Maximum range is described as firing with the greatest charge and elevation to send a shell as far as possible. That does not necessarily produce the most accurate fire, because dispersion can be greater. Effective range concerns whether the spread of shots is still useful against the intended target. The French gun is tentatively credited with the greater maximum range, while the Italian gun is credited with greater effective range. Caracciolo's seven-knot speed advantage matters because it could try to keep the engagement at the distance that favoured its own guns.
Notable Point · 1:26:25-1:27:41
Why effective gun range differs from maximum range
The Lyon-Caracciolo comparison separates a shell's maximum reach from the range at which dispersion permits useful fire.