Cast bullets with lead and antimony and with a touch of arsnic, are heat treatable to brinel 35 - max. I seem to remember that dead soft copper is brinel 40. Pure lead is brinel 5, WW run at about 9 to 13 depending on who made them, while Linotype is brinel 22 & brittle. Foundry type is brinel 28.
Ordinary lead/antimony WW can be heat treatable to brinel 34/35 & will penetrate animals just like a non-deforming FMJ RN or FN. Some jacketed ones aren't as good as the lead variety in penetration.

Speed allows penetration all out of proportion to the materials used. A .224", 48gr. soft varmint bullet going through 1/2" of armour plate, yet an issue FMJ '06 made .008" deep pock mark and a .270 130gr. nothing more than a lead splash on the same plate.

For more information on "Jacketed Performance From Cast Bullets", everyone needs Veral Smith's book. Google comes to mind or addresses ro Veral from castbulletassn.org.