I have no idea what kind of regulations there are in the state you will be hunting, but if you can use a slug then that's what I'd try. Most (not all) shotguns will shoot a rifled slug well enough to hit what you're aiming at out to 50 or 75 yards. Some better, some worse. You can even find inexpensive rifle-style sights to put on most smoothbore shotguns to help you place a slug. Just an idea.
Check all your options before you make a decision. I'm sure buckshot and slugs will both kill a bear. Just know your limitations with whatever you choose. Good luck with your hunt. We want to see pictures when you get home!
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