A nine-gun battery can fire one gun from each turret in three successive groups and then repeat the cycle. Each group supplies another data point while both the firing ship and its target continue to move. That rhythm lets the fire-control team walk the barrage toward the enemy instead of waiting on a single full salvo. Six guns can still work, as Renown and Repulse demonstrate, but their 15-inch weapons cycle much faster than Incomparable's proposed 20-inch guns. Gun number and reload rate therefore determine how quickly a nominally powerful battery becomes effective fire.
Notable Point · 5:43-8:04
Why gun number matters for ranging fire
Nine guns can be divided into repeated ranging groups, while a six-gun battery gives a slower-firing weapon fewer opportunities to correct onto a moving target.