I don't know much about Grizzlies, Brown, Kodiak or Polar bears, but I do know a little bit about Black Bears - and I'll share my experience:

First of all, there's no gun or spray or voodoo or magic spell that's gonnahelp you.

If you get into a bad situation with a blackbear - chances are - both parties will be "surprised" to see each other - and the "bad situation" involves a mother and cubs.

Hell, I didn't even know whatwas happening -just strolling down a logging road when I heard a calamity - and by the time I realized that a charging bearhad her sights set on my hide-the only instinct that you have is"run." Run fast. The 12-gauge inmy hands did not come into the equation. You either move or get mashed. Once you figure out where the cubs are - and you're clear, then you can start planning an exit strategy and pointing the gun and making Mr. Tough Guy idle threats. But when the chase is on - you damned sure aren't thinking about stopping and turning around to face your target. LOL

If you think you're fast - you've never raced an angry sow. That animal can cover some ground -fast. Really fast.

And from my interaction with bears - once you're safe, you're safe. Most bad situations (like mine) occur when unsuspecting person X inadvertently gets between momma A and Cub B. A - X - BThat's a very sticky situation.

Now, since things happened by accident - theydeteriorate equally quickly. You move it or lose it. It would take a set of 10-pound-balls and a complete lack of common sense to turn around, fish around in your pockets foryour gun and say "I'm gonna stand my ground, right here between momma and her cubs."

Once you clear the danger- and get to the "standoff" - when she's established positionbetween you and the cubs - you're safe. X - A - B. At that point, you start pointing your gun around and acting like John Rambo - and she's standing there popping her jaws and swinging her head. The game is already over at that point. You've already survived. She's asked you nicely to leave - and you should kindly oblige.