I was watching a TV show with my grandfather. It was the year 1979 if memory serves me well. A war movie with howitzers or cannons or something. Big guns that went BOOM! I said, "Grandpa, look at that big firearm!" He said, WHAT!! What are you talking about...fire arm???" I then asked him what those cannons were called then. He said that those were guns. I learned then you cannot use firearm and gun interchangeably in every context of something that shoots and makes a lot of noise. Gramps was actually an army vet from World War Two and therefore military-minded. He also taught me at age 13 that riles in the army are weapons and not guns.