Thread: 10 Shot Groups

Originally Posted by Stocky

So in my test rifle thread @Roarless20 brought up he thought there was something mechanically wrong because some if the 5 shot groups are rather large (he very well may be right). He may be right and once I have a baseline accuracy for the rifle things like Bedding, action screws torque, recrown, etc will all be tested and eliminated. He may be right but I think some of the reaction is people actually don't know how well their rifle shoots especially over larger sample sizes.


Statistical variance suggests typically a 5 shot group will be around 1.3 times larger than a 3 shot group on average.

And a 10 shot 1.3 times what the 5 shot was on average.

From there it's slows only usually increasing around 1.2times for the 20 shot group and so on.

That would mean a 1moa 3 shot group is more like a 1.3moa 5 shot or a 1.7 10 shot or a 2 inch 20 shot. Likely representing a true rifle precision in the 2-2.5moa range. Off course any 3 shot group could be the closest 3 shots or the worst. But on average they are likely.

Note that this correction factor applies to the AVERAGE group size. The AVERAGE 3-shot group size, established over enough groups to get a reasonably accurate mean, will increase by 15% to the AVERAGE size of 5 shot groups with the same system. A single group of less than 10 rounds tells you almost nothing, as the size varies wildly: 70% up or down from the average for 3-shot groups. Did you shoot a single 3-shot group at the minimum end, the average, or the maximum end? Who knows.