I just finished reading your analysis of musket efficiency. Not only was it a good read but you also made several interesting points. Thanks for sharing it
I had some thoughts on why firing downhill frequently led to overshooting the target. Not knowing where the data came from this can only be guess though. Brown Bess and other guns that was "sighted" at longer ranges would present a greater challenge when fired downhill (and uphill as well) stemming from the following facts:
* Firstly, the effect of gravity on the ball would be at its greatest when fired horisontally, say some 20 inches at a range of 100 yards. when fired more vertically the effect would lessen as the angle approaches vertical. Thus more compensation downwards is needed when aiming.
* Secondly, if compensation is made by moving the aiming point to lets say the knees, the change in elevation of the barrel would be less than when firing horisontally as the target would present a smaller aspect when fired downhill/uphill.
These points would be the same when firing upwards, but are the examples you got maybe of troops firing Brown Bess downwards at troops firing a charlesville "sighted" a shorter range
Anyhow a great read, I'll recommend it to others.
