Q: About 20 years ago moly-coated bullets were all the rage, but these days you never hear them mentioned in Yank gun magazines anymore. They were supposed to result in lower chamber pressures and increased velocity with less bore fouling, and reduced throat erosion, so you would think they’d have been a great success and still popular. You would have tried them , so what’s your opinion of them?
Jimmy James
A: Early in the piece, about 1998, I compared the results of bullets coated with molybdenum disulphide with uncoated bullets and my initial testing revealed that they did indeed produce less chamber pressure in a rifle chambered for the .243. The moly-coated bullets produced about 10 percent less pressure with the same load – 45,500 psi against the normal 50,000 psi. The load was 44gn of AR2209 in a Lapua case with a CCI 200 primer. The coated bullets produced 90fps less velocity as well. The extreme velocity spread was 21 fps with the coated bullets and 63 with the uncoated bullets. This was for a 10-
shot average. It took 1- 1/2 grains more powder with the coated bullets to equal the pressure developed with the uncoated bullets. Evidently, the moly-coated bullets did lubricate the bore the way they were supposed to. Later I tried moly-coated bullets in various brands before I decided I didn’t want to use them. I found they couldn’t always be relied upon to give improved accuracy, that they were messy to handle and produced moly fouling which was difficult to remove and required a special solvent. In time bulletmakers developed new baked-on molybdenum disulphide coatings that had all the advantages of conventional moly-coating without the messiness, such as the Winchester Fail Safe and the CT Ballistic Silvertip. Today, moly-coating is in the discard.
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