Hollis - The term/concept you are looking for is "point blank range" (
http://en.wikipedia.org/wiki/Point-blank_range). Your "cone of accuracy" is another descriptor for "circle of probable error" and is just one of the factors in the study of external ballistics. I'm sure LR1947 or GE have a couple of lectures laying aroung they can dust off and entertain us with - personally I'm not typing that much again unless somebody is paying me
. Peregrino