The reason I picked these three is they are so versitile.If you choose 2 bullet weights for each you have 6 rifles if you go with QD mounts and a couple of scopes.

7x57 120g & 175g covers 270-3006
9.3x62 250g TSX & 320g Woodleigh covers 3006-375h&h
404j 350g Woodleigh and 450g Woodleigh (I would just use the Woodleigh 400g Hydro for anything in the world)!!.Covers 375h&h-458.

JUST MY OPINION !!!.
Cheers Neale.