My dad, who owned a gun shop most of his life, used a 303 Savage almost exclusively on deer. I know over the years that he sure piled a lot of deer up with that gun. However, I don' t think there is anyone making factory ammo for it anymore!! You may want to double check that, but I think Winchester stopped making it a few years ago.

Anyway, I agree with the other post that mid-100s would be the best range for that gun.