Came across this thread and thought I'd add what was noted in a written commmunication between myself and Elmer Keith, back in about 79 or 80. Elmer suggested upon questioning, that I go ahead and load the 550gr. Lyman bullets, "hard cast" - about brinel 16 so as to not make them too brittle and shoot anything in Africa with them I wanted.

At that time, my two best loads were getting 1,975fps and 2,000fps with the heavy cast bullets and with with wonderful accuracy from my 'little' .458 2" that had a long throat. I also told him I was getting 2,050 with a 510 Winchester solids and he said to go with the cast bullet with no further mention as to why. He noted they'd be quite capable if placed properly.

Of course, the Lyman 550gr. had a very wide, flat nose, which creates cavitation in excess of that produced by a round nose.

I highly value our phone conversations and written correspondence of so long ago. Elmer was responsible for the purchase of my first M29 4" as my duty revolver, and in return for a very close friend of mine, also a policeman at that time, for buying his.