I don't know whether or not this a known process. I don't intend to file a patent. Talk about an unenforceable patent. How would I ever keep you from dipping your bullets in liquid nitrogen or burying them in dry ice?

Anyway, it occurred to me that maybe the idea has some merit. I suppose I could consult the lead/tin/antimony/arnesic quaternary phase diagrams, but it will take me less time to dip or bury a few dozen bullets in cryogen and measure Brinell hardness numbers.

I figure it could work if it caused the white to gray tin phase transition and introduced some grainy structure in the alloy. My uninformed imagination tells me that little grains of tin soldered together with lead as a composite would have more compressive strength than a homogeneous soild solution. I have no idea whether cooling down the bullets will cause the desired or any other phase transition. It will be cheap to find out.

A great big advantage of this (if it works at all) is that the hardening treatment could be applied to already-lubricated bullets. Even if the effect was time dependent, like the heat treatment of arsenic-containing bullets, a batch could be cryo-treated the day before or within a couple of weeks of the day the bullets would be shot. Heck, a Ziplock bag of loaded ammo (containing maybe a couple of those do-not-eat silica gel pouches that come with binoculars) could be dunked in liquid nitrogen or buried in a bucket of dry ice. If the bag is never opened, the rounds wouldn't frost up.

That's all assuming it works and speculating a lot of things I don't have any evidence for. I figure to have BHNs for dry ice and liquid nitrogen dipped bullets and control experiments (un-dipped) done withing a year or two; maybe this weekend. If I'm feeling excessively ambitious, I'll heat treat some from the same batch. I need to find a good setup for heat treating, because the smell of melted bullet lubricant is likely to tip off my wife that I'm heating lead in "the same oven we cook food in" as she would put it.

No idea whether my many boxes of 158 gr LRN "hard cast" are even heat treatable, but if they are, the improvement will be good to compare to the improvement, if any, of the cryo-treated batches.

H. C.

It would be very simple for you to keep me from dippin my bullets in liquid nitrogen. Just ask and I will make every effort not to do that. Not knowing what a quaternary phase diagram or a homogeneous soild solution is would make me plum afeerd of what results I would get anyway.
I was going to try adding some maiden pee to my wheelweights because it sure used to improve copenhagen but maidens are near as hard to find as liquid nitrogen nowdays.

Hmmm. Interesting concept. However, I see certain handicaps to the solution. The easiest to remove is but a toaster over with a dial that will give temperatures high enough to slump the bullets so as to determine where to set it. believe me, I use one for heat treating my bullets and the dials on those things are not all that accurate regarding the temerature.
Second, heating the lubed bullets to the proper temperature would more than likely not only creat on hell of a mess, but will most likely start a fire. When I heat treat bullets, I size them and gas check them but do not lube. After quenching them, I lube them with a sizing die at least .001" larger than what I sized the bullets.
There, where would you find a source of liquid nitrogen, and how would you retrieve the bullets after cooling them? Would you pour some into a container and wait for it to evaporate? Or would you use a wire mesh basket to lower and then retrieve the bullets?
Also, how would you protect yourself from any possible splashes? I once had a wart like growth removed from my arm with the doctor using liquid nitrogen. I'm here to tell you it hurt like hell and continued to hurt for well over a week. The growth was gone, but the pain lingered on. That stuff can be nasty.
Still, like I said, it is an interesting concept.
Paul B.

Paul,

There's the third advantage (assuming it works). You don't need two passes through the lubricator/sizer as you do when heat treating.

You can get liquid nitrogen where I work or across the street from where I live. They fill trucks full of it over there. Hospitals and doctors' offices use it.

Liquid nitrogen is not particularly hazardous stuff. I work with it daily, and I have spilled plenty of it over my hands and arms and feet. You can dip your finger in briefly. The vaporization of the liquid makes a barrier between you and the liquid. When pouring it, it helps to make sure the hand holding the receiving container is not cupped. Pouring it across the plam of your hand won't bother you a bit. Letting a little puddle sit there will give you frostbite.

