The Central Limit Theorem tells us that we should expect a normally distributed mean group size if we shoot enough groups with the same rifle, ammo, and conditions, but what I found interesting was Bryan’s comment that their testing shows a typical SD of 30%. I’ve worked with rifles/loads that showed more variation from group to group than others, and the CLT tells us that the SD in group size between different loads and rifles should also be normally distributed. I have to think that the SD would be smaller with ammo that is carefully handloaded in a node, and that 30% is likely with match-grade factory ammo.
