Moly coating

[dunerjeff]

I used to do a lot of longrange shooting and sometimes used moly coated bullets, While doing spring cleaning I found a pound container of moly that is intended to put bullets in a smaller container with some of this powder and into a vibrator tumbler to coat them. Has anyone done this in pistol? Is it a No-No or just not worth it. Since I've got it, I was thinking about trying it rather than simply throwing the stuff out, otherwise I would'nt consider this.
Thanks
no moly vs. non-moly wars please

[Ralph Allen]

I have used a rotary tumbler with size 9 lead shot and moly powder to coat rifle bullets. Can't remember if I've ever done pistol rounds. Probably not as my tumbler is small. No sense in me coating 20 at a whack.
Ralph

[mc223]

I coat all my cast pistol bullets. Seems to reduce the smoke a bit.

[Clark]

You can make up your own speed limit for your bullets to avoid fouling:

Soft cast bullets 1000 fps
hard cast bullets 1200 fps
hard cast gas checked bullets 1800 fps
Copper Jacketed bullets 2600 fps
Copper jacketed moly coated bullets 3500 fps

So I don't moly coat my pistol bullets.

[TATER]

I moly 9mm 147 grain JHPs that I shoot. I also use moly for a .256win mag. I Have noticed no throat erosion on what would other wise be known as a berrel burner. But, then again I dont shot the .256 every weekend.

[dunerjeff]

I decided to coat some bullets for the heck of it. I loaded up 20 165gr FP Berry's over WSF for my 40,half moly / half non-moly, bullets were grabbed randomly when seated. First 7 shots were non-moly and I got about a 4inch group @25yrds, not spectacular, next 7 moly coated,2.5" group!! I shot 3 more non-moly's, back out to original average. Another 3 moly's ,right in with the other 7!! Definately helped this load . I'm going to try this with several other bullets/powder combo in 40 & 45ACP.

[Unclenick]

Moly helps bullets funnel straighter into the throat of a bore. Walt Berger credits that for being the reason moly-coated bullets show very slightly higher ballistic coefficients than non-coated bullets. By going straight into the bore, the bullet has less opportunity to tilt inside the bore, and so has less pitch to go to sleep from at exit.

If this explains the accuracy difference, you can test it by seating some uncoated bullets out to touch the throat and headspace the round on the bullet. That happens when the back of the cartridge is flush with the back edge of the barrel (third from left in the image, below). That also improves the alignment for soft bullets like lead and plated ones. If those also group more tightly for, then alignment improvement is the effect you're observing from moly.



The other thing moly does is lower resistance to the bullet going down the bore. That reduces pressure and velocity a little. If your pressure was a little high for the bullet and was distorting it, the moly may have eased that effect. If you have a chronograph it would be interesting to learn the effect on velocity.

[zfk55]

A comparative in my AR10 with a 17-4 SS Electropolished, internally tapered bore:
No Moly, 175gr SMK, 43gr of RE15 2,500 fps 10 rounds SD 5
Moly, 175gr SMK, 43gr of RE15 2,345 fps 10 rounds SD 6

This particular rifle is a dedicated Moly rifle.

Edit for Spelling!

[Unclenick]

That's quite a difference. I'm used to seeing more like 50 fps difference, but every gun is a law unto itself. It indicates you could load the moly bullets up faster if you wanted to. Usually I have to put enough extra powder in to get them to about 50 fps faster than the plain bullets before the pressure is as high as it was in the plain bullet load, but YMMV.

[zfk55]

Uncle Nick, I'm pretty sure its that electro polished bore. The same test in a zfk55 Swiss rifle was only a 124 fps difference, but even taht seems quite a bit. Our Moly coating is a little different than Sierra's and we usually start the bore with Moly Grease.

[Unclenick]

My AR-15 has an electropolished BlackStar barrel I got hold of. I do run moly through it, but I'm not seeing that degree of velocity difference. Still interesting. I don't have any throat wear in mine at all, that I can see in my Hawkeye borescope. No alligator pattern forming. It's a very stable barrel. My bullets, though, are straight NECO process. I think maybe I did condition it with their Moly-slide grease first.

Have you tried combining it with Sprinco's Plate+ silver lube? It's a three day soak for the lube to bond to the bore and get their moly suspension into the surface imperfections, but they get about the usual 50 fps drop on a fixed load that I'm used to seeing even with plain bullets.

[zfk55]

We use a Hawkeye to monitor all of our bores using hBN and the one Moly rifle. Our coating is essentially a 1 Micron applied for 3 hours with high heat.
We don't use a media suspension.
I'll post the exact process when I get to the other computer later today.
Our coating is so tight that it takes a sharp implement to scratch the surface. It can't be lessened with a rough towel rubbing on the coated projectile. The Neco process can be lessened and mostly removed with a rough towel.

