Moly coated bullets

[northdude]

So I bought some speer 140gr spitzers which are moly coated. I didnt know they did one so does anyone know how the moly is put on them and can it be taken off again? Also does it leave fouling in the barrel?

[bladeracer]

So I bought some speer 140gr spitzers which are moly coated. I didnt know they did one so does anyone know how the moly is put on them and can it be taken off again? Also does it leave fouling in the barrel?

No idea, but Google found some ideas.
http://benchrest.com/archive/index.php/t-70517.html

Maybe try hitting one of them with some different products and see what works best.

[Bidgee]

So I bought some speer 140gr spitzers which are moly coated. I didnt know they did one so does anyone know how the moly is put on them and can it be taken off again? Also does it leave fouling in the barrel?

I used to moly coat bullets back when it first became fashionable. Wouldnt bother now. It can usually be removed by tumbling. I found that moly bullets have a lower velocity than uncoated with the same powder charge. So if you use them you'll need to redo load development.

They leave more of a coating than a fouling in the barrel. Some of the moly transfers from the bullets onto the barrel. The theory is that it can reduce copper fouling. It takes a barrel a while to settle back into normal performance if you switch back to uncoated.

IMO you either need to use them or dont. Switching between will give you inconsistent results.

[northdude]

Ive read that you need to stick with them if you are going to use them, thats why I was wondering if you can get the moly off

[Boundry Rider]

There's isses with moly and water, regarding the barrel. Don't get moly residue in any form near a barrel and water/ moisture.
Google will be your friend with this dilemma.

[northdude]

Just soaking them in engine degreaser at the moment. Seems to be getting some of it off

[Apollo]

Iosso Case Cleaner. Suggested by Berger Bullets, tried and tested. Gets rid of all traces of Moly. Tumble afterwards with Corn Cob to get the polish finish back if you like.

[JohnV]

There's isses with moly and water, regarding the barrel. Don't get moly residue in any form near a barrel and water/ moisture.
Google will be your friend with this dilemma.

No that's not really correct . Most people got into trouble because they thought that moly would protect the bore from normal corrosion and did not clean or use any oil in the bore . So naturally the bore rusted . It does not exclude air completely from the barrel steel . It can't because it's a lamellar structure . A lattice of sulphide bonds . Moly MoS2 is not hygroscopic .

[JohnV]

So I bought some speer 140gr spitzers which are moly coated. I didnt know they did one so does anyone know how the moly is put on them and can it be taken off again? Also does it leave fouling in the barrel?

I used to moly coat bullets back when it first became fashionable. Wouldnt bother now. It can usually be removed by tumbling. I found that moly bullets have a lower velocity than uncoated with the same powder charge. So if you use them you'll need to redo load development.

They leave more of a coating than a fouling in the barrel. Some of the moly transfers from the bullets onto the barrel. The theory is that it can reduce copper fouling. It takes a barrel a while to settle back into normal performance if you switch back to uncoated.

IMO you either need to use them or dont. Switching between will give you inconsistent results.

That's true . How moly works is it has a high coefficient of friction against the steel but a very low coefficient of friction against it's self . So once the bore gets a coating it hangs onto the barrel steel and then the bullet coating hangs onto the bullet jacket . As the bullet then passes up the bore the reduced drag is by the slip on the two opposed moly surfaces because there is some non bedded moly on the two surfaces . The sulphur atoms that make up the Lamellar structure break and slide . Moly MoS2 has a superior load bearing ability to graphite and HBN coatings .

[JohnV]

Just soaking them in engine degreaser at the moment. Seems to be getting some of it off

Just get some fine steel wool and polish it off . You won't get all off it off if it's been properly coated but the slight amount left bedded in will have no detrimental effect .

[JohnV]

Ive read that you need to stick with them if you are going to use them, thats why I was wondering if you can get the moly off

You can switch back to uncoated by just giving the barrel a good extra scrub out with Sweets 7.62 and a bronze brush an d patches . Run a few patches with turps on them through to flush out and dry patch . If your putting the gun away then oil the bore and chamber .

