Has anyone ever worked up numbers for a Qin crossbow? I just saw the Emperor's Ghost Army on Nova
http://www.pbs.org/wgbh/nova/ancient/emperors-ghost-army.html and a historian claimed the weapon was "two millenia ahead of its time." A test firing shows it penetrates laminated armor, etc. The mechanics supposedly allowed it to be used by peasants and fired much faster than European crossbows that had cranks, etc. Seems like it would make play unbalanced, but I'm curious.