perhaps a dumb question.... How exactly do you measure group size???

[StoneHendge]

I recently measured a group from outside edge to outside edge and subtracted .264 for a .980 group.
I measured center to center and got a larger group.
I then measured a single .264" bullet hole and got .220". WTF?
Measuring edges seems no more precise than estimating center.
Look at post #8 above. The computer hole fits are no better than human judged hole fits.
A human programmed the computer hole fits so it should be expected.
I better stick with center to center. It is the most honest.
"Honest", I haven't used or seen or heard that word used in quite a while. I guess it has fallen out of favor. Sad.

For whatever reason, bullets usually make a hole smaller than its caliber. Perhaps the resident physicists can explain. I always measure the size of the holes getting punched by the particular bullet in the particular paper that day and subtract THAT from edge to edge.