[JohnV]

So I bought some speer 140gr spitzers which are moly coated. I didnt know they did one so does anyone know how the moly is put on them and can it be taken off again? Also does it leave fouling in the barrel?

It depends on what you consider fouling . Does it deposit moly in the bore , Yes , does it increase copper fouling? No , does it reduce copper fouling ? Well yes if it's proper Mos2 coating done right and not some cheap graphite paint job on a commercial bullet .
Will it make the barrel last longer ? Well it depends on how you use it . If you clean it out every 20 or 30 shots then it will have no real beneficial effects .
If you leave the coating in for a long shooting session like 100 to 200 rounds then yes it can help protect the bore from fire cracking and throat erosion .
For the shooters who fires a few shots then puts the gun away for weeks , then moly is of no real benefit . If your firing long strings of bullets then it can reduce the need for cleaning so much because it reduces copper fouling . The thing is that very few people know how to coat properly and get a thin useless wash on the bullet and think it's right . They then don't get much benefit and declare moly coated as no good . It took me several years of research to work out exactly what moly was doing and how to best use it and I went as far afield as NASA and National Laboratory Los Alamos New Mexico USA for proven scientific information .

[northdude]

This appears to be well done. The degreaser is taking some of it off. As I can see it in the degreaser and the bullets arent as grey now. Looks like ill put them in my case tumbler thats got corn cob or crushed walnut shell media with a bit of brasso. Havnt seen that lasso here. I just bought these pills as they were cheap for shooting service rifle comps.

[JohnV]

Might be easier to just shoot the bullets and then clean the bore well .

[northdude]

yea could do but as I live urban now shooting time is cut down so have a bit of spare time to put into shooting related things. just been going through the pill collection and came across some moly coated .224s as well..

[JohnV]

I moly coat all my bullets not just for the antifouling benefits . I once did a 10 year storage test on reloads and the moly coated bullets had the most consistent bullet release and zero neck welding . The uncoated bullets suffered inconsistent bullet release and some had the start of neck welding . The image is of one of the uncoated projectiles with the beginning of neck welding . It took a collet puller to get this bullet out .

[Bidgee]

So I bought some speer 140gr spitzers which are moly coated. I didnt know they did one so does anyone know how the moly is put on them and can it be taken off again? Also does it leave fouling in the barrel?

It depends on what you consider fouling . Does it deposit moly in the bore , Yes , does it increase copper fouling? No , does it reduce copper fouling ? Well yes if it's proper Mos2 coating done right and not some cheap graphite paint job on a commercial bullet .
Will it make the barrel last longer ? Well it depends on how you use it . If you clean it out every 20 or 30 shots then it will have no real beneficial effects .
If you leave the coating in for a long shooting session like 100 to 200 rounds then yes it can help protect the bore from fire cracking and throat erosion .
For the shooters who fires a few shots then puts the gun away for weeks , then moly is of no real benefit . If your firing long strings of bullets then it can reduce the need for cleaning so much because it reduces copper fouling . The thing is that very few people know how to coat properly and get a thin useless wash on the bullet and think it's right . They then don't get much benefit and declare moly coated as no good . It took me several years of research to work out exactly what moly was doing and how to best use it and I went as far afield as NASA and National Laboratory Los Alamos New Mexico USA for proven scientific information .

I'm not sold on the longer barrel life argument. I suspect that increased powder charge required to get the velocity back up to where it was offsets +/- the benefit of the coating.

I'm not anti-moly but I found the extra stuffing around wasnt worth the hassle. But I mainly hunt and shoot gongs. My different on the target range.

[JohnV]

Everyone's requirements vary a bit so it does not suite all the ways people want to operate . Most people don't know enough about the true facts and operate on myth and misinformation so they may miss out on experiencing a benefit or they can't change the way they use the firearm and that cancels any benefit .
Barrel life is a very subjective thing and very hard to quantify due the myriad of different bore specs and metals used , different loads etc. Just using a magnum primer instead of a softer primer could skew any comparison . Testing barrel wear I have not done as it's way too expensive to just shoot out two reasonably identical barrels . However my experience over the past 30 years gives me the impression that if used properly some of my barrels are lasting very well but without a direct comparison test it's just a gut feeling really because I have only counted shots on one rifle which is lasting very well . I have the process worked out to a fine art now and it's easy to do and get a good deep coating that does not need any wax and does not come off on your fingers like some have experienced . I listened to a guy at the range explaining how he moly coated bullets in a pill bottle clamped in his lathe chuck and it only took a few minutes to do the job . I smiled and walked away because I knew that coating would be useless and he was a range officer that though he knew everything .

