Copper in lead alloy???


Staff member
I have a BS in chemistry and it isn't easy reading for me either!
Dry doesn't quite describe it.
Get the basics down and stuff starts to make more sense.


Active Member
Metallurgy is its own vast fountain of knowledge. A specialty beyond degrees.... My work required it and I have a lot of training in this field. Almost all was in steel, stainless steel, various monels, inconels..... Some in non-ferrous to like copper and brass. Very little in plumbic. We had some as we still poured Babbitt type bearings some back then....Funny, bullet casters shied away from Babbitt like the plague! Even antimony wasn't trusted! Binary alloys of lead/tin were preferred!
As I said above; lead alloys march to the beat of their own drum and do things ferrous alloys don't. I've only known one metallurgist in my whole career that was like the fellow in Lyman cast bullets #3! (He cast bullets by the way) He was a genius but he could overwhelm you with detail.
Some lead alloys with antimony can expand on solidification while most other metal shrink is another abnormality.
Metallurgy of Lead alloys is its own field...... And it's the field we play our game in!!



New Member
I've been casting since about '88-'89 and have done a bit of research, but I guess my findings were pretty rudimentary. Done a good amount of "alloying" but my main concern/goal was BHN. I think my knowledge/experience is just "common sense" type to just get leading free cast bullets. Other forms I've visited are a bit more "basic", I guess, than the vast experience of the members here. I don't mind sitting back and gleaning knowledge...

My father in law was a POW in Germany in WWII and had a saying; "It's OK to get crabs, but keeping them is not". Same with ignorance; it's OK to be ignorant, but don't stay that way...
Last edited:


Well-Known Member
German version research paper. As you go up and to the right, hardness(?) increases. Says you want more Sb than Cu but doesn't account for any lattice bound Cu or glob Cu as in the lower right corner.
Pb/Sb/Sn/Cu diagram is even worse. From what I can find, SnCu exists only temporarily during solidification.
Last edited:


West Central AR
I don't recall the exact wording but at some point someone wrote something to the effect of copper doesn't alloy , it is held in solution by the tin like sugar in coffee . The trick is to get it up to saturation by it's own draw in the alloy and keep it from falling out like rock candy .

Basically it's why there's little to no copper drops off copper washed 22 LR when you do a big bucket of sorted range metal . All the tin soaks up that copper that is electro plated to the lead because in that layer where they are actually stuck to each other chemically it's like blending oxides together and into the melt instead of trying to get a new metal into it .

That's pretty close anyway .

Think of tin like alcohol . It blends with water and it blends with gasoline . When blended with gasoline it will hold some water and more when it's hotter but water tends to fall out when it gets cold or the delution of alcohol changes . Keep it all in the window for blend and it's good add 50% more clean gasoline cutting the Alcohol by 50% and the water falls out every time . It also won't blend back in even if you double the alcohol until it gets back into the temperature window .


Well-Known Member
I know the feeling.

but there is some help there, look at the very bottom line after reading the first sentence below the picture.
you can see where you lose one of the constituents of the alloy, in other words you run out of the stuff to make a complete chain throughout the alloy. [whatever the E' is]
it's showing it binds in with one of the other parts of the alloy, there just isn't the same amount of the two.

now look at the top lines of the chart.
look how they become closer together as the percentage changes from 2.7 to 3.5%.
if you imagine the right side of the chart as a BHN scale you can see how little difference there is in hardness between the two alloys.

the chart is also illustrating how copper does not affect the BHN of an alloy. [at this point in time]
of course this is at that temperature [I'm guessing somewhere around 350-400-F about where a bullet would hit the water from the mold]
at room temperature and after a period of time the whole chart would change as things find their place.
if the same alloy's were tested and charted at the cooled off and after full hardness stages you would most likely see different lines.

that's how I see it, and I hope Pete or Popper correct me if I'm reading things wrong.


Well-Known Member
Cu does alloy, Cu2Sb is a molecule (alloy). E' is something that is a portion that 'could' be Pb or Cu or Sb ; not exactly 'measurable', a mixture of undetermined proportions. Just like in the normal charts for Pb/Sn & temp. Cu2Sb is a hard alloy - copper does not affect the BHN of an alloy - is not correct. Problem is it's hard to measure BHN on a HOT solid material. Cu added does heat treat to very high BHN.


Well-Known Member
Ahhh, so if we catch the copper alloy in suspended animation by quenching at a certain temperature, like a snapshot, it will toughen the alloy more. Like antimony, only different?


Well-Known Member
of course copper does affect the BHN of an alloy.
what I was seeing in the chart above is at this particular temperature it either wasn't measured or was still at a point it wasn't interacting with the SbPb mix.

IMO alloys change as thing settle down.
we know copper forms boundary layers with the antimony.
but it doesn't just surround the antimony the entire time it's in the alloy solution.
it really can't do that, we are talking about .5% surrounding 2.5% it's like basically physically impossible, especially when there is other stuff in the alloy trying to hang on also.
so it has to be somewhere pretty much all of the time.

think about an over tinned SbSn alloy.
the tin is chained in sequence on top of the SbSn chain but just kind of floating around out there, when the alloy tries to cool off a bit the excess tin breaks free but doesn't have the time to make a true SnPb type alloy [especially in conjunction with a SbSnPb alloy] so the excess basically becomes blobs of tin surrounded by excess now unalloyed lead.


Alloys do not have to have similar melting points to work. They have to have beneficial elemental properties. If you look at a table of elemental melting points, like this one, you can see some of the wide ranges of melting points that would suggest another process is involved other than heat alone. Steel is iron with a very small percentage of carbon. Cartridge brass is copper with 30% zinc.

There are elements that are beneficial when combined so even though I have never heard of combining copper to my bullet alloys, it doesn't surprise me that it has a positive effect. To be practical for my use, it has to be both safe and inexpensive. Take tin as an example. It is not inexpensive because it is relatively rarer than other elements in my bullet alloy. If it wasn't for the electrical/electronic industry, I doubt I could afford to use any.


Well-Known Member
I dunno about that.
the demand versus cost factor would surely be affected without their input.


Well-Known Member
what do you have to work with?
you can exchange copper sulphate for zinc.
you can melt stuff like 22 bullets or plated bullets.
you can use nibs of speaker wire.
you can even melt a couple of chunks of copper this or that and pour it in.
the easiest of course is to buy something [Babbit] with copper already in it.


Well-Known Member
wasn't measured Other articles show some BHN numbers for various amounts of added Cu to Pb/Sb. Up to 6% Cu. Cu up to 0.3% can be hold in the Pb lattice (crystal structure), excess goes into the SbCu molecule. From my experiments, SbCu is better at hardening than just in the structure. Cu added by replacement (CuSO4), tinned wires, no idea how the Babbitt manufacturers do it. Someone even added with Cu elec. welding rig.
Now you know as much about it as I do. It works well.