This technique comes from the CMP Garand Match. Say you are right on the line. You look at it, your scoring partner looks at it. The match director looks at it. Usually, if it takes all that, I say give them the point. But in cases where no one is sure, you take an unfired round, or a specially made plug in the correct caliber, and insert it in the hole. That reshapes the hole to the full diameter and removes any doubt.
In this case, I used an unfired .22 round. When inserted, it clearly shows this as cutting into the line of the scored area. If you have doubts about a hit/miss decision, try this. It usually makes the decision clear.
I got to the range late this afternoon. Practiced a while, then shot one target. 11 hits in the black, counting the one you see in the picture. The groups are at least clustered around the centers, sort of. Certainly better than yesterday. If I can, I’m going to try again next weekend. How are your efforts coming? Let me have some preliminary reports.
Practice is the best of all instructors.