Baiting eh?
What are you using for bait?
As for a gun..... whatever you feel comfortable with. A stout .243 would work or a 30-30 would do the trick too. Just put the shot where it counts.
I use bow only, so have little experience with rifles and bears. I set up my stand about 17yds away from the bait and shoot them there. With a rifle or muzzleloader I would set up a little farther away..... so 75 to 100yds if you can.
Alot of bears come in late around where hunt so being close gives me that few extra minutes that I may need to make a shot. Us e a scope with a gun and it will probabley do the same thing.
Enjoy your hunt.... when your first bear comes in it is a wild feeling