A guy I worked with hunted black bear in Ontario every year for as long as I knew him. He swore by Speer 180 gr Mag Tips in his 308. He claimed they were the only bullet he used for all his hunting, bear, deer, moose.
The Old Grand Slam is gone and has been replaced with a bullet very similar to the old Mag Tip. The `06 and 308 are close in velocity and what works in one should do in the other.
I`d go with any 180 gr bullet, Hornady (I`ve used them in my `06 hunting deer, black bear, moose, and caribou but have only connected on deer and Boo with them), Speer, or Sierra and expect to be well armed for deer or black bear. The Nosler Partition is a excellent choice as it always expands very well and the rear core penitrates deep. They are the original "Premium" bullet and still one of the very best. If you wish spend big on bullets that`s the one I`d choose.