Don't need bullets that hard for handgun rounds. Having them that hard will cause more problems than it solves. Wheel weight alloy is nearly perfect for mild handgun loads (38 special, 45acp, 380acp, mild 9mm loads), with a brinell hardness of about 9. Lead shot has a good amount of antimony, can be mixed with soft lead to improve hardness.
Bullets can also be dropped into water out of the mold, which makes them considerably harder. I shoot modest 30 cal rifle velocities (2500fps with a gas check) from water dropped bullets, made from straight wheel weight alloy. A good lube and proper sizing are key to good function.
