weapons system vs ammo

weapons system and ammo both are nouns.

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

As nouns, ammo is a hyponym of weapons system; that is, ammo is a word with a more specific, narrower meaning than weapons system:

Other hyponyms of weapons system include ammunition, armament, bomb, defence system, defense system, gunnery, hardware, naval weaponry.

weapons system (noun)	ammo (noun)
weapons considered collectively	projectiles to be fired from a gun