OK, it seems like I'm swimming up stream here with everybody else trying to heat-treat their Wheel Weight alloys to make them harder, adding lynotype, cast bullets with huge meplats so they don't have to worry about expansion, etc.
But me? I'm finding air cooled wheel weights are too hard for my purposes! I cast a lot of .38 spl, mild .357 Mag, and if I go hotter, I paper-patch or use a jacketed bullet. I LIKE to see a bullet expand well. In fact I would prefer to use pure lead, except that it's just too difficult to find - as opposed to wheel weights.
So how soft CAN you make wheel weights?
I've got a little toaster oven from a garage sale to anneal them. I start 'em out at 400 let 'em bake for an hour, turn it down to 300 for 1/2 hour, then 200 for 1/2 hour, then off 'til cool. They don't really seem all that much softer.
Can the way you cast them affect their hardness?
For example, I think I run my molds a little hot. When I cut the sprue it breaks off giving a jagged mark at the base rather than the smooth shear-mark. I sometimes notice a smooth shear-mark with the first few when the mold is warming up still, but those also tend to have wrinkles. After dropping the bullets, they look shiny, but then they take on a frosty look, almost like galvanized sheet metal - they're still smooth though. Again, if I run things a little cooler, they stay shiny.
If I do anneal them, how long will that last?
I cast when I have time to cast and I shoot when I have time to shoot. It won't work if I have to shoot a bullet within X number of days of casting it. I'm looking for something practical. Pure lead isn't practical, and neither is a "best when used by" date on my bullets.
And finally, will annealing them make up for any differences in casting methods?
I cast in an unheated garage in all sorts of weather. So when I air cool, that air might be 20 degrees or it might be 80 degrees. Plus there's the differences in mold temperature when I start a casting session, til when the mold heats up.