[No1_49er]

I moly coat all my bullets not just for the antifouling benefits . I once did a 10 year storage test on reloads and the moly coated bullets had the most consistent bullet release and zero neck welding . The uncoated bullets suffered inconsistent bullet release and some had the start of neck welding . The image is of one of the uncoated projectiles with the beginning of neck welding . It took a collet puller to get this bullet out .

Any chance that you'd care to share the method with us?
It's interesting that Norma 6mmBR is moly coated. There must be some benefit, other than just the marketing.

[JohnV]

Ok but you will need a good horizontal tumbler . You won't get a good coating in a vibrator type . Do you also want article one which is the science so to speak it does tend to scare some people who misinterpret it ?
How I Moly Coat Bullets.

Article 2.
Written by John Valentine 20 / 05 /1991. Copyright.
Revised and updated 07 / 12 / 2006.

First of all you will need a horizontal tumbler of some kind it needs to turn at about 60 RPM . Don’t laugh but you can use an electric concrete mixer with the Tumbler barrel held in the middle with bits off foam rubber it works great . This gives you an idea of the correct speed of rotation . The barrel should be large enough to accommodate the maximum amount of the largest calibre that you will do . It should have 3 or 4 small fins along it’s inside length about 10 mm high . This makes sure that the projectiles mix around, rise and fall. A square shape container should work too . The barrel should be filled with approx. 3 to 4 kilo’s of 3 to 3.5 mm steel balls . The quantity will depend on the size of the barrel and the amount of projectiles put in. I use an RCBS tumbler barrel and my tumbler was made to take this barrel . It turns faster than the RCBS tumbler and the barrel runs horizontal to the centre axis . It does everything from 17 cal. to 50cal projectiles . Any of the commercial tumblers on the market will work fine but will need extra running time per coating session or an extra session as they turn slower than my unit. They make them turn very slowly so they are not practical for mass production. The bigger the calibre the smaller the number of projectiles you can do at one time . The only projectile design that is easy to moly coat is the hollow point or protected point that means any jacketed projectile that has no lead exposed at the nose. Be careful with large hollow points that are the same size as the steel balls as they tend to get a ball stuck in the jacket nose. You can fill large hollow points with nail polish, leave it a few days to dry. No! I don't have a favourite colour!
If you are real desperate you can trim exposed lead off with a sharp knife exactly at the jacket nose to make a flat protected point that will coat ok. I do this with Rem Core Lock projectiles and it works great.
Some people will tell you, that you don’t need steel balls at all when coating large calibre projectiles. This is partially true but I do not recommend the idea as the resultant coating will be patchy and inferior and the projectiles may suffer damage to the meplat (nose) or base edge affecting accuracy. The steel balls act as a buffer between the projectiles when they fall during the process and make sure that the surface of the projectile is evenly coated. I have tried this idea with some old 30 cal projectiles, it works but I did not like the results.

