lubricant in industry.

MoS2 does in fact coat barrel steel, and it PASSIVATES it towards corrosion (it does not corrode it). It protects the steel from corrosion. There is a great deal of emprical evidence to support this conclusion.

I have been shooting a moly-based bullet lube in ALL of my guns for the last 16 years, and I do clean them occassionaly, but not all that often -- no corrosion.

PS -- c3b4d2 -- as for your "galavnic potential argument", sorry, that doesn't hold any water. There are no dissimilar metals here. There is a metal (steel) and there is a metal sulfide (MoS2). If there were steel and metallic molybdenum, then that argument might hold (although the oxide coating on the steel would probably be a sufficiently large kinetic barrier that the corrosion reaction would be very slow). Molybdenum disulfide does NOT form sulfuric acid in a gun barrel.

Bottom-line -- MoS2 does not corrode barrel steel.

Interesting reference:

http://www.norma.cc/content.asp?Typ=27&Lang=2&DocumentID=398&Submeny=3&Rubrik=Diamond%20line&Title=Barrels%20retain%20accuracy%20longer%20with% 20Diamond%20Line

[shotman]

I like the nuts. You havent used it and wont cause some "gunbook" jerk said it dont work. Take some Lee TL and add moly powder to it. You will never see a better bore . I have run about 5000 44 mags and never cleaned, an oiled patch will be clean the second time though. Guy on feebay has it or I have some if you want to buy. rick

[c3d4b2]

Glen,

You may be correct, however there are several papers that report seeing corrosion / etching in studies with Molly Disulfide. Based on the papers I was able to find, I have been afraid to use Moly. To be honest, I do not understand why the studies differ from your explanation. I have attached links to a couple of the studies I had found along with the disturbing text I found . Could you kindly check the reports and help me understand their observations.


http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930083561_1993083561.pdf

During the experiments with mixtures of water and MoS2 reported
herein, it was observed, as has been reported by others (ref. 10),
that water became acidic upon contact with MoS2. As previously mentioned,
after friction runs at high humidity and also with mixtures
of water and MoS2, steel surfaces were stained as if etched by acids.

http://resources.metapress.com/pdf-preview.axd?code=n17r4hvq646j0g43&size=largest

The tests showed that in every case solid molybdenum disulfide coatings greatly heighten the corrosion of metals in a thermo-moisture chamber and an SO2 chamber, i.e., in condensation tests, simulating atmospheric corrosion.

[odoh]

Interesting. The Navy guided missile launcher (MK-13) I worked on was constantly exposed to salt spray. We had a daily maintenance requirement to wipe down, then re-coat the exposed steel guide rail with a special moly grease. It consisted of what the Navy called General Purpose Grease, STP and MoS2 powder. It was sticky and nasty, but kept the rail well-lubricated and rust-free. It was also capable of jumping an honest 3 feet of space, up wind, if there was any possibility of it attaching itself to a passing sailor's white dress uniform.

Regards,

Stew

I suppose if we (USAF) had a daily maint requirement to wipe out the moly on a daily basis and re-lubed w/fresh moly the acid issue would have been moot. IIRC as this was back in the late 70's, the Navy came up w/polymer elipitical lobe sleeve/insert that as opposed to the splined stub shafts, negated need for lubrication.

[Linstrum]

Like has already been said, graphite is the preferred material for use as an anti-static charge build-up coating and powder flow lubricant. Molybdenum dislufide is not used commercially as a propellant coating. It has catalytic properties that very likely could lead to rapid instability of stored powder; and because of its catalytic properties it could cause all sorts of propellant combustion problems.

Glen is quite right on the chemistry involved with molybdenum disulfide. It is indeed unreactive under the high temperature reducing conditions that exist in a gun barrel during powder combustion.

