Why I reverted to 10 shot groups by 2019.

 The 10 shot group provides a more statistically reliable picture of a firearm's accuracy because it offers a larger sample size, whereas a 3 shot group, or even a 5 shot group, might not fully represent the gun's consistency due to potential outliers in a smaller data set.  For high power rifles, a 3 shot group can be sufficient for quick assessments in certain situations, especially for hunting.  Even though, 10 shot groups are best with high powered rifles using factory ammunition, or mediocre handloads.