perhaps a dumb question.... How exactly do you measure group size???

[JASmith]

For whatever reason, bullets usually make a hole smaller than its caliber. Perhaps the resident physicists can explain. I always measure the size of the holes getting punched by the particular bullet in the particular paper that day and subtract THAT from edge to edge.

The bullet point tends to shove the paper aside. The effect is more pronounced at low impact velocities.

It is also the reason wadcutter bullets were very popular among competition shooters who used revolvers. Semi-wadcutters work almost as well and are more friendly to semi-auto pistols.