Looking at Chinese images of crossbowmen, I realized something I had not noticed before, that the Song dynasty crossbows were quite a bit different in design from the Han dynasty crossbows. I knew that Ming dynasty crossbows had a different design than those of the Han dynasty, but that had been assigned to be due to the use of guns in the Ming Dynasty. But that explanation doesn't seem to account for the change in Song dynasty crossbow design, since hand cannons really didn't become a factor toward the end of the Song dynasty or even into the Ming dynasty.

Han dynasty crossbows typically located the trigger at the end of the crossbow stock, and the pulled the string back all the way to the end of the stock, as can be seen in the picture below






The Han dynasty crossbows, those found in the tomb with the Terra Cotta army, and in Han dynasty images, all show crossbows with relatively short stocks and and the trigger located at the end of the stock. But images of Song dynasty crossbows show a significantly different design, with much longer stocks, and triggers obviously not at the end of the stock.

Looking at this image of Northern Song dynasty crossbows (but painting dates from the preceding Yuan dynasty) slung over the shoulders of the front rank of horsemen, you can clearly see the crossbows are ot like the Han dynasty crossbows. The other thing interesting to note is that these Song crossbows have a foot stirrup, which the earlier Han dynasty crossbows did not have. The foot stirrups show up on medieval European crossbows at around the same time period. Could there have been some transmission of the idea of a foot strap from China to Europe, perhaps via the Mongols? It is not clear where the foot strap shows up first, China or Europe.



Looking at this image from a Ming dynasty handscroll, you can clearly see a crossbow on the right very similar to the Song dynasty crossbows above. The crossbow trigger is nowhere near the end of the stock. At least some of the Ming dynasty crossbows did not have foot stirrups, as one can see from the crossbowman on the left of the scroll. Note also, the crossbow on the left has a considerably shorter stock than the crossbow on the right, and is being held in a different position to shoot. The crossbow on the right




But pictures from a 1621 text of Ming crossbowmen toward the end of the Ming dynasty show crossbows more similar to the Han dynasty crossbows, with a shorter crossbow stock and again the string pulled back closer toward the end of the stock, but not all the way to the end aa you saw with Han dynasty crossbows. It is hard to see, but these Ming crossbows are using foot straps to cock the crossbow, not solid foot stirrups as on the Song crossbows The draw length of these Ming crossbows are also shorter than Han dynasty crossbows, and the prod is a different shape.




The Song dynasty crossbow actually look somewhat similar to the crossbows we see on these medieval Genoese crossbowmen below. The prod of these Genoese crossbows are considerably wider than you often see on medieval European pictures of crossbows, and based on the trigger location, might have a longer draw length, more similar to the Song dynasty crossbow.




One thing to also note, is that the Han dynasty crossbow prods have an "M" type shape to them, typical of the normal hand bows, which have the same M shape to them. If you look at the far right side of the upper picture for Ming crossbows, you can just make out this "M" shape on the normal bow. The Song an Ming crossbows all have a thicker prod, without this "M" shape, similar to the European crossbows. This suggest the Song and Ming crossbows might have had higher draw weights, but seem to have had a shorter draw length than the Han crossbow.