Mike I heat treat almost everything that goes down a 30 caliber barrel. Set the oven by trial and error to the setting that is just below the slump temperature of ww alloy slugs. Most use scrap bullets to determine this, but then note that setting and do place the bullets in the same place each time. Around 450 degrees works.. something just below that works too but doesn't produce quite the final hardness. 1/2 hr makes them hard-- one hr is about max required, and then quench quickly in cool water. WW alloy normally falls in the range of 26-30 some bhn- depending on it's contents.

Arsenic is the agent responsible for this effect along with atimony. A lead/tin alloy will not heat treat as it contains no arsenic.