I dont use a .270 when I am hunting grizzly, but do have some .270 "bear loads" using a 150 grain Grand Slam. I carry them while sheep hunting in case I see a nice grizzly. I am confident they will work.
A friend of mine killed a nice interior grizzly with his .257 Roberts with 100 grain Nosler Ballistic Tip bullets. One shot through the ribs was all it took.
As was said, a big difference in what is needed to kill a grizzly compared to reliably and quickly stopping a charge. If you are hunting with a guide, he will have the stopping covered.