The ballista was an ancient weapon that launched either bolts or stones at a distant target. This replica ballista is on display in our museum at Melrose.
The ballista was a highly accurate weapon but accuracy could be compromised for range. The maximum range was around 500 yards (460 m), but effective combat range for many targets was far shorter.
The Romans consistently aimed to perfect the development of the ballista and it became a highly prized and valued weapon in the Roman army.
Early Roman ballistae were made of wood and held together with iron plates around the frames and iron nails in the stand. The main stand had a slider on the top and bolts or stone shot were loaded into this. A pair of winches and a claw were used to ratchet the bowstring back to the armed firing position, these were attached at the rear of the device.
A type of short, solid arrow point was found in the ditch of the Trimontium fort in the pits at Newstead. It measured about 3¼ inches in length and had a circular or heptagonal head that would accept a wooden shaft. They have been associated with the sockets with a spherical end as illustrated in James Curle’s paper. It’s possible these sockets were fitted to the ends of shafts and may have served as ballista-bolts.
http://www.curlesnewstead.org.uk/platexxxvi.htm
http://www.curlesnewstead.org.uk/platexxxviii.htm
To See Curle’s volume, online in full :