Alloy question...

fiver

Well-Known Member
okay now your catching on to why I also use zinc in some applications.
there is a limit to what each thing can do, and when they are subjected to stress they react quite different.
they also react differently when in the presence of other constituents in the alloy.

think about copper it's tough and strong [about 50 bhn] but you can bend and twist a wire around in all kinds of directions.
tin is airc 35 bhn but it breaks if you bend it.
add tin to the copper and you get bronze, you can sharpen it to a fine cutting edge and cut down a tree.

antimony in a lead alloy will break down and lets the lead slide over itself easier.
we use that combination in swaging, and they use it in extruded lead products.
you know those dead soft Hornady wad cutters that you can only push to 700 fps?
they have 5% antimony in them....

add 2% tin and you'll break your swaging dies.

there is hard, there is tough, and there is malleable.
you can get all three from a 3 part alloy all you gotta do is manipulate things properly.
heat treated low Sb alloys are hard until you stroke them then they become malleable.
 

Ian

Notorious member
With a relatively short, fat handgun bullet, you'll see a lot of effect from a little more tin. The bullets are strong to begin with, not having much unsupported area, so if you're pushing them hard enough to plasticize the entire bullet, you'll see a huge change with just a little tin. I'd try some at 2:1 and some at 1:1 Sb/Sn ratio and if you can recover them and see what the results are I'm certain it will support your theory. Remember, Sb will still let the bullet "draw" even if it you add more and make it harder. Even heat treatment won't reduce this draw tendency much (a GOOD thing with well-supported rifle bullets at high launch pressure), but increasing the Sb/Sn matrix by adding more Sn to your alloy increases the over-all plastic strength of the bullet at all heat treat levels.
 

Ian

Notorious member
BTW Fiver's post #22 = best explanation I've ever read on the subject. PERFECT.
 

Brad

Benevolent Overlord and site owner
Staff member
This has been very enlightening.
Thanks guys, I now have a far better understanding of how the Sn and Sb interact in the alloy. I can now better understand how small changes in percentages in either one can lead to significant changes in the bullets behaviour.
 

Rick

Moderator
Staff member
Say I'm using a 2% Sb, .25% Sn alloy. It is heat treated. Think of my new 44 mag bullets and how the lube groove almost entirely went away.
If I added another .5% Sn and heat treated the same would I get a noticeable difference in the appearance of fired bullets? Would the reduced obturation potentially increase accuracy?

Uh . . . NO. Tin will not turn a pig's ear into a silk purse. That was a radical overload and not an alloy issue per se. Tin is very useful but it is not a magic wand.
.
 

Brad

Benevolent Overlord and site owner
Staff member
I was speaking in general terms. Even with reasonable loads my bullets are losing grooves. I may well add 1/2% tin and see what happens.
 

fiver

Well-Known Member
I would, it's one of those learning opportunity's.

airc Popper was having an issue some time back and I recommended adding copper to his alloy.
it didn't make a lot of sense to him at that time, but IMO he has acquired a pretty dang good handle on alloys.
 

Uncle Grinch

Active Member
There is a lot of information and theory in this thread. I have read it several times trying to take it in and get more confused each time. It’s like info overload and it causes me to question my alloy. My goal is GC rifle loads ranging from 1400 to 1800 fps. I have WW, Linotype, and Stereotype of which I alloyed together using the cast boolit calculator to give me a 2% tin, 6% antimony, and 92% WW.

I’m thinking now that my numbers are off in my quest for a usable alloy. Am I over thinking it?
 

Brad

Benevolent Overlord and site owner
Staff member
For those velocities you could use a far more dilute alloy.
Even 2%Sb, 1% Sn would be fine.
 

Rick

Moderator
Staff member
I use CWW +2% Sn air cooled in all my rifle loads to 1900+ fps without issues of any kind. It's also my magnum handgun alloy heat treated. Your straight WW metal should be right at 2% Sb and 1/2 to 1% Sn and would most likely be fine for what your doing. You can get really wrapped around the axle over many aspects of casting including blending alloys but for your described use I would just use what ya got and don't try to be a metallurgist. It works fine.
 

Rick

Moderator
Staff member
I've had my WW alloy XrF tested at three different locations around the country, all 3 tests of my weights were fairly consistent at close to 2% Sb and 0.5% Sn. I add 2% pure bar tin. The point of my post above was simply that you can/should expect a little variation in WW alloy especially newer weights.
 

Rally Hess

Well-Known Member
Thanks Rick. That .5 was what I had always understood, but have noticed some coww coming out of Canada is a touch “harder”. Way more steel than zinc the last couple years.
I.think of adding tin about like adding fiber to concrete. Too much is detrimental, while too little is just a waste of money.
 
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