A heart shot is not a "stopping" shot on anything. The heart rate is not relevant. What works for large animals stoppers is a shot that breaks bones and/or disrupts the CNS. Heavy solids do this more consistantly than other loads in handguns.
The question of "can you hit...." is individual, some are obviously up to the job, and some folks are just as obviously not up to the job. To surmise that nobody can do it or it is nearly impossible because so-and-so could not isn't really a useful statement in the discussion in light of many recorded instances of folks effectively defending themselves with a sixgun.
I agree that bear spray has a valid place in the bear defense picture, but I rate it somewhere far behind a heavy sixgun. The limitations of bear spray are very real, wind in your face, strong cross wind, canister depleted. Some brands can freeze. Several accounts I have heard using bear spray the person hit the button and emptied the can, and not always effectively. Then we have the fact that about 2 to 4% of bears,(and people) are not affected by pepper spray. I think many bears ars killed that do not need to be, and pepper can be a help in detering these bears, but I also would not choose pepper INSTEAD of a decent pistol, but as a supplement to a good pistol or rifle.
The best defense is keeping a clean camp, being very aware of your surroundings, and keeping the mindset that you can deal with whatever happens if you keep your head. Having ones head in the clouds, or not staying aware of aproach cover etc when in the woods, is what can lead to problems. in other words, don't make it easy for them. Bear attacks are fairly rare, but not as rare as many think. I live on the edge of good grizzly country in Wyoming, and it is a rare year that we do not hear of several grizzly attacks and charges that lead to bears being shot, and people getting "fluffed up" at least, or seriously chewed up. Black bears even more rarely attack people, but when they choose to, they are more dangerous because it tends to be predatory(meaning they intend to kill and eat you).