The Process
First step in the process is clean the projectiles, this must be done just before you are ready to tumble, don’t use old heavily tarnished bullets , use fairly new stuff .
If bullets are badly tarnished they will need polishing in the tumbler using treated walnut media in a separate barrel, not the one used for moly coating. Then continue with the instructions immediately below.
To remove mild tarnish from projectiles place a litre of warm tap water in a plastic bowl and add half cup of CLR and stir . Place bullets in and stir them around with a plastic spoon you will see the tarnish disappear . Take them out and rinse in clean hot water twice . Place on a very clean tray and put out in sun to dry . You can use a hairdryer to speed it up but don’t use it too close and don’t use anything with more heat as you could melt the bullet cores . Make sure that there is no water left in hollow points . Don’t touch the bullets with bare hands as you will put grease on them . In a well ventilated area while wearing an approved protective breathing mask and after the bullets are dry rinse them in Shellite and dry again , this will not take long as the Shellite will evaporate quickly .
While you are waiting for them to dry place one quarter of a tea spoon of Molybdenum Disulphide in the tumbler containing the steel balls and tumble for 2 minutes this just gets everything inside coated up, you don't have to do it again unless you clean the inside of the barrel at some stage . Open the barrel wearing a face mask and place another quarter of a tea spoon of Moly powder in , put in the ( 2-300 , 224 ) bullets without touching them with bare hands , tumble for 30 minutes .
Wearing a protective mask remove projectiles by pouring the bullets and steel balls into a sive of a size that will allow the balls to escape to a container below the sive , return the balls to tumbler barrel and close lid . Place bullets on a CLEAN cloth of adequate size to polish off the excess moly by rubbing gently over the bullets without touching them with bare skin. Place your hands under the edges of the cloth and fold up and over the projectiles and rub them around inside the cloth until they appear a shinny silvery grey. This cloth rubbing idea came from a recent article by Brendan Atkinson it is quicker cheaper and easier than the way I was doing it thanks Brendan . You are only trying to remove the loose surface moly so go easy . It only takes a few minutes . Replace in tumbler and add another quarter tea spoon of Moly powder . Tumble for a further half hour and repeat excess moly removal . Place bullets back in tumbler for third time but don’t add any more moly powder . Tumble for 15 to 20 minutes and remove and rub off excess . You should notice that very little moly will now come off on the cloth . Pick one up and it should not blacken your fingers . This is not the only way of doing it but I have found that it is simple and gives a very good coating in my equipment . Short cutting the process usually means short cutting the quality also .

Be very Stingy with the amount of moly you put in the tumbler barrel at first as it is easier to add extra and tumble again than it is to clean out the barrel if it becomes overloaded with moly.
Excessive moly on the projectiles will stop the steel balls from doing their job of pushing the moly powder into the pores of the projectiles jacket metal. The excess powder acts as a shock absorber on the surface of the jacket metal and no useful coating is achieved. This is the most common mistake. You will get a thin coating and that’s all no matter how long you tumble.
If the barrel does become badly overloaded with too much moly, separate projectiles from the steel balls and wash the balls in shellite and the inside of the tumbler barrel and leave to dry then start again. If there is only a slight overload then you can cut up some clean cloth into small pieces and place a dozen or so into the barrel and tumble for 5 minutes or so then separate them from the steel balls and discard the cloth patches. This will soak up moly from inside the tumbler barrel. After a bit of experience and experimentation it is very easy to achieve good results.
You will have to experiment a bit with the time as all tumblers are a bit different .
If bullets appear to have lumps of moly on them then you have too much moly in the tumbler , rub it off by placing projectiles on a clean cloth as described above and don’t add any more moly for the next tumble, until it clears . If they come out very shinny and the coat appears thin then add more moly but only a bit. It is very difficult to give absolute values as to the amount of Moly to use as it depends on so many factors such as number of bullets, calibre, amount of steel balls, speed of rotation, size of barrel and it goes on and on.
You will learn the correct amount as you gain experience with your own system.
Materials
CLR is a household cleaning product.
Containing Sulfamic acid (also known as amidosulfonic acid, amidosulfuric acid, aminosulfonic acid, and sulfamidic acid, )

Numerous other cleaning products contain Sulfamic acid and would work also.
Don’t heat Sulfamic acid to over 140 F as it can hydrolyze some to a stronger acid , Sulfuric .
Don’t reuse old solutions of Sulfamic acid as some will hydrolyze to ammonium bisulfate as it ages.
Make it up fresh each time. Ammonium of any kind is bad for bullets jackets and brass in general as it can harden them and attack the zinc in the alloy.

