They must have moulded the balls in probably an earthen die-cast, and then machined off the gates on a small mobile lathe. That is easy. They might even have acheived some buffing/polish-milling.
What would be even more wondrous is how did they do the buffing/polishing on the inside of the cannons (did they?). Certainly that will be needed for the guns if not cannons. Was boring operation/machine known to them? Or did they just hand-polish?
A portable hand lathe in ancient India:
<img src='http://ourworld.compuserve.com/homepages/jeharr/indlathe.jpg' border='0' alt='user posted image' />
<!--QuoteBegin-->QUOTE<!--QuoteEBegin-->turner sitting down and guiding the turning tool across the tool rest with his toes while controlling the tool at its handled end with his hands. An assistant provides power by alternatively pulling on each end of the cord wrapped around the workpiece. (From Holtzapffel, vol. IV)
http://ourworld.compuserve.com/homepages/j...history.htm#h1a
<!--QuoteEnd--><!--QuoteEEnd-->
What would be even more wondrous is how did they do the buffing/polishing on the inside of the cannons (did they?). Certainly that will be needed for the guns if not cannons. Was boring operation/machine known to them? Or did they just hand-polish?
A portable hand lathe in ancient India:
<img src='http://ourworld.compuserve.com/homepages/jeharr/indlathe.jpg' border='0' alt='user posted image' />
<!--QuoteBegin-->QUOTE<!--QuoteEBegin-->turner sitting down and guiding the turning tool across the tool rest with his toes while controlling the tool at its handled end with his hands. An assistant provides power by alternatively pulling on each end of the cord wrapped around the workpiece. (From Holtzapffel, vol. IV)
http://ourworld.compuserve.com/homepages/j...history.htm#h1a
<!--QuoteEnd--><!--QuoteEEnd-->