I've been shooting .357 and .44 mag SWC-GC loads at speeds of 1300, and a bit more, fps since '65. I get very little leading, usually just a soft smear that brushes out easily. It's really not difficult to obtain normal full velocities and little leading with cast bullets in a handgun with a smooth bore. I get normal speeds for a .38 and .45ACP with only light traces of bullet rub, no more than I would get from jacketed bullets actually.
My alloy is 5-6# of lead for most of the alloy, 4-5# Wheel Weights for the antimony, 1# of either 50:50 tin/lead solder OR 60:40 electical solder for the tin needed to make the alloy mix and cast well. Bullets are hard enough not to strip out with full charges of 2400 or H-110 and soft enough to easily obturate in the bore.
My lube is simply the excellant old NRA formula of a 50:50 mix of Alox and beeswax, commonly available from most lube makers. In the quanities I use it, it's too cheap to buy rather than mixing something that may not protect the bore or shoot nearly as well.
Bullets are sized at bore size or one thousanth over, no more, to obtain a good bore seal.
I've never heat treated a cast bullet in any special way. Not opposed to it, just haven't done it.