I measure outside to outside at the widest point. Then subtract whatever the diameter of the hole is in the target.
For .30's this often ends up being ~.290 in my targets. It varies with the targets and backing. Measure some bullet holes in your targets and you will see that subtracting .224 for .22 centerfires isn't quite right.
I dont shoot BR though so it is mostly irrevelant. /ubbthreads/images/graemlins/laugh.gif
