Discovery, Scientific
The first firearm (not from the Modern Plane/future) is invented. These existed before matchlock guns were created, and were fired by holding a burning wick to a "touch hole" in the barrel igniting the powder inside. Fire magic or fire runes carved into the outside could also be used instead of a wick. A shooter used one hand for firing, and a prop was needed to steady the gun.
Description of guns pulled from this article.