Moly-Coating
[a champion’s perspective]
David Tubb

MOLY EXPLAINED
Coating bullets with molybdenum disulfide (MoS2) is not a new idea. Recent popularity increases due to the ready availability of coated bullets and various bullet coating kits, however, have brought moly coated bullets to the forefront of discussion among competitive shooters.
Obviously, I think moly coating provides the shooter with superior performance; as you may know, I own and operate Moly Coatings Inc., which we believe to be the premiere commercial facility of its type. I wouldn’t have invested in this operation, however, if I didn’t believe that moly coating provided a viable performance increase and, certainly, if I didn’t believe that the advantages far outweighed any drawbacks.

My focus in this article is giving an overview of what moly coating accomplishes, why it does so, and share a few tips I have used successfully to get the most benefit from this technology.

MOLY EFFECT
Moly coating accomplishes one main thing: it greatly reduces friction between bullet and firearm bore. This effect is shown in several ways and, likewise, has various singular effects on the bullet. All these effects are positive.

The foremost effect, in my opinion, of reduced friction is that moly coating makes it possible to increase bullet velocity at the same chamber pressure.

For example, if we take one specific load that uses an uncoated bullet and simply replace the bullet with a moly coated bullet, velocity will drop. For instance, let’s say a .243 produces 2900 fps with an uncoated Sierra 107 gr MatchKing. The load is 41.5 gr IMR-4350. Replace the uncoated bullet with a moly coated Sierra 107 gr MatchKing and there will be an approximate velocity loss of 40 to 50 fps, (1-2 percent).
Pressure, however, will likely fall from approximately 52,000 psi to 49,000 psi, or lower (about 4 -5 percent reduction). Note that pressure decrease is greater than velocity loss, and this is the key to increased speed with moly coating. Note also that while all cartridge and bullet combinations will respond similarly, some will demonstrate more or less variance between coated and uncoated bullet figures due to many unpredictable variables (barrel configuration, individual component lots, etc.).

We would take the load now and increase the powder charge with moly coated bullets to attain the “old” uncoated bullet velocity level of 2900 fps. Now we’re back at the same velocity as before, but chamber pressures are still lower, so we can increase the charge a little more than that and increase velocity as a result. The net effect is higher velocity at the same or lower chamber pressures. Furthermore, if you only load back to the original velocity of 2900 fps using a moly coated bullet, you will now be working the rifle at a reduced pressure which translates into a longer barrel life and more than likely you will experience an increase in accuracy. Kind of like operating a diesel motor at 2100 rpm vs 1800 rpm -- which one will last longer and operates more efficiently?

Because it is such a tremendous friction reducer, moly also eases bullet entry into the lands. Whether the bullet is seated into the rifling or jumping, the initial contact and acceleration is facilitated with moly coated bullets. Recovered bullets have shown improved jacket integrity and greatly reduced impressions made from the lands. There’s no question that moly coating makes the bullet’s trip down the barrel much “easier.”

DOWNRANGE PERFORMANCE
Other performance advantages from moly coating again come from reduced friction and can be related to enhanced bullet flight. I have found that accuracy is usually better comparing moly coated to uncoated bullets. I believe that less stress on the bullet plays a key role in this. I further believe that moly coated bullets can be more consistent shot to shot and possibly more stable in flight. These differences are difficult to quantify due to the great number of variables that come into play when shooting 600 yards and beyond.

One entirely plausible reason for enhanced flight is again due to lowered friction:
a moly coated bullet will enter the bore much easier and, therefore, probably with less disturbance to the jacket and less stress on the core. Recovered moly coated bullets usually exhibit shallower rifling impressions, and these impressions have a more uniform appearance.

BARREL LIFE
I have found that moly coated bullets provide extended barrel life. I believe that the coating itself provides a “buffer” of sorts between the powder gases and barrel surface, and also that moly coated bullets result in less heat being transmitted to the barrel. Many time Bianchi Cup champion, Doug Koenig, told me that he can make several more practice runs firing the Barricade Event using moly coated bullets. In this event the shooter secures the handgun barrel against the barricade using his hand:
barrel heat build up dictates how long the shooter can make practice runs.
Again, moly coating reduced heat build up sufficiently that Doug could get in 3-5 more 6-shot strings before having to stop and allow the barrel to cool.

