Lances are directed-energy weapons scaled to deliver a concentrated blow against a warship. Their housings are so power-hungry that cruiser and light-cruiser batteries are often fixed along the hull, while only grand cruisers and larger ships can carry them in more flexible dorsal turrets. That engineering constraint is credible, but fixed batteries could still be angled to overlap ahead as well as on the broadside. The example separates a mounting limit from a design decision about how the available arc is used.
Notable Point · 2:16:40-2:20:14
Lance power comes at the cost of flexible mounting
Lances deliver concentrated ship-breaking energy, but their power and mounting requirements leave many cruiser batteries fixed into narrow arcs.