Cheiroballistra

The cheiroballistra was a Roman siege engine from the imperial period. It shot bolts that were smaller than those in other types of ballistae and mainly made of metal. It was designed by Hero of Alexandria and was mostly built of metal (the spring mechanism and the skeins). It was the next significant advancement after the Scorpio. The Scorpio was a sort of Roman torsion siege engine and a field artillery piece. It was recorded in detail by the early-imperial Roman architect and engineer Vitruvius in the first century BC and by the officer and historian Ammianus Marcellinus in the fourth century AD. The scorpio was a small version of the ballista. Its reduced size, metal head, and concave arms provided it with better accuracy and power, allowing it to fire metal bolts with enough force to rip through two opposing soldiers at once under competent hands.

Another first-century CE creation was the cheiroballistra. The weapon was also small enough to be operated by a single shooter and was almost entirely made of metal, including the arms, making it more weather resistant and accurate enough that a sight arch could be inserted between the two copper-encased springs. The weapon's name is a combination of the Greek words for "hand" and "shooter," hinting that portable versions, akin to crossbows, may have existed (a crossbow is a ranged weapon using an elastic launching device consisting of a bow-like assembly called a prod, mounted horizontally on the main frame called a tiller, which is hand-held in a similar fashion to the stock of a long firearm).