cannon fire vs firing

cannon fire and firing both are nouns.

Word	Noun	Adjective	Verb	Adverb
cannon fire	Yes	No	No	No
firing	Yes	No	No	No

As nouns, firing is a hypernym of cannon fire; that is, firing is a word with a broader meaning than cannon fire:

Other hypernyms of cannon fire include fire.

cannon fire (noun)	firing (noun)
fire delivered by artillery	the act of setting something on fire
	the termination of someone's employment (leaving them free to depart)
	the act of discharging a gun
	the act of firing weapons or artillery at an enemy