Testing Friction Reduction of Bullet Coatings

[Michael Courtney]

The Aug 2012 issue of Precision Shooting contains an article comparing the friction reducing effects of MS2, WS2, HBN, and Lubalox. The research was performed with cadets at the Air Force Academy who co-authored the article. The title is "Friction Effects of Common Bullet Coatings in 5.56mm NATO" and uses the same technique as the earlier article originally published in the March 2012 issue of Precision Shooting and reprinted here. The results were somewhat surprising to us.

 

[Michael Courtney]

Anybody read the article? Any questions or comments?

 

[Outlaw6.0]

I don't suppose the is a link to a website we can use is there?

I'm seriously considering HBN on one or two of my rigs....

 

[Michael Courtney]

I don't suppose the is a link to a website we can use is there?

I'm seriously considering HBN on one or two of my rigs....

In the 5.56mm test barrel, HBN reduced the friction on the 55 NBT by 15%, the 62 BFB by 12%, and the 55 TTSX by < 1%. The report is not available on the web that I know of. The earlier report describing the method was posted here:

Measuring Barrel Friction In The 5.56mm NATO

To me, these modest friction reductions do not warrant the time, effort, and expense of coating with HBN.

 

[Outlaw6.0]

In the 5.56mm test barrel, HBN reduced the friction on the 55 NBT by 15%, the 62 BFB by 12%, and the 55 TTSX by < 1%. The report is not available on the web that I know of. The earlier report describing the method was posted here:

Measuring Barrel Friction In The 5.56mm NATO

To me, these modest friction reductions do not warrant the time, effort, and expense of coating with HBN.

I wouldn't mind seeing the same test conducted on a bullet with a long bearing surface, say a 7mm-180grn Berger or a 338- 300grn SMK. It makes me think (I hate it when that happens!) that as bearing surface goes up, friction reduction would also go up...? Who knows....


As far as price, effort etc goes, Copper Creek will HBN up to 1k projectiles for $30.00 & that includes return shipping. At less than .03/round, I am going to give'er a try

http://coppercreekammo.com/index.php?main_page=product_info&cPath=34&products_id=94


t

 

[Michael Courtney]

I wouldn't mind seeing the same test conducted on a bullet with a long bearing surface, say a 7mm-180grn Berger or a 338- 300grn SMK. It makes me think (I hate it when that happens!) that as bearing surface goes up, friction reduction would also go up...? Who knows....


As far as price, effort etc goes, Copper Creek will HBN up to 1k projectiles for $30.00 & that includes return shipping. At less than .03/round, I am going to give'er a try

Boron Nitride Coating Boron Nitride Bullet Coating [] - $29.99 : Copper Creek Cartridge Co.


t

You have some good insights. As bearing surface increases, friction usually increases also for the bullets we've tested. However, bullet construction is a bigger factor, and a solid copper bullet or a bullet with a steel core will usually have much more friction than a similar length jacketed lead bullet.

However, I would not think a lubricant would reduce friction by more than about the same percentage in a bullet with a longer bearing surface. It might be 12% of a bigger uncoated friction, therefore a bigger gain, but the percentage gain would be unlikely to be more than 12-15%. We've tested a lot of bullets with a lot of coatings and 15% is the best friction reduction we've ever seen.

For example, the 55 NBT lost 245 ft-lbs of energy to friction uncoated, and the 62 BFB (longer bearing surface) lost 330 ft-lbs of energy to friction uncoated. The coating of HBN reduced the friction by 15% and 12%, respectively. After these mediocre results, I've stopped coating my 140 AMAX (very long bearing surface) bullets in 6.5x284 and I've seen no negative results.

In fact, the testing we've done also shows that uncoated bullets have smaller shot-to-shot velocity variations. Not that coated bullets can't have impressive extreme spreads and standard deviations in velocity. In some cases they can. But in the bullet's we've tested, extreme spreads and standard deviations of uncoated bullets are consistently smaller.

 

[Outlaw6.0]

Interesting topic for sure. In your 6.5x284 with 140 A-Max setup, what was the velocity difference utilizing the same load running coated vs uncoated?

