Grizzlies aren't made of steel. Their hides puncture about the same as black bears and people have no difficulty chasing blackies with 55# er's. Sure they can be a little bigger, but that just gives you a slightly larger heart/lung area.

If I ever manage to pull a griz draw here I'll probably chase 'em with my 55# curve, because I shoot it a lot better than my 60# longbow. But I'd also have someone I trust backing me up with a longarm they feel competent with. BC has a 40# minimum for all big game, except bison which is 50#, and as mentioned before, sharp broadhead, proper placement will get the job done.

Oh, LB;
For bear backup I'd recommend 12g. slug, slug, slug, slug, slug closely followed by practice, practice, practice...

RC