Well, I' ll just go with what I have now.

1. 12 gauge (can hunt squirrels to deer; including birds)
2. 260 remington (varmints, deer, antelope)
3. 30-06 (varmints, deer, elk, black bear)
4. 35 Whelen (elk, moose, brown bear)

Since you said we could pick up a fifth for bear exclusively, I' d get a 338.