weapons system vs arms

weapons system and arms both are nouns.

Word	Noun	Adjective	Verb	Adverb
weapons system	Yes	No	No	No
arms	Yes	No	No	No

As nouns, weapons system and arms are synonyms defined as:

Other synonyms of weapons system include implements of war, munition, weaponry.

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