<Snipped quote by Nerevarine>What separates early-mid medieval ages from late medieval ages can be often narrowed down to guns and metallurgy.
Actually, metallurgical developments weren't even new that big since other cultures had blast furnances prior. Guns and chemistry are a similar deal or the idea of military drills.
We have random pieces lying around which people can use as inspiration. I think it does make sense if people catch up with them.
Not saying we'd go beyond the medieval setting but for example seeing a modern gun would put the idea in people to make their medieval weapons shaped more like that. Which is strangely means in a certain aspect that leads to hundreds of years of leap in gun development (firearms took a "gun-like shape" by the 16th century). Mechanism of a modern gun can also help people inventing mechanical locks for guns earlier.
With 12th century developments things are still rather crude in quality but the above for example still aid them to create better tools.
Also it'd lead them to make plate armors and more decent quality metal products early.
Those are just my thoughts on the matter.
While that is fair, It really depends on how much PolishKing wants to diverge from the source mod (being Crusader Kings, it follows the Middle Ages up to the End of the Crusades). I'd rather not diverge too far from his vision of the RP
As pointed by Dinh, the use of automatic and semi-automatic is probably very very inefficient in a pre-industrial setting, and so I imagine firearms to be rather primitive, but I also do see them being more advanced than what we would have seen in the actual 12th century.