Honest questions about bullet coating(s)

[Michael Courtney]

MC, I realize you are trying to be evenhanded in your research. But your statement that your protocol is the "best method available" becomes an overreach and defensive of the protocol.

Please cite a published paper determining friction with a better method.

Of course, it does not take much thought to come up with a better ideas that could be implemented with infinite money. If a method only exists in someone's mind, then it isn't really available, now is it? Our statement is only an "overreach" if you can cite a published paper or patent describing where a better available method has been demonstrated. In science, a method is not really available unless it has been demonstrated in an actual implementation, not just hypothesized about by an anonymous poster on an internet forum.

Methods that require large investments in specialized equipment do not lend themselves to repeatability by independent parties, especially in times when research budgets are tight, as they have been since 2009. Our method has the advantages of both accessible costs as well as the ability to apply the method in any rifle, and therefore with any barrel. Methods that depend on universal receivers or specialized barrels are of limited usefulness for determining friction in rifle barrels, because barrel friction is a combined effect of bullet and barrel.

Testing bullet friction only in specialized barrels that mate with a custom test system is not really an "available" method compared with our method that can be applied to any rifle with any barrel once the relationship between muzzle energy and powder charge is shown to be linear over a wide range of powder charges.

You don't need 110 barrels and a dozen cartridges to disprove the patent claim that WS2 and MS2 reduce barrel friction sufficiently to increase velocity by 5-10% with increased powder charges. Disproof by counterexample requires a sample size of 1. Yes, it leaves open the possibility that there are some rifle barrels out there where WS2 and MS2 reduce barrel friction sufficiently to increase velocity by 5-10% without increasing pressure beyond the level specified for the cartridge. But I doubt it, as in the many years since the claims of the Martin Patent, there has not been a single published case supporting the claim with both pressure and velocity measurements.

 

[stool]

there is a big difference in PUBLISHING and publishing USEFUL information.

real world shooters have seen your claims and have said no way..the "test' is not real world, so the "conclusion" have no value to real world shooters.

please just go away

better yet have the person that you work for at the air force contact me so i can set him straight..and get the junk pulled.

you are spreading internet myth.......

 

[Michael Courtney]

there is a big difference in PUBLISHING and publishing USEFUL information.

We've gotten feedback from a number of ballistics labs which find our published methods useful and are making plans to implement them. My expertise is also recognized by a number or organizations and journal editors as I am frequently selected to serve as a peer reviewer for papers in ballistics.

The specific papers on our friction measuring method were peer-reviewed both by Air Force scientists and also by external reviewers prior to publication. Their feedback was incorporated into the published manuscripts, but no doubts were raised regarding the basic soundness of the methods employed or results obtained. Publication of the manuscripts was approved both by the immediate chain of command and by the research office.

The soundness of the method and the results is also demonstrated by the sensible trends demonstrated in our friction determinations: 1. Other factors being as constant as possible, bullets with longer bearing surfaces have more friction than bullets with shorter bearing surfaces. 2. Other factors being as constant as possible, bullets with thin jackets show less friction than bullets with thick jackets. 3. Other factors being as constant as possible, solid copper bullets have more friction than jacketed lead bullets. 4. With the same bullet and other factors constant, barrels with faster twist rates demonstrate more friction than barrels with slower twist rates.

Assertions that our coating experiments may be in error depend upon this method showing sensible trends in all these other cases, but somehow failing to measure the proper friction values in the case of coatings. This is unlikely, but not impossible, so I think it is reasonable to ask for more concrete evidence that the coatings significantly reduce friction (as claimed in the Patent and advertising).

real world shooters have seen your claims and have said no way..the "test' is not real world, so the "conclusion" have no value to real world shooters.

Some real world shooters have expressed disagreement, but in science the arbiter of truth is repeatable experiment rather than "expert" opinion. We are still waiting for publication of results showing that these coatings actually reduce friction (provide the same velocities at lower pressure or higher velocities at equal pressure, especially the 5-10% velocity increases claimed in the Martin patent). We are open minded that future experimental results may cast doubt on our results or support the idea that most other barrels respond to coatings differently than the barrels we happened to use in our testing.

please just go away

better yet have the person that you work for at the air force contact me so i can set him straight..and get the junk pulled.

