gunnery vs arms

gunnery and arms both are nouns.

Word	Noun	Adjective	Verb	Adverb
gunnery	Yes	No	No	No
arms	Yes	No	No	No

As nouns, arms is a hypernym of gunnery; that is, arms is a word with a broader meaning than gunnery:

Other hypernyms of gunnery include implements of war, munition, weaponry, weapons system.

gunnery (noun)	arms (noun)
guns collectively	weapons considered collectively
	the official symbols of a family, state, etc.