Here is a watercolor of ca. 1410 from the famous Cod. vind. 3069, fol 40, Austrian National Library, Vienna. The gunner is depicted firing a smaller
Steinbüchse by means of a long igniting iron* (
Loseisen). A lime stone ball (not to scale as was usual at that period of time) is seen leaving the muzzle and flying over the moat towards a tower as part of the wall of a city laid siege to.
Two details are remarkable:
- the way the guy is balancing a bowl with stone balls in his left hand (which does not really make much sense

)
- the carriage is already adjustable in height and its wheels show a very special form of parallel spokes (
Parallelspeichenräder) characteristic of the alpine regions where they were kept in use for hundreds of years until the early 20th century.
*For a detailed discussion of igniting irons and linstocks, please see my thread
http://www.vikingsword.com/vb/showthread.php?t=10029
Best,
Michael