So if my knowledge of Harry Potter is correct wands just help channel the users energy so they can use spells. So in theory any object could be used to channel magic, and if that object is say a gun then the user could in theory cast magic spells that can bind to the bullets when they exit the barrel which would make firearms a deadly weapon against wizards and witches.
So if that's possible you'd assume they would've figured that out by now?
So let's finally get to the point I'm trying to make which is why not make a Harry Potter movie where someone shows up to Hogwarts wielding an AKM assualt rifle and everything devolves into extreme gun violence.