I've always let my chain of command know when our results may be met with some skepticism. As long as our publications met with the department's internal peer-review requirements, and the Air Force requirements for approval by the research office, my chain of command was ok with the possibility of scientific disagreement regarding our published results. In the case of our friction papers, we went beyond the Air Force requirements and also obtained external peer reviews. If you disagree with our results after this level of due diligence, we invite you to publish a comment or criticism of our published work in the open literature. Of course, since your published comment or criticism will contain your real name and affiliations, you will be subject to some level of personal and professional embarrassment if our reply to your comment reveals substantial flaws in your data, presentation, or reasoning. That's why we get a lot more criticism from anonymous internet "experts" than in the open literature.

 

[mikegaiz]

I am not taking any sides, and as I said earlier: " I do not have a scientific back ground, but have an applied knowledge of the product."

1, I would think that friction would be a major component of barrel ware. So why do barrels not wear as much using Molly?
???

2, Also, having examined identical bullets shot in the same barrel, at the same velocity, molly and non-molly. Why are the rifling marks in the bullet less pronounced in the molly coated bullets?
???

 

[Keith Glasscock]

Michael,

I do enjoy reading your work. It has been a while since I read this paper, so correct me if I get any of the details of your experiment incorrect.

First, I'm sure we can agree that gas law is adequate proof that volume and pressure are inversely proportional. With that in mind, what measures did you take in your experiment to prevent the bullet from moving out of the case neck at a different timing from the control (uncoated bullet)?

As you can imagine, I am a touch concerned that a simple matter such as the friction of the bullet in the neck could provide a significantly confounding factor. In laymans' terms, if the bullet moves too soon in the firing cycle, the powder's gas will expand to fill a slightly larger area, reducing the initial pressure. Handloaders can see the difference that this makes by simply loading multiple, otherwise identical, rounds of ammunition with different sized neck diameters (neck tension) and checking the average velocity of each sample.

I think we can also agree that nearly all smokeless powders exhibit a more rapid burn under pressure than they do when uncontained. If it were not for that characteristic, I think we would still be using firearms with the ballistics of civil war times.

While I agree that blue dot does provide nearly linear energy to charge ratios in your experiment, I wonder what effect the progressive burn rate would have if we consider the possibility that the burn is completed further down the barrel for one sample compared to another.

Would you be willing to run another experiment to see if a much faster powder would change the outcomes? My thought is that the original lots of primers, brass, and bullets fired in the same barrel would be a more useful data point if we, for example, used an extremely fast burning pistol powder to ensure that the powder burn was completed as early in the firing cycle as possible. I believe that by completing the pressure increase portion of the cycle quickly, the pressure in the barrel would stabilize sooner. A more stable pressure would then give better friction indication.

Of course, all of this is just my opinion.

Keith Glasscock

 

[Michael Courtney]

I am not taking any sides, and as I said earlier: " I do not have a scientific back ground, but have an applied knowledge of the product."

1, I would think that friction would be a major component of barrel ware. So why do barrels not wear as much using Molly?
???

Thanks for these good questions.

There are several possibilities here. Most important barrel wear (detrimental to accuracy and determining barrel life) is in the throat area. This throat erosion is more likely due to the hot expanding gases following the bullet than from the friction of pushing the bullet through. Coating the throat area with materials that resist heat and pressure of the hot gasses may have the effect of reducing the erosive effects of the heat and pressure of the hot gases without necessarily reducing the forces required to push the bullet through.

Another contributing factor is likely the fact that coated bullets lead to a coating on the barrel. Rather than wearing on the inside metal surface of the barrel, the coating is worn and replaced repeatedly as bullets pass. The bullet-coating-barrel creates two interfaces (bullet-coating and coating-barrel) that can reduce fouling by reducing direct contact between the bullet and barrel without necessarily reducing friction by a significant amount.

Wear depends not only on friction, but also on hardness. The coatings may reduce the hardness of the material in direct contact with the barrel without reducing the net friction experienced by the bullet.

2, Also, having examined identical bullets shot in the same barrel, at the same velocity, molly and non-molly. Why are the rifling marks in the bullet less pronounced in the molly coated bullets?
???

