Armes
Ballista
It takes 1 action to load the ballista, 1 action to aim it, and 1 action to fire it.
Mangonels
It takes 2 actions to load a mangonel, 2 actions to aim it, and 1 action to fire it.
Blunt Ram
The ship's spelljammer can make the following attack when the ship runs into another object or into a Gargantuan creature (see "Crashing" in chapter 2 of Astral Adventurer's Guide).