Ok well, maybe we need to trace a hard line whether or not guns have been invented even simple ones?

Regarding history, keep in mind that:

-People at that time may not realize yet that guns are going to change warfare and also some aspect of society (No more armor, stoned wall castle and walled cities become less important) We do because it happened in the past that's why it's so obvious.
-Changes usually take time and do not happen on a dime. For example, 1492 did not change the world much as 1453. In 1453 the political world changed significantly, thus marking the beginning of the Renaissance but that's more like an exception. 1750 is often regarded as the beginning of the industrial revolution but factories and railroads only became important around 1820-1830 in Europe.