In the late 1990s a process was developed to coat the surface of bullets with a coating of Molybdenum Disulfide (moly). This process resulted in many befits for the shooter which can include:
- higher velocity due to reduced friction
- increased interval between cleaning (before decrease in accuracy)
- bore cleaning is much easier
- more pronounce effects in standard production barrels
Many companies offer loaded ammunition featuring a moly coating on their bullets and both Sierra and Hornady offer selected bullets moly coated for the reloader. But what about all the bullets out there that don’t come with the moly option? Note that most people recommend that you shoot moly bullets exclusively in a gun for best performance and accuracy. Mixing coated and uncoated bullets could give you headaches.
How does one go about coating all those naked bullets? Well the first company to offer a complete system was NECO. That is what I started with many years ago. Over the years I have tried other processes and will give you a system that I have found to give consistent results.
I still u
se the same old vibrating tumbler that I purchased for this process many years ago. The moly gets in everything, so there is no way you can do anything but coat bullets with this tumbler.
Where I changed the process was in the tumbling media. Lyman at one time offered a ceramic tumbling media which the recommended for moly coating bullets. It doesn’t wear out, so I am still using it. From a quick online search it appears to be similar to: Vibrafinish Angle Cut Triangles. 3/16″ x 3/16″ Polish Compound. Some people use steel shot, but I have had the shot oxidize and rust into clumps. Ceramic media al
so allows you to wash the media in water with normal household cleaners. This is required from time to time to ensure the best results.
Use Simple Green (on any other good degreaser) to wash the bullets. Rinse thoroughly and let them dry before adding to tumbler. Sierra Match Kings can trap water for a long time in that little hollow point! In winter, I will sent them on top of the wood stove to speed drying. In summer, I use a lamp to provide addition heat. I determine the maximum tumbler load by weight resulting in loads of 100 30 cal 168 gr bullets to 200 223 cal 52 gr bullets. A simple word of advice – do not mix bullet sizes or types in a single batch. It is a pain to sort them as you pick them about.
I recommend wearing gloves and a respirator when loading and unloading the tumbler. The moly powder is very fine and gets in everything! Now add you the moly powder. I still get the powder from NECO. I find about 1/2 tsp to be a normal amount once the media is well coated. I then let the tumbler run on a timer overnight. It is noisy so think about where and when you run it! It needs to run between 2-3 hours to get a good solid coating. Once you have run a few batches, you will be able to look at the bullets and quickly determine if they need to tumble longer or need more moly. Use an old towel or dish rag and wipe off any excess powder that may be sticking to the outside of the bullets when removing the bullets from the tumbler.
If all goes well, this is the result.
Now you can shoot moly coated bullets!
As mentioned earlier, after a few batches, or not using the moly tumbler for a while, you may need to wash the tumbling media. The first sign is when the moly will clump or ball on the bullets and media. Simple wash the media in the Simple Green you have been using to wash the bullets. Not all the moly will come off. But wash and rise several times. Allow to completely dry before putting the media back in the tumbler and attempting to coat another batch of bullets.
Hatcher's Notebook 