Shellite is available in supermarkets and hardware.
Molybdenum disulfide ( Moly powder) is available from bearing manufacturers and suppliers. Generally use finer grades but coarse grades may be useful for solid copper or machined type bullets because of its higher load bearing ability.
Steel balls are available from bearing manufacturers and suppliers. Steel shot from gun shops No2 (.150) or BB (.180) should work ok.
Treated walnut polishing media is available from gun shops, large granular size if possible. Or other suitable polishing media . SS pins are good also.
Elbow grease well you have to supply that!

Wear a face mask when opening the molly tumbler barrel and when removing the excess molly and at any time when there could be molly in the air, to protect your lungs . Don’t hang about near the tumbler during the waiting part of the process without wearing your mask .

[No1_49er]

Ok but you will need a good horizontal tumbler . You won't get a good coating in a vibrator type . Do you also want article one which is the science so to speak it does tend to scare some people who misinterpret it ?

Yes, that would be great. Science has never frightened me
A horizontal tumbler is all that I use. Have several, in fact.

[northdude]

tumbler walnut media and brasso seems to do the trick

[JohnV]

Ok but you will need a good horizontal tumbler . You won't get a good coating in a vibrator type . Do you also want article one which is the science so to speak it does tend to scare some people who misinterpret it ?

Yes, that would be great. Science has never frightened me
A horizontal tumbler is all that I use. Have several, in fact.

Ok then you are well setup . Remember you asked for it lol.

Pure Moly Coating .


Article 1.
Written by John Valentine 15 / 11 / 90 Copyright .
Revised and updated 07/ 12 /06

I started experimenting with moly greasing and moly coating projectiles about 30 years ago now , using them in several center fires .
As far as I am concerned it works well for me .
During one of my tests I fired a CMC Howa 223 Rem , 300 times without cleaning and the accuracy at 300 rounds was just as good as it was at 30 rounds .
It had just returned from a two week trip where it fired 200 odd rounds without cleaning with any bore solvents just a wipe through with oil when I got home each night .
This was some years ago and under the same circumstances today , I would clean properly each day.

During coating , Molybdenum Disulphide and nothing else goes on the projectiles .
The tumbling process at 1 to 1.5 revolutions per second with 3 mm hard steel balls produces a different product to other commercial processes .
If done properly it results in a deep coating that doesn’t come off on your fingers .
I believe that pure moly coating will give increased barrel life , cooler barrel temperatures , greatly reduced copper fouling , reduced barrel cleaning , and increased accuracy , although I need to qualify this last statement .

I have found the following to be true in my barrels .
If you compare a 10 shot group from a clean barrel using moly projectiles against uncoated projectiles from the same clean barrel there generally will be little difference and I have noticed a tendency for the uncoated projectiles to group slightly tighter under these conditions .
The nature of the test favours the uncoated projectiles , but if you fire 100 rounds of both projectiles without cleaning at 20 to 30 rounds the uncoated projectiles will start to loose accuracy due to fouling and the moly projectiles will still retain accuracy way beyond that .
The nature of this test favours the Moly projectiles .
It takes a while for the moly to coat the barrel and settle down .
The results of a test depends on what test you do and how you analyse the results .
This is what I have experienced and anyone who is interested needs to try for themselves to see if they like Moly coating or not , but you need to Know what is on your projectiles , just because its black doesn’t mean its Pure Moly .
If you do try it , here are some of the things I discovered .
Never push a dry tight patch through a barrel that has used moly as it can grab the patch and be very difficult to move .
Molybdenum Disulphide has a high coefficient of friction against other materials but a low coefficient of friction against itself .
This is why it can grip to the barrel and bed into the pores of the steel but not build up on itself to any harmful degree but there is some build up going on for it to work as a friction modifier .
It does the same to the projectile as a result the atoms of Sulphur between the bore and projectile act as a friction modifier .
I don’t like to described it as a lubricant .
I believe what’s happening is , the projectile is introducing new molecules of moly into the barrel with every shot and for what ever reason there is a slight build up of free Moly on the surface of the deeper bedded Moly this build up stays about the same for at least 300 shots , which is as far as I have gone without cleaning .
This slight build-up is enough to allow the sulphur atoms within the moly on the projectile and barrel to slide over each other and reduce bullet to bore friction.
Also a property of Moly (MOS2) is that friction decreases as load and speed increase. The bonds between the Sulphur layers are weaker than the bonds between the Molybdenum layers. The covalent bonds of both are strong in the basal plane of the Lamellar structure. The “slip” occurs on the Sulphur atoms.
Even between highly loaded stationary surfaces the lamellar structure is able to prevent contact. In the direction of motion the lamellas easily shear over each other resulting in low friction. After a body has caused a sliding frictional movement against the Lamellar structure the particles line up in an end to end linear arrangement in the direction of movement that gives moly its load bearing ability.

