The potential of the crossbow was well understood by the ancient Chinese. The trade-off for the simplicity and added accuracy over the bow was the low rate of fire. Reloading the crossbow was a cumbersome task, especially in its simplest designs. In a defensive situation, such as a siege, where the crossbowman could take cover behind walls to load a new projectile, the crossbow made good sense. But in a military formation of an offensive battle, where two armies were about to collide, an army of few archers did significantly more damage than a large group of crossbowmen simply due to their higher rate of fire. The Chinese knew this, so they began developing what can perhaps be viewed as one of the great grandfathers of semi-automatic weapons – a repeating crossbow.
The chinese repeating crossbow is nothing short of genius. It featured a projectile magazine fixed on top of the stock and a lever mechanism that reset the bowstring that would serve as a trigger at the same time. By pulling the lever forward you lift the entire magazine moving it forward, until it would latch the bow to the back of the magazine. By pulling the lever back, you stretched the bowstring back until the magazine made contact with a special pin that pushes the bowstring into the magazine, releasing the projectile inside. To illustrate just how fast you could shoot, imagine shooting a bolt-action shotgun, except the motion is done above the weapon’s stock, and completing the motion automatically fires the weapon without pulling the trigger. With this weapon, the crossbowman could now rival the firing rate of the archer. The minimal amount of moving parts, and the ability to make the weapon almost entirely out of wood, without the need for a bronze bolt mechanism, meant that this weapon could be produced on mass.
However, as with any weapon that has a release mechanism, that mechanism had a tendency to jam. While the manufacturing process was not complex, if it was sloppy, the crossbow would jam repeatedly, making it unusable in the battlefield. The trick was to make the bow enter the magazine neatly so that it wouldn’t jump in between the ammunition. The gaps within which the bow travels had to be carved out with relative precision. But even in the best made crossbow, as the firing speed increases, so does the probability of jamming. The most challenging part was the bow string. Its tension must be just right for the amount of travel it required, while also maximising the force with which the projectile is released. The chinese chrossbow’s string was made primarily from twisted animal sinew and had bird quills added to reinforce it and make it more durable. This was perhaps the greatest limit on how many crossbows could be produced in a short period of time, and why making a makeshift bowstring mid-battle was nearly impossible. This also meant that the power of the weapon was fixed. The average crossbow had a range of about 100 meters, with about 70 of those meters being lethal. The longbow, for comparison, could project an arrow as far as 300 meters.