Even fewer bad guys are immune to the full sized cannister of Bear Spray. It is not much larger than a 16 oz aerosol can but can deliver a choking and penetrating cloud where the attacker cannot avoid taking in a lungful of the dense cloud. The "plume is about 20"-30" wide, thick and sprays at that volume for 20-30 seconds making breathing almost impossible for the bad guy. A Grizzly's keen sense of smell makes it unbelievably fast and effective no matter how big the animal is.
Here is a link to a You Tube clip explaining one type of Bear Spray:
http://www.youtube.com/watch?v=TA_DXeWTOG8
With a bear, the key is to be able to access it and get him before the momentum of a charge gets him too close before he can turn around. Even then, most who have used the spray say the bear would not stay there to hurt you but you might be injured just from the massive animal trying to turn on a dime and hitting you with a claw or something.
These cans put out about as much volume as a small fire extinguisher and the advice is to buy at least two and use the first one immediately so you can see for yourself the spray pattern and the coverage and how best to aim it. Once you know that and have one at the ready, you're locked and loaded.
Of course with a human attacker there is no charge so a burst to the chest and another to the head is recommended so that both the breathing, smell and sight of the attacker are affected.
I have a CHL. I am not in LE but I have been forced to pull a firearm on three separate occasions. In each case I avoided ever having to fire it at the bad guys. One encounter was with a small band of thugs who thought better of their planned attack once they saw I was armed and ready to fire.