This is the kind of visual impression that would be nice to have quantified with some reliable measurement to confirm a real effect rather than an optical illusion or error in subjective human perception. I've reviewed numerous papers on ballistic identification systems where the depth of each rifling mark and striation are precisely mapped as a function of position, so the technology exists to measure these depths precisely.

Are the rifling mark depths really less pronounced? If so, is this caused by the lands having less of an effect or by the grooves having a greater effect? Recall that the grooves get coated also so that the outer diameter of a bullet emerging from a coated barrel may end up smaller than the outer diameter of an uncoated bullet pushed through an uncoated barrel. One might be wrong by assuming that the friction is dominated by the lands. Could it be that coating reduces friction with the lands, but those gains are offset by increased friction with the grooves and the need to squeeze the bullet through a groove diameter that is effectively narrowed by the coating?

 

[mikegaiz]

Valid points, I did not measure the actual size, but the indentations were less detailed (softer lines).

Do you think the ball powder I used burning cooler could have had some effect on that I am seeing as far as barrel wear and land marks?

 

[Michael Courtney]

Valid points, I did not measure the actual size, but the indentations were less detailed (softer lines).

Do you think the ball powder I used burning cooler could have had some effect on that I am seeing as far as barrel wear and land marks?

Cooler temps and lower pressures will slow throat erosion. But how do you know your ball powder is cooler burning? And cooler burning than what?

The new Army M855A1 load uses ball powder, but it's a barrel burner because it's such a high pressure load.

 

[Michael Courtney]

I do enjoy reading your work. It has been a while since I read this paper, so correct me if I get any of the details of your experiment incorrect.

Of course, all of this is just my opinion.

And interesting opinions they are. Thanks for sharing.

First, I'm sure we can agree that gas law is adequate proof that volume and pressure are inversely proportional. With that in mind, what measures did you take in your experiment to prevent the bullet from moving out of the case neck at a different timing from the control (uncoated bullet)?

We load with a very light neck tension so that the force needed to overcome neck tension << the force needed to overcome bullet inertia in the time the bullet begins to move from the case. We also use bullets long enough and seat to an OAL so that bullets begin to engage the rifling before moving much within the neck.

While I agree that blue dot does provide nearly linear energy to charge ratios in your experiment, I wonder what effect the progressive burn rate would have if we consider the possibility that the burn is completed further down the barrel for one sample compared to another.

Would you be willing to run another experiment to see if a much faster powder would change the outcomes? My thought is that the original lots of primers, brass, and bullets fired in the same barrel would be a more useful data point if we, for example, used an extremely fast burning pistol powder to ensure that the powder burn was completed as early in the firing cycle as possible. I believe that by completing the pressure increase portion of the cycle quickly, the pressure in the barrel would stabilize sooner. A more stable pressure would then give better friction indication.

Most importantly, you need to realize that if the friction determination depended on precisely when the pressure peak occurred, then the energy vs. powder charge curve would not be a near perfect line. The bullet travel at Pmax changes much more over the range of powder charges than it does with different coatings.

We considered performing the experiment with a faster powder, such as Red Dot. However, we had been using Blue Dot over a wide range of loads from 4 to 14 grains since 2004, so we were sure it was safe, and other parties had also reported the safe use of Blue Dot for reduced loads over a wide range. We wanted an experimental protocol that could span a factor of 2 in muzzle energy (for reliable determination of the vertical intercept), be easily repeatable by other laboratories, and get as close as possible to "full" muzzle velocities.

A faster powder such as Red Dot maxes out at around 9 grains and 2450 fps (730 ft-lbs). We were able to get to 2850 fps and 1000 ft-lbs with Blue Dot. Getting down to 50% of the max load with Red Dot requires taking regular steps down to 4 grains (315 ft-lbs). We were not sure we could do that without risk of detonation, and even had we done it, other laboratories would have reasonable reservations about attempting to use our method in their labs. Another down side of such low powder charges is that the primer begins to have a proportionally larger effect.

Blue Dot is just about the perfect powder for providing a linear response over a wide range (barely supersonic to near full power). Significantly faster powders run the risk of detonation and allow for covering a much smaller portion of the velocity range.

