Alloy hardness anomalies

JonB

Halcyon member
I know some of you will recommend the usual "it don't matter, just shoot'm" and that's fine :cool: ...But I am just OCD enough to wonder why.

This turned out to be longer than I planned, there are a couple questions at the end, if you chose to read through this whole post.

I measure hardness of my batches of bullets quite often, and I regularly get "expected" results.
But, once in a while I get a batch of bullets that age hardens more than expected. I usually don't give it much thought and just save that batch of harder bullets for a different/increased load. I do keep a chronological log of each casting session, and try to enter BHN readings in there.

In the last few weeks, I've been loading ammo like crazy. (500) 38 super, (2000+) 45 acp, (2000+) 41 mag.

>One batch of bullets were cast (air-dropped) in Jan 2018 from 40% COWW, 60% soft.
BHN was 8 @ 1 hour (1-5-2018)
BHN was 11 @ 6 weeks (2-20-2018)
BHN was 14 @ 25 months (2-19-2020)

Another batch of bullets were cast (air-dropped) with straight COWW.
BHN was 10 @ 1 hour (9-29-2016)
BHN was 18 @ 4 years (2-22-2020)
...I wish I had another one or two measurements from 2016 :(

When I looked into my casting Log, I seen that I had used my Auto-Battery term alloy prior to both of those casting sessions I mention above, where I got hardness anomalies. The story of the Auto-Battery term alloy is as follows. I got three 5-gal buckets of battery cables ends from a auto-recycler when I first started casting, there was a few strange items in the buckets which by look and feel, I figured they were soft lead...one item was reportedly a weight that Chrysler put in some steering systems? Anyway, I got a yield of about 200 lbs of ingots from those buckets. I smelt in 40 to 50 lbs batches. So there was 5 batches of ingots, that could have been different...and of course Newbie Me didn't keep them separated. Over the years, when I've used that alloy, I'd get BHN numbers from 12 to 18 in different batches of bullets.

Next, I have habit of dumping the metal rich dross from the previous casting session into the pot, then flux with a light layer of sawdust. This provides a insulation barrier to help the melter pot maintain consistent temperature, as well as a layer to help float the sprues I drop into the pot as I am casting (that practice is for pistol bullets only). So dross from the prior Auto-Battery term alloy casting session, ended up in both of the batchs of bullets I mention above. I have decided that habit of using the previous dross is a bad one. I will discontinue that, and just start saving all the metal rich dross for a range scrap smelting session. I cast inside, so I never do a thorough fluxing in the casting pot.

1st Conclusion and question:
I am still wondering exactly what is in some batches of my Auto-Battery term alloy, where just adding a lb or two of dross could jack-up the BHN that much?

2nd Conclusion and question:
The first batch I mention, 40% COWW, 60% soft, was cast in January (Minnesota). My casting room is upstairs in my 2+ story house and isn't really heated, the door is always open, as well as a open stairway, for heat to flow up there from the first floor where the wood stove it. That room can be as cold as 50º. So the question there is, could air-dropping bullets onto a towel (not in a pile), with ambient air being 50º, increase the hardness any, if even that much? (BHN 14, when it should have stayed around 11). That would be in addition to the Auto-Battery term alloy dross addition.
 

Spindrift

Well-Known Member
Were the bullets from the same mould? If not, were they approximately the same caliber/weight?

I have found, with my alloy, I get around 3BHN more when I water drop bullets from a brass or iron mould, in contrast to aluminum moulds. My bullets also seem to harden more from the water quench the heavier the bullet is. Which probably has to do with heat retention.

By the way, I’m impressed by your log keeping. I try to take notes too, but often find batches of bullets with a rather enigmatic history....

Note to self: make better notes
 

Dusty Bannister

Active Member
It sounds as if you are questioning if the alloy is consistent, or is there some other method of hardening at work. Perhaps you could just take one bullet from each batch and melt off a drip onto a clean surface and have that sample subjected to an XRF scan. That might clear up any questions about a mystery metal being present.
 

JonB

Halcyon member
Were the bullets from the same mould? If not, were they approximately the same caliber/weight?
I have found, with my alloy, I get around 3BHN more when I water drop bullets from a brass or iron mould, in contrast to aluminum moulds. My bullets also seem to harden more from the water quench the heavier the bullet is. Which probably has to do with heat retention.

>>>SNIP
The first example 40-60 alloy was the Saeco 411 (41 cal, 230gr SWC, four cav Iron mold)
the second example COWW was a NOE 41 Keith/SWC RG Hollow point, 210gr, two Cavity aluminum mold
 
F

freebullet

Guest
No expert on alloy. Learning to...

Question.
When you say dross... are you skimming the oatmeal like coagulation off the surface? I'll admit I saved that for years & put back in the smelt with the next batch of scrap. Only melt clean ingots in the pouring furnace.

I'm assuming yer dross definition & mine are same with this answer..to part of your question. The other part out of my realm.

Flux more times, till all recombined. Leave the melt covered with fresh saw dust when you start pouring. No "dross" forms using this process for bottom pouring unless the temperature climbs out of control.

Can you rig ventilation for when you cast? Even a little hood & fan you rig out the window temporary while casting?

The dross removal will continuously change your alloy content, thus testing #. That & temp control. If the melt gets warmer as the pot drains, the pile of bullets stay warm longer, the air cooled # will be different. Eliminate all variables as possible especially with mystery alloy.

