One of the early pictures showed what is wrong with 00 or 000 buck. There is so much space left with nothing it in. If you go with # 1 buck, it fills up all of the available extra space.
Another consideration is the actual weight of the projectile. You will get a much heavier grain weight from smaller buck than with the larger version. Therefore a greater felt impact by the recipient.
Peter Hathaway Capstick did an article on this very subject. His argument for small buck is very convincing.
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Hard times create strong men. Strong men create good times. Good times create weak men. And, weak men create hard times.