Large particles best perform on relative rough surfaces at low speed, finer particles on relative smooth surface and higher speeds. Particle size affects load carrying ability. Large particle size carries more load but can create more abrasion. Friction is not affected by particle size.
Friction decreases as load and speed increase. Test results suggest that removing water vapor contamination decreases friction in molybdenum disulfide. *** Within its operating range Moly (MOS2) has superior load bearing and surface speed performance values as compared to Graphite or Tungsten Disulphide ***

This is the reason why it is important to achieve a good deep coating of Moly on the projectile because the projectile sacrifices most of its coating to the bore. A bad coating will run out of Moly as the projectile moves up the barrel and can result in an increase of copper fouling at the muzzle end compared to the chamber end.
I did notice some slightly darker and more obvious marks just on the lands of the barrel after about 200 shots , after thorough cleaning at 300 shots they had completely gone . This was observed with a doctors otoscope .
The thickness would have been microscopic but I believe that it was the slight build-up that I refer to above showing up a bit more at the lands.
Never believe that Moly will protect your bore from corrosion it will not exclude oxygen or moisture from the surface of the steel as well as an oil or grease based coating, clean and oil your barrel after shooting as normal, clean the oil out before shooting with patches as normal .
I believe that the section below shows that there is good scientific indication that it is possible for Moly to hold some moisture or other corrosive elements in intimate contact with the barrel if stored incorrectly and without proper cleaning the bore .
This is the only potential negative that I have experienced with Moly.

Molybdenum disulfide (MoS2) is insoluble in water and unreactive toward dilute acids in its normal state.
MoS2 oxidizes very slowly in atmospheres up to 600° F. In these low temperature ranges it oxidizes more slowly than Tungsten Disulfide (WS2). In dry oxygen free atmospheres it functions as a friction modifier up to 1300° F.
Its melting point is 1185 °C,
It starts oxidizing in air at around 315 °C.
We need to ask, what is the flame temperature in the chamber and can it be considered an oxygen free environment. Research information has suggested that the temperature in the chamber and the first couple of inches of the barrel can reach 1400° F or more for a short period of time. Further more, oxygen is required to burn and the powder carries its own supply of oxygen.
This would tend to suggest that there is the potential for some oxidation of the Molybdenum disulfide ( MoS2) in the barrel.
Oxidation products would be formed in the chamber end of the barrel and carried by the passing of subsequent bullets along the barrel.
The most likely spots for oxidation to occur are the same areas likely to suffer from normal flame erosion; peaks and edges.
These are exposed to more of the hot gasses so the temperature can more closely approach the temperature required to produce oxidation products.
There is also the coating effect of the moly to consider.
It will have a protecting effect against some of the flame heat because the oxidation products are working at the surface of the lamellar structure where there is more potential oxygen.
I feel this will cancel out some of the erosion and as long as proper cleaning and lubricating happens after shooting it should limit the potential for any damage.

The oxidation products of Molybdenum disulfide (MoS2) are :-----
Molybdenum trioxide (MoO3) and Sulfur dioxide. (SO2).

