I realize this post is under Bear Hunting, but the question of this topic is one rifle for bear and OTHER BIG game. A .450 could be used for sheep and most certainly be more than adequate, but I bet I would have more successful sheep hunting trips with a .338 Win Mag than someone with a .450. A .450 for antelope would be the ultimate in hunting for the man who has months to spend shooting one. The same applies with any bore that hasn't got the range to accurately at typical distances shoot the animals. A .30 cal round will effectively take black bear and most other typical deer sized game, but not as effectively on Big game, brown bear, or moose as the .338 Win Mag. It has been done but not as consistently as bigger bores with similar trajectories using heavier bullets. Admittedly the .375's are even better than the .338 for BIG game but not quite as versatile as the .338 rounds having similar ballistics as the Win Mag. For every area of the country, arguments can be made for other cartridges, but the question was one rifle for everything with no limitation on where it is used. The cartridges and our favorites (by the way, I do not own a .338 Win Mag or similar round, but have used them) are posted by most but nothing has been suggested for the overall rifle and action type.