My first trip to Alaska, I talked to the Fish and Game officer and asked about defending myself from a Grizzly
He told me that they can run 35 mph, Have a heart rate of 14 bpm, He said I could shoot one thru the heart at 100 yards and the bear could run me down and maul me before he realized his heart had stopped working.
He instructions to me were that I needed to shoot to break serious bones. Spine, Shoulders. Something to slow the bear down so it could not run as fast. The nexct shots should be double 00 buck and be aimed for the nose and eyes, Effectively blinding and destroying any sense of smell so the bear could not find me, Then I was supposed to run.
The few black bears we shot over the years have never been hard to kill and you can usually shoo them away. But the grizzlies are a totally different game plan.
I've been fortunate that the few grizzlies we have seen in the wild, did not want to harm us. They were more interested in forging for food and leaving us alone.