Triple-turret guns were staggered to control muzzle-blast interference

Why does the centre gun in some triple naval turrets not extend as far as the outer guns?

The stagger reduces muzzle-blast interference, although recoil position can also make the guns look uneven in photographs.

Staggering the centre gun helped prevent pressure waves from three nearby muzzles from combining at the same instant. Photographs can also exaggerate the effect when one gun is at a different point in its recoil cycle. British dummy-shell trials showed that blast interaction could knock shells off course. Turret geometry and firing sequence were therefore ballistic problems as well as mechanical arrangements.