One thing to avoid is letting it soak into your clothes, because that will hold it in contact with your skin long enough to cause you trouble. Rolled up sleeves and no gloves is best. Nonporous gloves, or leather gloves are fine. Cloth gloves are a bad idea.

I would probably do the treatment by pouring the liquid nitrogen into a styrofoam cup of bullets until the bullets were cold enough that the liquid covered them and stopped boiling violently. I'd either sit a loose fitting lid over them (to let them treat a long time) or dump them out on the ground using a gloved hand (if only brief treatment is needed). That, or your wire basket idea sounds good.

H. C.

So far, it's a lot easier and less messy than heat treating.

I filed the bases of sixty 158 grain LRN "hard cast" bullets (bought from a local commercial caster) until all traces of the sprue marks were gone. This is in order to get accurate Brinell tests later. In case it's interesting, a total of 38 grains of lead was removed from sixty bullets. That's about 0.4% weight loss upon filing.

These bullets were divided into lots of ten in plastic 35 mm film cannisters. The tops and bottoms of the canisters were punctured with a 18 gauge hypodermic needle to allow gases to enter and escape without blowing the caps off. Through one of the cannisters was threaded a length of 20 gauge copper wire, and a knot was made outside the bottom of the cannister. The wire was later used to lift the cannister out of the liquid nitrogen (see below).

In order to make sure the bullets in dry ice actually got cold, I drilled a 3/16" hole in the lid of one cannister and pushed the bulb of an alcohol-filled thermometer in among the bullets as the lid was replaced.

Two large glass Dewar flasks (thermoses) were used. In each was placed two film cannisters, each containing ten bullets. The flasks were filled with either liquid nitrogen or dry ice. The tempertature among the bullets in the dry-ice-containing flask was monitored by reading the alcohol-filled thermometer, and it took about 30 minutes until the temperature reached minus 75 Celcius. The cannister containing the thermometer was removed from the dry ice after 90 minutes longer and allowed to warm in a flow of dry nitrogen gas (to avoid condensation of water on the bullets). The other cannister was left in dry ice overnight.

One cannister was withdrawn from liquid nitrogen after 90 minutes of immersion. The bullets were similarly allowed to warm in a stream of dry nitrogen gas to avoid condensation. The other cannister was left in liquid nitrogen overnight. No attempt was made to measure the temperature in the liquid nitrogen immersed cannisters because the bullets are in direct contact with liquid nitrogen (as opposed to being in a cannister that's cooled from the outside as in the dry ice experiment) and heat transfer is very efficient.

The remaining twenty bullets were divided into two lots. One was set aside as a control group (to see what BHN I started with), and the last ten were de-lubricated by scraping out the bullet lube and then washing with toluene. The de-lubricated bullets will be heat treated when I get a satisfactory setup to do so. An additional 6 bullets were de-lubricated for "slump-point" testing so I can properly adjust the temperature of my heat treating oven and still have ten bullets left to measure BHN.

And the results are...

Well, I'm still waiting for those overnight bullets to finish sitting in the cold overnight.

I can comment that putting these bullets into dry ice or liquid nitrogen was very easy and trouble free. It's already less of a pain than trying to get ready to heat treat. Maybe that's just my own style of working. I'm a chemist and have been at this stuff for 20+ years. Now, heating things to 300 Celcius (about where lead alloys melt), that's a matter that I have less experience with. Almost all organic chemistry happens below 200 Celcius, so even at work, I don't have much that goes a hundred degrees hotter than that. I am still looking for a satisfactory setup that does not leave me questioning the edibility of my next box of fish sticks.

H. C.

quote:

Originally posted by pathfndr:
It would be very simple for you to keep me from dippin my bullets in liquid nitrogen. Just ask and I will make every effort not to do that. Not knowing what a quaternary phase diagram or a homogeneous soild solution is would make me plum afeerd of what results I would get anyway.
I was going to try adding some maiden pee to my wheelweights because it sure used to improve copenhagen but maidens are near as hard to find as liquid nitrogen nowdays.

Ahem.

