By Art Merrill | Contributing Editor
Coating bullets with molybdenum disulfide (L) may – or may not – shrink groups.
“So, what’s the deal with the black bullets?” another shooter asked me at the local range, where I was experimenting with molybdenum disulfide coated bullets in a competition rifle.
The deal is that some competition shooters believe coating jacketed bullets with molybdenum disulfide reduces combustion gas breech pressures as the moly acts as a lubricant between bullet and bore, thereby reducing friction. There’s also a belief that the practice reduces bore wear and, more specifically, throat erosion, as the moly deposited in that area upon firing supposedly protects it.
Army trials: insignificant
The moly coating concept is not new. It was in the last century that the US Army Ordnance department tested molybdenum disulfide (and graphite) by applying it to bores and to projectiles. Long story short, researchers found no significant reduction in friction or pressures applying moly to either component. When we consider that bullets need only about five percent of the energy from powder combustion to overcome friction with the bore, we can see why any expected lubricating benefit from moly coated bullets would be difficult to detect in even a large data sampling, which the Army apparently gathered.
These three tools—top to bottom a toothbrush, a chamber iron, and a screwdriver—can repair most feeding or ignition problems in semiauto .22s.
Yet many Long Range and Bench Rest shooters have found that a bore “seasoned” with 30 or more moly coated bullets requires a slightly increased powder charge to send such bullets at the same velocity as before using moly. The inference is that breech pressure has dropped, thereby dropping velocity, and the assumption is that the pressure drop is caused by moly deposited the length of the bore reducing bullet-to-bore friction. Alternatively, some point at case neck-bullet lubricity as the factor. Whatever is going on between moly and the inside of a rifle, the end result is sometimes smaller groups.
Competition shooter: significant
So, what do competition shooters know that Army ordnance experts do not? Note that the Army was concerned with larger ordnance (canon) and with rapid- or continuous-fire small arms, and that long range competitors leisurely engage in slow firing of precision-made rifles intended only for clustering bullets as closely together as possible. While several decades of shooters using moly coated bullets in competition constitutes a large data sampling, the lack of deliberate and consistent sampling and objective measurement protocols renders such data unconvincing for drawing any unshakable conclusions.
Also consider that the Army is also very much concerned with counting beans – the old joke is that soldiers go into combat armed with weapons made by the lowest bidder – and that moly coating projectiles apparently doesn’t pass the cost-vs-benefit cutoff, even if any real benefit was discovered. Referring back to an earlier statement, in testing moly, the Army was looking for and did not find a significant benefit in coating bullets and canon shells with the stuff; however, what is insignificant to the needs of an entire army may well be of significance to an individual competition shooter.
Nutshell: sometimes
Citing the arguments pro and con for using moly coated bullets would fill pages, and most of those arguments are based on anecdotal evidence, assumption, supposition and inference rather than quantifiable, objective measurement beyond shrunken groups. However, we may be able to nutshell the moly coating adventure thus: it appears moly coating bullets can sometimes shrink groups fired from barrels that otherwise will not shoot well. That’s about it. And a point to note: most competition shooters decline to use moly because it adds a significant complication – not just in coating bullets, but also in modifying powder charges and in cleaning bores – without an equally significant benefit. Which is pretty much what the Army decided decades ago.
Dangerfield .22s
We’re going to diverge from the handloading path here to share a topic that I hope will benefit you. I’m not a certified gunsmith, though I am an armorer, and I work with a gunsmith friend a couple days each week with firearm modifications, troubleshooting and minor repairs. When asked, “Are you the gunsmith?” I usually reply, “No, I’m the perennial apprentice.”
Perhaps the single most common problem gun that customers bring in is a .22 rimfire rifle that suffers misfires; if a semiauto, it may suffer stoppages. Troubleshooting these problems in old .22s often leads to discovering the same cause in a great many cases: like little Rodney Dangerfields, they just ain’t gettin’ no respect. In repairing quite a few such .22 rifles, the tools I’ve used most often are a screwdriver, toothbrush and chamber iron.
No cleaning?
I’m not sure where the idea originated that .22s don’t need to be cleaned. Maybe it harkens from the days when ammo makers switched to noncorrosive priming. Maybe other shooters heard that Smallbore competitors never clean their rifles. The latter is partially true, as many competitors typically don’t scrub their bores with solvent during competition season because doing so removes the bullet lube deposited in the bore, moving the point of impact for the next five to ten shots on the target. However, rimfire competitors usually run a few dry patches through the bore after a match to remove the worst of the fouling.
For the rest of the world’s .22 shooters, however, there is no reason not to clean after a hunt or shooting session, and every reason to do so. And for the person who doesn’t occasionally clean the buildup of fouling and carbon in the action of their semiauto .22, stoppages and/or ignition failures are simply a matter of time. How does crud cause misfires? A couple of different ways!
Light strike
When .22 rimfire cartridges fail to fire, a shooter may see an unusually light dent in the cartridge’s rim and assume the culprit is a broken firing pin or weak hammer spring. While a buildup of fouling in a firing pin channel and/or gunking up a firing pin spring might slow a firing pin enough to cause a light strike and no ignition, in semiautos another cause is the buildup of fouling preventing the bolt from closing fully. The bolt may complete closing with the blow of the hammer or striker, but the bolt absorbs enough of that energy in its forward motion to prevent a strong-enough blow to ignite the priming.
The chamber iron is simple to use but is becoming harder to find.
This is where the screwdriver and toothbrush come in. I can’t tell you how many times someone has brought me a .22 exhibiting misfires, balky feeding or failed extraction, which I repaired simply by a complete disassembly, scrubbing with a toothbrush and solvent, and sending the parts through the ultrasonic cleaner.
Reassembly brings up another point. Some gun owners apparently believe if a little bit of lube is good, a lot is better. However, too much gun oil can actually contribute to function failures, as the oil will hold firing residue that might otherwise dissipate as particulates in the air. The end result is an even dirtier action that needs more frequent cleaning.
Ironing .22s
You’ve heard that we should not dry fire a rimfire firearm because if there is no cartridge present in the chamber, the firing pin may strike and peen the edge of the chamber face. Dry fire enough times and it will peen a tiny bit of steel over the chamber mouth and prevent a cartridge from seating, or it may grip a fired case tightly enough to cause the extractor to fail to extract the case. In some .22s the firing pin doesn’t reach the chamber mouth absent a cartridge case, but the rule generally holds.
The fix here is an ironing tool that swages the chamber mouth to remove the bit of peened, protruding steel. The tool is not expensive, and it’s simple to use, but it’s become somewhat difficult to find. An imperfect alternative is to use a mallet and the back end of a drill bit. SAAMI dimension for the .22LR chamber at the mouth is .2307 inch, and a #1 drill at .228 inch is the closest fit. However, a tapered punch may be a better choice, for obvious reasons. Insert your “swage” into the chamber and tap with a mallet a few times, then inspect; repeat if necessary.
With either one, you must ensure the tool does not contact the front of the chamber where it tapers into the leade before it can contact the peened steel. Also note that .22LR match rifles typically have chambers somewhat “tighter” (smaller diameter) than SAAMI standard chambers, and some custom or semi-custom .22s have “Bentz” chambers, the dimensions of which fall between standard and match chambers.
And yes, you may first have to separate the receiver from the barrel to use such ersatz swages. For these reasons, it may be a job for a gunsmith or his perennial apprentice and the proper tool. But with a little bit of respect, you can avoid these problems with .22s.
