I would have thought a switch barrel was the obvious choice. There are some really good affordable switch barrel options these days, though for me obviously the choice has to be R8.

If i couldn't have a switch barrel, 30-06, 270WSM or 300WSM seem reasonable compromises. And i'd probably choose a Sako 85, with Swarovski Z6 1.7-10x42.

If your dad doesn't have a beard, you've got two mums