I know a fellow who put a griz that was attacking a fellow hiker to flight with a blast of pepper spray. This was on the Grantite Park Chalet trail in Glacier, a notorious griz location. The stuff works pretty well and is easy to bring into contact with target... you can see the jet of spray very well and just move it a little if you are off target. This is the stuff to carry on all trails in Glacier Park. Outside the park I would recommend carrying a pistol of caliber .357 or larger in addition to pepper spray. Personally I would use the pepper spray first. Grizzle bears are very tough to bring down with a pistol shot.
Old joke:
When in bear country, tie small bells to your shoes and carry pepper spray to ward off bears.
You can tell what kind of bears are around by examining the droppings. Grizzly droppings contain small bells and smell like peppers.
Ted Nugent took one down with a 357 in alaska