If the .300 is a .300 Win. Mag. I'd use that. Tracking a wounded bear into the brush gets a little tense.
Seriously.
If the .300 is a .300 Savage, use the '06, that's decent for a black bear (but I've seen some seriously large black bear in Idaho a couple of times).
Good luck and be careful. /ubbthreads/images/graemlins/grinning-smiley-003.gif