There is a TON of information regarding the effects of lubricant on the bullet; how about the effects on the bore? Less friction should, & I say should, promote longevity of the bore life; should it not? 2nd, running a coated bullet, shouldn't copper fouling be reduced to a near zero amount?


t

 

[Michael Courtney]

Interesting topic for sure. In your 6.5x284 with 140 A-Max setup, what was the velocity difference utilizing the same load running coated vs uncoated?

There is a TON of information regarding the effects of lubricant on the bullet; how about the effects on the bore? Less friction should, & I say should, promote longevity of the bore life; should it not? 2nd, running a coated bullet, shouldn't copper fouling be reduced to a near zero amount?


t

The velocity difference in the 6.5x284 is small and not attributable to the coating as it was not my intent to do a scientific test and hold all the other factors constant (new vs. fired brass, temperature, degree of bore cleaning, lot of bullets, lot of primers, lot of powder, etc.) The tests in the 5.56mm NATO were scientific and these factors were carefully controlled.

Less friction may well increase bore life, but I would not expect a 15% decrease in friction to increase bore life by more than 15%, and I expect the benefit might not even be that much if throat erosion due to the pressure and temperature of the hot gases are the main cause of accuracy degradation at the end of bore life.

We have not been able to do a convincing quantitative test of copper fouling to say that any coating decreases fouling. We have discussed with chemists how we might quantify the amount of fouling we pull out after shooting, but the available techniques are prohibitively expensive.

On the theoretical side the field of tribology (the science of friction and wear) suggests that wear is not usually reduced disproportionately to friction and that as long as there are high levels of friction, both surfaces will continue to experience wear. The tribology journals and other scientific works suggest that the lubricants under discussion tend to reduce wear in rough proportion to their reduction of friction.

On the experience side, we have never failed to pull out copper when cleaning a rifle after shooting coated bullets. Even as few as 10 to 20 bullets produce copper fouling. We cannot even conclude subjectively that the amount of copper seems to be less.

 

[Outlaw6.0]

The velocity difference in the 6.5x284 is small and not attributable to the coating as it was not my intent to do a scientific test and hold all the other factors constant (new vs. fired brass, temperature, degree of bore cleaning, lot of bullets, lot of primers, lot of powder, etc.) The tests in the 5.56mm NATO were scientific and these factors were carefully controlled.

Less friction may well increase bore life, but I would not expect a 15% decrease in friction to increase bore life by more than 15%, and I expect the benefit might not even be that much if throat erosion due to the pressure and temperature of the hot gases are the main cause of accuracy degradation at the end of bore life.

We have not been able to do a convincing quantitative test of copper fouling to say that any coating decreases fouling. We have discussed with chemists how we might quantify the amount of fouling we pull out after shooting, but the available techniques are prohibitively expensive.

On the theoretical side the field of tribology (the science of friction and wear) suggests that wear is not usually reduced disproportionately to friction and that as long as there are high levels of friction, both surfaces will continue to experience wear. The tribology journals and other scientific works suggest that the lubricants under discussion tend to reduce wear in rough proportion to their reduction of friction.

On the experience side, we have never failed to pull out copper when cleaning a rifle after shooting coated bullets. Even as few as 10 to 20 bullets produce copper fouling. We cannot even conclude subjectively that the amount of copper seems to be less.

Your statement about bore life vs throat life is something I didn't consider when posing my question (I really do know better ). There is a possibility of slight accuracy retention utilizing coated bullets in a "long in the tooth" bore as the coating could help to fill in the cracks & provide a smoother transition across that section of the throat. Of course that is very subjective & pure hypothesis on my part.

I don't know that the copper fouling test really needs to be that controlled. At least from the shooter's perspective. Take one rifle, chambered in a cartridge noted for very good bore life as to not be detrimental to the test. Start with a roto-rooter, squeaky clean bore & fire say 200 rounds new brass, uncoated, note accuracy every 25 or 50 rounds until either accuracy completely dies or your test concludes.

Now, go back to the roto-rooter, squeaky clean bore. Now load 200 coated bullets with new brass & repeat the test. Granted it is a waste of a bore, but i'd be willing to wager (a very small one) a test like that, although not labratory grade would lead to some fairly conclusive evidence?

Heck after the 200 round (tentative number of course) session, stick your bore scope in there & take a look at what's going on. Now obviously you aren't going to be able to take exact measurements of the fouling but visual indications may very well be present.


