The ballista crew chief uses material from the book Heroes of Battle
Ballista Crew Chief CR 1/2
N Medium Humanoid (Human)
, Senses ;
AC 14, touch 11, flat-footed 13 (+1 Dex, +3 armor)
hp 5 (HD)
Spd 30 ft.
Melee short sword +1 (1d6/19-20)
Ranged Light ballista +2 (3d8/19-20) or light crossbow +2 (1d8/19-20)
Combat Gear light ballista, 20 ballista bolts, light crossbow, 10 crossbow bolts, dagger, studded leather armour
Abilities, , , , ,
Feats Ballista Proficiency, Weapon Focus (light ballista)
Skills Climb +3, Profession: (Siege Engineer) +2
Ballista crew chiefs are supported by a team of 4 first-level commoners, each with 4 ranks in profession: siege engineer. Each commoner that succeeds on a DC 10 aid another check adds a cumulative +2 on the crew chief's attack roll when they fire; with four commoner supporters, two use the aid another action each round.
Loading a new bolt in a light ballista requires two full-round actions, which means two crew members can load the ballista in a single round. This allows the crew to get off one shot per round.
This build allows the use of ship-mounted ballistas. If the ballista is used in a battlefield situation, consider the possibility of heavier armor.