Bullet mould blocks...what material?
Sounds like a perfect morning for bullet casting!!!
In my days of casting balls and mini bullets for shooting black powder weapons I soon found that aluminum mold blocks are easier to use, cast better bullets, and are far more forgiving of temperature changes in the lead. I have several steel molds for rifle and pistol balls and some ball and conical bullet molds from Lee that are aluminum, that I use. Believe me, the aluminum are much more pleasant to use and produce better quality balls.
You should be able to machine these yourself with only a basic shop setup (Lathe and Mill).
Just my $0.02, you know.
Only fools abuse their tools.