How are those actually measured? Surely not with calipers.
I need to find a photo of the device. i gave mine a few years ago to a club in Michigan. It is a device that mounts to a caliper. It has 3 circular reticles for 22,6mm, and 30 cal. While looking through an attached magnifying piece you center the the circular reticle over the bullet hole to one side and open the calipers until it was centered over the furthest bullet hole. kinda hard to explain without seeing the device. possible World Record groups are sent to the committee of 3 that independently remeasure the group or groups. Also, to eliminate cheating, Short Range BR mandates that behind the targets are both a stationary backer and a moving backer. They have to be sent with the targets to the committee. The moving backers will have to have 5 holes in them.
My 2 unlimited guns weighed about the same as DocEd's. They are a great tool for a person to learn how to read wind conditions. I sold mine as we just didn't have enough matches to justify one. My last one was sold to a Canadian that lived in the eastern part of Canada.