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Old August 23, 2005, 08:15 PM   #1
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Coating Bullets With Moly, Help needed

I am thinking about coating my bullets with molybdenum. I have been told that there are several methods of doing this, one is to spray it on using Ms. Moly available in a spray can, the other is to tumble the bullets in a powdered moly, and another involves tumbleing in wax after the moly. Any information on this subject would be appriciated.

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Old August 23, 2005, 09:49 PM   #2
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The impact plating method was the original developed by NECO. It involves tumbling the bullets together with moly and steel shot. This takes a couple of hours and must be done in a tumbler whose drum isn't neoprene or other material that has an affinity for the molybdenum disulfide powder (and will actually remove it if you tumble long enough). It is followed by ten minutes or so of tumbling with steel shot that has been prepared by tumbling in carnauba wax powder. This puts a thin layer of the wax over top of the moly so it doesn't tend to rub off on your fingers when you handle them. The NECO kit uses laboratory grade moly because the moly market is flooded with used moly from metal forming plants that has iron contaminants which encourage rust. The lab moly is very fine (I own this kit, if you couldn't tell) and it takes only an eighth of a teaspoon to do hundreds of bullets.

The wax/moly combination reduces rifle bullet velocity by around 50 for a given powder charge. This was originally thought to be due to the lowered friction reducing start pressure. However, Harold Vaughn (Rifle Accuracy Facts, 2nd ed., Precision Shooting pub., 2000) proved that it is actually due to enthalpies of vaporization and fusion as the wax evaporates and the moly melts and absorb enough heat to lower the chamber combustion temperature. Theoretically this should increase throat life by reducing heat stress cracking, but I don't believe it has been documented to do so. The loss of velocity can be compensated for with extra powder.

Ms. Moly has some kind of binding agent, I believe (I haven't tried it myself), because I've seen it referred to as a "hard" moly coating. This would also keep if from rubbing off on your hands.

If you use moly bullets, let me pass along a secret: After you trim and chamfer your rifle cases, dip the necks in case neck lube and put them in your press and run the neck over the sizing ball a couple of times to dull the edge of the case mouth. The sizing ball should be polished or be a carbide ball. A sharp case mouth shaves moly off the bullet when you seat it. You can pull a moly bullet from a freshly trimmed and chamfered case and see almost no moly left on the sides of the bullet at all. If you use a polished sizing ball, a pulled moly bullet will have almost no moly missing.

I would also fire-lap the barrel to take the rough spots of the lead onto the rifling and for the same reason: to keep the moly intact as much as possible for maximum lubricating effect.

Molybdenum disulphide always has a certain amount of free sulfur in it which will form sulfurous acid radicals in combination with moisture, so you want to clean thoroughly after using moly coated bullets, especially at the case mouth corner leading onto the freebore. That said, in my experience the coating does help lower the overall rate of fouling. Before I fire-lapped the barrel on my Garand, it had trouble getting all the way through the National Match Course. It fouled so badly that accuracy began to fall apart in the middle of the 600 yard slow fire phase. This didn't occur using moly coated bullets, though fire-lapping also seemed to resolved the problem.

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Old August 24, 2005, 02:41 AM   #3
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The most important thing whichever method you use, is to clean the bullets thoroughly and DO NOT touch after cleaning as just the oils from your fingers will keep the moly from adhering. When I was using moly,I'd spray them down in a bowl with STP engine degreaser,rinse well and dry them. All the time wearing disposable surgical type gloves. You don't necessarily need a separate tumbler drum to apply the powdered moly,a small plastic peanut butter jar or large pill bottle that'll fit in your tumbler works fine. The shot or BBs aren't absolutely necessary either as the bullets provide their own peening action.I used the moly and also the carnuba wax from NECO as it will keep the moly from rubbing off. An important note re the wax-keep an eye on the bullets while tumbling with the wax as theres a good likelyhood it'll clump due to the heat generated if vibrated too long. 7-8 minutes generally does the trick with no clumping. You can get the small refills of moly and wax from NECO for around $35 or so and thats enough for 1000s of bullets.
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Old August 24, 2005, 04:01 AM   #4
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On a related note, polish your bore to a mirror bright because moly is an SOB to clean out of your barrel.
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Old August 24, 2005, 08:56 AM   #5
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Lots of us rifle-shooter-persons moly without the wax and steel shot, using the "pill bottle" method. I use Midway moly with excellent results. Put a buncha bullets in a degreased pill bottle (eg., 500 pill generic Ibuprofen bottle), sprinkle the prescribed amount of moly powder into the bottle. Place bottle of bullets into vibratory tumbler with cases and media.

I always polish the excess moly off by tumbling the moly'd bullets in cc media for a few minutes.

The "why" of the reduced velocity doesn't really matter to me; I just adjust my loads accordingly.
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Old August 24, 2005, 11:07 AM   #6
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I like moly, but just for ease of cleaning and quick return to zero. As Unclenic pointed out, make sure you get oil into a MK barrel ASAP after firing. I have had pitting with MK in humid places.

I use a peanut butter jar, midway's moly and do 200-250 bullets a time. Make sure you clean the barrel down to bare metal before you start shooting MK. Don't mix MK and non-moly'd bullets.

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Old August 24, 2005, 07:01 PM   #7
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Heres a good article on moly coating....
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Old August 25, 2005, 11:07 AM   #8
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Thanks to all of you who have shared thier knowledge of moly coating with me. My next question is, what is the advantage of coating your oun bullets as apposed to buying factory moly coated bullets ?

Thank again, Rich
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Old August 25, 2005, 11:44 AM   #9
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conrich: $$$ is the only advantage.
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