We all know that lubricants are needed to prevent specific problems caused by friction, and if deterioration of a surface occurs where lubricants are required, then it is highly likely that any damage to the surface is caused by friction rather than the lubricant. However, lubricants can moderate the kinds of damage seen on a surface when the lubricants do not work well. For example, poor or insufficient lubrication can change the form of observed friction damage from grooving to pitting. Another thing that causes damage to surfaces is cavitation, and lubricants very definitely can cause cavitation damage to finely finished parts when vector forces combine to focus a tremendous amount of energy on a very small surface area. Cavitation damage is seen where there is a sudden and dramatic change in pressure on a surface, and that particular condition does exist inside a gun barrel since sudden and dramatic changes in pressure are in part how a gun works. Hydraulic pumps and motors often suffer from cavitation damage when starved for hydraulic fluid and even though the internal parts of a hydraulic pump or motor remain completely lubricated they erode catastrophically when the pressure on the adequately-lubricated surface of the parts changes within milliseconds from a near-vacuum to thousands of pounds per square inch pressure. It would not surprise me at all if the conditions that cause vector-force cavitation damage occur inside a gun barrel, especially when a projectile has way too much of a fluid lubricant (like oil, grease, wax, soap, etc) on its surface. Then too, lubricants themselves can be the source of damage when trapped and not allowed to flow out of the way, like oil in an engine cylinder when the piston is on the compression stroke. Along that line, the "pinch" area where the projectile ogive meets the barrel surface could conceivably push up a growing wave of lubricant in front of it that, when high enough, could dent and pit a steel surface after a critical projectile velocity is reached that causes a shock wave in the build-up of lubricant. A solid lubricant like MoS2 or graphite would have way more of a tendency to do this than a liquid lubricant since it could not flow and escape fast enough into the rifling, or wherever.

In a high temperature oxidizing environment, molybdenum disulfide undergoes a series of reactions that ultimately result in the formation of sulfur trioxide and hex-valent molybdenum oxide - MoO3. In combination with water, the sulfur trioxide forms sulfuric acid, which is highly reactive with iron and definitely causes damage to steel surfaces. However, the presence of oxygen is required for the formation of sulfur trioxide from MoS2, and during normal powder combustion there is no extra oxygen available to do this since it is all consumed by the excess of carbon and hydrogen or their oxidizable compounds that are present. Several quite evident and easily observed things offer proof of the reducing environment that exists inside the barrel during powder combustion, one of which is the muzzle flash that happens when the combustion products exit the barrel and ignite because of a new supply of oxygen from the air. Another is the condition of the steel surface inside the bore, if an oxidizing environment existed then the iron of the steel would erode quite rapidly from a process called "corrasion". The most visible evidence of "corrasion" is like what is seen in motorcycle drive chains that lack lubrication, it shows up as bright red-brown powdery iron oxide that coats the chain links. It is caused by friction that spot-heats the points of contact between the roller chain pins, bushings, and sprocket gear teeth. This is not seen in barrel bores where even higher temperatures and point-pressures exist on the steel surface as a projectile passes over them. The engineering term for the spot "corrasion" of steel surfaces is fretting. Ball and roller bearings that have failed from lack of lubrication also have deposits of the powdery bright red-brown iron oxide. Besides, as Glen already pointed out, if the powder combustion chemical reaction equation is balanced it shows that there is a lack of oxidant in the system, which by definition produces a reducing environment inside the gun barrel.

But the bigger picture is that for some users there seems to be some kind of problem associated with using MoS2. Molybdenum disulfide is a semi-conductor, and that opens a whole other can of worms. The kinds of alloys used for gun barrels hasn't been mentioned, either. But whatever is going on, it is not sulfuric acid from the MoS2.


rl572

[schutzen]

I have no direct knowledge of the suitability of Mo2 or WS2 as a coating for cast boolets, but I do coat my jacketed .224 bullets with Tungsten Disulfide (WS2). On the jacketed bullets, I have seen a slight improvement in the groups. In general, I have not reduced my group sizes significantly. However, on a 5 shot group of WS2 coated bullets 3 of the five shots will touch each other in every group. I have not been able to duplicate this with non coated bullets. Now before everyone asks, yes everything was the same. Same lot of bullets (500 bulk pack, 1/2 coated & 1/2 left naked), all brass from the same lot processed together, all primers from the same brick, and identical powder charges all from the same 8lb jug. My shooting partner has experienced the same results. The cost to coat the bullets yourself is negligible. We have coated all of our .224 bullets for the past 2 years and have been very satisfied with the results. Besides, I need all the help I can get to hit the target.

