Since I am the only person who lives with grizzlies on a daily basis to chime in here I'll say this. Bear spray is your only chance to not get hurt. You can not hit a charging grizzly with the one round you are going to get off before he/she rips you to pieces! I have a buddy who carries spray and a gun. He works with grizzlies. He figures the best thing the gun is for is to shoot yourself when you're getting mauled to save yourself the suffering.
Bear spray blinds them and fries their nose for a whole lot longer than a few minutes.