Know about gallery guns that worked on the bellows principle but just heard of a 19th century example that propels the ball/dart from a charge of air created by a built in pump in the butt? That sounds a good idea.
Realising all gallery guns were probably all made as one off items for the rich in those days my question is how many different means of driving a dart down the barrel have members encountered.
I dont mean variations of the same principle.