Reloaders Corner: Coated Bullets

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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

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19 thoughts on “Reloaders Corner: Coated Bullets”

  1. Sounds like a pain in the ass to me. I don’t think my skill level is high enough to notice a difference. I ain’t the best or the worst, just a person who’s satisfied with his premium barrel. I get enough 1/4″ – 1/2″ groups & sometimes 4-shot groups under 3/16″. Yes, those are rare!
    I’m 76 & my eyes could be better, but they ain’t. I can live with it. 🙂

  2. Thanks for the article, good info. I’m good shooting my hand loads and factory loads and cleaning with solvent, brush and patch.
    Im not a competitive shooter, I’m out to relax and enjoy the boom. Don’t get me wrong, I want to shoot for accuracy but I’m not willing to toss all these other variables into the mix. I have enough just fixing my issues of holding steady, breathing and swearing!

  3. I was an early adopter of moly. I never had any issues using the lab grade moly the original NECO patent product kit supplies. A lot of folks using technical grade moly seemed to get lumps building up and there is apparently a lot more free sulfur in the cheap moly that is the source of the acid. I cleaned my guns, where some folks wanted to see if they could leave them without cleaning all season. I’ve done it for a couple of days, here and there, but not weeks or months at a time, which I think was the source of a lot of the bad publicity.

    If you are using moly, among cleaners, give Gunzilla a try. It’s a vegetable oil-based product that penetrates like Kroil, but also debonds carbon over time. My borescope revealed one result of shooting moly bullets was the neck portion of my Compass Lake AR’s chamber had developed a black ring packed into the corner of the shoulder at the end of the neck-receiving portion that corresponds to a case mouth. No doubt a collection of carbon and moly. I was using Kroil and Iosso Bore Cleaner (another mild abrasive paste), but it just never came out, Nor did other common brand name cleaners remove it, regardless of soaking time. Brush bristles seemed unable to get into the corner. But when I got my first sample of Gunzilla at the National Matches at Camp Perry one year, I used it to get the normal carbon residue out of the bore using it like any other cleaner, and after the last wet patch I let it sit in the bore overnight, same as I did with Kroil. The next day I ran a dry patch through and it came out with a circle of black on it at the corner of the jag. Surprised by that, I got out the borescope and found that black ring was completely gone. No scrubbing or abrasive required.

    I pulled a few coated bullets one time. To my surprise, they were clean copper where they were inside the neck. It turns out, oblique though it is, the angled edge of the chamfer can shave that coating right off. I assume the same happens with an hBN coating. Indeed, even on commercial ammo I found there was often a ring of scraped copper at the case mouth where it meets the bullet, so this scraping effect has potential to affect bullet balance. With scraped moly the ogive still lubricates the bullet entry into the bore well enough, but it just bugged me to have cases altering my bullets in any way, so I did some experimenting and found that if I burnished the chamfer, either by spinning a sharpened dowel in the case mouth with a drill or by running the mouth over the carbide expander ball I have in my sizing die a few times, that scraping was prevented. Later a former U.S. Palma team member pointed out to me that he burnished cases to prevent scraping the copper, too, and had polished up an EZ-out for the purpose. The reverse thread doesn’t try to pull it into the case, so if you buff the outside smooth it does a good job of this.

    PTFE’s aren’t the only bore treatment out there. I’ve been trying Sprinco’s Plate+ Silver. It’s a NASA patent-based lube that is a suspension of micronized acid-neutralized moly in an oil that bonds electrostatically to iron atoms. So far, using bullets that aren’t coated, I see the same velocity drop moly coating produces. The maker says it lasts about 1000 rounds without re-treatment. It may be used on any ferrous metal, and because of the acid-neutralizing, produces none of the corrosion associated with cheap moly. The main nuisance is keeping it out of the chamber (I use a glue applicator syringe to dribble in into the neck with the muzzle down), and the fact it takes about 72 hours to finish bonding. But it does seem to work as advertised and looks like it gets around the whole break-in issue, as normal cleaning doesn’t seem to remove it.

