I was thinking about clever things to do with my pyrokinetic mages, who have the ability to heat things with their minds by burning calories of their own energy. It occurred to me they might be able (or even likely) to invent air guns in prehistory ... if the following premise holds.
The mage attaches a fiber mesh to one end of a bamboo rod and then caps it with an air bladder. He then drops a dart or pellet down the open end of the rod. The projectile hits the mesh, so it doesn't fall into the bladder. He then takes aim with the bamboo rod and uses pyrokinesis to instantly heat the air inside the bladder, causing it to expand and shoot out the rod, taking the projectile with it. As the bladder is not airtight, he can presumably quickly reload.
The basic premise seems solid to me at first glance, but I'd like to check it. I don't know if it would have adequate power and accuracy in practice, or (importantly) how many joules of energy the bladder would need per shot, what temperature the air would need to be heated to, if the bladder would require a cooling period between shots, etc.
Edit: To better clarify what I meant in the below question, I'm not just asking just the guy with the bamboo, but more importantly if and how a feasible air-based gun with that or a like design could be developed into a viable weapon, and what the construction, strengths, and weaknesses of that weapon might be. The opening is intended to explain the genesis of the design. As an example, I agree the early gun would be unreliable and inaccurate, but I'd be curious if better materials tech might change that? But back to the question.
- Would this or a similar design work effectively, or is there a better way? And what are the probable capabilities and construction of the air gun that would be in use by the time of my story during the technological equivalent of the high middle ages?