Tag Archives: moly coated bullets

RELOADERS CORNER: What Happened To Moly-Coated Bullets?


All the rage in 1998 and all but dead 2018: here’s a look at some reasons why. KEEP READING

moly coated bullets

Glen Zediker

In a way, I guess nothing really happened to molybdenum-disulfide-coated bullets (“moly-coated”). They’re still for sale, as are means to make up your own. What I mean is why didn’t they attain the sustained popularity they started with about 20 years ago, back when many forecasted they would virtually replace bare bullets? Here’s my take, from my experience, on “what happened.”

I don’t know any shooter who tried them and wasn’t excited about results. I sho was!

Performance-wise, moly has a lot of benefits. A lot. The first and most: take two bullets, one coated and one bare, put the same load behind them, then shoot and chronograph. The coated bullet goes slower. How is that a help? The reason it goes slower is because moly drops chamber pressure (into and through the bore easier). And! That velocity loss (at least 50 fps, usually more) is not, proportionately, nearly as much as the accompanying drop in pressure (usually ballpark 4000+ psi). (These figures vary with the cartridge, but all show similar universal influence.) So. The moly-load can be increased beyond previous “maximum” velocity: the idea is to take the coated load up to normal chamber pressure. It works! It’s common to need at the least 1+ grain more propellant to level the coated load with the original bare-bullet load.

Other advantages: Most see improved velocity consistency, evidently resulting from the coating alone. The coated bullets seem to have no limit to the number of rounds that can be fired with no change in accuracy or impact location. Of course there is a limit, but I knew many going beyond 500 rounds between cleanings. And when I say “many,” I’m talking about serious competitive shooters. Another benefit is increased barrel life (less rapid throat erosion), and this is, I think, due to a faster-accelerating bullet getting into and through the throat more quickly (less intense flame). Moly bullets also release sooner from the case neck (additional “tension” is recommended).

I “switched.” (The motivation to write this came from a weekend shop-cleaning where I restacked a huge many boxes of coated bullets, and wondered if I’d ever shoot them…)

I got more bullet speed and zero loss of zero: big benefits to an NRA High Power Service Rifle shooter. 88 rounds per day, and 80gr bullets through a 20-inch barrel trying their best to get to 600 yards in close proximity of one another.

moly barrel cleaning
Here was my solution to cleaning up after moly: Kroil penetrating oil and abrasive-type bore paste. This combination got it gone, and zero didn’t leave in the process.

What is bad, then, about moly-coated bullets? Moly itself! It coats the bore with a layer of residue. This layer traps moisture and will, not can, corrode the steel underneath it.  More: molybdenum disulfide outgases (outgas is the release of an occluded gas vapor that was part of the compound; a state change, pretty much) at lower than firing temperatures. That creates a chemical that, when mixed with water (including post-firing condensation), becomes, pretty much, sulfuric acid. That meant that the whole “zillion rounds between cleanings” didn’t really work. I know many who “lost” barrels, expensive barrels.

If the barrel is cleaned (correctly) after each use, no problems. But then another advantage is lost because starting with a clean barrel it takes quite a few rounds to return to zero. The layer has to be recreated.

The residue is x-difficult to remove. It doesn’t respond to routine means for bore maintenance, mostly meaning brush-and-solvent. The only way I found to get it gone was using micro-penetrating oil in conjunction with an abrasive paste-type cleaner, such as USP Bore Paste or JB Bore Compound.

bn coated bullets
Boron Nitride (BN) is an alternative that functions, in my experience, the same but with fewer drawbacks. One is that it’s “clear,” not as messy. Bullet on the left is coated. Still, though, I think that shooting coated bullets is an “all or nothing” proposition. Good groups are not likely to come “mixing” bare and coated bullets through the same barrel.

I no longer use coated bullets. There are other coatings that have fewer disadvantages, like boron-nitride (doesn’t outgas), and some of the proprietary baked-on coatings a few major makers (like Barnes and Winchester) use don’t exhibit the post-firing issues “conventional” moly-coating creates (which usually was moly powder, followed by wax, which added to the tenacity of the residue).

However, another issue is that accuracy tends to suffer running bare bullets though a residue-coated bore (which results after only a few coated rounds, that are coated with anything). All that means, in short, is that running coated bullets is something that really has to be bought into. It’s a commitment, as I see it, and, as with many such things, pushing the limits on performance requires more attention to detail, more effort. It’s a matter of value.

lyman moly kit
Here’s an easy way to get bullets coated: Lyman’s Super Moly Kit. Just add a tumbler. The two bowls contain the media, moly, and bullets and then go into a vibratory-type tumbler. The 6 ounces worth of moly powder will coat thousands of bullets. It works well.

Weigh the pros and cons. I honestly cannot, and will not, tell anyone not to use them. Coating can provide a serious performance increase. I don’t use moly-coat anymore, but that’s because my shooting needs are not so “serious” as they once were. I, yes, have gotten a tad amount lazy. I want to go to the range and enjoy my rifles and not lose sleep over the possibility of creeping corrosion if I didn’t clean up. I also want to be able to shoot different loads, including factory ammo, and maintain accuracy.

Last words: IF you choose moly, take steps to protect the barrel bore against the potential for damage. At the least, run some petroleum-based oil through the bore after shooting if you can’t clean it soon.

Tell about your experiences with moly.

See what Midsouth offers HERE

This article is adapted from Glen’s books, Handloading For Competition and Top-Grade Ammo, available at Midsouth HERE. For more information about other books by Glen, visit ZedikerPublishing.com

Reloaders Corner: Coated Bullets


Bullet coatings promise better performance, but are they the right choice for you? Find out.

