Beginner looking for advice on HBN coating

[warpig6]

I've read the threads on Hexagonal Boron Nitride coating. I'm new to long range shooting, and my goal is to shoot steel for fun at ~1000M with a 243 Ackley Improved. My question is whether it will be advantageous for me to use HBN from the beginning (during fire forming)? I'll be doing a lot of learning with this rifle, and I'd like to make the bore last as long as possible. I plan on using a rotary tumbler with SS media to clean brass, and I figured it wouldn't be much more work to use it for impact plating bullets.

I'm building a budget long range rifle with the help of a friend who's a gunsmith. I'm using an old model 700 short action I already have. Here are the specifics.

Shilen 1:8 standard varmint contour CM barrel finished at 28"
PTG 243 Ackley Improved reamer
Action trued
Choate varmint/tactical stock skim bedded with Devcon
SWFA SS 10x42M scope
EGW 20 MOA base
SWFA SS rings
Redding neck sizing and seating dies
Lapua brass
Berger 107 gr bullets

Any advice will be greatly appreciated

 

[redbullitt]

IMHO I'd try to run them naked. THEN go to moly or hbn if you need to.

Usually when you run moly you want to always run moly etc (unless you switch to naked or hbn), and try not to mix. I would think that would apply to fire forming as well.

If you are just running an AI you should be able to get good accuracy during fire forming fwiw.

 

[Temp9]

There really isn't enough information out there on the new bullet coatings (hBN and WS2) to say if it really increases barrel life or not. Both those coatings require very little effort to apply, though, so I WS2 coat my 6XC bullets on the off-chance it may improve the barrel life. I have no clue if it will or not.

I shot coated bullets from the first shot to the last shot, although some say to "break in" the barrel using naked bullets. Since I don't believe in using a "break in" routine, I didn't see a reason to use naked bullets at all. Load work up should be done with the bullets coated.

I coat my bullets in a vibratory tumbler, which works great. I haven't tried in my rotary tumbler.

 

[gewehr]

Hbn is a great coating that has helped my rifles consistency tremendously. It seams to reduce pressure a quite a bit but speed not quite as much as moly

 

[warpig6]

IMHO I'd try to run them naked. THEN go to moly or hbn if you need to.

Usually when you run moly you want to always run moly etc (unless you switch to naked or hbn), and try not to mix. I would think that would apply to fire forming as well.

If you are just running an AI you should be able to get good accuracy during fire forming fwiw.

Thanks Red. I've heard that the Ackleys shoot pretty well whilst fire forming. Can't wait to see for myself.

 

[warpig6]

There really isn't enough information out there on the new bullet coatings (hBN and WS2) to say if it really increases barrel life or not. Both those coatings require very little effort to apply, though, so I WS2 coat my 6XC bullets on the off-chance it may improve the barrel life. I have no clue if it will or not.

I shot coated bullets from the first shot to the last shot, although some say to "break in" the barrel using naked bullets. Since I don't believe in using a "break in" routine, I didn't see a reason to use naked bullets at all. Load work up should be done with the bullets coated.

I coat my bullets in a vibratory tumbler, which works great. I haven't tried in my rotary tumbler.

Thanks a bunch for the input Temp! I was thinking along the same lines. It seems like one might as well err on the side of caution since the coating process seems so simple. I've seen where people are using a rotary tumbler for coating, but there aren't as many pictures available as with vibratory tumblers. Maybe I should plan on having both?

 

[warpig6]

Hbn is a great coating that has helped my rifles consistency tremendously. It seams to reduce pressure a quite a bit but speed not quite as much as moly

Thanks gewehr! I appreciate the input. I also like the advantages of cold bore shots being on target and decreased pressure.

 

[High Binder]

I coat all of my bullets of every caliber with hBN. First off you need to know that there's a ton of bad information out there including in this very thread. Coating bullets isn't about barrel life, it's about Cu fouling and extending the cleaning interval, that's it (meaning longer periods of consistent shooting). Also any coating will require you to up the charge to get the same effect but I only had to change my charges by .1gr - .2gr (depending on the load and rifle) but it is something you have to account for and know that you're going to have to do test loads just like any un-coated pill. You should start out with hBN/etc. coated pills if that's what you intend to feed it for it's lifespan. There is no point going naked just for fire-forming because you're just have to clean more.

hBN is the better of the coatings and it's easy as hell to apply. I use a rotary tumbler and it takes about 6hrs to fully coat ~50/100 pills depending on caliber, shorter if I pre-heat the pills.

When done they should look frosted like:

 

[warpig6]

High Binder,

Thanks for taking the time to give advice. I've read most of your posts on HBN coating while doing my preliminary research. Thanks for sharing so much information. It does seem super easy. I did make a mental note that velocity should decrease due to lower pressures.

My primary objective would be increasing bore longevity. If there's no appreciable difference there using coated bullets, that brings on more talk. I'm still interested in coating if it will help in other ways with my application, but it does make me question whether it's worth while.

On another note about HBN, David Tubb's Final Finish bullets look suspiciously similar to HBN coated pills. Is HBN actually polishing the bore? I saw this mentioned in another thread with no direct conclusion.

