mrwhitetailhunter, you can do what you please when you hunt dangerous game or big bears. However when or ifyou ask for opinions on what to take on such a hunt be prepared to hear other than your beloved .308 win suggested.
I will not argue shot placements and bullet selection or for that matter confidence in a particular rifle aren't large keys to success in the field. However just because someone used a knife to kill a grizzly doesn't mean its the best choice!!!! I personally don't believe their is one tool for every hunt. In terms of possibility of being the hunted vs the hunterI don't think you can be over gunned!!! So if I ever have the interest to pursue such game I will make sure I am proficent and able to handle guns best suited to the task before embarking on the hunt. If not possible Iwouldn't bother going on that hunt.
BTW I no longer have any desire to hunt black bears with a firearm, so I know they aren't required to cleanly kill a black bear. My reasoning is simply from a personal challenge perspective with blackies. That said I still respect them and the threat they can pose. I wouldn't dream of chasing a grizzly or kodiak with a bow, not because of lack of skill or confidence in my equipment but rather out of respect of the animals power/unpredictability. I kind like living to see the next day.
If this makes me a wuss...Guilty but I can live with that

.