I shot my grizzly with a 2 blade Zwickey Eskimo. I also took my moose and caribou with the same head. Shot placement is the important part. My grizzly was shot at 20 - 25 yards and ran back on my to about 10 yards, then dropped. One arrow through the heart. My wife was about 100 yards away watching. I tease her, that she was counting the life insurance money!
Zwickey broadheads have been around for years - easy to sharpen and have taken LOTS of game, including all of mine (elk, deer, mt. lions)