November 10th, 2018

The Moly Saga — Why Moly-Coating Has Fallen from Favor

Glen Zediker Molybdenum Moly bullets moly-coated Top Grade Ammo book Handloading Competition

Moly — yay or nay? Moly bullet-coating was all the rage in 1998 yet is all but dead in 2018. Glen Zediker, who has considerable experience with moly, provides some reasons why moly coating has fallen from favor.

The Pros and Cons of Moly Coating for Bullets

by 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 sure 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 easier from the case neck (additional “tension” is recommended).

I “switched.” (The motivation to write this came from a weekend shop-cleaning where I restacked 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.

Glen Zediker Molybdenum Moly bullets moly-coated Top Grade Ammo book Handloading Competition
Here was my solution to cleaning up after moly: Kroil penetrating oil and abrasive-type bore paste. This combination worked, and my zero didn’t change in the process.

Cleaning Barrels Used for Moly-Coated Bullets
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 difficult to remove from the bore. 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.

boron nitride moly coating
Hexagonal Boron Nitride (HBN) bullet coating is an alternative that functions, in my experience, well but with fewer drawbacks. First, BN is “clear”, not as messy. Bullet on the left is HBN 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.

Using Coated Bullets Requires Commitment
I no longer use coated bullets. There are other coatings that have fewer disadvantages, such as Hexagonal Boron Nitride (doesn’t outgas). Some of the proprietary baked-on coatings a few major makers (such as Barnes and Winchester) use don’t exhibit the post-firing issues that “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.

Glen Zediker Molybdenum Moly bullets moly-coated Top Grade Ammo book Handloading Competition

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.

Deciding Whether to Use Coated Bullets
Weigh the pros and cons. I honestly cannot, and will not, tell anyone not to use coated bullets. Coating can provide a serious performance increase. I don’t use moly-coating 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.

CONCLUSION: 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.

See what Midsouth offers HERE.

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

Read more informative articles in the Midsouth BLOG

Glen Zediker Molybdenum Moly bullets moly-coated Top Grade Ammo book Handloading Competition midsouth blog newsletter

Permalink Bullets, Brass, Ammo, Reloading, Tech Tip 5 Comments »
June 30th, 2016

Efficient Method for Bullet Coating with Moly, WS2, HBN

Reader Mike Etzel has come up with a simple, cost-effective way to apply moly or danzac coatings to your bullets. And you won’t need any expensive gear other than your regular vibratory tumbler and some small plastic containers.

Mike explains: “For a number of years I have been using a very convenient way of coating my projectiles with DANZAC in a tumbler. Instead of using a separate tumbler filled with DANZAC and stainless steel balls for coating applications, use small resealable plastic cake or pudding cups filled with stainless balls and DANZAC. Each cup will accommodate between 20 to 70 projectiles depending on caliber once the polishing balls and DANZAC are added. When I need to polish some cases, I insert the sealable plastic container(s) into the polishing material in the tumbler, add cases to the media, and in the process clean cases and coat the projectiles simultaneously in one tumbler. This does two operations in one session, saving on time and resources.”

While Mike uses DANZAC (Tungsten DiSulfide or WS2), you can use the same impact-tumbling-in-a-cup method to moly-coat your bullets, or to apply HBN (Hexagonal Boron Nitride).

bullet coatings source hbn moly danzac

TIPS for COATING your BULLETS, by “GS Arizona”

1. Start with Clean Bullets. This is simple enough, but some people overlook it and others overdo it. Get the bullets out of the box, wash them with warm water and dish soap and dry them. No need for harsh chemicals, after all, we’re only removing some surface dirt from shipping and maybe some left over lanolin from the forming process. Don’t handle them with bare hands once they’re clean, your skin oils will contaminate them.

2. Get Everything Hot — Real Hot. This is probably the single most important element in producing good-looking moly-coated bullets. I put the tumbler, the drum and the bullets out in the sun for at least 30 minutes before starting and then do all the tumbling in direct sunlight. On a summer day in Arizona, everything gets to the point that its uncomfortably hot to handle. If you are tumbling in the winter, you should heat the bullets in some form, a hair dryer can be useful, but they will cool off in the drum if you’re tumbling in cold temperatures. Your best bet is to plan ahead and do your coating in the summer. I coated about 3000 bullets in a couple of days recently to see me through our winter season (we’re a bit reversed from the rest of the country in terms of shooting season).

Permalink Bullets, Brass, Ammo, Tech Tip 10 Comments »
November 4th, 2015

Neck Tension 101 — It Ain’t As Simple as You Think

If you want to load ultra-accurate ammo and shoot very small groups, you should read this article, which we are re-publishing by popular demand. Many novice handloaders believe that neck bushing Inside Diameter (ID) size is the only important factor in neck tension. In fact, many different things will influence the grip on your bullet and its ability to release from the case neck. To learn the ins and outs of neck tension, take some time and read this article carefully.

