How To Measuring Group Size??

[Winged]

My son and I are VERY competitive. Earlier today while getting to know my new Wildcat .25, it naturally turned into a competition and when we were measuring "who's group was the best" we noticed the holes were quite ragged, so determining the exact center of the hole somewhat ambiguous.

​Would be it valid to measure outside to outside of the most distant shots and subtract the bullet diameter to yield the size of the group center to center?

​And just for the record I did win and may have cheated inadvertently (sort of), gave my son the gun to shot after it dropped below 140 bar, ie off the regulator, or wouldn't that be considered wisdom winning over youth? I have a feeling I'm gonna get a phone call when he reads this post!

 

[Strikey]

I use digital vernier calipers to measure my groups, zero them on the diameter of the pellet and measure to the outside of the holes or you can measure from the inside to the outside of the holes that are the furthest apart, both methods should give the same measurement. If your targets are paper try glueing them onto thin cardboard, the type kids use for school projects, I find the pellets cut a better hole making it easier to measure groups.
Or you could download some of the target measuring apps off the net, I'm still learning how to use one called Range Budd probably not the best but it is a bit of fun,
And letting the rifle drop off the reg before handing it over is cheating but I also take any necessary steps to stop my son from making me look average