You always want to bring enough gun (portable) and always want to be prepared to take on the animal you wouldn't like to see on the, in this case a grizzly of large proportions. Assuming you are proficient with big bore revolvers, you would look at the 475 and various 50 calibers on the market. A properly loaded 480 ruger will drop anything on the north America continent. For less than a $1,000 you can pick up a Ruger Single action in 4.62 inch or 6.5 inch barrel. If double action is preferred you have the option of the Ruger Alaskan with 2.58 inch barrel or a longer tube in the Ruger redhawk. All of the noted firearms should be loaded with 410 hardcast from Buffalo bore. Out of the 6.5 inch barrel muzzle velocity is approximately 1225. That is your best bet. Good luck and stay safe on the trail.