We don't know anything about what you want to hunt, so it's somewhat difficult to offer an informed opinion. Having said that, if you want something other than the .308 you already have, I'd suggest .35 Whelen. As MachIV posted above, it has an expansion ratio even lower than .308, so it shouldn't lose much performance in a short barrel. It would also offer something very different than your .308. Finally, you are much more likely to find ammo if you don't reload for the .35 Whelen than the .358 win (same with brass if you do reload). Just checked Midway: they show 3 ammo options for .358 win, none are in stock; they show 10 ammo options for .35 whelen and one is in stock.