Having the correct diameter projectile is more important than hardness. There have been times when I got more leading from hard commercial cast than I have with bullets that I cast myself.
When looking for a lead alloy, my primary concern is how well the mould gets filled out. Then size the bullet a little on the large size, and use a SOFT bullet lube like Alox. *I never messed with powder coating. The old Lyman Lubrisizer always worked great. I have no desire to reinvent the wheel.

When everything goes right, casting was satisfying. I can't find lead anymore. Truth be told, I shoot a lot of XTPs now. My lead supply is gone.