I don't hunt grizzly country,
But reminds me of an article I was reading
Person was attacked by a black bear at the time,
As they stated, if/when a bear is attacking, you generally have 3 seconds to react.
Their advice, pepper spray is more effective than your gun
Faster than drawing, releasing safety, aiming, firing a gun
Also most aren't carrying type of gun that will drop a large bear instantly.