PS For the purists among us. I shoot jacketed bullets in my .223, but is only because I have been unable to push a PB boolet to 3000 FPS no matter what lube I tried.

[felix]

Excellent, Linstrum! ... felix

[Glen]

c3d4b2 -- You asked me to review the two refrerences you posted, so here are my comments:

1st paper (from 1953) -- in this paper they took a 1/4" layer of MoS2 between two rotating discs (in air) and measured friction as a function of time, and found that friction increased over time, and that addition of water (either liquid water or vapor phase humidity) had an impact on friction. They make one comment about how "the water was observed to be acidic" and yet their apparatus (and the procedure described) has NO method for measuring any kind of pH, or change in pH. They say something about a "stained surface" that looked like it might have been acid etched, but MoS2 is very dark and could have easily impregnated the pores of the steel to create this "stained surface" (after all it had been ground under a 1/4" of the stuff for 6 hours!), or possibly the steel could have undergone a surface sulfidation reaction which would have also discolored the surface. With a 1/4" layer of the stuff in between the discs, the observed change in friction could be due to changes in how the MoS2 was aggregated (something that liquid water/humidity is known to do to powdered ceramics), and that in turn would impact how the MoS2 would be able to lubricate (hence change in friction). As for the "corrosion" they observe, it's hard to comment on that as the photographs are of such poor quality, but I am skeptical of the conclusions because of the primitive nature of the experimental design and execution. Besides, liquid water has been known to corrode metal surfaces for centuries.

Bottom-line: This experiment has virtually nothing to do with how MoS2 would behave in a gun barrel. This experiment was carried out under oxidizing conditions, with a 1/4" of MoS2, with liquid water, and their conclusions are based on a visual discoloration of the metal surface. If I had been asked to review this manuscript for a peer-reveiwed technical journal (something I do on a regular basis for journals in the areas of chemistry and nanomaterials), I would recommend to the editor that this paper only be considered after major revision, and additional experimental work, because the conclusions are not adequately supported by the experimental observations.

As for the second paper (the Soviet journal from 1960) -- I'm not sure I got everything straight from that one because it's kind of hard to read, but they were studying the corrosion effects of MoS2 in electrochemical reactions, specifically anodic corrosion (once again oxidizing conditions), implying that there was an applied potential on the metal surface. There are no experimental details given in this abstract, only conclusions, so it's hard to really comment substantively, but one clarification that I can offer is that the comment you cited about the "SO2 chamber" refers to studies that were carried out in a chamber containing SO2 in the atmosphere, intentionally added for accelerated aging studies, it did NOT come from the MoS2.

We have MUCH better tools for studying surface chemistry today than they did back in 1953 or 1960. The question I have to ask is, "If this MoS2 corrosion is a real phenomenon, with the widespread use of MoS2 industrially, why haven't other folks used these newer, better tools to study this problem?".

I stand by my opinion that MoS2 is safe to use in gun barrels and in bullet lube, and I will continue to do so (and no, I do not have any commercial interest in any products involving MoS2).

[c3d4b2]

Glen,

Thanks for the clarifications.

[XWrench3]

well, my $0.02 worth on moly is this. it makes wonderful bullet lube, and a fine dry firearm lubricant as well. i have used it on many things from motorcycle chains, to assembly lube (cams, rockers, final drive gears, etc.), to spray bullet lube (lyman) which i have also used for dry lubing my ccw semi-auto loaders. i have never had a bad experience with it yet, except in one case, and that was the manufacturers fault, telling me to use it on crankshaft main bearings (automobile style plain bearings) that was a mess! but anyway. in any other application i have used it in, it shines!

[runfiverun]

one of the things i have noticed about the moly is the way it holds heat.
i have wondered if it pulls heat away from the boolit/bbl as it moves along and soaks it up.
i know as i am mixing it in the b-wax and it is hot it will stay that way for an extremely long time and i have to keep mixing and mixing. it will keep the mix hot for a long time in the lubrisizer too i can warm it up and run about 4-500 boolits through the star and the lube will still be soft on the boolits for quite a long time till it cools dow.

[leftiye]

I've seen it here before, but can't remember the percentage that was recommended. Members were saying to use the moly sparingly when adding it to lubes. Does anyone remember what the percentage that was recommended was?