How to differentially harden cast bullets?

[Naphtali]

I am casting .459- and .512-inch bullets, both of which have nose-to-crimp length of .400 inch. I understand there is a method to differentially harden these bullets -- that is cast a hard bullet, then anneal a portion of it.

If what I wrote is accurate, what is the procedure to soften the .400-inch nose of a gas check bullet while retaining full hardness on the remainder?

1. When do I size and install the gas check to retain base hardness?

2. Must bullets cure before annealing noses?

3. Must bullets cure before sizing?

4. What must be present in the alloy to allow differential hardening? What would be among the more useful lead mixture chemistries or compositions to achieve reliable differential hardening?

5. How uniform will be the annealing process -- that is, will gradient or demarkation between harder and softer lead be uniform in distance from base to nose, so that bullet's performance is predictable from shot #1 through #5? How can uniformity be ensured?

6. What is the procedure, from first wobbly step to finished, differentially hardened bullet?

[felix]

Rule: whenever doing anything mechanical to a boolit, do it at its maximum hardness to maintain circumferential integrity. It you want to soften something before any kind of sizing, then soften the gas check. A sufficiently hard shank should bend a gas check to fit. You don't want the vice-versa possibility. Soften the nose before applying any lube. If you want the very best boolits, gas check and crimp on, and don't size the boolit until after pan lubing. This will hold the lube grooves straight. Now soften the noses, and then re-lube. ... felix

[yondering]

I'd also be interested in how to soften the noses. I've read about this in the distant past, but don't remember the details, or where I read it.

[runfiverun]

pan o water [a heat barrier of sorts]
a torch. glen fryxel has a good article on this.

[leftiye]

Pan of water up at least to top of front driving band like R5R said, and mark the noses with tempil sticks (probly in the 250 - 300 degree range). Heat with small point propane or Mapp gas torch (or even acetylene, small welding tip - hotter and smaller is better) individually until tempil mark changes.