Well Jim,
It is of general knowledge that gunpowder was infinitely less potent in those days (Ming dinasty), as also the signaling hypothesis must not be discarded; indeed they had signaling systems in the wall, so called Beacon Towers.
But i take it that the explanation for this stone cannon phenomenum must reside somewhere else.
It would be great to get enlightened by some of our forum mates ... the first to find out about it
.
Without such explanation, i would even wonder whether the loading breech is not occupied with a (shifting) chamber but simply filled directly with gunpowder and closed with a locking lid ... or some other sort of Colombus egg
.
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