Huh? That's field artillery, not guns.
Huh? Field artillery is the most justifiable use of the descriptor "guns". Handheld weapons should ideally be named according to their subtypes (pistols, rifles, etc), with "gun" as an acceptable abbreviation for "shotgun".
Call your rifle a "gun" during basic training in the British Army, and you can expect a world of humiliation and abuse from your NCOs. Artillerymen have guns. Riflemen have rifles. Officers have pistols.
Ask a gunsmith, and he will tell you that even artillery is mostly rifles these days. In the technical usage, "gun" implies a smooth bore (hence its applicability to shotguns).