Standard for Measuring Groups?
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Measure the widest point of the group, then subtract the bullet diameter, i.e. .224 for a 22 cal.
Slight clarification to this approach.... rather than just subtracting bullet diameter, measure the diameter of a hole left by a single bullet passing through your target and subtract that amount. You may find that the mark is not the same size as the bullet diameter, depending on the type of target used. Measure both the single hole and the edge of your group in the same way and you'll have a more accurate result.
Of course the proper SH way to measure and post up groups is to shoot 10 three shot groups, pick the best one and post that.... all day long!
I believe this is how the benchrest folks do it, and it works well.
For me, I've come to realize that at most I care about the tenths of inches. 1.0XX inches vs .7XX inches vs .4XX inches and so on, so I don't worry about it much and just eyeball the calipers to the center of the outside bullet holes. If I'm recording data, it'll just say "6's for 10", "3's for 5" or similar.
Yeah, me too. It's not that hard to put the point of the caliper in the center of the two outside holes. Only time I use the subtract bullet hole diameter approach is when trying to get an exact number.
Agree with Sheldon, if youre gonna be precise, the hole in the paper is the way. Any consistent point you can measure off of works. I zero my caliper on a single hole, and then measure outside to outside of the group. Caliper reading will be the center to center measurement.
I believe that "doing my part" involves taking a photo of said cherry picked group, then posting it on the internet. 
If it's a one hole group I measure outside to outside and subtract the bullet diameter.
At distance, when holes are usually spaced apart, meansure the inside edge to outside edge of the two farthest holes. No need for math that way.
At distance, when holes are usually spaced apart, meansure the inside edge to outside edge of the two farthest holes. No need for math that way.
I guess you guys like doing math. All you have to do is measure from the inside of one hole to the outside of the other...think about it
Doesn't work when you shoot a 5 shot group like this...
Note that a bullet hole measured .236, not .243 (not that it really matters).
Touche Supersubes and Sheldon, the inside/outside method doesn't work for every application but in looking at the groups in the first post, it does.
You are too, just look at it. It is good, bad or ok. Going beyond that is like picking fly shit out of pepper.
I just measure from outside to outside with calipers. Yes I know it may not be the correct or fashionable way of doing things but it works for me.
So long as your measurements are consistent and make sense to YOU, it doesn't matter how you measure groups. No one else will be looking at your notes. And, except for getting an "atta boy" no one cares on the internet anyway.