    I have yet to try the hBN alternative. The bore coating looks like it may well eliminate the need, but I’m an experimenter, so I’ll probably have to try it anyway.

  4. I agree with Spencer. Unless your a high volume shooter coating bullets just doesn’t make sense. Even then I would question the wisdom of using coated bullets. Winchester uses coated bullets in some of there ammo. That to me is nothing more than a sales gimmick . At 70 years of age I have done my share of reading on the subject over the years. None of that reading convinced me coated bullets were an improvement over regular jacketed bullets.

  5. Moly coated bullets (which I use) are easier on the barrel than jacketed and the barrel cleans up very easy. They are cheaper than FMJs and even copper plated bullets. I shoot them in all different calibers and even with full-power 357 or 44 magnums the barrels come clean easily.

  6. I had used moly-disulfide for years, until I discovered tungsten-disulfide which has a lot lower coefficient of friction, and is a lot less hydrophilic (attraction to moisture) than MoS2. The dry climate in Colorado/Wyoming minimizes the risk of moisture mixing with the firing residues.

    I use X-disulfide coated bullets for my high-volume shooting (High Power Rifle Matches & prairie dogging). I have fired well over 6,000 rounds of X-disulfide bullets, and the throats of my barrels still look almost like-new with minimal throat erosion.

    I avoid using these coatings in my big-game rifles because of inclement weather and risk of condensation with large, sudden changes in temperature in the fall/winter seasons.

    This year, I am going to try Boron Nitride (BN)on my big game bullets since they are pure copper/lead bonded bullets that leave a lot of copper fouling. I want to see if I can reduce the fouling so I can hunt with a seasoned barrel.

    Here is an interesting link to an experiment performed at the US Air Force Academy whose data tends to minimize or show an opposite effects of the X-disulfide & BN coatings, as compared with bare jacketed bullets.

    http://www.dtic.mil/dtic/tr/fulltext/u2/a568594.pdf

  7. I have searched for reference material on the moly problems outlined here, and can find none.

    I have been using moly coated bullets for over 20 years on the great majority of my rifles, which I do not always immediately clean after use, and have witnessed absolutely none of the issues mentioned here.

    Further, I usually clean with Ed’s Red, followed by Wipe Out, which is a copper solvent. No troubles. None. Nada. Nichts. Zip. Zero.

    I live in The People’s Republik of Southern Kalifornia, where it is dry most of the year (except when it is not) and keep my weapons in a heated safe year round.

    Please advise.

    The BN does look interesting.

    1. I thought they ( Soviet Kalifornika) out-lawed EVERYTHING including sling shots.
      I lived there for 32 years and finely got my fill and left in 2012, went to “free America” Idaho. My heart goes out to honest gun folks out there, it’s only a bit more time before them subversives ban everything but armed armies for the rich and infamous.

    2. Pop over the TheFiringLine.com forum and run the search engine. You’ll find people who dropped out of moly because of problems, but I always find they were using the cheap kits. I was told by a lubricant sales rep one time that some inexpensive moly is reclaimed from metal stamping operations and can have trace iron in it, which, if you’ve ever watched a rust knot form and pit a surface, is a good oxidation seed. So I expect cheap moly works out sometimes and not others, depending on the source of the particular lot.

      Like you, I’ve never seen an issue, but I always used the lab grade moly from NECO, for which a tiny quantity goes a long way, or Sierra or Norma bullets, both of which licensed NECO’s patent (indirectly, in Sierra’s case). So the material quality there is good. The patent jumpers, like Wheeler, and numerous others typically have the cheap moly, which I can’t bring myself to trust.

      Incidentally, Sprinco’s discussion of its Plate+ product also mentions their formulation prevents what they call “rebonding” where moly builds up on itself to form lumps. I don’t know how material grade affects this.

      1. Well, the NECO moly kit has enough materials to last nearly a lifetime. I’ve done over 50K bullets with my kit and you can hardly tell I’ve used the materials.

