The 308 with the proper bullets would take all American and Canadian big game. This would include the big bears. It would not however be ideal for the latter. The 308 with bullets up to 180 or 190 grain are basically equal to the 30-06 which has taken all N. A. Big game. Many here will tell you that you need a 338 Mag or even bigger for grizzly and Brown bears. It would be a good idea to use a bigger gun but in a pinch you could make due with a 308 by picking your shots. If you are serious about hunting the big bears then I would start with a 300 Win Mag. However most hunters will never hunt the big bears and the 308 will handle everything else with ease if you can do your part.