Whenever sulfur compounds are involved rising temperature excites the bonds that hold the various molecules together. Too much temperature breaks the bonds.
The breakdown products containing sulfur are not good and can cause corrosion . When sulfur compounds are heated they react with any oxygen present to make Sulfur dioxide (SO2) which reacts with water when present to make the primary product Sulfurous acid) H2SO3 (weak acid) and a lesser reaction product of SO3 (sulfur trioxide) which reacts with water to make H2SO4 (sulfuric acid) (very strong corrosive acid).
So, since there is H2O present from the combustion of the nitrocellulose powder at elevated temp, the O2 (oxygen ) and water could get a jump start on breaking down the MoO3 ( Molybdenum trioxide ) especially if some were in the vapor phase for a few micro seconds from the flash of the powder.
The interior barrel surfaces warming up would also support the reaction of the O2 and H2O with the MoO3 when present . Over time , atmospheric moisture ( humidity) could also react with any residual MoS3.


Molybdenum trisulfide ( MoS3) is potentially hygroscopic based on some reports from National Laboratory , Los Alamos USA and causes many of the friction problems in a standard atmosphere.
MoS3 is the less common form of the Sulfides of Molybdenum. It is most likely less stable than MoS2 and can break down. When it does, there is an extra sulfide atom looking to "mate" with something. It could be air or water or both together.
Molybdenum trisulfide is itself a lubricant in dry atmospheres.
Molybdenum trioxide (MoO3) is not abrasive on its own , “ but attracts moisture vapor contamination”. Sulfur dioxide (SO2) can react further in the presence of water vapor to produce acidic compounds like Sulfuric acid (H2SO4).”
The presence of the Sulfur Dioxide ( SO2 ) alone is enough to react with water vapor to cause concern without any of the other potential multi-valent reactions.
Moly powder in its normal state is not corrosive but there is a “ Potential “ for the reactions of its broken down chemical components to combine to assist corrosion.

Question to Industrial Chemist :---

“Would you say that there is a big possibility that after Molybdenum trisulfide (MoS3) is formed that this chemical could be the culprit that attracts the Water ( H20) from the air into reaction with Sulfur Dioxide ( SO2) to form Sulfurous Acid ( H2SO3) & Sulfuric Acid (H2SO4)?”

Chemists answer :---

“Most likely. The reaction product is going to be predominately H2SO3 (sulfurous acid - weak) but at the higher temps of burning powder it is hard to say how much extra H2SO4 is formed.
Any amount would not be good over the long run if it stayed in contact with the barrel. H2SO4 would just stay in the barrel and not evaporate. Some of the MoS2 may be protecting the barrel surface as it has filled in the microscopic pores ; that is why it is a lubricant in the first place.
Most likely the MoS2 could not provide a perfect barrier against corrosion.
If the MoS3 is co-mingled with the MoS2 or just on the surface of a relatively thin layer, the reaction could take place over time.

Regarding oxidation and temperature, look at it this way. You have overly excited molecules of Molybdenum and Sulfur "in heat". They want to mate with somebody else at elevated temperatures and share electrons to make themselves complete again. Well along comes some Oxygen (O2) molecules and maybe some Water (H2O). Some of the Moly will join with O2, some will find other molecules such as sulfides and link up with them to make Molybdenum Trisulfide ( MoS3). Some of the sulfides will link with some of the Oxygen (O2) to make sulfur dioxide.
Everybody is looking to find a mate. The molecules are breaking bonds . The situation is very dynamic.
If there is one product that has a lower final energy state and precipitates out, then everything goes that way and the side reactions are very limited. In this dynamic Moly situation some of the less stable combinations break down about as fast as they mate together. If one were to deprive the reaction environment of Oxygen (O2), the products would be different. As the temp comes down, the reactions may shift around and finally settle out with MoS2, MoS3, SO2, etc in various quantities. As the reaction products like SO2 wait around on the surface at the lower temps, they can react with H2O and make H2SO3 or the less amount of SO3 reacts with H2O to form H2SO4 .” End of quote.

