Yes those Brenneke Black Magic 607 grain hardened slugs would be stout medicine for a bear of any size. I'd pack them in my double barrel slugger and rest easy...

Double barrels with MONSTER slugs (with no chambering and no throwing a bolt, produce a very confidence inducing protective feeling).

Nasty and amazing looking photos eh? That guy was basically scalped by the bear, but looks like he escaped brain damage or deep cranial damage of any sort.