Obviously, i'm just thinking out loud for conversation sake. As i'm sure you can tell, i'm no expert, just an enthusiast who suffers severely from "tinkeritis".


gun)

 

[Michael Courtney]

I don't know that the copper fouling test really needs to be that controlled. At least from the shooter's perspective. Take one rifle, chambered in a cartridge noted for very good bore life as to not be detrimental to the test. Start with a roto-rooter, squeaky clean bore & fire say 200 rounds new brass, uncoated, note accuracy every 25 or 50 rounds until either accuracy completely dies or your test concludes.

Now, go back to the roto-rooter, squeaky clean bore. Now load 200 coated bullets with new brass & repeat the test. Granted it is a waste of a bore, but i'd be willing to wager (a very small one) a test like that, although not labratory grade would lead to some fairly conclusive evidence?

Heck after the 200 round (tentative number of course) session, stick your bore scope in there & take a look at what's going on. Now obviously you aren't going to be able to take exact measurements of the fouling but visual indications may very well be present.

Obviously, i'm just thinking out loud for conversation sake. As i'm sure you can tell, i'm no expert, just an enthusiast who suffers severely from "tinkeritis".


gun)

We've always considered most accuracy testing as more anecdotal (possibly valid for one rifle and shooter in a given circumstance) than scientific (most likely applying to a broad class of rifles and ammunition rather than just the specific test cases).

The way most accuracy testing is conducted, there is simply too much room for confounding factors to draw convincing conclusions from small sample sizes. We've considered possible accuracy testing to answer various scientific questions that arise (including bullet coating and more fouling) but the sample sizes and facility costs to do rigorous scientific testing seem prohibitive. None of our team feels personally confident to be a reliable shooter for such testing. Have you priced machine rests that are good to 1/4 MOA? Also, we feel that reliable accuracy testing over the required sample sizes would most likely require an indoor range on the order of 300 yards long like Barnes has (to remove wind as a confounding variable).

Finally, we think we'd likely need between three and five bullets in the coated and uncoated states, so with 200 shots in each condition (coated and uncoated), we're looking at 1200-2000 shots to compare HBN with uncoated. Of course, everyone will want their coating included in the study, so we're talking about 600-1000 more shots for MS2 and WS2 (each). Of course, by this point, we're beyond the life of the barrel for most cartridges and whether a given coating was tested early or late in the barrel life is now a confounding factor, so we need a multi barrel test where the test is repeated with each coating occurring at a different stage of the barrel life.

Accuracy tests are very hard to do with the level of scientific rigor needed to infer with confidence that the results can be expected to apply broadly to situations other than the rifle and bullet combinations included in the actual test.

 

[arizona mike]

Rather than bullet coatings, how about coating the bore such as with Dyna Bore Coat. This product suposedly leaves behind a .25 micron ceramic coating that is suppose to last the life of the barrel and reportably reduces copper fouling significantly. Does anyone have any experience or knowledge of this product?

 

[Michael Courtney]

Rather than bullet coatings, how about coating the bore such as with Dyna Bore Coat. This product suposedly leaves behind a .25 micron ceramic coating that is suppose to last the life of the barrel and reportably reduces copper fouling significantly. Does anyone have any experience or knowledge of this product?

It seems like snake oil to me. I can find no scientific test results to back up the marketing claims. Furthermore the claim of no change in velocity is inconsistent with the claim of reduced fouling. Reducing fouling means reducing wear. Reducing wear means reducing friction. A change in friction means a change in velocity. You cannot significantly reduce fouling without changing velocity.

 

[arizona mike]

That makes sense that there should be an increase, however slight, in velocity. I'd hate to fall into that catagory that PT Barnum when he said "there's a sucker born evey minute! Sure would like to hear from anyone that has either tried this product or knows someone who has! Thanks for your input!

Kinda on the same subject, how the heck does one determine what "excessive" fouling is anyway? I see that term thrown around a lot but have never really known how one would actually measure this. My 22-250 load travels around 4000fps. I cannot imagine a bullet traveling that fast not leaving a little of itself behind in the tube. But how would I know what is "too much"???

 

[jake50]

I used some snake oil in my 30/378 Accumark. Did the before and after on the crony, before 180 grnx 114.5 Retumbo 3480 (hot) treated the barrel
then i used 190 grn Berger with 110.5 Retumbo 3460 fps
Groups 3 shot x 3 avereged .54" For me Accuvel works ..