Typically, when any of us tests the accuracy of our guns, we shoot a bunch of groups, measure the two worst shots in each group, and then average those together. This method uses Extreme Spread to measure accuracy, and it winds up using a lot of ammunition. This kinda sucks these days, given the recent squeeze in the ammo supply.
The military, however, uses Mean Radius, which uses math, not ammo. When we use Extreme Spread to measure group size, what we are really measuring is the performance of our two worst shots in any given group. With Extreme Spread, four groups of five shots each doesn’t result in 20 measurement points, rather, it results in just eight measurement points, the two worst shots in each group.
By using Mean Radius, though, we get data points from every shot we send downrange. By using Mean Radius to measure groups, we get a clear picture of the consistent performance, rather than just feedback on the two worst shots in any particular group. However, the math of measuring groups with mean radius can be a bit tedious. The military has PFC’s to do that sort of (literal) grunt work, we don’t.
Enter the age of internet and web-based apps. Thanks to some help from a friend of mine who’s good at both such things, we’ve built a web-based Shot Group Analyzer over at Ammoman.com to help with the math part of measuring marksmanship via Mean Radius. And if you’re still confused about Mean Radius vs. Extreme Spread, well, we’ve got more info on that as well. Using this information, you should be able to quickly judge your performance with a minimal amount of rounds headed downrange.
The improving your marksmanship and getting smaller groups part of this equation? Well, that’s still up to you…