Are we willing to run an experiment with a much faster powder? Sure, if someone else pays for it. Send me an email with the details of what you want and we'll work up a quote. Are we willing to pay for the experiment out of our own pocket? Probably not, for the reasons outlined above and we prefer lab resources to be used for paid work and higher priority experiments.

 

[stool]

anyone notice that real world facts do not get in the way of this guys OPINION ?
he is CORRECT because he has PUBLISHED his OPINION.
we cannot be correct because we have not published our facts.
we cannot question him unless we PUBLISH our facts.
( did you notice HIS company PAID for HIS report?)

did you notice he basically generated a data set to support HIS opinion, which is not related to the real world ??

 

[Michael Courtney]

one final statement and then i am done on this thread.

...

The arbiter in a scientific debate regarding conflicting ideas is published data from repeatable experiments. Our experiments are repeatable, and our data is published. Publish your data along with enough of the methodological details for it to be repeated by third parties, and then it would be possible to discuss possible interpretations. Repeating that lower velocity implies lower pressure implies lower friction is underwhelming if the pressure was not actually measured. Publishing your data is not a very high bar. If you send me a draft of a paper, I can probably provide the required endorsements to some electronic publication venues.

One key indicator for me in internet discussions is whether participants are consistent in arguing from facts and reason or resort to rhetorical fallacies and emotional appeals. Jumping back in after claiming to have made your "one final statement" is revealing ...

It is also revealing that you first criticized the project for being a waste of taxpayers money, then later criticized it for being privately funded. There is no conflict of interest for me in any funding source, because I had no financial interest in the outcome of the experiment. But it is not uncommon for an author to be attacked personally when there is no data available to refute the findings.

 

[Scott Harris]

Michael Courtney,

Thank you for sharing the analysis you have provided on coatings. I read your report and was intrigued. We need more scientific studies to be done in our hobby to help separate fact from conjecture and opinion. With that introduction, I have a question for you. I have been HbN-coating my bullets for several years and have observed that the velocity definitely drops when shooting coated bullets. It usually takes at least 1gr extra powder (308-sized case) to achieve the same velocity as uncoated bullets in the same barrel. After shooting many thousands of rounds, I feel pretty confident this is not a figment of my imagination. How would you explain this effect?

Thanks,
Scott

 

[stool]

this is an internet public forum, YET you and only you, ARE CLAIMING rules for proof that do not exist in a open public forum.

YOU do not get to make the rules.

i have a call in to the lab at the AIR FORCE .

have you noticed, not a single real world user of the components has jumped in and supported your position ??

why did i come back....because you will not stop your verbal diarrhea.

 

[Michael Courtney]

this is an internet public forum, YET you and only you, ARE CLAIMING rules for proof that do not exist in a open public forum.

YOU do not get to make the rules.

The rules that scientific debate is based on published data were established long ago and are a hallmark of the scientific method. I adhere to these rules, but I have no claim on originating them.

 

[Michael Courtney]

Michael Courtney,

Thank you for sharing the analysis you have provided on coatings. I read your report and was intrigued. We need more scientific studies to be done in our hobby to help separate fact from conjecture and opinion. With that introduction, I have a question for you. I have been HbN-coating my bullets for several years and have observed that the velocity definitely drops when shooting coated bullets. It usually takes at least 1gr extra powder (308-sized case) to achieve the same velocity as uncoated bullets in the same barrel. After shooting many thousands of rounds, I feel pretty confident this is not a figment of my imagination. How would you explain this effect?

Thanks,
Scott

There are so many factors in internal ballistics that the information you have provided is not sufficient to ascribe causality to your observations with any degree of certainty. In most cases, the logical chain from purported changes in friction to observed changes in velocity require making unverified assumptions about whether the pressure has increased or decreased. Measured pressure curves would greatly increase the certainty of interpretations, especially if all the other factors are carefully held constant.

 

[stool]

does anyone want to look at the results and the "conclusion" of this PAPER ??.
of the 3 coating systems available to the shooter( not winchester's coated bullet), of the 3 bullets tested...FIVE OF the nine tests reduced friction! SO MAJORITY WINS..EXCEPT IN THIS CASE.
the papers conclusion is that it is not COST EFFECTIVE to coat bullets.....lol

do any of you use a coating system to SAVE MONEY ?

bullets are coated by the shooter for typically one of two reasons:
a) to maintain accuracy over a long string of shooting without cleaning. high power shooting; pd shooting
b) to maintain accuracy in competition without cleaning, even when the number of shots is not high....600/1000yd br.

you are just plain lost when it comes to the real world...go back to your lab.

