Using birdshot on a grizzly bear at such close range would be extremely dangerous and unethical. It's highly unlikely to be effective in stopping the bear, and could potentially enrage it, leading to a more dangerous situation.
It's important to remember:
* Grizzly bears are incredibly powerful and dangerous animals. They are not susceptible to small-caliber projectiles like birdshot.
* Using firearms against wildlife is highly regulated. You need proper permits and training to handle firearms safely and responsibly.
* There are much safer and more humane ways to deter or protect yourself from bears. This includes carrying bear spray, making noise while hiking, and storing food properly.
If you are concerned about bear encounters, I strongly recommend seeking advice from wildlife experts and following their guidelines for safe wildlife interaction.