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What is the real truth about Moly?

As published in SHOOTERS NEWS April 1999

"Can I eat game shot with moly coated bullets?"
Is moly toxic or hazardous in any way?"

There is a two-part answer to this question.

(A) Moly is necessary in the human body in order to maintain good health and is usually ingested by eating vegetables, which take up Moly from the soil. One need only read the back panel of almost all man made fertilizers to see that one of the ingredients is Moly as shown by the chemical symbol Mo. Any excess ingestion of Moly will result in the excess being thrown off by the body in the same manner as an excess of vitamins. Therefore, there is no danger at all in eating game animal killed with a Moly bullet.

(B) Breathing dry Moly is another story entirely. Moly with a particle size of seven microns or below is comparable to a droplet of fog suspended in the air and is very easily inhaled. Dry Moly in the presence of moisture (such as in the lungs) quickly becomes acidic and just as quickly begins to irritate lung tissue. The latter, irritated lung tissue, allows rapid invasion of bacteria and viruses which quickly lead to respiratory infections. Prolonged or regular inhalation of dry moly and the continued irritation of lung tissue can lead to lung cancer and death. Anyone who works with dry moly should wear a respirator and safety glasses at all times.

"Is all moly the same?"

Most certainly not. Moly can be found in an infinite number of particle sizes and levels of purity depending upon the mining/refining source. The most desirable type of moly for weapons application is lubricant grade (1.5 microns or below), 99% pure (100% pure is not possible) and should be a wetted and inhibited formula in a colloidal suspension. Poorly refined or impure moly can contain undesirable quantities of Cadmium, Chromium, Copper, Iron, Mercury, Nickel and Lead. Such impurities in quantity can be very detrimental to any weapon.

"I have heard that moly is corrosive. Is this true?"

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 (S02). When the Sulfur or Sulfur Dioxide is exposed to the humidity in air, it combines with water vapor to form Sulfuric Acid (H2S04) 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 there upon 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.

"I am a precision competition shooter and already get almost twice the life out of my target barrel using dry moly-coated bullets when compared to my use of standard non-coated bullets. Why do I need to worry about corrosion, etc.?"

If you have no problem with the time, aggravation and expense of replacing your target barrel every 3,000 to 4,000 rounds (maximum life as reported by moly bullet users) and also have no problem with other drawbacks of using dry or uninhibited moly (velocity decreases, buildup/caking, etc.) then you should continue to use the dry moly coated bullets. If, on the other hand, you would like a viable alternative, then you should seek out a moly weapons oil formulation which is remicronized, inhibited and in the form of a colloidal suspension. Use of the latter as instructed will eliminate velocity decreases in rifle length barrels, virtually eliminate all fouling and provide an almost indefinite barrel life.

"What causes me to experience a reduction in velocity when firing moly-coated bullets?

