[Dale Rader]

Since it is very difficult to "eyeball" the center of your bullet holes, measure your groups outside to outside and then subtract one bullet diameter (.308") to give you your center to center measurement. All groups are measured center to center.

Dale

 

[Dale Rader]

I just read your post again and looked at your picture. You need to find the two bullet holes farthest apart to measure them. Not necessairlly side by side, it may be at an angle or top-bottom. The four holes I see in your photo are larger than a 1/4" group. not sure where your fifth round is. Measure your holes from top right to bottom left and see what your group size is. (Your calipers appear to be off also. Your 1/4" is larger than your .308" bullet hole!)

Dale