“The epicenter was a major production center of gunpowder
[…]
a military storage facility that "dispatches 3000 catties (about 1.8 metric tons) of gunpowder every five days"”
This was 400 years ago, about 800 years after the invention of gunpowder (https://en.wikipedia.org/wiki/Gunpowder#China) and about 600 after the first primitive guns (https://en.wikipedia.org/wiki/Gun#History)