It’s been my experience that moly coating adds at least 20 percent to accurate barrel life. Barrel wear in a centerfire rifle is almost exclusively due to throat erosion (cracks and roughness in the first 3-4 inches ahead of the chamber caused by heat, flame, and pressure).

An additional 500-plus rounds may not seem like much, but it will add up over the course of a few barrels. However, that, like many advantages of moly coated bullets, are welcome side benefits to the major improvements that result from their use.

CLEANING FREQUENCY
There is far less bullet jacket fouling in the bore with moly coated bullets. Specifically, I have found there to be both less fouling in terms of the amount of deposits left behind after shooting, and a much slower accumulation of fouling. Norma AG found there to be a reduction in metal fouling of 30-40 percent. Now, the amount of fouling any one barrel exhibits has a lot to do with the barrel itself, but I think that this estimate is reliable, if not conservative. I normally shoot between two and three times as many rounds through my barrels before cleaning, depending on the caliber.

The effect here is obvious: I can get many more accurate shots between cleanings with moly coated bullets. In the past, I had to clean after each day of shooting at a major event, such as Camp Perry. Now I can shoot the entire four days there without cleaning.

This is not only a convenience but greatly enhances the consistency of my sight zeros. No matter what steps are taken in cleaning, the first two (or more) rounds through a clean barrel are always a little outside the group (moly coated or not) -- not anymore! This is the sort of advantage that can make the difference between losing and winning.

OTHER BENEFITS
There are other benefits to using moly coated bullets.
Since there is a coating between the bullet and case neck, moly coated bullets will not suffer from the “sticktion” many have reported with uncoated bullets. This dangerous circumstance results from simple corrosion between the bullet and case neck, and the result is elevated pressures.
Likewise, coated bullets won’t tarnish or corrode after handling. And there are others, but -- the reason to use moly coated bullets is because they provide better performance! Shooting them because they add to barrel life or so you don’t have to clean the barrel as often are, again, side benefits.

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'n Uittreksel uit Harold R Vaughn se boek "Rifle Accuracy Facts" vertaal en verwerk deur Prof. Willie van Aardt van Noord-Wes Universiteit -

Molibdeen-disulfied bedekte Koeëls -
Die afgelope 10 jaar is veral in die Amerikaanse tydskrifte, wat oor skyfskiet en jag handel, talle aansprake gemaak op die vermoë van 'n lagie molibdeen-disulfied (ook genoem moly) en karnaubawas op die koeël se gedrag. Hiervolgens veroorsaak moly dat die skietakkuraatheid dramaties toeneem en dit bewerkstellig ook 'n betekenisvolle vermindering in kamerdruk.
In Suid-Afrika is die voordelige eienskappe en waarde van moly ook wyd geadverteer. Daar word beweer dat 'n moly-lagie en karnaubawas minder wrywing en 'n skoner boor van die loop tot gevolg het sodat die snelheid van die projektiel verhoog word.
Die lagie molibdeen-disulfied word aangewend deur die koeëlpunte in 'n tuimelaar saam met koeëllaers te laat tuimel nadat die koeëlpunt se oppervlak eers skoon gemaak is.
Die gedagte is dat moly, 'n bekende smeermiddel in masjiene, ook die loop/koeëlwrywing sal verminder, akkuraatheid bevorder en snelheid laat toeneem.

Vaughn toets vervolgens moly bedekte en onbedekte 68-grein 6mm kaliber koeëls vir trompsnelheid en kamerdruk. Hy vind dat die gemiddelde trompsnelheid van die moly onbedekte koeël 3175 vt/s is en die bedekte koeël 3083 vt/s. Die verskil in snelheid is 92 vt/s of 2.9%.
Die kamerdruk met onbedekte koeëls is 54 000 pond per vierkante duim (pvd) en met moly bedekte koeëls 47 000 pvd.
Die effek van kamerdruk en snelheid verander nie as onbedekte en bedekte koeëls afwisselend gedurende die toetse geskiet word nie. Dit beteken dat daar nie 'n residu-effek van die lagie is nie want die moly word uit die loop geblaas met elke onbedekte koeël.
Die verlaging in kamerdruk word nie veroorsaak deur vermindering in loopwrywing soos deur die Norma-fabriek vir ammunisie in Swede verduidelik word nie.

