How accurate is my rifle

[stokesrj]

Center to center is the proper way to measure, which is the same as outside edge to inside edge of widest shots. However three shot groups, although not meaningless are a poor indication of the rifles capabilities. MOA gus will occasionally shoot three shot groups in the .2 MOA range but that does not mean they are .2 MOA guns, if you shoot five groups of five shots and take the average then you have a meaningful measure of your guns capabilities for hunting and informal target work. For serious work I require my match rifles to group 20 shots in .5 MOA because it is typical to shoot 20 shot strings in the matches I participate in.
Bob