 

[High Binder]

High Binder,

Thanks for taking the time to give advice. I've read most of your posts on HBN coating while doing my preliminary research. Thanks for sharing so much information. It does seem super easy. I did make a mental note that velocity should decrease due to lower pressures.

My primary objective would be increasing bore longevity. If there's no appreciable difference there using coated bullets, that brings on more talk. I'm still interested in coating if it will help in other ways with my application, but it does make me question whether it's worth while.

On another note about HBN, David Tubb's Final Finish bullets look suspiciously similar to HBN coated pills. Is HBN actually polishing the bore? I saw this mentioned in another thread with no direct conclusion.

You're very welcome. I'm a Tribologist so this is the world I work in (for another few months) and I'm glad to share. I'll try to keep this as laymen as possible. Right off, barrel life is another topic where there is a ton of misinformation. The bullet (coated or not) sliding down the barrel isn't really causing any wear/damage the Cu coating on the bullet is far softer than the barrel so life in terms of coated vs. non-coated isn't really an issue that will effect barrel life at least in terms of what your typical shooter will care about or even notice the Cu jacket is in effect a "lube" in this situation already and is the very reason we jacket bullets in Cu. Where barrels get most of their damage is from the hot gas right in the throat area, i.e. the gas starts tearing up the area where the bullet initially engages the rifling and then as you shoot more and more it's tears is up farther and farther until the bullet engages the lands off-axis and the bullet subsequently flies inconstantly downrange. So as I eluded to above, there is always going to be wear anytime two surfaces interact but in terms of what we as shooters who have countless other factors almost all of which are weighted far heavier than this interaction, barrel wear just isn't an issue you can really attribute to the bullet, coated or not. Another point here is that when you coat the bullet with hBN/whatever that coating is only ~.002mm deep (good coating) and that's all it needs to be but if you think about it, the bullet itself is deformed via the lands and grooves sometimes as much as .100mm and this exposes uncoated Cu to the corners of the lands right off the bat so even if Cu jackets (coated or not) caused significant barrel wear you still couldn't solve the wear problem by coating the bullets because no matter what you do you're always 100% of the time going to have that same interaction of the raw Cu jacket on the steal of the barrel but with a little lube thrown into the mix which help slow down the build up of excess Cu. So in a nut-shell you can't solve a wear problem but coating a bullet in anything but it's not really a significant problem anyway. That's not the end of the story though. You could have your barrel treated. The inside of the barrel can be coated in TiN (Titanium nitride)/TiAlN/or any number of other coatings and that would actually solve the problem you're looking to fix but I would just buy a new barrel before I $$$$ around with that.

Any bullet coating is simply going to reduce the interval between cleanings and that means that if you have a rifle that shoots awesome for 500 rounds and then needs to be cleaned, then the hBN/moly/etc. coatings will simply increase that interval to some higher number all of which simply means it remains consistent for longer periods of time.

The Tubb Final Finish pills are coated in a dry polishing compound of different "grits" (the exact opposite of hBN). hBN/most dry lubes are actually really hard substances a lot like the mica you find on a beach. cBN (hBN's cubic brother is the ~2nd hardest substance on the planet) hBN is made up a a ton of parallel sheets (mica on the beach) laying on top of each-other and as the surfaces interact with another surface, thin sheets slide off and create a "lube" effect. Think of it as sitting on a giant pile of papers and then sliding down the pile. The individual papers have zero lube effect on their own but when put together you slide right down as if it were snow (snow is the same way too). The process of coating with polish is pretty much the same as with the hBN/etc. and you could do it yourself but the polish compound is pretty expensive given the very small amount you'd need.

 

[warpig6]

High Binder,

Thanks for the detailed explanation. I'll have to shift my research to the true benefits of HBN coating now. I'm still uncertain whether it's worthwhile given my proposed application. I'm not overly concerned with cleaning, but I guess the question is whether I can clean without disturbing the Cu equilibrium to the point that it takes many rounds to get back on target. If cleaning is likely to change POI for several rounds, then I can see the benefit of coating.

Thanks again for your input.

 

[High Binder]

High Binder,

Thanks for the detailed explanation. I'll have to shift my research to the true benefits of HBN coating now. I'm still uncertain whether it's worthwhile given my proposed application. I'm not overly concerned with cleaning, but I guess the question is whether I can clean without disturbing the Cu equilibrium to the point that it takes many rounds to get back on target. If cleaning is likely to change POI for several rounds, then I can see the benefit of coating.

Thanks again for your input.

No prob, let me know if you have any questions!

 

[warpig6]

How about some opinions on whether or not to pretreat my barrel with an hBN/alcohol solution? I read about this a while back, but can't seem to find it now.

 

[Fred_C_Dobbs]

I tried Moly but found it too fussy. When I found out about WS2 (tungsten disulphide), I went through a couple of ounces of it, and found it cured the complaints I'd had with Moly. When that ran out, I switched to hBN, just because it was something new, and because I got a killer deal on a pound of it. Application-wise, and performance-wise, I can't tell any difference between WS2 and hBN, but I think the hBN coating might be a bit more durable, less prone to scuffing and minor blemishes.

