shelling vs firing

shelling and firing both are nouns.

Word	Noun	Adjective	Verb	Adverb
shelling	Yes	No	No	No
firing	Yes	No	No	No

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

shelling: the heavy fire of artillery to saturate an area rather than hit a specific target
firing: the act of firing weapons or artillery at an enemy

Other hypernyms of shelling include fire.

shelling (noun)	firing (noun)
the heavy fire of artillery to saturate an area rather than hit a specific target	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