A tentative date for iron shot in early shipboard cannon

Did early cannon mounted in ships use stone or iron cannonballs?

The provisional reading suggests iron shot by the middle of the fifteenth century, while allowing continued use of smaller stone projectiles.

Iron cannonballs appear to have been in use by the middle of the fifteenth century, around the period assigned here to the mounting of cannon in ships. The reading mentions cannonballs of up to 91 kg, mostly fired from bronze weapons. Smaller stone projectiles could still have been used. Cost and ease are suggested as reasons for iron's rapid adoption, though the chronology remains tentative.