Neck Tension (i.e. Grip on Bullets) Is a Complex Phenomenon
While we certainly have considerable control over neck tension by using tighter or looser bushings (with smaller or bigger Inside Diameters), bushing size is only one factor at work. It’s important to understand the multiple factors that can increase or decrease the resistance to bullet release. Think in terms of overall brass-on-bullet “grip” instead of just bushing size.

Bullet grip is affected by many things, such as:

1. Neck-wall thickness.
2. Amount of bearing surface (shank) in the neck.
3. Surface condition inside of neck (residual carbon can act as a lubricant; ultrasonic cleaning makes necks “grabby”).
4. Length of neck (e.g. 6mmBR neck vs. 6mm Dasher).
5. Whether or not the bullets have an anti-friction coating.
6. The springiness of the brass (which is related to degree of work-hardening; number of firings etc.)
7. The bullet jacket material.
8. The outside diameter of the bullet and whether it has a pressure ridge.
9. Time duration between bullet seating and firing (necks can stiffen with time).
10. How often the brass is annealed

— and there are others…

One needs to understand that bushing size isn’t the beginning and end of neck tension questions, because, even if bushing size is held constant, the amount of bullet “grip” can change dramatically as the condition of your brass changes. Bullet “grip” can also change if you alter your seating depth significantly, and it can even change if you ultrasonically clean your cases.

Redding neck bushingsIn our Shooters’ Forum a reader recently asked: “How much neck tension should I use?” This prompted a Forum discussion in which other Forum members recommended a specific number based on their experience, such as .001″, .002″, or .003″. These numbers, as commonly used, correspond to the difference between case-neck OD after sizing and the neck OD of a loaded round, with bullet in place. In other words, the numbers refer to the nominal amount of interference fit (after sizing).

While these commonly-used “tension numbers” (of .001″, .002″ etc.) can be useful as starting points, neck tension is actually a fairly complex subject. The actual amount of “grip” on the bullet is a function of many factors, of which neck-OD reduction during sizing is just one. Understanding these many factors will help you maintain consistent neck tension as your brass “evolves” over the course of multiple reloadings.

Seating Depth Changes Can Increase or Decrease Grip on Bullet
You can do this simple experiment. Seat a boat-tail bullet in your sized neck with .150″ of bearing surface (shank) in the neck. Now remove the bullet with an impact hammer. Next, take another identical bullet and seat it with .300″ of bearing surface in another sized case (same bushing size/same nominal tension). You’ll find the deeper-seated bullet is gripped much harder.

PPC lapua brassNeck-Wall Thickness is Important Too
I have also found that thinner necks, particularly the very thin necks used by many PPC shooters, require more sizing to give equivalent “grip”. Again, do your own experiment. Seat a bullet in a case turned to .008″ neckwall thickness and sized down .003″. Now compare that to a case with .014″ neckwall thickness and sized down .0015″. You may find that the bullet in the thin necks actually pulls out easier, though it supposedly has more “neck tension”, if one were to consider bushing size alone.

In practical terms, because thick necks are less elastic than very thin necks, when you turn necks you may need to run tighter bushings to maintain the same amount of actual grip on the bullets (as compared to no-turn brass). Consequently, I suspect the guys using .0015″ “tension” on no-turn brass may be a lot closer to the guys using .003″ “tension” on turned necks than either group may realize.

Toward a Better Definition of Neck Tension
As a convenient short-cut, we tend to describe neck tension by bushing size alone. When a guy says, “I run .002 neck tension”, that normally means he is using a die/bushing that sizes the necks .002″ smaller than a loaded round. Well we know something about his post-sizing neck OD, but do we really have a reliable idea about how much force is required to release his bullets? Maybe not… This use of the term “neck tension” when we are really only describing the amount of neck diameter reduction with a die/bushing is really kind of incomplete.

My point here is that it is overly simplistic to ask, “should I load with .001 tension or .003?” In reality, an .001″ reduction (after springback) on a thick neck might provide MORE “grip” on a deep-seated bullet than an .003″ reduction on a very thin-walled neck holding a bullet with minimal bearing surface in the neck. Bushing ID is something we can easily measure and verify. We use bushing size as a descriptor of neck tension because it is convenient and because the other important factors are hard to quantify. But those factors shouldn’t be ignored if you want to maintain consistent neck tension for optimal accuracy.

