noun
General term for handheld firearms such as rifles and pistols; does not typically refer to cannons or artillery.
彼は銃を構えた。
He raised his gun.
この国では銃の所持が厳しく規制されている。
Possession of firearms is strictly regulated in this country.
鉄砲 is a broader, older term for guns, including matchlocks and sometimes cannons; 銃 is the modern standard word for small arms.
拳銃 specifically means 'pistol' or 'handgun', while 銃 is a more general term for firearms.
The kanji 銃 is a phono-semantic compound: the metal radical 金 and the phonetic 充 (じゅう). The character originally referred to an ancient weapon, later adopted for 'gun'.