I understand that hardcast bullets are made of an alloy of various metals that make them harder than just lead. But what are they and how much do they make up of each bullet. ie metal A is this percent and metal B is this percent.

I have read that they may contain something called antimony. What is antimony and what does it do?

Thanks in advance for the help.

Antimony is an element. It is itself, not a combination of other things - like carbon or hydrogen or gold or uranium.

When added to lead, it makes the resulting alloy harder and more brittle, and does some other stuff with melting points and such. Mostly it's used to make lead alloys harder - meaning slugs made from it deform less upon impact and have greater penetration potential.

https://www.webelements.com/antimony/

Sb.

An element.

#51 in the periodic table.

It makes lead alloys harder and more brittle.
It is an ancient metal. Like tin.

Delete.  

Cast lead bullet info:  people who know what they are doing.

https://www.dardascastbullets.com/mm5/merchant.mvc?Session_ID=a03998177b9e462fcd17a819e35b42da&Screen=SFNT&Order=0&Store_Code=dardas

Also a good read on lead and lead alloys

http://www.lasc.us/castbulletalloy.htm

John:  Fantastic details in the long article. Thank you.

The Dardas site is simple.  Use the right diameter.  0.001" over groove diameter.  With 9mm and .40 Glocks, never a bit of leading.  Bullseye is cheap per load.

With S&W revolvers, you never know since the cylinder throats are often smaller than the barrel grooves and F up any lead bullet you use.  In Smith's, the 148 hollow base watcutters are so accurate because they are soft enough to smash in the throat and re-fill the barrel grooves.  

I have a M66 with throats at 0.355/4 and a barrel of .357/8.  Stupid combo.  No normal lead bullet works in it, but 148HBWC are super accurate.  Federal 147 +P HydraShoks hover near an inch at 25 yards.  You gotta test them.

I found casting bullets a waste of time when they are available for 9mm/40S&W so cheaply.  Reloaded thousands over the last 8 years. Only down side is the smoke while firing.  FMJs don't smoke.  The cost was bullet and primer equaling the unfindable .22LR I really wanted.  Bullseye makes so many loads per pound, I don't even count the cost.  No Bullseye?  Find WW231.

Antimonial Lead
An alloy composed of from 3 to 10% antimony with the balance lead, used for storage battery plates, bullets, type metal and tank linings. The anitmony hardens the lead and increases the tensile strength. The usual alloy contains from 4 to 6% antimony and has about twice the tensile strength of pure lead. Up to about .10% of arsenic stabilizes and hardens the alloy. It weighs .398 lb per cu in and melts between 475 and 555F

Antimony
A bluish-white metal symbol Sb having crystalline scalelike structure. It is brittle and easily reduced to powder. It is neither malleable nor ductile and is used only in alloys, especially lead for solder, battery plates and type metals. The specific gravity is 6.62 and melting point 824F. It burns with a bluish light when heated to redness in the air. Antimony imparts hardness and a smooth surface to soft metal alloys, and alloys with antimony expand on cooling, thus reproducing the fine details of molds. Much of the antimony comes from the Hunan Province of China, but production is found in Mexico, Chile, Peru and Bolivia. The cheif ore is stribnite (see also Kermesite and Stephanite).

Taken from the Materials Handbook pub 1944

BTW wheel weights used to be used for pouring bullets until they introduced a 14% and greater antimony content.
Now it is unknown what wheel weights are made of since consumption has been blamed for the great cancer epidemic of 2004 in California. Bullets made from similar composition are illegal in California since they cause lead poisoning... go figure.

Antimony was originally used in wheel weights to make them harder. Tin was the original metal preferred for this application, but with rising prices, they switched over to Antimony. Originally everyone use to cast, and lead was very common, however due to restrictions becoming tighter, it was harder to find pure lead, so casters starting switching over to WWs. With this switch, Antimony became a common metal in their alloys.

The problem with antimony (SB) , is that it doesn't add anything beneficial to a lead bullet. Any alloy with SB can be made much better with the use of Tin. As people became more and more use to SB in there alloy, they just starting accepting the problems that came with it. Alloy with SB in it is almost always way to hard, for a lead bullet to properly seal in a barrel/chamber, it needs to be soft. Hardball alloy (with SB in it) does not allow proper bullet obturation.

People still use alloy with SB in it, but SB will cause your bullets to be way to hard, and very brittle. If you ever tried to cast a HP with an SB alloy, you'll notice when you recover it, all the petals will be completely sheared off, due to the brittleness problem.



If you cast, and actually care about a proper alloy, pure lead, with tin, is the way to go. You can harden it up to proper BHN with only tin, and it'll work just fine in about anything you put it in, as long as you have the bullet properly sized to bore, and use the proper lube and/or gas check.

As I understand it, Antimony is for hardness, Tin helps the lead flow and fill molds better.   It doesn't take much of either alloying metal to do the trick.  Conventional clip on wheel weights  seem to be about right for most pistol loads.  I used to use Lyman #2 alloy (90% lead, 5% tin, 5% antimony) for heavy .45-70 loads.

Tin also helps limit oxidation in the melt.