belt ammunition vs ammo

belt ammunition and ammo both are nouns.

Word	Noun	Adjective	Verb	Adverb
belt ammunition	Yes	No	No	No
ammo	Yes	No	No	No

As nouns, ammo is a hypernym of belt ammunition; that is, ammo is a word with a broader meaning than belt ammunition:

belt ammunition: ammunition (usually of small caliber) loaded in flexible linked strips for use in a machine gun
ammo: projectiles to be fired from a gun

Other hypernyms of belt ammunition include ammunition.

belt ammunition (noun)	ammo (noun)
ammunition (usually of small caliber) loaded in flexible linked strips for use in a machine gun	projectiles to be fired from a gun