What is the best way to measure 3 shot groups on targets

[Wildhog]

Ive read to measure the 2 furtherest holes outside to outside and subtract the OD of bullet your using. Also if a dime covers 3 shots its .50 inches. also center to center to center and divide by 3 which I would think to be ballpark. would like to know the most widely used method without using a tool made for this. Your response would be appreciated. Thanks Stan

[CRNA]

I always do outside to outside minus bore like you mentioned above.

[grizlywinkleman]

I just measure the two shots furthest from each other from the center of the holes and call it a day.

[rscott5028]

Center to center of the farthest two shots.

Or, outside to outside of the farthest two shots minus the bullet diameter.

Either of these works for me.

I'm more interested in group after group after group consistency than I am about measuring a single group to the nearest .001".

-- richard

[Mikecr]

For consistency, I go furthest center to center.
For accuracy, I go furthest center to center of mark.

Hole diameters won't likely match actual bullet diameters.

[Gene]

Many years ago, I measured outside edge of two widest holes. After I started shooting benchrest, I began measuring wide spread, then deduct the bore diameter.

It doesn't matter which you use for your personal records. The important thing is to always use the same system, and keep good records. On the computer, I run a spread sheet for each gun. I record date, temp., wind, no. of shots, case, powder, primer, bullet, OAL, sizer bushing, trim length, group size and a few notes. It makes it easy to return to my records and find the best load.