Produce cannon balls out of 2 unprocessed iron.
- These can be 1-2 levels below your cannons.
- You don't need these as leveled as Arrow Factorys.
- As cannons aren't as important in the midgame, you don't need to focus on them as much as the other defenses ammo sources.
- Make sure to check your production with the z button. If red increase iron production.
- Be careful upgrading these, as it's iron use can stifle arrow production.
- before placing/upgrading these, make sure your defense towers are upgraded/placed.
Characteristics at different levels
 original reference