Trouble with hBN bullet coating

[David Bookstaber]

I've been occasionally impact-plating bullets with HCPL-grade hBN using #7 steel shot in a Lyman vibratory cleaner.

I've been trying to do a batch of 220gr SMKs for the last two days and it's not working! Whatever hBN comes out on the bullets rubs right off and they are not left any more slippery than before. (The last batch I ran some months ago after buffing the bullets would be so slippery it was hard to pick them up.)

Here are things I've tried to do to fix this (with re-runs between each step):
[list type=decimal]
[*]Soaked the bullets in acetone.
[*]Washed bullets in hot water with dish soap; rinsed thoroughly; air-dried on clean paper towel.
[*]Considered that perhaps the hBN and steel media have picked up moisture, so baked on clean aluminum-foil-covered tray at 175F for an hour (assuming that would desiccate the hBN). Then while still hot put back in vibrator.
[*]Tried a batch of Hornady 225gr OTMs. Same failure.
[*]Revisited the moisture theory: baked media and bullets at 275F for five hours, then immediately returned to vibrator bowl and ran for an hour.
[/list]

What could I be missing or doing wrong? Any tips greatly appreciated!

Update: I just opened the bowl again and noticed a strong ammonia odor. My chemistry is rusty but I think this points to a residual moisture problem? Update2: Further websearch reveals that ammonia is a byproduct of synthesizing boron nitride so it's not uncommon to have some residual in the powder.

 

[beginner]

Don't know if this makes a difference, but I tumble in the peanut butter jar for 45 minutes to an hour, versus vibrating. Works very well.
I clean bullets by soaking in lacquer thinner for a few minutes, then drying before tumbling.
Hope that helps

 

[jonbearman]

Why would you bake the bullets,they aren't made of anything that would hold any amount of moisture to hurt the process.You don't need that kind of heat for any of the process.All I do is pour from the box into a peanut butter jar with a small amont of bb's that were degreased and add a small amont of hbn and tumble for an hour and done.

 

[Nomad47]

My method is very similar to jonbearman's. I pour 100 (6mm, 105 grain) bullets directly into an already coated vitamin bottle that has around 100 coated BBs already in it. I then wedge the vitamin bottle in an empty small bowl on my tumbler, then tumble for 2 hours.

 

[David Bookstaber]

I have read some people who claim heat improves the plating process. I didn't think it could hurt. Also, the bullets had already been through a few cycles so even though it wasn't sticking to them I thought it would ensure all hBN in the mix was dry.

 

[stool]

it is TUMBLE IMPACT PLATING...which does not always work in a vib machine.
i use an rcbs sidewinder.
while i do moly in large batches, i do hbn in smaller bottles inside the sidewinder.

 

[Scott Harris]

I use a thumlers tumbler for 3 hours(two large peanut butter jars with steel bbs) and preheat the bullets and the container at the beginning with a heat gun. It has always worked well. My only thought is that maybe the vibratory tumbler is getting overloaded with too many bullets and not working effectively???

 

[Keith Glasscock]

Yes, not enough air space is a problem. I did that!

I run 50 7mm bullets in a vitamin bottle that is about 1/4 full of steel shot (degreased and run alone with HBN for 4-5 hours before first use). I put 2 of the bottles on their sides inside the empty bowl of my tumbler. They roll, shake and make quite a racket, but I'm getting consistent, slippery bullets. I run them for 3.5 hours.

I think the fact that they are rolling is actually helpful in the process.

 

[David Bookstaber]

I'm only running 50 bullets, and there's good flow in the bowl. But I'll try it with new shot in 2 bottles today -- 1/4 full of shot, pre-coated, then bullets up to 2/3 full.

 

[David Bookstaber]

Not sure how I can rule that out. It's the same shot in the same container I've been using since I began coating a few years ago. I keep it in a climate-controlled workroom. But I suppose it could have developed some rust, although there's no visible rust.

Just to be sure I poured some new shot, rinsed it in acetone, and am pre-coating that now in the bottles for today's test.

 

[JRS]

Use ceramic media and a "tumbler"

 

[David Bookstaber]

For reference here are videos showing the circulation of both vibratory configurations:

[youtube]http://youtu.be/6VhxBnW8FGU[/youtube]
[youtube]http://youtu.be/ZSxvDWOBta0[/youtube]

 

[David Bookstaber]

Use ceramic media and a "tumbler"

What ceramic media do you prefer for this purpose?

 

[stool]

but the process is based on impact from rotary tumbling....
no one said vib does not circulate..just no rotation over the top to create impact from the balls.

yes sometime vib works...but not always

For reference here are videos showing the circulation of both vibratory configurations:

[youtube]http://youtu.be/6VhxBnW8FGU[/youtube]
[youtube]http://youtu.be/ZSxvDWOBta0[/youtube]

 

[David Bookstaber]

but the process is based on impact from rotary tumbling....
no one said vib does not circulate..just no rotation over the top to create impact from the balls.

This is the first time I've heard that. Since everyone from NECO to Tubbs sells plating kits for vibrators, not rotary tumblers, could you elaborate on why rotary tumbling would be different and more successful, and not just slower?

 

[stool]

sorry, but neco not only required a rotary, they sold them also.
the original system is simple based on IMPACT COATING..THE STEEL BALLS POUNDING, IN A MICRO SCALE, THE COATING ONTO THE BULLET.
direct from NECO'S site:
"The patented NECO-Coatâ„¢ Process ("Moly Coating/plating") is a method of "impact plating" molybdenum disulfide ("moly," MoS2) into the surface of cast or jacketed bullets, followed by an outer coating of carnauba wax."

tubbs does use vib for hbn, but no longer sells or markets moly..which was an impact system.

try starting over with new clean parts...

but the process is based on impact from rotary tumbling....
no one said vib does not circulate..just no rotation over the top to create impact from the balls.

This is the first time I've heard that. Since everyone from NECO to Tubbs sells plating kits for vibrators, not rotary tumblers, could you elaborate on why rotary tumbling would be different and more successful, and not just slower?

 

[JRS]

Use ceramic media and a "tumbler"

What ceramic media do you prefer for this purpose?

I use a mixture of polyhedron and triangular shapes. I was using hBN long before David Tubb knew anything about it. Mine was formulated by a retired chemist who worked for ROBAR. He also played a large part in the formulation of the famed NP3 and Roguard finishes. BTW… I always tumbled mine.

 

[David Bookstaber]

Well none of my current attempts are working. My new steel media in the vibrating jars seems to be leaving a bit of a coating, but test firing them I'm getting the same muzzle velocities as uncoated bullets.

So I'll buy a Thumler's Model B and Lyman's ceramic media for moly coating. For people using this setup what proportions of media to bullets, sizes of containers, runtimes, and any other prep do you use?

 

[stool]

i would skip moly and fix the hbn issue.
( this from a guy that has moly'd for over 15yrs)
hbn appears to be better, quicker and cleaner.

if you are going to buy all that just do hbn.......

no matter which you chose...cleaning the bbl changes when you use coated bullets...
it is a system, bbl and bullet.

 

[David Bookstaber]

I'm not interested in moly; I just can't find "ceramic media for hBN coating" so I assume the media sold and used for moly coating would be the best for this application. Any recommendations on better media appreciated!

Are you saying that I shouldn't expect lower muzzle velocities just by switching to hBN coated bullets from uncoated unless I clean the barrel first?