My bear hunting buddy tells me that most guides won’t go out with you for grizz with .30-06. Too dangerous: The round is simply too small.
He has taken a grizz in Allaska with his .30-06 but it took three perfectly placed heart lung shots to bring him down. A very tough animal.
.45-70 is minimum.
If you read the Chronicles of the Lewis and Clark expedition, one grizzly took 9 close range shots to the chest from Kentucky long rifles to bring down.