Conclusion:-- It is obvious from the above that the Oxidation products of Moly have an affinity with moisture and Oxygen and that some are “ Hygroscopic ”. There is a real potential for harm to the barrel of the “ unprepared ” owner. Proper precautions should be taken to store firearms in the driest conditions possible. Clean barrels properly after a shooting session and lubricate or grease the barrel before putting it away.
If the gun is to be stored for the season then thoroughly scrub out as much moly as possible with bore solvents, JB paste, kroil etc. and grease the bore up well.
Inspect the bore from time to time during storage and patch it out and re lubricate.
Weapons that are used and stored in humid hot climates continually would be at a greater risk.
Stainless Steel barrels may have better resistance to potential corrosion but they are not immune. One should not dismiss any precautions just because you have a SS barrel.
Perspective:--
To put this all in context I must say that I am still going to use Moly (MOS2) in the same barrels that I have in the past. This new information has not changed the beneficial aspects that I have gained from using Moly for many years. I have always known that there was an potential “ affinity ” with moisture and I have observed the affects of not cleaning properly. This information is not designed to put fear into the moly user, quite the contrary.
The more you know about a subject the better you can use it to your advantage.
I hope this will allow people to make a more informed decision whether to use Moly and the correct purpose and conditions to use it in.
Pattern of use, Climate in your area, storage conditions, ability to clean regularly all play a part in the decision.
Experience has shown me that with care and correct use the risks of premature corrosion problems are minimal

A special thanks to Ron Teufel for providing chemical reaction information and proof reading of this section concerning the Oxidation products of Moly.
I would also like to thank Carl Porter of Precision Shooter for his help in providing information and being the catalyst to bring me to try for a better understanding of any potential down side to moly coating ( MoS2) and how to manage it. I would also like to thank NASA and National Laboratory Los Alamos New Mexico USA for their help .

Never substitute an uncoated projectile or a projectile with unknown coating material into a case with a powder load worked up for Pure Moly coated projectiles .
Moly will lower the chamber pressures for a given load so you will have to gently increase the load to get back to original velocity .
Moly is not a cure all for bad shooting guns if it shoots bad with uncoated it will probably do similar with coated .
Clean your barrel thoroughly before using Moly projectiles and if you like them don’t use uncoated ones in that barrel again . However you can return to uncoated bullets at any time by just giving the barrel an extra good clean. Powder loads should be reduced also.
Moly works best in shorter barrels as it tends to run out as it moves down the barrel if you get any fouling it will be worse near the muzzle . This can be fixed by making your coating process put on a good deep layer of moly , after you have finished coating take a projectile out into full sunlight and if you can see any coppery colour ( except in cannular ) through the moly coat then it’s not good enough . Also you can condition the bore before or during shooting , with moly slide , work it in with a back and forth rod action then loose patch out the excess . Look down the bore if you can see globs of moly slide it’s too much , patch it out and remove the excess . It's best to let the barrel dry for 5 minuets before shooting . I don’t bother with moly conditioning as my coating does all I need .
Moly has shown a decrease in the amount of deformation to the base of the projectile and a reduction in the depth of the engraving effect of the rifling after firing due to its load carrying Lamellar structure as explained above , this could explain why in America they have put forward theories that Moly increases the ballistic coefficient of projectiles . I can’t confirm this but I suspect that it does give a slight Ballistic Coefficient increase but is hard to measure.
The reduction of base damage done by the lands could also reduce precession as a function of reducing drag .

[No1_49er]

Superb. Thanks very much.

[JohnV]

Your welcome mate I like a person who appreciates knowledge and the time and effort that it took to learn , research , test and assemble that info .

[JohnV]

tumbler walnut media and brasso seems to do the trick

Just make sure you wash the bullets off well in shellite so no ammonia from the brasso stays on them .

[northdude]

We dont have that over here. Is it some kind of solvent or something?

[No1_49er]

We dont have that over here. Is it some kind of solvent or something?

Shellite - used to common 'camping stove fuel'.
I'm sure you'll find it somewhere.

[JohnV]

We dont have that over here. Is it some kind of solvent or something?

Shellite is also called Naphtha , lighter fluid , Solvent x55 in NZ , Hydrocarbon Solvent , Coleman fuel .
Aliphatic Hydrocarbon Solvent, Petroleum Spirit, Peg 1425, Calite, Pegasol 1425, Fuelite brake cleaner. Fuelite: Lighting, cooking and heating Fuel.
It's a good solvent for cleaning bullets because it evaporates quickly and does not leave any residues .

[northdude]

Ok meths no good? I use meths in bore if ive used an ammonia cleaner in it