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Your input desired on design of barrel friction experiment with bullet coatings

 
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Old 11-06-2011, 11:12 AM
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Your input desired on design of barrel friction experiment with bullet coatings

We've developed a method to accurately determine the average frictional force between the bullet and the rifle bore that is accurate within 1-2% and requires about 20 test shots to determine the friction of a particular bullet/coating/bore combination.

Naturally, our next inclination is to quantify the barrel friction resulting from different bullet coatings: HBN, Moly, and WS2. We are leaning toward testing each coating in each of two bullet designs, a conventional jacketed lead bullet and a solid copper bullet in our .223 test rifle. Of course, the rifle barrel will need to be thoroughly cleaned when moving between coatings and before beginning.

A few questions, if you are willing to lend your advice to our experimental design:

1. Should we also test lubalox, the Combined Technology coating? This would constrain our design to one of the .224" bullets available from the factory with this coating. We would also obtain the equivalent uncoated Nosler ballistic tip and get them coated with the other three coatings. Frankly, we'd prefer not to test lubalox, because it locks us into the ballistic tip, and we'd rather test a match bullet from Sierra, Berger, or Hornady. On the other hand, we do think Nosler might be exaggerating the friction reducing claims of lubalox and it would be nice to debunk test the claim.

2. In order to enhance uniformity (because we have so little bullet coating experience), we plan to send the bullets to NECO for moly coating and SSS for HBN. Is there a commercial service that offers WS2 coating, or do we need to roll our own here? Perhaps you can suggest someone with experience coating bullets with WS2 who might be willing to coat a couple of boxes for us. Is WS2 even still used as a common bullet coating? Is it a waste of time to test it, or is there interest?

3. Our .223 Rem test barrel has a 1 in 12" twist which limits us to bullet weights up to 69 grains at our test facility. (We can shoot heavier bullets because of the thin air up here.) Is there a particular match bullet you'd recommend. A bullet with the most uniform bearing surface would be optimal, because preliminary testing (uncoated bullets) suggests that bearing surface has an impact on friction, and it would be optimal to minimize confounding factors so we can emphasize the effects of the coating.

Of course, any other insight or advice you can offer would be greatly appreciated.
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Old 11-06-2011, 12:13 PM
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Re: Your input desired on design of barrel friction experiment with bullet coatings

I don't have any experience whatsoever with handling, loading or shooting coated bullets.

Having said that, I'm experienced in innovative activities such as your's.

More power to ya!

Much will be learned from your innovation. Who knows what will be revealed from your work.

As one who exists where bore friction and jacket torture are an everyday major consideration I will be looking forward to what is learned from your work.

Quote:
Originally Posted by Michael Courtney View Post

1. Should we also test lubalox, the Combined Technology coating? This would constrain our design to one of the .224" bullets available from the factory with this coating. We would also obtain the equivalent uncoated Nosler ballistic tip and get them coated with the other three coatings. Frankly, we'd prefer not to test lubalox, because it locks us into the ballistic tip, and we'd rather test a match bullet from Sierra, Berger, or Hornady. On the other hand, we do think Nosler might be exaggerating the friction reducing claims of lubalox and it would be nice to debunk test the claim.

I have a completely selfish interest for inclusion of Lubalox in the project. I tend to push extreme magnums to the extreme. How extreme is determined by the bullet's ability to sustain it's experience within the bore. My guess is that friction is a large contributor to bullet failure in extreme conditions. For my needs mass produced, readily available bullets that will hold together in extreme conditions are limited to Nosler and Hornadys bullets. Nosler offerings being the better choice, all things considered.


Of course, any other insight or advice you can offer would be greatly appreciated.

I'm assuming that your test rifle is rigged with built in measurement devices of one type or another. If not, I'd be willing to entertain provision a rifle of a different caliber cartridge, bullets (uncoated), powder, cases, primers.

As interesting as friction data would be, effective of methods used to return the barrel to original conditions prior to testing the next coating material will be additionally informative. The ability to remove coating from the bore has been THE barrier preventing my use of a coated the first time. As I said, I have no experience with coatings.
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Old 11-06-2011, 12:18 PM
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Re: Your input desired on design of barrel friction experiment with bullet coatings

I would easily forego the Noslers. Anything that really adds a noticeable improvement or change catches on. It only took a few years for moly's characteristics to get sorted out.
Would be nice to see some real data. Have fun with it.
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Old 11-06-2011, 12:53 PM
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Re: Your input desired on design of barrel friction experiment with bullet coatings

I don't have any input regarding your testing but if barrel friction is an area of expertise for you, perhaps you could help me understand something I was told about friction in a barrel.

Quote:
It has been fairly consistent that at around 500~700 rounds the barrel is worn enough that the level of friction is high enough to cause the heat needed to melt the core.
I don't understand why the friction increases as the barrel wears.
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Old 11-06-2011, 01:28 PM
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Re: Your input desired on design of barrel friction experiment with bullet coatings

Quote:
Originally Posted by Edd View Post
I
I don't understand why the friction increases as the barrel wears.
Often times due to improper cleaning, the barrel becomes more polished. This increases the surface area and subsequent friction. In addittion, as the throat wears and cracks, it grips the bullet. In this case, much of the increased friction is in the first inch of the barrel.

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Old 11-06-2011, 05:44 PM
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Re: Your input desired on design of barrel friction experiment with bullet coatings

What is the objective of this frictional testing?
What do you hope to gain in it?
If one bullet/coating combo provides less friction(following friction coefficients of coatings or otherwise), what will that mean?

I can coat your bullets in WS2, no problem.
I don't coat bullets to reduce friction though(don't know why anyone would).
I coat to manage fouling.
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Old 11-06-2011, 06:29 PM
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Re: Your input desired on design of barrel friction experiment with bullet coatings

Quote:
Originally Posted by Mikecr View Post
What is the objective of this frictional testing?
What do you hope to gain in it?
If one bullet/coating combo provides less friction(following friction coefficients of coatings or otherwise), what will that mean?

I can coat your bullets in WS2, no problem.
I don't coat bullets to reduce friction though(don't know why anyone would).
I coat to manage fouling.
Thanks for your insights.

Managing fouling can be important to many shooters. In other applications, an increase in muzzle energy is more desirable. Our preliminary work suggests that many bullets lose 200-1000 ft-lbs of energy to barrel friction. For organizations that have already made large scale investments in specific cartridges, increasing powder capacity is not an economical option, and increasing energy by increasing powder capacity carries with it penalties of decreased barrel life, increased recoil, and increased noise. Reduced barrel friction will also increase the benefits of longer barrels where the pressure curve is pretty small, and friction robs most of the benefits of increased barrel length.
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