Library
The statistics of precision shooting, explained with pictures. These articles cover the ideas behind every number DimeShooters reports, written for shooters first and backed by the math for those who want it.
The Rayleigh σ: One Number for Your Rifle’s Precision
What the Rayleigh sigma is, explained with pictures: where the number comes from, what it looks like on a target, why the R50/R90/R95 circles are fixed multiples of it, and why no measure of the same shots can beat it.
Read the articleExtreme Spread: What It's Good For, and What It Isn't
When to trust extreme spread, the most common group measure, and when to reach for something better: what it measures, why it is fine for a quick read of one small group, and why it wastes rounds the moment you compare loads or build a record.
Read the articleMean Radius: The Intuitive Measure of Group Size
The most intuitive way to size a group: the average distance of your shots from the group center. What it measures, the two ways to arrive at it, why DimeShooters measures it directly rather than deriving it from the Rayleigh sigma, and why the raw average reads low for small groups until it is bias-corrected.
Read the articleWhy Sample Size Matters: How Many Shots Make a Group?
How much a 3-shot group can lie, why bigger groups are simply bigger, what your best group hides, and how many shots real decisions actually take: the statistics of small samples, in pictures.
Read the articleComposite Groups: Split Your Rounds for Free
Why splitting a round budget across many aim points costs nothing for the Rayleigh sigma and mean radius: DimeShooters combines shots fired at different aim points into one composite group, as precise as a single big group of the same size, right down to a single shot at each aim point.
Read the articleDensity Altitude: One Number for the Air You Shoot Through
What density altitude is, why shooters trade dope by it, and exactly how it is calculated from temperature, pressure, and humidity: the standard atmosphere, worked formulas, and what a summer day does to your 1,000-yard dope.
Read the articleReference
Data rather than argument: tables, sources, and tools to look something up and take it with you.
The Precision Statistics Library
A curated, maintained bibliography of the primary sources behind the statistics of shot dispersion: every entry annotated with what it establishes, where to get it, and what its copyright status actually is.
Open the referenceRange Statistics: Extreme Spread Tables
What a group of a given size is expected to measure and how much it varies by chance: extreme spread, mean radius, and Rayleigh sigma for every group size from 2 to 300, with quantiles, stated uncertainties, and a converter.
Open the reference