Well, so far, the treatment is not leaving the lubricant on the bullets. This may be lubricant dependent, and it may have to do with treating the bullets too roughly while they were cold. In any event, the lubricant curled up, cracked, and fell out of the grooves in the 90 minute liquid nitrogen set and in the 90 minute dry ice set. If, if these bullets are any harder than they started out being, a little development work will be required in regard to lubricant retention.

My Brinell tester's indenter ball is wherever it ended up as of a year ago (lost) when we moved, and I can't test hardness until I get another. Late next week, I guess. The liquid nitrogen held up pretty well overnight, and I topped it up, so maybe this will be a 24 or 48 hour test.

I'm still at a loss as to heating these things in the confines of an apartment that houses a small curious baby. I can say with 98.5% certainty that we are moving within a month. This has to do with my job searching activities, and not my company's plans to transfer me to Headquarters. That's a good thing.

H. C.

So far, so good.

It looks as if letting the dry ice evaporate is preferable to my earlier method of a dry stream of nitrogen gas. All ten overnight in dry ice bullets had intact lubricant in the grooves. Sadly, I don't know exactly how long the bullets were at dry ice temperature. The dry ice was gone by the time I checked. The bullets were still shiny, so if they did condense some moisture, it didn't cause corrosion.

I haven't peeked at the overnight in liquid nitrogen bullets. These are sitting in their perforated film cannister in a Ziplock baggie with a silica gel dessicant thingy. One of those regenerable silica gel things that looks about like a sardine can that you can buy from Brownells. I don't remember what it's called.

Good news, however. My wife was getting ready to hang a picture with flower arrangement wire. I explained the difference and offered to look for proper picture wire, and failed to find it. I did, however, find the indenter ball for my Brinnell tester. I am being sent to Wal-Mart for picture wire and dinner. I should be making dents by tomorrow evening, and I will report back whether this whole mess was worth it or whether we're best sticking to maiden pee.

H. C.

Update:

My indenter ball is lost again. I shot it across the room, and the nearest I can figure, it's under a set of shelves that's got closer to a full ton than a half ton on them, and too much crap in front to bother pulling it all out to check for sure. My new indenter should be here Wednesday or Thursday. I'm pretty sure I'm the only one on the edge of his seat over this. It's probably not going to have worked anyway.

AAK!

We wait with bated breath Henry.

Dan,

You might as well unbate that breath and just relax for a while. I have started a new job, I'm only halfway done moving our stuff, and I've gone and bought a house. My wife refers to this house as a "fixer upper". I'm sure she says that simply because wives hate nothing more than the sight of an idle man. In any event, I don't guess I'll enjoy much peace and quiet and loud gunshot sounds and be able to determine whether those bullets got any harder any time soon.

The work at this new place is very engaging, and the culture is day if my old company's was night. I don't know if it bears mentioning, ... ahh, so I won't mention it.

I'm only an hour from a Cabela's store now, and that will be our first big Sunday drive once the Mrs. and young'n are up here and settled.

Ak!

H. C.

Well my friend,you are making it a LOT harder than it needs to be.
Cast bullets,dump into cold water from hot mould,size them within a couple of hours
BHN- 24-28.Will go thru 95% of animals on the planet.

Sean

Hello;
I don't know about the validity of the process, but anyone who does artificial insemination on cattle, would have some liquid nitrogen kicking around .
Grizz

Leftover bull sperm might work as well as maiden pee.

quote:

Originally posted by Ricochet:
Leftover bull sperm might work as well as maiden pee.

Not for sale.

Sean is right and you don't need to stroke the bull either!!

5 gallon bucket with 3 gallons of water will work just fine for 100 bullets or so then I change the water with cold water out of the well....works like a champ!!

One of these days I'll try a saltwater brine for quench hardening my bullets, out of curiosity.

That said, I'm a lazy caster, and don't want to put any more effort into casting than necessary. I either air cool or water quench my ww bullets, visually sort them, lube/size the ones that pass then load em and shoot em.

If'n one of my water quenched bullets won't shoot clear through what I'm hunting with it, then perhaps its something I ought not to be shooting