A shot group carries three separate measurements — how big it is, how consistent it is, and where its centre sits. Only the last one is fixed with a turret.
Five holes in paper answer three different questions: how tight the rifle-ammo-shooter system shoots, how honestly that tightness was measured, and whether the sights point where the group lands. Mixing those up is how people dial turrets to fix a shooting problem, or blame ammunition for a sight problem.
Extreme spread — centre-to-centre distance between the two widest shots — is the number everyone quotes, because it needs only a caliper. Its weakness: it is defined by the two worst shots and ignores everything else, so it only ever grows as you add rounds. A “half-MOA” 3-shot group and a half-MOA rifle are very different claims.
Mean radius is the statistician’s answer: it uses all the shots, converges on the system’s true dispersion after 10–15 rounds, and barely moves when one flyer lands wide. Two groups with identical extreme spread can have very different mean radii — the one with the smaller mean radius is the better-shooting rifle.
The third number is the offset between the group’s centre and where you were aiming. This is the only one of the three that is a zeroing problem — and the only one the turrets can fix. Measure the offset in inches, convert to your turret’s unit at that distance, dial, confirm.
| GROUP | GOOD FOR | NOT GOOD FOR |
|---|---|---|
| 3 shots | Rough zero check, barrel warm-up | Any claim about precision |
| 5 shots | Zero confirmation, load comparison | Bragging-rights group size |
| 10+ shots | True dispersion, mean radius | Cheap afternoons |
Photograph your target and the analyzer returns extreme spread, mean radius and the exact click correction to centre the group.