Volgens Vaughn se eksperimente word dit veroorsaak deur warm (3133 grade Celcius) dryfmiddelgasse wat die lagie moly laat verdamp (sublimeer) met die gevolg dat die dryfmiddelgasse afgekoel word met 382 grade Celcius.
Hy gee twee redes vir sy verklaring:
1) As hy sy DOF6-rekenaarprogram gebruik en loopwrywing in die vergelykings drasties verminder, verminder die kamerdruk baie min en verhoog die snelheid ook min. Loopwrywing het slegs 'n klein effek op snelheid.
2) Verdamping van 'n smeermiddel neem 'n groot hoeveelheid energie op sodat 'n verlaging van 382 °C wel moontlik is. Molibdeen-disulfied sublimeer ("verdamp") by 450 grade Celcius en smelt by 2650 °C.

Om hierdie teorie te bewys, plaas hy 0.07 grein moly en 0.07 grein karnauba bo-op die dryfmiddel en plaas dan die koeël op. Dit is die hoeveelheid massa van die moly-lagie en karnaubawas wat gemiddeld op 'n 68-grein koeël aangetref word.
Hy vind dat die kamerdruk met 4 500 pvd daal, maar verminder die gemiddelde snelheid slegs 50 vt/s. Dit is byna dieselfde resultate wat hy met onbedekte en bedekte koeëls vroeër gekry het.
Hierdie toets is 'n verdere bewys dat moly die temperatuur van die dryfmiddelgasse verlaag en dus het die verlies in kamerdruk niks te doen met wrywing van die koeël nie.

Daar word beweer dat die bedekte koeëls op lang afstande hoër op die skyf skiet met 'n platter trajek. Vaughn meet vervolgens die verlies van snelheid by 20 bedekte en 20 onbedekte koeëls. Die onbedekte koeëls verloor gemiddeld 325 vt/s en die bedekte koeëls verloor gemiddeld 323 vt/s op 100 jaart afstand. Die verskil van 2 vt/s is binne die perke van meetakkuraatheid en kom hy tot die gevolgtrekking dat daar nie 'n verskil in die ballistiese koëffisiënt tussen moly en nie-moly koeëls is nie.

Ook word beweer dat die akkuraatheid met tot 20% verbeter word met moly bedekte koeëls. Met die hulp van sy spoorgeweer (Eng. rial gun) van 70 kg in massa wat groeperings van 0.175 kan skiet, op 100 jaarts, maak hy dieselfde kruitladings op tussen moly en nie-moly koeëls. Ook gebruik hy dieselfde lot nommer koeëls vir moly en nie-moly behandelde projektiele. Hy kry 'n gemiddeld van 0.179 duim in vergelyking met 0.175 duim vir nie-moly koeëls wat duidelik uitwys dat die akkuraatheid nie deur moly behandelde koeëls verbeter word nie.

Hy stem egter ten slotte met ander kenners se bevindings saam dat moly-koeëls vuilheid van lope verminder en ook dat molibdeen-disulfied die lope se lewe kan verleng.
Bron: SA Jagter, Februarie 2007.

With Harold R Vaughn's more conservative view and findings, it is still a fact that with moly coated bullets barrels can run cleaner and have a longer barrel life expectancy.
Gerard Schultz wys ook op die volgende:
"Die GS Custom deklaag bevat wel molibdeen disulfied, maar dit is eintlik 'n drieledige deklaag wat nie met enige gewone 'moly coating' vergelyk kan word nie. Daar is net voordele teenoor kaal koeëls, geen nadele nie."
That, combined with the drive band principle introduced by GS Custom in their HV, FN and SP series of bullets, make your choice of the right bullet for the job so much easier!