There is so much misinformation out there on making and using heat-treated cast bullets (some from commercial casters who should know better) I'm posting what I learned from research and experiments as a commercial bullet caster.

You HAVE to use a proper lead mixture containing:
Lead
Tin (for good flow in the mold)
Antimony (For hardness)
Arsenic (Available commercially as "arsenical lead" absolutely necessary for heat treating to work )

The hot cast bullet is dropped from the mold into water for rapid cooling.

It takes about 30 days for full hardness to develop. I don't know how it works, but that's what I've seen in my tests. Fresh heat-treated bullets aren't any harder than regular bullets.

ANY working of the bullet, like sizing in a die or lubricator, will cause the hardness to dissapate within seconds. It is my untested opinion that only the surface that is worked will lose hardness, and the unworked core will retain it's 'hardened" effect on the target. Other testers have written that the short time in the bore is not enough time for surface hardness to dissapate, and the hardened bullets lead significantly less in rifle bores.

I won't bore you with the numbers, but this is what you need to know if you want to make real heat-treated bullets (first used in the old black-powder rifles).

I used to cast many years ago and just shot the bullets as they came from the mold. While out visiting RGS last month we did some casting, his first, and dropped them into a bucket of water... The surface was so hard it could not be scratched with a nail...and there were nothing special just weelweight material.

They were sized the next day and shot a day later...great groups from both a Marlin rifle and two different handguns...and no leading at all...

You are probably correct about waiting to let the bullets "age" to full hardness as there is probably some mechanical/chemical reaction that takes place as they "age"... But these did work as cast. I wonder if any of the "Premium" casters like Beartooth or Cast Performance "age" their bullets. I have visited Kelly Broast at CPBC and there was no indication there was an "ageing" area before the bullets were sized. And his bullets are very hard...

Bob

Lots of good detailed information here:

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

I just use Linotype.

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quote:

I just use Linotype.

+1 on the Linotype!

Older wheel weights work great for heat treating. I used the same technique Keith described by dropping them in water from the mould. Everything I'd read before I started said to heat them in an oven until they were just under melting temp. I thought they would be at that temperature as soon as the sprue set up and gave it a try. I took two bullets from the same pot, one treated, one not, and put them nose to nose in a vise. The non-treated bullet wrapped around the treated bullet which barely showed deformation from the vise jaws.

I still have a lot of wheel weights from a local tire shop owned by a guy who liked to shoot but didn't like to cast his own bullets. I also have a lot of industrial alloy similar to the wheel weights that I got from a guy at a steel mill that I made fishing lures for. They are my favorite alloy because untreated they are fairly soft and treated they get pretty hard.