Well, I was involved with Bear "Control" many years ago, and shot many, many Black bears
that were a nuisance in fruit orchards.
Most were taken with the 30-06 and 165/180 Partitions.
Probably 15 with the 7x57 and the 140/150 Partition.
A couple with the 6mm Rem and the old style 100 Partition.
Individual bears were taken with several other chamberings. [303 Brit, 6.5x55, 264 Win Mag, 270 Win, 300 mag, etc]
The lung shot was always the preferred shot.
Never lost a bear shot solidly in the lungs.....they would run, but not far.
Shoot one a bit too far back though, and they would travel quite a way, and the blood trail was sparse in some cases.
I do not consider a Black Bear hard to kill, but the hair, fat and hide conspire to hide blood that might otherwise be visible.
Regards, Dave.