Who voted them the " best dictionary"? You?<quoted text>
Let's look at what the OED has to say about guns.
Definition of gun
a weapon incorporating a metal tube from which bullets, shells, or other missiles are propelled by explosive force, typically making a characteristic loud, sharp noise.
Note how OED - the voted BEST dictionary - disagrees with you.
However - seeing as definitions can vary, I'd like to point out that you keep saying that guns can be used as tools, but WEAPONS ARE TOOLS. Tools that are meant to cause harm.
Merriam-Webster would disagree with you....