For Wolves and smaller stuff I use a 30-06 Handi. For bigger stuff like this Grizzly I use a .338/378 Weatherby.
The only thing I have done to the Handi has been put an O-ring under the forearm, mount the scope and shoot it. The more I shoot it the better it gets.
The Weatherby, I just mounted the scope, (major problem here, ruined three base plates and sets of rings trying to hold down that 2 pound scope) and shoot it. Aside from the scope mounting problem, nothing done to the gun itself since it left the factory.