    3. For several years I used Wipe Out & always figured it did a good job. Even using it a 2nd time didn’t remove anymore copper. Then I was reading about the importance of carbon removal…. especially if it wasn’t all removed & built up over time. So I decided to give “Bore Tech C4 Carbon Remover” a try. The cleaning ritual is significantly longer the Wipe Out. But I discovered it removed copper that was left behind after using Wipe Out 2 times….. even leaving wipe Out in the bore overnight.
      So now I use both.

  8. There are some other home applied options out there. Hi Tek manufactured in Australia is another that I am using. You can buy it here in the States and Canada through High Performance Bullet Coatings in Louisiana. If you don’t want to home apply, High Performance also sells coated bullets. This coating does what the rest do by putting a layer of lubrication between the bullet and the barrel. Stops copper fouling giving more shots between cleaning.

    I know this article was about coating jacketed bullets, but where Hi Tek has helped me is with shooting the lead bullets. At this time, I have only used it with my lead bullets to prevent leading of the barrel. It does a great job with those allowing me to shoot .308 lead bullets a jacketed speeds. But, I have been told by the company rep in Australia that they use it to coat jacketed bullets there for competition. And I may try that soon.

    1. Almost forgot, it is my understanding that there is no gassing off of the coating, when it is properly applied, leaving behind corrosives.

      1. Dennus,

        It’s just PTFE’s that can outgas, I believe. There was a brief spat of Teflon bore coating in the early 90’s when S&W and others OEM’d a product called Friction Block that was just PTFE. But it wasn’t long before rifle shooters reported in Precision Shooting and other publications that it actually deteriorated shot-to-shot accuracy. The problem is that the properties of Teflon change as it heats to barrel temperatures, creating a friction temperature dependency and possibly the gassing off as well. If you are a hunter who is always firing from a cold bore, it’s not an issue, but if you are in a match with a sustained string of fire, it becomes one.

        I don’t believe moly outgasses. The issue with free sulfur in it is a process issue and it can be eliminated by treatment with a basic solution to acid-neutralized the moly, and I believe that is part of creating the high purity lab grade stuff as well. The pulverizing of moly to superfine particle size is done by impacting its particles against themselves to break them up without contamination.

        1. I used to be an Industrial Hygienist for Kemper Corp. We had a problem with lung irritation at a place that did plating. Turned out they were using Teflon to protect the parts of the pieces that they din’t want to plate.

          And the HYDROFLOURIC ACID byproduct from heating TEFLON over about 480 degrees F put that into the work airspace. I won’t EVER put Teflon in a bore, dudes.

  9. Spencer,

    C4 is good at carbon, but it is specialized for it. Bore Tech’s C++ for copper, used right afterward, will amaze you. It acts so fast that I can’t use brass jags with it, or the copper in the brass has started to turn the patch blue by the time I’ve pushed it from one end of the bore to the other. Worth mentioning, apropos of this thread, is that Bore Tech also makes a special blend called Moly Magic for cleaning barrels with moly build-up.

    1. I stopped using anything but nylon brushes, especially in my premium BR barrel. C4 Bore Tech does remove copper that Wipe Out leaves behind. It ain’t much, but it’s there. Being retired, I’m never in a hurry. I often allow Wipe Out to sit in the bore overnight.
      I never shoot over 40 rounds in a day from my BR rifle without a thorough cleaning. Fortunately I believe I never get much copper build-up. It’s also rare I shoot more than twice a week. I average 2-3 minutes between shots. Keeping the barrel cool enough to put my hand on it saves me money from throat erosion.
      The last time I had my bore checked with a bore scope it was perfect after 500 rounds had been put thru it.

  10. I just wish I could find some aluminum jags, as the WIPE OUT does attach the brass ones. Still, when you unwrap the patch from the jag and PAY ATTENTION to what you are seeing, it is usually pretty obvious what part of that blue color came from the jag.

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