RE: .270 for black bear?
The only bear I have taken by way of a CF fell to a 270 win with 130 gr Hornady Interlock SP, shot distance was around 100 yards and the bear measured over 6.5' (300 lbs range). He rolled around chewed at the hit sight and dropped for good before exiting the oats field - less than 50 yards.
I agree shot placement is the key, they have extremely large shoulder blades causing many to shoot to far forward (they are not whitetail so aim a bit further back!). I only bowhunt them now and let the near shoulder clear (stepping forward) then aim for the opposite leg, this opens up a direct path to his vitals. I suggest for any new bear hunter to stick to a premium bullet like a Nosler Partion, Barnes, Failsafe...this way if you clip that shoulder you have a bullet that is designed to penetrate heavy mass.