There is an article somewhere regarding a clockwork Italian gun from the early 17th century, but I haven't been able to find it. It launched ammunition like a modern spring-air rifle and was truly fully automatic. (you wound it up and a trigger pull controlled firing). You used to be able to do an internet search for "clockwork gun" and it would come right up, but apparently some video game has a clockwork gun and four Google pages deep that and steampunk props are all I can find.
I ran into the same thing recently trying to explain to someone that the first "car" was steam powered and that it was built in France in the 18th century. It is easier to find, but still pretty buried.