IMO, the 300gr is not needed.
I have been more than satisfied with 210gr TSX's and NP's out of my 338-06's.
I messed around with some old Speer? 275gr? Never felt the need to use them on anything.
I cannot imagine anything that a 250gr premium would not handle with the exception of a body shot on elephant or hippo. Then solids could come into play.