This will be a complex answer with several factors involved. First, modern gun powder is in reality a solid propellant which is chemically formulated in a precise manner to burn at a controlled rate not unlike the solid propellant found in the booster rockets of the Space Shuttle and other spacecraft. Controlled burning is a critical factor in understanding the answer to this question. Another fact to keep in mind is that to our knowledge, no reloading charts or ballistic tables exist which were computed on the basis of a weapon firing moly coated bullets. In addition, it must also be understood that the popular "tumbling" method of coating bullets with dry moly leaves only a very thin layer of moly on the projectile as the attraction by molecular polarity between the moly and the gilding metal (bullet jacket) is relatively weak compared to moly's attraction to steel. Now, keeping the above factors in mind, let us actually track the path of a moly bullet as it is fired in a modern rifle. Once the primer is struck ignition begins in the solid propellant at the rear of the cartridge case. Expanding gas from the controlled burning of the propellant creates pressure which then forces the moly bullet out of the end of the cartridge case and into the throat of the bore. This initial leap of the bullet into the bore throat is a harsh environment for the bullet as it must not only size itself to the bore but must also conform itself to the lands and grooves of the rifling to begin its stabilizing spin. By virtue of its moly coating reducing friction, the bullet moves more easily and sooner in time (not speed) into the bore throat achieving its conformity and spin much sooner than an uncoated bullet. As this bullet travel is taking place, the propellant continues to burn at the controlled rate dictated by its chemical formulation which was compounded for non-coated bullets. Let us now imagine that the bullet has reached the half way point or 50% (approximately) down the length of the barrel. In our mind's eye we now "freeze frame" the tracking of the bullet at the approximate 50% point in its trip down the barrel in order to see what has happened and is happening. Since the bullet began its trip into the bore throat easier and with less effort than an uncoated bullet, the amount of propellant which had burned was less in relation to the position of the bullet down the bore. The reason being the moly bullet, having to overcome less friction in starting its movement, has required less energy from the burning propellant to begin its trip. As a result of this, the area or volume of space available to the expanding gas from the burning propellant has become greater due to the more rapid entry (sooner in time, not speed) of the moly bullet into the bore. It is a known scientific fact that pressure from an expanding gas is inversely proportional to the space in which the gas is allowed to expand. This means that the greater the space available for expansion of the gas, the less pressure the expanding gas exerts. One now readily sees that the overall pressure of the expanding gas, which has a direct effect on bullet velocity, has been reduced due to a larger volume of space in which to expand with the latter being caused by the quicker entry (in time, not speed) of the bullet into the bore. In addition, the propellant has now almost, if not completely, burned with little or no more to burn to create pressure. Let us now look at yet another thing which has happened at this approximate 50% mark. The moly bullet, due to the very thin coating of moly on its jacket, has had most, if not all, of the moly rubbed off and redeposited onto the steel of the first 50% of the bore length (this will vary to some degree depending upon the thickness of the moly coating on the bullet). The moly bullet has now become almost, if not completely, a standard non-coated bullet. The remaining thing which has happened is that the heat generated by firing the bullet has also been reduced due first to a larger area within the throat and bore in which the heat is transferred and secondly due to the reduction in frictional heat caused by the increased lubricity of the moly bullet. This reduction in heat is the primary reason for the increased life of the bore throat of the barrel when firing moly bullets. Let us now put things back into motion and track the bullet the rest of the way out of the barrel. In the remaining length of the bore, the bullet now begins to encounter increased friction as most, if not all, of the moly is now gone. This increased friction further slows the bullet and when the projectile finally exits the barrel, chronographic measurements clearly show a reduced bullet velocity when compared to the firing of standard non-coated bullets.

"How can I regain or set back the lost velocity?"

There are three ways this can be done. First, you can use a faster burning propellant (powder) in which case you will lose some of the extended life of the bore throat. Second, you can increase the charge of the same powder in order to provide a longer burn time and continued pressure as the moly bullet travels down the barrel. Use of the second method can leave unburned powder in the bore. Third, you can abandon entirely the use of moly bullets and use a properly formulated moly weapons oil.

"I have been firing moly bullets for some time and I'm getting some kind of buildup or caking in the bore. What is this stuff?"

The buildup/caking can be caused by two factors (or a combination of both) as follows: When one first begins to fire bullets with a burnished or impacted coating of moly, the moly quickly rubs off the bullet and is redeposited onto the walls of the bore. Continued firing of moly bullets continues to redeposit moly onto the bore but instead of in a burnished deposition of moly it becomes a compressed deposition of moly caused by the mechanical pressure of the bullet against the bore wall. Compressed deposition of moly will cause a thicker layer of moly to be plated onto the bore which then causes an undesirable buildup. There is great deal of truth in the old saying that "there can be too much of a good thing". In addition, one could be using a dry moly powder with an excessive amount of impurities in which case the buildup is being caused by not only the compressed deposition of too much moly but also by the impurities in the dry moly powder. For example, there is one metal working company in the US which consumes some 40,000 to 50,000 pounds of dry moly powder each year. The moly powder is used to "tumble coat" various mild steel shapes in preparation of a cold extrusion process which converts the steel into its desirable configuration. The wire drawing industry is another example of large consumers of dry moly powder used to coat steel rods which are then "cold drawn" into wire. The dry moly powder (many times not a true lubricant grade particle size) used by these industries soon becomes ineffective due to the accumulation of various impurities. Most of these impurities are oxides of iron, Zinc in the form of stearates and many other types. This used, ineffective and contaminated moly powder should then be disposed of in a land fill; however, it is known that much of it finds its way back into the market place through local machines shops, etc. who are unaware of the level of contamination it contains. Some of this contaminated moly powder is being purchased by shooters, also unaware of its contamination, to "tumble coat" bullets. And, it should be noted here that the popular method of tumble coating bullets with moly is nothing more than an adaptation of an industrial process used for well over 25 years in the metal working industry. In addition to used and contaminated moly being available, a great deal of poorly refined and impure moly has been coming into the US from such countries as mainland China, Mexico, Poland and other sources and this moly is no better than the used and contaminated type.

"How do I get this buildup / caking out of my rifle?"