 

[tonysnoo]

I'm curious. I am a very anal newbie trying to learn as much as possible. I know there are many factors that I can not measure or control, but there are many that I can. I have measured velocity many, many times trying measurably different charges and then again trying some measurably promising charge with differing seating depths. I have spent a fair amount of time testing bare vs coated(HBN). I have noted environmental conditions. I've measured the difference in charges that it takes to reach the velocity nodes that produce the most consistent groups. I've looked at the difference in pressure signs or rather the lack of pressure signs at higher velocities with coated bullets (certainly subjective). I'm sure that I am not alone in this type of testing as I learned most of my techniques on this forum. My many personal tests and results tell me that there is validity to using my coating of choice. I certainly can not tell you your paper is flawed by any specific value. I just feel there may be something missing in the testing technique used.

One question that I keep running over in my mind is the linearity that your test has shown. I have found during my testing little linearity...mostly an upward trend made up of a series of flatter nodes. I see none of that in your chart so I wonder if you took you speeds up closer to the 3000fps zone if other dynamics might enter the picture that might change your results.

I don't have the money to pay for you time or expertise for such a test....just throwing ideas and personal observations out there

 

[Keith Glasscock]

We load with a very light neck tension so that the force needed to overcome neck tension << the force needed to overcome bullet inertia in the time the bullet begins to move from the case. We also use bullets long enough and seat to an OAL so that bullets begin to engage the rifling before moving much within the neck.

Thank you for your response. I'm not sure I understand your meaning here. Are you saying that because the neck tension is very light, and the force required to overcome it is less than the force required to overcome the inertia of the bullet, that the effect thereof is negligible?

I would think that the force required to move the bullet would be the sum of the two forces. Am I wrong in that?

Are we willing to run an experiment with a much faster powder? Sure, if someone else pays for it. Send me an email with the details of what you want and we'll work up a quote.

I'll tell you what, I'll pay for another experiment, and do it myself. I'm a bit better equipped than you might give me credit for.

In the interest of scientific integrity, would you forward me your base data so that I can repeat your experiment with my equipment? I want to have a good, solid baseline to compute the delta velocities before deviating from your protocol.

I am reachable via e-mail. Just click the envelope icon in the left column.

 

[Michael Courtney]

We load with a very light neck tension so that the force needed to overcome neck tension << the force needed to overcome bullet inertia in the time the bullet begins to move from the case. We also use bullets long enough and seat to an OAL so that bullets begin to engage the rifling before moving much within the neck.

Thank you for your response. I'm not sure I understand your meaning here. Are you saying that because the neck tension is very light, and the force required to overcome it is less than the force required to overcome the inertia of the bullet, that the effect thereof is negligible?

I would think that the force required to move the bullet would be the sum of the two forces. Am I wrong in that?

The mathematical symbol < means is less than. The symbol << means "is much less than." So while the total force on an object is the sum of all the forces acting, the force to overcome light neck tension is much less than the force overcoming the intertia and accelerating the bullet. For example, the this case the positive force of the pressure behind the bullet might be 1800 lbs and the negative force of the light neck tension trying to hold the bullet in the case might be 5 lbs. Variations of +/- 0.5 lbs in the force required to overcome neck tension are going to have a negligible effect on the burn rate of the powder, especially a relatively fast powder like Blue Dot. A half pound force increase needed to push the bullet from the case means the bullet doesn't move until the pressure is about 13 PSI higher. For comparison, the primer alone exerts a pressure of about 450 PSI on the base of the bullet and the powder exerts about 20,000 PSI on the base of the bullet before it leaves the case.

As I mentioned before, the near perfect linearity of muzzle energy vs. powder charge demonstrates that varying burn rates over the whole range of powder charges (8-14 grains) do not change the additional energy per grain if powder, so we can confidently conclude that small changes in neck tension do not either.

