Time hardening?

Today I bought some lead alloy that was made from wheel weights that had been melted, fluxed and cast into 1 lb ingots for a good price. I will cast them into bullets for Cowboy Action shooting ( 700fps ). I used my Lee hardness tester kit and it said that this alloy is 11~12 BHN? this afternoon I cast about 1,000 125 grain bullets with my new Lee mold. A few minutes ago I used my Lee hardness tester kit on one of the new bullets and it is 8 BHN. I would expect wheel weight alloy to be about 8~9 BHN.
I have read that some lead alloys can over time. That much for wheel weights? 11~12 BHN is hard enough for most of my shooting needs, can I cast, age, load and shoot?

Like fine wine "we shoot no bullets before their time"

Francis
 
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Rick

Moderator
Staff member
I get very little age hardening with CWW, it runs about 10 or so air cooled. I shoot mostly the CWW +2% Sn added which runs 12 BHN on my LBT tester. My softer alloy is SWW +2% Sn at 8-9 BHN for low velocity/pressure stuff like the 45 ACP.

If you tested the BHN the same day you cast it will read low, give it a week or two and test them again. Any additional age hardening after that will be very little and very slow.
 

Ian

Notorious member
The wheelweights I work with (modern ones) air cool to about 8 and age in a fairly linear fashion to 12 in 7 days and then end up about 13 in a few weeks. If I add 2% tin to make 2.5/2.5 it ends up approaching 15.
 

freebullet

Well-Known Member
After getting a cabine tree I learned all my stuff was softer than I thought. The pure we have is dead soft. Won't make 5 on the tester. Ww here are testing 8bhn.
 

fiver

Well-Known Member
Ric makes a good learning suggestion but I bet he knows the answer as well as the rest of us.

you can shoot them whenever you want. but the whole batch will be close to the final BHN and closer to each other after a few weeks.
 

Ian

Notorious member
The problem with shooting them in the middle of the ripening cycle is the bhn will be vastly different from one bullet to the next no matter how rock-solid your timing is. I've even seen this with batches of bullets all oven-treated and quenched together. Once the precipitation-hardening starts to settle down and taper off, the numbers get consistent again. Someone told me long ago (regarding ternary alloy bullets) to either shoot them the day they're cast or wait until they finish hardening, never in between. Took me damned near a decade and a lot of testing to figure out not only that he was right, but just exactly why.
 

Bret4207

Perma-member, Northern NY
If you're just popping them out at 700 fps, you could pretty much get away with pure lead with the right load and lube if they fit. Yes, even WW alloy hardens over time. It isn't likely going to matter shooting large targets in fast draw work.

I will repeat, you need to stop worrying about Bhn and start looking at fit. Bhn is just a number and with a Lee tester it's a somewhat subjective number. You're going to get what you get. Learn to work with what you have. The limitations will reveal themselves as you push them harder and harder, but that can also be addressed through tools other than Bhn.
 

Bret4207

Perma-member, Northern NY
If you're using scrap lead alloy or an alloy of unknown origin the Bhn can be all over the board and you still don't know what's in the alloy. Any of us can take the same alloy and make it give 3 very different readings or take 3 widely different alloys and make them give the same Bhn reading. It's just a number.

Bhn is one of those things in this game that seems like it should make all the difference in the world and should be the answer to so many problems...but it's not. Bhn is a part of fit, but it's not even a big part of it.
 

fiver

Well-Known Member
let's back this up just a little.
BHN? well,, that's not what we are really talking about here.
what we are talking about is 2 other things.
the first is alloy composition.
the second is waiting for those parts and pieces to find their way to where they belong inside the matrix.


compare it to watching paint dry.
you can put a second coat on in a couple of hours because the first is dry enough [set] to accept it without being disturbed.
but it isn't cured and fully hardened, even though the surface has mostly dried.
if you get the second coat on at the right time it will become part of the first coat.
if you wait too long it just becomes another first coat of paint because the one under it has cured off.

that curing process is what your really waiting for.
those little bonds have to get formed, and things have to re-structure themselves.
they gotta find the little cracks and fissures where they reside and spread out to lock in.
I know it's hard to think of things in a solid glob of metal as having to move around and form relationships etc. but that's basically what's going on in there.
 

JonB

Halcyon member
I agree with all the comments here...and I have a few comments I'd like to add.
You don't really need to measure hardness if you pretty much know what your alloy is, and have read enough metallurgy to understand how it will likely cast and age.

Now if you are like me, and scrounge whatever you can find to save $$$. Then a hardness tester is a great benefit to figure out what you have and what you end up with once it's mixed, cast, and aged. Also, finding the melt temp/freeze temp and slush state are also important factors when deciphering a unknown alloy. I better add something here, you will likely not find out the exact composition of the alloy with this info, but you will likely find out what you can use it for, in regards to casting/loading/shooting. and the results of the shooting, will tell you even more. Take good notes :)

Now, when measuring hardness, you need to do more than just measuring one bullet the day after a casting session, although that will tell you something.
AND, you need to pay close attention to the process of measuring, especially if using the Lee Kit. I never measure ingots, as they cool at a different rate than a bullet, so you can get varied results.
I measure at least 3 bullets, and will measure a batch of three every few days until I no longer see a change. I did a Heat treat experiment with 94-3-3 that was drawn out a couple years.
 
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