My Win mod70 .270 has killed 15 black bears from 100 lbs to over 400 lbs with Federal Premium or Classic in 130 or 140 grains. Distances varied from 30 yds to over 300 yds. It is all about shot placement.
my .303 always works for bears and ya i say the exact same things as all these guys use a bigger cal for bear just so they dont have to suffer its always best for one shot one kill with big game and im sure you all know that.
When it comes to scent, there are basically two types; those that attract and those that mask. I've tried both on many occasions. There are lots and lots of "doe in heat" scents, designed to attract a big buck into range. I've also used a "cow in heat" scent while elk hunting.
Another scent would almost be better named as a "coverup smell". The main goal is to cover up human odor or mask it. Though I don't believe you can ever totally eliminate all human...