I do throw sprue back in for volume stuff like 9mm. Do so every 3-4 pours as temp allows once going hot & fast.
 

JonB

Halcyon member
It sounds as if you are questioning if the alloy is consistent, or is there some other method of hardening at work. Perhaps you could just take one bullet from each batch and melt off a drip onto a clean surface and have that sample subjected to an XRF scan. That might clear up any questions about a mystery metal being present.
That'd be too easy, LOL :p
They are all loaded now, so I'd have to pull one of each.
 

JonB

Halcyon member
No expert on alloy. Learning to...

Question.
When you say dross... are you skimming the oatmeal like coagulation off the surface? I'll admit I saved that for years & put back in the smelt with the next batch of scrap. Only melt clean ingots in the pouring furnace.

I'm assuming yer dross definition & mine are same with this answer..to part of your question. The other part out of my realm.

Flux more times, till all recombined. Leave the melt covered with fresh saw dust when you start pouring. No "dross" forms using this process for bottom pouring unless the temperature climbs out of control.

Can you rig ventilation for when you cast? Even a little hood & fan you rig out the window temporary while casting?

The dross removal will continuously change your alloy content, thus testing #. That & temp control. If the melt gets warmer as the pot drains, the pile of bullets stay warm longer, the air cooled # will be different. Eliminate all variables as possible especially with mystery alloy.

I do throw sprue back in for volume stuff like 9mm. Do so every 3-4 pours as temp allows once going hot & fast.
Yes, I call it metal rich dross. Besides the "oatmeal like coagulation off the surface", I drain the pot (pouring that into ingots) after each casting session and the last bits that don't pour out, get scooped out, and put in a soup can.

Ventilation:
I cast next to a open window with fan blowing outside...it's not enough to handle fluxing smoke. and the window is only cracked open in wintertime.

dross removal will continuously change your alloy content
I don;t remove Dross during a casting session, only at the end, when I empty the pot.

temp control. If the melt gets warmer as the pot drains
I use a PID, so that doesn't happen.

the pile of bullets stay warm longer
I never drop in a pile, mostly to avoid dents/damage...but for the cooling differential also.
When I cast heavy bullets, I will have a fan blowing over the drop area to cool my mold, but the bullets in my examples are not heavy enough for me to do that, so that didn't to them.
 

Bret4207

Undesirable member in absentia, Northern NY
I don't know why they'd vary, but iron vs aluminum is as good a start as any. Ading mystery metal is always a risk. This is part of why I cast LARGE batches. Well, large to me anyway. My smelting pot holds almost 200 lbs near as I can tell. It'll be roughly 2 nearly full 5 gallon buckets of WW in there by the time I get done. I made a few enormous batches some years back and I've still got about 1/3 left, plus a few more buckets of old WW. I actually used to throw the stick on's away! Not anymore of course, but that shows how far back this was. Anyway, my point was that if you cast up big batches and try to get things "evened out" I guess, it should cut down on the variance. Even if you have one batch that mostly COWW and decent stuff and another that's stick on's and softer sheet stuff or some unknown mystery metal, you can use 7 lbs of the better stuff and 3 of the other, or something like that. Shouldn't be too hard to figure a recipe out.
 
F

freebullet

Guest
Appears you have mitigated most of those variables.

Still, letting the dross build up would change the # just the same as removing. The sb & sn continue separating.

I never remove the last 1-1.5" on the bottom pour. Don't want to clog the spout & melts faster next time.

Reckon anyone's guess is good on terminal content. Use to have some soft ones around here alot, but they're much more hard as of recent years.
 
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Bret4207

Undesirable member in absentia, Northern NY
Yup, gotta flux, flux, flux!

Absolutely correct on terminal clamp ends getting harder, or maybe more brittle. in the past few years. I wonder if they're adding more zinc. Whatever it is, it's not the old soft lead of years gone by.
 
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Ian

Notorious member
I have a theory, not based on lots of positive data but years of anecdotal observations of the "huh, it did that thing again" variety. Every time I use clipoy wheel weight alloy that includes a significant percentage (say 20-30%?) of battery cable ends or a certain big batch of stick-on wheel weights that included the painted ones, two things happen: tje bullets harden way up to 14-16 BHN (when I was trying to reduce 12-13 down to 10 or so with the "softer" scrap addition) and the bullets grow significantly as they age over a period of weeks to months so much that chambering problems ensue.

My personal explanation is calcium contamination as the most likely culprit but being firmly in the "just choot 'em and don' worry 'bout it" camp have never bothered with the trouble and expense of having the metal analyzed.
 

StrawHat

Active Member
The “alloy” used in wheel weights is not necessarily consistent from company to company or even batch to batch. All they need is something that fills the mold. If the tire guy needs to add another one or clip a bit off they don’t care as long as the tire is balanced. It would be nice if it was a given alloy but it is not.
For your handgun use it may not matter but if you want repeatability it does matter.

Kevin
 

John

Active Member
The smartest thing I did when alloying was to make ingots in large numbers. I melt WW and PB or lino into a pot made from 12" pipe with legs welded to just get it above my turkey fryer burner. I dip with a soup ladle into ingot molds but make sure I have 100+ lbs at a time when I pour them. Lay it out on old chip board and repeat as soon as the ingot is cool enough to remove. If you have an old oven rack or too it speeds cooling to have air circulate under them.
 

popper

Well-Known Member
Alloy dropped from the mould is hotter than re-heated and atoms are in proper places, AC lets them move around and not be optimal.