Consistency and accuracy — that’s really what this all about isn’t it? We want to find the best neck tension for accuracy, and then maintain that amount of grip-on-bullet over time. To do that you need to look not only at your bushing size, but also at how your brass has changed (work-hardened) with time, and whether other variables (such as the amount of carbon in the neck) have changed. Ultimately, optimal neck tension must be ascertained experimentally. You have to go out and test empirically to see what works, in YOUR rifle, with YOUR bullets and YOUR brass. And you may have to change the nominal tension setting (i.e. bushing size) as your brass work-hardens or IF YOU CHANGE SEATING DEPTHS.

Remember that bushing size alone does not tell us all we need to know about the neck’s true “holding power” on a bullet, or the energy required for bullet release. True bullet grip is a more complicated phenomenon, one that is affected by numerous factors, some of which are very hard to quantify.

Permalink Bullets, Brass, Ammo, Reloading 12 Comments »
May 21st, 2013

Ultrasonic Cleaning, Case-Neck Friction and Bullet Seating

ultrasonic cleaningOur IT guy, Jay (aka JayChris in the Forum), was having some issues with his .260 AI. A load with known accuracy had suddenly and mysteriously stopped shooting well. Jay couldn’t figure out what was going wrong. Then he remembered he had cleaned his brass using a powerful ultrasonic machine.

He inspected his brass carefully and saw that the ultrasonically-cleaned necks were so “squeaky clean” that he was actually scratching the jackets on his bullets when seating them. As well, Jay noticed that it took more force to seat the bullets and the seating force became less uniform case to case. Jay solved the problem by applying NECO Moly dry-lube inside the necks of his brass before seating the bullets.

The Perils of Ultrasonic Brass Cleaning by JayChris
I rotate my brass so that I can keep track of each firing, so I keep a “clean/ready to load” bin and a “fired” bin. I have 400 pieces of .260 AI brass. So, all of it was on its first firing (after doing a Cream of Wheat fire-forming) until I hit the 400-round mark. To my surprise, things went south at the 500-round mark. The first time I noticed it (according to my range log) was at a match last year, when I dropped several points and had some vertical stringing issues. After that match, I had 400 rounds through the barrel and all of my brass had a single firing on it. So, it was time to clean.

ultrasonic cleaningI have used an ultrasonic cleaner for a while now. I recently got a more powerful Ultrasonic cleaner, although I don’t know if that makes a difference. My brass comes out dry and squeaky. Emphasis on the “squeaky”.

I found that my new US machine may have been getting the necks TOO clean. After ultrasonically cleaning my brass, I had noticed that it required a little more force to seat the bullets, but I didn’t really think too much about it. But then, after going over my ordeal with a shooting buddy and going over my process in minutiae, we had an “AH HA” moment when it came to cleaning (he uses good ol’ vibratory cleaning).

So, I used some moly dry-lube to pre-lube the case necks and took some rounds out to test at 200 yards. I used my last known good load and sure enough, the vertical flyers disappeared! I shot two, 10-rounds groups with .335 and .353 MOA vertical dispersion, which is consistent with the results I was originally getting.

Other folks have suggested necks may get “too clean” after ultrasonic cleaning. It was pretty sobering to actually witness, first hand, what can happen when brass is “too clean”. I had read some discussions of issues with neck friction/bullet seating after ultrasonic cleaning, but, frankly, I dismissed the idea. Now I understand. The “too clean” effect doesn’t seem to affect my Dasher at all (perhaps because Dasher necks are very short), but on the bigger .260 AI, it definitely does.

Close-Up Photos of Case-Necks

Here are photos Jay took with a microscope. You can see the difference between tumbled brass and ultrasonically-cleaned brass. Jay says: “Here, in sequence, are the Ultrasound-squeaky-clean case neck, a case neck after treatment with NECO moly dry-lube (you can see the particles that will help coat the neck during seating), and, finally, the neck from a case cleaned with corncob media in a vibratory tumbler. You can clearly see how much smoother the inside of the tumbled neck is. Yes, it’s dirty, but it’s also very, very smooth.

ultrasonic cleaning

ultrasonic cleaning

ultrasonic cleaning

Close-Up of Scratched Bullet

Here is a close-up of a bullet that was seated in an ultrasonically-cleaned (“squeaky clean”) neck, with no lubrication. You can clearly see the damage done to the jacket — in fact, in a couple spots you can see the lead core through the scratches! Jay also observed that quite a bit more seating force was required to seat the bullet in a “squeaky clean” neck.

ultrasonic cleaning

NOTE: The bullet jacket is naked — NOT coated in any way. It looks a little dark because of the shadow from the microscope lens, and the high contrast.
Permalink Bullets, Brass, Ammo, Reloading, Tech Tip 5 Comments »