I would rather be heavier than too light.
I believe that with all guns you should shoot the largest bullet and caliber (within good taste - A Barrett 50 Cal for a Cottontail does cross the line) that you can handle and shoot accurately.
I believe that with all guns you should shoot the largest bullet and caliber (within good taste - A Barrett 50 Cal for a Cottontail does cross the line) that you can handle and shoot accurately.