Once moly has plated to steel, removing it is not an easy task. If the buildup is not too severe, it can be removed by using a dry powder chemical compound called Alkanox (your local chemical supply house should have it) and some very vigorous scrubbing with a brass brush. If Alkanox is not available, then use the gel type detergent made for dish washing machines with even more intense scrubbing with a brass brush. In severe cases, you will have to resort to using a mild abrasive and some elbow grease. They key word is "mild." Some products will rub the rifling right out of your barrel. Be careful!

"In the future, how can I avoid any buildup or caking and other undesirable side effects of using moly bullets?"

The most objective and honest answer we can give to this question is to discontinue the use of all moly-coated bullets. You can achieve better shooting results and a much longer barrel life with a properly formulated moly weapons oil as outlined. A properly formulated moly weapons oil deposits moly onto the bore by the "insitu deposition" method and completely eliminates buildup, caking, corrosion and loss of velocity together with providing you with many other benefits. In closing, let us recognize that Molybdenum Disulfide is the finest and most effective lubricant known to modern science - provided it is both formulated properly and applied correctly.


1st June 1999
Parsec Group

There appears to be continued confusion regarding certain aspects of using Molybdenum Disulfide in weapons environment. The following information is added to clear up some of this confusion:

1. It is claimed that removing moly (caked or not) from a barrel is not difficult and that simply running a patch through the bore will suffice. This is decidedly NOT correct and is based upon seeing the grey to black color coming out on the patch. The discoloration is being caused by the patch cleaning out the ultra thin layer of Molybdenum Trioxide (MoO3) which has formed on the surface of the Molybdenum Disulfide (MoS2) due to the heat of firing, MoS2 begins to oxidize to MoO3 at a temperature of around 1000 degrees F. This ultra thin coating of MoO3 tends to protect the MoS2 from further oxidation but DOES NOT seal the MoS2 from moisture in the air. The latter, picking up moisture from the air, is what reacts with the Sulfur and Sulfur Dioxide (SO2) contained in the MoS2 to form corrosive acids. The only way to completely remove MoS2 after it has plated to the steel is to use a mild abrasive such as JB Bore Paste. Great care should be taken in order not to damage the lands and grooves of the bore when using any abrasive. MoO3 does have some lubricating ability (less than MoS2) but it does NOT have the layer / lattice structure of MoS2 nor does it have any affinity for steel or any other metal.

2. It has been stated that thousands of rifle shooters have used moly-coated bullets without excessive caking or corrosion. As caking and corrosion are related to the purity level, particle size and absence of acid neutralizers of the dry MoS2, there are thousands of rifle shooters who HAVE HAD problems with both caking and corrosion. The obvious conclusion here is to simply abandon the use of moly coated bullets and use a properly formulated moly weapons oil which has been inhibited against corrosion, is remicronized and with a purity level of 99% plus.

3. There are many who believe that swabbing the bore with a patch saturated with a penetrating oil called "Kroil" will eliminate all possibilities of corrosion. Again, the concept is NOT correct. The application of Kroil is only a temporary "fix" and will (for a maximum of about 2 days) seal off the MoS2 FROM MOISTURE IN THE AIR. Afterward, the Kroil film dries ruptures and again allows moisture in the air to contact the MoS2 crystals with acid formation as a result. Kroil contains no acid neutralizers and is formulated for the sole purpose of using it to loosen frozen and corroded nuts, bolts and other fasteners. Kroil obviously does a very good job in applications for which it was formulated. However, Kroil was NOT formulated as a weapons oil and was never intended to be used for weapons application. This information may be verified by speaking with the Kroil Chief Chemist, Mr. Joe Sinclair, who may be reached at 1-800-311-3374. It must be remembered and recognized that all chemical formulas should be used only for the purpose intended by its formula. One does not use motor oil to fry eggs for breakfast even though it is an oil. Motor oil was not formulated as a cooking oil and certainly should not be used as such. This logic holds true for any lubricant, solid or liquid, regarding its application to weapons of any kind. The end user of any chemical formula should first ask himself "am I using this product for the purpose intended and for which the product was formulated?" If the answer to either part of this question is "no," then you should certain not use it.

We trust this information will further clarify the confusion surrounding using MoS2 in a weapons application.

The Parsec Group
Weapons Engineering

Editor's Note:
John Gammuto, Editor

I like the ring of this report...a lot. A technical discussion of Molybdenum Disulfide, devoid of salesmanship, has been long in coming. I cannot remember when a single product has caused such consternation among shooters of similar mind and stated goals. If you would like to speak with some folks that truly know what they are talking about on this subject contact:

Sprinco USA

7804 Danz Blvd.
Austin, TX 78724
Phone: 512-331-8797

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