This probably sounds petty but I like the color of hBN better because it doesn't look so obviously different from nekkid. I'd got tired of being interrogated about my black bullets every time I went to a public range to shoot WS2. And WS2 left an indelible black stain on any fabric I spilled it on (especially the cotton diapers I used for the final polish). hBN powder is white, so if it stains, it isn't noticeable.

Chamber pressure will come down with the slick bullets, but MV doesn't fall by an equivalent proportion. QuickLoad internal ballistics software ballparks the pMax reduction, IIRC, at 2000-3000 psi. Which means factory load specs for nekkid bullets are not directly applicable to slick bullets. I know some rabid crow hunters (rabid hunters, not rabid crows) who'd load their 220 Swifts and 22-250s to 6000 fps, if they thought they could get away with it. They shoot slick bullets, and load progressively hotter until either they get one of the customary symptoms of an overpressure (stiff bolt lift, extractor mark, top-hatted primers, etc) or their bullets begin failing in flight. That's how they determine their "slick bullet" max loads. Me, I'm not that adventurous. Until I manage to save up enough to buy myself a PressureTrace II, my comfort zone only extends up to the predicted MV of the factory's max charge weight, if that high.

I don't shoot out barrels fast enough to have a dog in that fight but several highly regarded gun guys, Walt Berger and Bryan Litz among them, are positive that slick bullets extend barrel life. It definitely reduces barrel heating, which could be the mechanism that improves barrel life, especially in high volume shooting sessions. I've read guesstimates of 5%-15% improved, but I can't see where the extra bother of coating my own bullets is worth an added 15% barrel life if that's all I'm doing it for.

I started prepping barrels with Lock-Ease colloidal graphite before I started loading slick bullets, primarily because it reduces the POI shift in the CBS. Just for giggles, when I still was using WS2, I tried substituting Lock-Ease for the WS2/alcohol. Couldn't tell a lick of difference, but the Lock-Ease is simpler to apply because you don't have to mix anything, and it comes in its own squirt bottle. So I still use it with hBN. And I already was using it in everything I shoot nekkid bullets through, so it wasn't like I had to add something else to my reloading shelves. I tried the aerosol once, because it was easier to find, but it was worthless. Definitely stick with the liquid squeeze bottle.

 

[warpig6]

Fred,

Thanks for the info. I appreciate you sharing your experience. Looks like I am going to coat my bullets for the cold bore advantage, and any added barrel life will be a fringe benefit. I'll have to check out Lock-Ease. I can't say that I'm familiar with that product. Sounds much easier than mixing an hBN solution though. I have some choke tube lube that is graphite suspended or possibly in a colloid with some oil. I wonder if that would work the same?

 

[High Binder]

How about some opinions on whether or not to pretreat my barrel with an hBN/alcohol solution? I read about this a while back, but can't seem to find it now.

It is a waste of time and the inability to apply an even coat would cause more problems (for your first shot) than it would do good. You'll have deviation by not pre-treating but the deviation from a cold barrel is far higher. Pre-treating would only be done after cleaning and the barrel would only not be treated before the first shot.

 

[warpig6]

High Binder,

Thanks again for the advice. Sounds like I'd best hBN coat the bullets, and get to shootin.

 

[warpig6]

So here are the bullets from my first experiment with hBN. I feel like they still look shiny. The bullet on the end is uncoated for reference. Any thoughts?

 

[rifleman700]

Boron Nitride « Daily Bulletin

Lower Friction

 

[warpig6]

I read through that earlier today. I guess when you compare the picture there to mine, they look pretty close to the same. When you look at the pictures posted by High Binder though, mine look a little shiny IMO.

 

[rifleman700]

As long as they are slippery I am sure they are fine. Did you wash them before coating them? I wash and then heat them and then put them in tumbler.

I use hbn on all of my high velocity cartridges 3200-4000 fps with great success.

 

[warpig6]

Thanks for the helpful advice rifleman700! I must admit that I did not wash the bullets before tumbling. I'm going to add a bath and a suntan to my coating process. They did feel slippery, but I would like to see a more uniform appearance.

 

[High Binder]

War, it's really hard to coat with a vibratory compared to a drum tumbler but that being said your pills look pretty good. You're really only going for a coating depth of ~.002mm (2 microns) and you certainly have that already based on the picture you posted. I'd say load 'em up and shoot them. On a side note, I don't wash or prep my virgin bullets at all, I simply warm them up in a toaster oven to ~200F and throw them into the tumbler.

 

[warpig6]

HB,

Thanks for giving them a look. I'm gonna run this batch and see how it goes. I'll definitely heat the next batch though. The time savings is worth the extra step for sure.

 

[High Binder]

The time savings is worth the extra step for sure.

Totally worth it!

 

[gewehr]

I soak mine in acetone and then let them dry on a towel before inserting them into a pill bottle filled with zinc coated bbs and hbn, then insert in the tumbler for 6 hours.


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