Here's an interesting study by Randy Garrett (Garrett Cartridges) on penetration in the .458 dia cartridges. His findings are interesting to say the least. Sorry if this has already been posted & I missed it.
The conclusions I draw from them are that the only thing speeds above 1800fps will gain you is a flatter traectory.
I'm just starting to play with a guide gun again in 450 & looking forward to load development.