Another problem with cast loads, is pressure vs bullet alloy. I don't have the formula at my fingertips, but suffice to say, there is a pressure limit for the brinel of the bullet.

Pistol and shotgun powders exceed the pressure limits of WW alloys around 1,500fps in many caibres, while the slower rifle powders which bulk better in the case, will allow up to 2,000fps and in larger calibres even higher velocities.

Joining the Cast Bullet Association and frequenting their forum will give very good advice on a variety of cast bullet shooting problems.

The last web address I had was something like: http://www.castbulletassoc.org/forum/

Information on bullet hardening and tempering is available there. There are a lot of very knowledgable cast bullet shooters on that site in a variety of disciplines.

Note that ordinary WW alloy can be made 50% harder than Linotype - easily, and will withstand velocities over 3,000fps. The Author of 'Jacketed Performance with Cast Bullets", Veral Smith, frequents that site. He is also the maker of extraordinary moulds.