If I were going to guesstimate as your suggesting, I would
just use an average size, about the same as a German Shepard
average, say for instance, shoulder height of approx. 18".
That should give you a reasonable kill zone. BUT, That's
also dependent on the Shooter and Weapon. If BOTH are able
to provide 1" groupings consistently at 1 / 2 / 300 yds,
then there's no reason you couldn't do it the way your
suggesting. Now if were talking 6" groups at 100 yds, that's
a Horse of a different color.
