I am an avid bear hunter (blackies only).
I was going to answer this thread with a question.... which is, "why would you be hunting Black Bears at long range?"....
A black bear is quite a formidable animal to take down. If you have hunted them in the past, you know that they will often run for quite a ways from even a close range hit in the vitals. Penetration through an animal that runs as high as 600lbs is a real concern and shouldn't be taken lightly. They are
very hardy animals.... many harvested bears are found to have buried bullets, and even broadheads in their flesh.....A head shot at such distances is questionable at best unless you are a very skilled shooter, and their skulls are quite thick as well.
Most states allow for bear hunting in a manner that brings you pretty close to the animal (stand over bait or dogs). I think there is a basic reason for that.
I am not saying it can't be done, or even that it hasn't, but I think you're taking a lot of risks (albeit most of them the bears risks) with a shot like that.
That being said, a very well placed shot at such a distance from a 30-06 will do the job if you don't mind tracking a wounded bear for quite a ways, if it comes to that.
I use a .308 150gr SP, but again, at MUCH closer distances.
<EDIT>- I stand corrected-
http://fwp.mt.gov/content/getItem.aspx?id=37025 (Montana Bear Regs)
Montana Bear Hunting Regulations said:
Prohibited Methods of Taking
• It is illegal to bait bears or to hunt bears with dogs. No scents
may be used to attract black bears.
That makes bear hunting in Montana much more challenging from a shooting standpoint.... it pretty much means you have to try to track them (unless perhaps they are thick as flies there?)... which might result in doing a follow up shot from quite a distance... good valid question all things considered....</EDIT>