Well, I would still rather have a 12 gague loaded up with a 385 grain slug or better IMO would be Winchesters full 1 ounce (437 grains) slug coming out the muzzle at 1760 fps. This scenario is a close range attack and a big arse slug slapping a bear in the chest will not only penetrate to the vitals but offer up one hell of a whollop at the same time. A heck of a lot bigger whollop than any .308 bullet could think about doing.

I am sure the 308 bullet will penetrate farther but that is not my concern in this scenario. My concern is puting the biggest chunk of lead possible in the bears chest and stopping the bear ASAP. The farther a given bullet penetrates the longer it takes that bullet to expend all of its energy and the less "punch" that bullet will have, more like a shove.

Do not discount big slow (snales) chunks of lead as very effective ammo. It's kind of like being hit with a baseball at 90 mph or a bowling ball ar 20 mph. Sure the baseball is gonna hurt really bad and may even break something but that bowling ball is gonna knock the hell out of you and keep you down for a long time.

I would still rather have a slow running guide. At least slower than me.