Growing up, every steer that we slaughtered, was brain shot with a 30/30...never had any issues. Plus, there's a difference between point blank to the brain and 30 yards to the heart.....use what you have, but I wouldn't pick the 40 S&W for a Brown Bear hunt 😉 Either....a 22 Magnum will penetrate most skulls too, but a bull that big, I'd definitely rather have the 40