I haven't tried that Sprinco's process, but Im going to check into it for sure. The Hawkeye shows little if any bonding of the Moly in the AR10's bore at all.

[zfk55]

Uncle Nick, I just noticed you mentioned "imperfections" in your bore. The 17-4 SS elctro polished bore in this one is glass smooth under the Hawkeye. So tight that we had to give up on hBN negative 5 Micron. We thought it might have worked instead of Moly, but there was no penetration at all and nothing left to "slough" off in the bore. Odd but Moly works without leaving any trace of copper at all but the hBN doesn't work like that in this particular bore. It stands alone in that respect.

Latigo

Edited to add: A lot of those "pristine bores" on a bunch of our rifles turned out to be visible "rocky roads" under that Hawkeye Borescope. What a surprise!

[Unclenick]

That may be right with the electropolished bore. What I call surface imperfections are what are commonly mis-termed "pores". Steel is, of course, not porous, which is why you can make vacuum tube envelopes from it. But there will still be grain boundaries that may accommodate a little of the sub-micron moly here and there in the polished bore.

I've not put Plate+ Silver in my BlackStar barrel, either, since I was already shooting moly bullets in it when I learned about the product. But now that its got near three thousand rounds through it, the surface may have enough wear roughening to be more likely to see some effect. I'll have to set up an experiment with some before and after comparison and try it. I've left it be since I figure I'll have to reestablish my sweet spot loads, so I haven't. That's why I thought I'd ask if you have.

Plate+ is a NASA patent license. It's got both a permanent hydrocarbon lube that bonds electrostatically to the metal and can't be removed except by wear, and it has the sub-micron colloidal suspension of acid-neutralized moly. The moly needs somewhere to go to anchor, though, or it can presumably be swept off a perfectly smooth surface, leaving only the hydrocarbon product and heat eventually gets to that. It lasts around 1000 rounds, according to the literature, but I've never tested the number as I refresh the bores I have it in periodically.

Note that Plate+ only bonds to ferrous materials. It needs the iron to stick to. So its fine for a bore, but it won't do anything for a bullet that doesn't have an exposed soft steel jacket. Not many of those to worry about, thank goodness.

The NECO moly "plating" process is about 20 years old now. I'm interested in your heat bonding approach, but will say I've not had any problems with the old method. It doesn't bond all that hard to the bullets, as you point out. Indeed, if you pull a NECO process bullet from a case that had been chamfered just before seating the bullet, you find the moly scraped clean off by the wire edges of the chamfer. However, that still leaves it on the ogive where it guides the bullet into the throat, and I think that's most of its trick. I burnish case mouths after chamfering just by spinning a sharpened hard wood dowel inside the mouth, and that stops the scraping. But I'm not sure it's really necessary to do. It just makes me feel better about it.

I got started with the plated bullets when my first Garand's military barrel couldn't get through the 50 round National Match Course without loosing accuracy over the last twenty rounds; 600 yard slow fire. It then needed several hours working with Sweets to get the copper out. The moly process stopped that problem cold. I later firelapped the barrel, which also stopped it even for plain bullets. I seem to keep trying new things.

Your hex-form Boron Nitride should have about half the coefficient of friction that moly does, IIRC. I'm curious how the velocity drop compares?

[zfk55]

Thanks for the great info! I'm up to my rear end in gators so I'll answer later today. I do have velocity comparisons in the log books out in Lost Prairie.
I'll post them later.
Thanks again!

Latigo

[reloader28]

I shoot moly bulles in my 2 varmint guns, 223WSSM and 257Rbts.
I aint shot any non-moly bullets thru them to compare with, but my other guns are usually pretty close to the published book speeds and these 2 guns are about 150fps slower than the book.
Without comparing non-moly rounds, this really dont mean much, but like I said, my other guns are pretty close.

[zfk55]

This is going to take me a little longer with all the photos involved.
Back when I can.

Latigo

[FrankenMauser]

You can make up your own speed limit for your bullets to avoid fouling:

Soft cast bullets 1000 fps
hard cast bullets 1200 fps
hard cast gas checked bullets 1800 fps

That really depends on what the person considers "hard cast".

Some people consider BHN 12-14 to be "hard cast".
Some people consider BHN 18 the minimum for "hard cast".
There can be a noticeable difference in how fast the bullets can be pushed.

As always... the hardness number won't matter, if the bullet diameter isn't matched to the bore.