ORIGINAL: driftrider
I measure mine center to center, but I don't guess at the center. Just measure the largest outside span to the edge of the holes, then subtract bullet diameter. That's how BR competitors groups are measures, usually with a micrometer! [8D] Otherwise, even a perfect one hole group from a .308 would still, by your method, measure .308" minimum. You're cheating yourself the way you measure.
I measure my groups so I can tell how well I am shooting relative to my other visits to the range, so I don't think I'm cheating myself. The reason I measure the way I do is twofold; first, I am lazy and it's easier to measure my groups using my old traffic accident template that fits in my pocket, and second, I know it is human nature to "fudge" a little (I've played golf), so doing it this way gives me a more accurate measure of my performance over time.
A micrometer? Seriously?
If Lewis (xpatriot) says he can't do it, I don't think it can be done. Dude's a friggin' mutant.
