Refers to large firearms such as cannons and artillery pieces, often in military or historical contexts.
The enemy artillery fired heavily.
Old cannons are on display at this museum.
火砲 refers to the artillery guns themselves, whereas 砲火 refers to the fire or flame they produce.
Compound of 火 (fire) and 砲 (cannon, gun), literally 'fire cannon'. The exact historical derivation is uncertain, but the spelling is conventionally associated with large firearms.