I was just thinking he would make the connection between the dragons and infantry weapons and might come up with something like a blunderbuss or musket. He's already going to be mining a lot, so how about some musket shot too.

Even a primitive gun might require more complicated parts though. And in terms of load time, unless he used pre-made paper powder cartridges like the British were using in India circa the Sepoy Rebellion, I could see it taking longer to powder, pack, load, and fire each time than his already pretty good rate with the crossbow cranks.

Incidentally, the handgun form of a blunderbuss (early shotgun) was apparently sometimes referred to as a dragon.