Safety Tip for Shooting Coated Bullets
Coating bullets with a friction-reducing compound such as Molybdenum Disulfide (Moly) offers potential benefits, including reduced barrel heat, and being able to shoot longer strings of fire between bore cleanings. One of the effects of reduced friction can be the lessening of internal barrel pressures. This, in turn, means that coated bullets may run slower than naked bullets (with charges held equal). To restore velocities, shooters running coated bullets are inclined to “bump up” the load — but you need to be cautious.
Be Careful When Increasing Loads for Coated Bullets
We caution shooters that when your start out with coated bullets in a “fresh barrel” you should NOT immediately raise the charge weight. It may take a couple dozen coated rounds before the anti-friction coating is distributed through the bore, and you really start to see the reduced pressures. Some guys will automatically add a grain or so to recommended “naked” bullet charge weights when they shoot coated bullets. That’s a risky undertaking.
Instead we recommend that you use “naked” bullet loads for the first dozen coated rounds through a new barrel. Use a chronograph and monitor velocities. It may take up to 30 rounds before you see a reduction in velocity of 30-50 fps that indicates that your anti-friction coating is fully effective.
We have a friend who was recently testing moly-coated 6mm bullets in a 6-6.5×47. Moly had not been used in the barrel before. Our friend had added a grain to his “naked” bullet load, thinking that would compensate for the predicted lower pressures. What he found instead was that his loads were WAY too hot initially. It took 30+ moly-coated rounds through the bore before he saw his velocities drop — a sign that the pressure had lowered due to the moly. For the rounds fired before that point his pressures were too high, and he ended up tossing some expensive Lapua brass into the trash because the primer pockets had expanded excessively.
LESSON: Start low, even with coated bullets. Don’t increase your charge weights (over naked bullet loads) until you have clear evidence of lower pressure and reduced velocity.
Procedure After Barrel Cleaning
If you shoot Moly, and clean the barrel aggressively after a match, you may want to shoot a dozen coated “foulers” before starting your record string. Robert Whitley, who has used Moly in some of his rifles, tells us he liked to have 10-15 coated rounds through the bore before commencing record fire. In a “squeaky-clean” bore, you won’t get the full “benefits” of moly immediately.
To learn more about the properties of dry lubricants for bullets, read our Guide to Coating Bullets. This covers the three most popular bullet coatings: Molybdenum Disulfide (Moly), Tungsten Disulfide (WS2 or ‘Danzac’), and Hexagonal Boron Nitride (HBN). The article discusses the pros and cons of the different bullet coatings and offers step-by-step, illustrated instructions on how to coat your bullets using a tumbler.
Similar Posts:
- Safety Tip for Loading With Coated Bullets
- Safety Tip: When Using Coated Bullets, Adjust Loads with Caution
- Safety Tip: Adjust Loads Conservatively with Coated Bullets
- Reloading Tip for Coated Bullets — Adjust Loads Cautiously
- Reloading Advice: With Coated Bullets, Adjust Loads Cautiously
Tags: HBN, Moly, Moly Coated, Tungsten
I wonder if someone would/could comment on coated bullet issues compared with the recent article on Melonite coating of the barrel?
Do they have similar velocity characteristics?
In the Melonite coated barrel, does the lubricity aspect disipate as the round count rises between cleanings? If so, would you “foul” this barrel as well to get the Muzzle Velocities stabilized?
I’m wonder what happens if instead of 20 rounds to get the internal barrel coating, simply apply moly to the naked barrel like the brownells moly compound. That maybe can reduce the fouling string?
The above article refers to “..potential benefits, including reduced barrel heat..” which seems a reasonable expectation, however does anyone have any actual data to support this? Is the effect significant or trivial?
How is moly going to reduce barrel heat? The flame behind the bullet is what causes barrel heat and the guys that use moly coated bullets add more powder so there should be more heat, not less.
You mentioned that your friend lost several cases because of excessive pressure. I find that it is common for shooters not be convinced by one over pressure load, and to continue on for several more shots, sometimes with drastic results.
Perhaps a related tip would be that at the first sign of excessive pressure, you should stop shooting, and investigate to determine the cause. Surely loads that were hot enough to expand primer pockets were excessively flattened, and the bolt lift would have required more effort.
Louis, a major source of heat is friction.
I, like many forum contributors am a habitual experimenter. I use coated bullets now as a matter of course and am reluctant to use anything else, but it took a long time to learn how.
Boyd is correct when he says, if you change any component in a load, you must start your load development again. For me though, I don’t see the point of any load that that requires a large number of foulers to settle in and then ultimately requires a clean out.
I like to swab coat my bore with an emulsion of Eezox and HBN as well as using HBN coated bullets I coat myself. In two of my rifles, using this process even negates the need for fouling shots altogether (within the inch at 300 m). In others, a couple of foulers are still required. They are all rules unto themselves.
Unlike moly, HBN is easy to remove and easy to replace and is totally inert for our purposes.
The only trick is to make absolutely certain that the Eezox is dry before the next firing, and this usually takes around 20 minutes where I live. It could be a bit of a drag between rounds at a competition.
You might also be surprised just how quickly your rifle now cleans up.
For practice, we shoot at static clay targets at 900 m (roughly 980 yards) once a week. 3 and 4 out of 5 first round hits are fairly normal now for most on the team. (I live to see the day when one of us can make it 5 out of 5 in our mountainous conditions!)
These comments do not constitute a recommendation or advice. Just a description of what we do, and it works for us.