I have 2 Mausers in the rifle set so far and with 4 I think would have to be a "classic" selection
.275 Rigby
.375 H&H
.416 Rigby
.505 Gibbs

pretty well covers everything from Rat to Elephant, 20 yards to 350, just need to get Holland detachables for them all and a complete set of Swarovskis - 11/2 to 16 by 24 by 50