Lyman Cast Bullet Handbook, is the best reference book on bullet casting. I have the 3rd edition and the 4th is the current one. There is a casting section in all the Lyman Loading Manuals, but many editions don't have al the little secrets the CBH does.

Since you are Coating the hardness won't be a major issue. But different alloys produce different "As Cast" diameters from the same mold and different weights too. That should be important to you.

Ivan