Group measurment

[moonsign]

If I were shooting competiton, how would I measure my groups?
edge to edge-subtract .243, or center to center-subtract .243?
Using this last measurement, I come out in the hole, minus.
Last range session doing load workups for my Savage M12, LRPV, w/ 8 twist-Mcgowen barrel, chambered in .243, using 95 Berger VLD bullets, i shot a 3 shot group, through same hole.
Today shooting 90 grain Bergers, and 108 grain Bergers/Re-19, shot a same hole group with the 108's and also another with the 90's. all at 100 yds, during load workups.
Here are some pics, from last session and also todays session.
Last week

This last session

Thanks 'Moon'

 

[number40Fan]

Take the third target down and measure one of the holes in the top right. That is the diameter that you subtract from the outside to outside of your group.

 

[Kodiak99317]

It would be best if you used a regular target instead of the shoot-n-see. On a regular target, the hole will not measure as big as the bullet, on a shoot-n-see, the hole is still the same, but the 'splash' or yellow is frick'n huge!

In benchrest we use a reticle that attaches to a caliper that you can center the hole in, lock the device to the target via a press pin, then drag it over to the furthest bullet hole, center the reticle on this hole and you have the measurement. Made by Jones.

The poor mans way is edge to edge, less one caliber but this will give you a smaller group size than it really is. Ex. group edge to edge is say .452, less .243 is a .209 group, but a single hole in the paper is really more like .234 not .243 so you edge to edge less 1 cal are smaller by about 18 thou,.243-.234*2= .018) and with the real measuring device, it would be a .227'