Measuring Groups

[chriswillis87]

Question. When measuring groups do you measure outside to outseide or center to center. So if you are measuring a group from a 223 centre to centre you would zero your caliper at 0.24. Correct

 

[SS427]

I measure inside to outside of the two bullet holes the farthest apart, with calipers. That effectively gives a fairly accurate center to center measurement. If you try to measure center to center, you can only approximately find the center of each hole, so the measurement isn't as accurate.

When I'm lucky and get a group so tight the outside to inside measurement can't be found because there isn't enough paper left, I measure outside to outside and subtract the caliber size to get a center to center. However, if I'm shooting a .224 bullet, I actually only subtract about .210. Why .210? Because when I measure the carbon marks left on the paper from a single bullet hole, it measures .210, not .224. Not sure why.

 

[chriswillis87]

thankyou mate i thought so. Just wanted to know cause i shoot some screamer of groups thos morning and i just wanted to measure them right. My best with my Anschutz 22 was .05 at 50m not bad aye.

 

[Gearheadpyro]

I measure outside to outside and subtract 1 bullet diamter.

 

[BoydAllen]

That will get you close, but in my experience, bullet holes are smaller than bullet diameter, and since you are measuring to the outside of bullet holes when you measure the group, you should subtract what one actually measures, if you don't want to understate your group sizes by the difference.