I am building a .338 RUM right now for a future Griz hunt.(it'll double for an africa trip that I am taking in summer '09) I will also be adding a 500 S&W short barrel sidearm for insurance. I think I would rather have too much and not need it than have too little and want more. Nothing would be worse than realizing too late that you need a little more horsepower. I have no doubt that a well placed .243 would kill a big bear, but I like to have the what if's covered. (like what if I make a marginal shot--don't say you won't, we all have done it)