A trebuchet (French trebuchet) trébuchet is a type of catapult that was used as a siege engine in The Middle. Ages it is sometimes called a counterweight trebuchet or counterpoise, trebuchet to distinguish it from an earlier weapon called the traction, trebuchet where men pulling ropes provided the. powern 1421 the future Charles VII of France commissioned a trebuchet (coyllar) that could shoot a stone of 800 kg, while in 1188 at Ashyun, rocks up to 1,500 kg were used. Average mass of the projectiles was probably around 50–100 kg, with a range of c. 300 meters.