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.
Try to put your tree stand in a tree with plenty of background cover, keep the prevailing winds for that time of the year to your face, and take care of those pesky squeaks and creaks your stand may have developed while sitting in the shed. A good treestand lube can be made by heating petroleum jelly until it reaches a liquid form. Some hunters have reported success by including a cover scent in this mixture before applying it to their stands.