Glen Zediker

There are a few bullet coatings available, and Moly (MoS2: molybdenum-disulfide) is the best known, and also the most notorious. More in a bit.

moly coated bulets
Molybdenum Disulfide is the most popular bullet coating. It has exceedingly positive effects on performance, but there are may be some serious consequences for the uninformed user. Without correct (and frequent) cleaning, it can cause long-term damage to a barrel. Use it as outlined in this article and the extra speed and improved accuracy can pay back big to a serious shooter.

First, here’s how and why bullet coating works: Fire a coated bullet and a bare bullet using the same propellant charge. The coated bullet will go slower. However. The pressure will be lower. The reason is easy to figure: the increased lubrication reduces friction, resistance to movement, especially upon entry into the bore. It gets kind of a head start. The deal is that the pressure drops relatively more than the bullet speed, so, the bullet speed can be increased by adding more propellant and still have the same level of pressure. Win. Win. And, since there’s what amounts to a barrier between the bullet jacket and the barrel steel, the promise of more accurate rounds between cleanings is all true too. The bullet jacket isn’t leaving much of itself behind on the bore.

Among competitive shooters there was a huge shift toward coated bullets a few years back, but they’ve since fallen from favor for many. It wasn’t because they don’t perform well, because they do, but there are ancillary, and important, liabilities. Mostly: moly-coated bullets can corrode barrel steel, including stainless. Molybdenum disulfide outgases (outgas is the release of an occluded gas vapor that was part of the compound; a state change, pretty much) at temperatures lower than firing temperatures, and that creates a residue that, when mixed with water (moisture from condensation included, like what happens after firing), is pretty much sulfuric acid. Yikes. Right. If a moly-coated barrel is cleaned (correctly) each use, no problems. But one of the big draws is the potential to get literally hundreds of rounds, on zero, before the barrel needed cleaning. After a conventional cleaning (solvent and brush) it also takes time, which is rounds through the barrel, before zero will return.

I am a fan of coated bullets, and they’ve convincingly demonstrated their superiority to me after many thousands of rounds reaping rewards from the ballistic advantages. The improvement can be significant, and some bullets in particular escalate in performance more than others. Shorter bearing surface designs, by my notes, get that much more additional speed with no pressure trade-offs. Coating seems to have a disproportionately positive effect on thinner-skinned bullets, for reasons that likewise are clear. The effect here is smaller group sizes. Anything with a “J4” jacket responds well to coating (common in custom bullets).

My solution to the worries about moly was, as suggested, simply to clean the barrel each time back from the range and, also, to change my cleaning method to better accommodate the residue composition. More in a bit.

I don’t use moly any more, though. I’ve switched to Boron Nitride (BN) because it has all the advantages with none of the drawbacks, so far. BN is virtually the same in its effects as moly, based on my notes (same level of velocity drop and subsequent future increase). It’s easy to apply using a vibratory-style case cleaner.

BN coated bullet
This is a Boron-Nitride-coated bullet (right) compared to a bare bullet. BN is clear, slick, and doesn’t cause the chemical reactions other coatings are notorious for. It’s what I use.

I do not recommend any sort of lubrication inside a barrel, not for a promise of increased bullet performance. PFTE, for instance, has been touted as a great “break-in” agent for a barrel. Some use it after each cleaning to prep a barrel. Well. When it outgases, and it does outgas, it releases fluorine, a very powerful eater of all things metal.

Cleaning: Don’t use copper solvent with moly! The ingredients don’t mix well. Use only petroleum-based solvent. I switched to Kroil pentrating oil in conjuction with something like USP Bore Paste, JB Bore Compound, or similar (abrasive paste-type formulations). No room here now to convince anyone that abrasives are a safe and wise choice, but used correctly they are both. “Correctly” means a rod guide, stainless-steel rod, and keeping the rod shaft clean each pass. With that combination the bore is being protected against corrosion and the residues get gone, and, of huge importance, zero returns right away.

moly coated barrel cleaning
Bullet coating leaves an entirely different residue that conventional cleaners might not be effective on, and there’s also some chemistry involved that can inadvertently create big problems. I’ve had best results, all around, with a combination of micro-penetrating oil and abrasive paste. Keep the rod clean and feed it through a rod guide using abrasives and there’ll be no damage done.

Last on this: Just in the same as how I do not recommend “mixing” bullets or propellants through the same barrel, same day, coatings are pretty much the same. Zero will, not can, change for the number of rounds it takes to “re-season” the barrel. If you use it, use it.

I’ve seen great gaps in the quality of coated bullet finishes. Factory-coated bullets are the way to go. It’s tough to get a good job at home, and the reason is the carnuba wax application is temperature sensitive, and also because commercial coaters use industrial-level tumblers to apply the powder. The wax is necessary to avoid a smudgy mess just from handling the bullets. If you want to do it yourself, make sure the bullets are cleaned before application. Likewise, moly can build up in a bullet seating die so clean it out every now and again.

BN Coating Kit
BN can be applied easily using a vibratory tumbler and the contents shown. Put the BN powder in the bottle with the bullets, run the bottle in a vibratory cleaner for a spell, and that’s that. Check HERE for more information on bullet coating.

The preceding was adapted from Glen’s newest book, Top-Grade Ammo, available here at Midsouth. For more information on this book, and others, plus articles and information for download, visit ZedikerPublishing.com