Why Repeating Crossbows not common in history?
Channel: Historical Weapons
Date: 2020-05-29

I know that repeating crossbows did exist in history, but why were they not widely adopted elsewhere? The Mongols spread gunpowder but why not the repeating crossbow? 
After seeing Joerg Sprave from the Slingshot Channel and his Instant Legolas devices, it got me wondering. Other cultures could have improved the device and potentially make a more effective repeating crossbow, but this idea never took off besides East Asia and Europe.

Regarding the existence of the Instant Legolas, we do not have historical evidence of this specific design, but there were similar rapid arrow shooting devices used throughout history, such as the Chinese repeating crossbow or the Greek polybolos. Now archers of various cultures throughout history were able to shoot similar speeds, without any devices. In fact, there are specific archery techniques that I will show you today, which will allow you to shoot similar speeds compared to the instant Legolas.  Some of these techniques are more commonly mentioned in historical texts while others have very scarce references, but shoot faster. 

So even though we have historical repeating devices in history, why did they not become popular, fielding massive armies of these? In fact the Mongols invaded China and have seen repeating crossbows, so why not use them?
I have 4 reasons.
firstly, the bow is simpler and cheaper to make. Even during ww1 when semi auto guns were emerging the average infantry carried the simpler bolt action rifle. Same concept here. You can't beat that simplicity.
secondly. Many professional soldiers had armor or shields at the time, so a light poundage bow would not be very useful.  Sure you could put a heavy bow on these devices but then you would be decreasing your rate of fire, and keep in mind tire your solders a lot more quicker. The English and various Asiatic cultures used heavy bows above 100lbs,  which are more suitable to penetrate shields and medium armor but they required a lot of strength to use. Certainly there would be situations were shooting rapidly could be useful, such as shooting at unarmored people or animals, prisoners, flanking maneuvers to shoot at the unshielded sides, or for reducing the enemy's morale. 
The third reason why repeaters were not common is because other ranged weapons may be more suitable for close range such as javelins or throwing axes, and none of those require complicated mechanisms and are fast enough and deadly at close range. eventually at point blank range you need to switch to a melee weapon. and these repeating devices are cumbersome to switch without breaking.
And finally my last point is, Archers can shoot similar speeds to the instant Legolas.
Here is me, not lars anderson, speed shooting 5 arrows very rapidly. This is a variant of the Slavic draw which was only mentioned in the text " Arab Archery" during the medieval period. The Slavs (al-Ṣaqālibah) have a peculiar draw which consists of locking the little finger, the ring finger, and the middle finger on the string, holding the index finger outstretched along the arrow, and completely ignoring the thumb. What this does is it allow you to have a thumb to hold the arrows conveniently like a magazine, which allows the arrows to be loaded very rapidly. But this was only mentioned in one historical text. And more importantly I used wide nocks so it is easier to nock these arrows.  This increases your chance of dry firing which can damage the bow, and will throw off the arrow flight and accuracy. Now if you used normal nocks which are not wide gap, you can see I am struggling a lot more to shoot rapidly. Yes Lars Anderson employs a variation of this technique.
Here is a more common and more reliable draw style, the Mongolian thumb draw. Look how fast he shoots even though he is pulling the arrow from the quiver one by one. Here are some other variants of speed shooting which I would like to discuss in the future, but my point is, you can shoot very fast already without a device. The time difference between this and repeaters is negligible. Also keep in mind arrows were not cheap to make. Often you would want to make sure each shot counted so many archers would take their time shooting each arrow with heavier draw weights. As a garrisoned archer in a city during a siege, you would want to make sure each arrow counts.

Music:
Wholesome by Kevin MacLeod
Link: https://incompetech.filmmusic.io/song/5050-wholesome
License: http://creativecommons.org/licenses/by/4.0/