This thread is headed into the, "Whats the biggest magnum you can think of, and that's what you should have" area.
Of course, a 35 Whelan and all the magnums will kill game if you can hit them. That's not the point. The question was, would his 308 be suitable for hunting in the Yukon. Most of us who know something about it, or have had some experience, have told him his 308 is suitable.
Hosea Sarber was considered the greatest bear guide and bear authority in Alaska. He usually carried a 375 H&H to protect his clients.
But he once went after a big Alaskan brown that had killed a forest ranger on Admiralty Island. The bear had been wounded and a year had elapsed. Hosea thought he may know where the bear was, thick bush and a creek. He went after the bear alone, carrying his favourite 30-06. He came across the bear, short range and thick bush. Bear charged, he killed it with one shot.
aperature sights, by the way, with the disc removed.
This is written up in the book, "No room for Bears," by Frank Dufresne.
His only explanation for taking the rifle that he did, was that he thought he would be better off with his fast handling 30-06, in the thick bush.