 

[Michael Courtney]

of the 3 coating systems available to the shooter( not winchester's coated bullet), of the 3 bullets tested...FIVE OF the nine tests reduced friction! SO MAJORITY WINS..EXCEPT IN THIS CASE.

Right, ignoring the uncertainties, there was a five-five split between reducing and increasing friction in our tests. Factoring in uncertainties, friction increased in 3 cases, decreased in 4 cases, and had a change smaller than the uncertainties in 3 cases.

So the experiment showed that using coated bullets fails to reduce friction much of the time, and when the coatings do reduce friction, friction is reduced by amounts much smaller than claimed in the Martin patent.

I should also point out that we are not the only parties to call into question the value of bullet coatings. Dan Lilja (of Lilja Precision Rifle Barrels) has written:

First, as described in our section on barrel break-in, we do not recommend the use of moly coated bullets for break-in. The break-in process requires the use of an uncoated jacket if it is to be successful.

Secondly, at the risk of offending those that promote the use of moly, we can't see much benefit to it for a couple of reasons. There are two basic claims made for the use of moly, reduced fouling and increased barrel life. We'll look at both of these.

We agree that bullet jacket fouling in a barrel can and will cause accuracy problems in a barrel. But for the most part, jacket fouling in a hand-lapped, match-grade barrel is minimal. For the small amount of copper fouling that does remain in most barrels, conventional cleaning methods can and will stay on top of the fouling. We recommend cleaning solutions like Shooter's Choice and/or GM Top engine cleaner mixed with Kroil oil and the limited use of Sweet's solvent. Our suggestions for cleaning can be found in the Cleaning and Break-in section.

We have examined barrels with our bore scope that have had an excessive amount of moly fouling layered with powder and jacket fouling. The only way we could remove this buildup was through relapping of the barrel. Perhaps part of this type of problem results from a mindset that says "Hey, I'm using moly now and I don't have to clean very often." So if you do elect to use moly coated bullets we recommend that you still clean as often as before.

So, the obvious question to us is, if regular cleaning is still required with moly and if a bullet/cartridge/barrel combination does not foul to any great degree without moly, what is the advantage to moly?

This leads us to the second part of our answer. Some of the promoters of moly claim an increase in barrel life. While this sounds good on the surface we must ask the question: what causes a barrel to shoot out? Barrels wear out, or no longer shoot up to their original performance levels, because of erosion to the throat area of the barrel. This erosion is caused by heat and pressure created by burning powder. As a throat lengthens, velocities fall off and accuracy can suffer too. Eventually more and more of the throat will be eroded and moved forward. Also the diameter of this eroded section will increase. We have seen take-off barrels that had fully 1/2 of the length of the rifling completely eroded.

The key to this type of erosion is that it is caused by hot powder gases under high pressures and not by friction between the bullet and the barrel. We have read a report from a military test that examined this type of barrel wear. It was found that over the course of tens of thousands of rounds the actual groove diameter of the barrel was only increased by a few ten thousandths of an inch. It is this type of wear that moly might prevent or slow down. But in this test the throat area grew progressively longer and larger in diameter from gas erosion, not friction between the bullet and barrel.

So from our point of view, moly coated bullets are not going to prevent the type of throat erosion we have described, that the type of wear caused by friction between the bullet and barrel is insignificant, and that the prevention of jacket fouling through the use of moly is marginal at best and that moly may add another type of fouling to the barrel.

Post Script: In the January, 1999 issue of PRECISION SHOOTING Magazine there is an excellent article by Kevin Thomas of Sierra Bullets about his experiences with moly. I would suggest that anyone considering using moly read that article first. In summary, Kevin found almost the same results as we've outlined above. In short he found that moly had no effect on extending barrel life in their controlled accuracy testing of bullets during production. He did not see any improvement in accuracy and to the contrary even found some degradation in accuracy at times, and that moly could create its own fouling problems. Mr. Thomas found that moly did reduce jacket fouling a little but that a regular cleaning schedule was still required. Like us he wondered what if any benefit there was to using moly?

From: http://www.riflebarrels.com/faq_lilja_rifle_barrels.htm#moly coated bullets

Kevin Thomas was a ballistician for Sierra Bullets for many, many years. He is a co-author on Sierra's prestigious reloading manual. I think he works for Lapua USA now.