ammo vs ammunition

ammo and ammunition both are nouns.

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

As nouns, ammo and ammunition are synonyms defined as:

ammo (noun)	ammunition (noun)
projectiles to be fired from a gun	projectiles to be fired from a gun
	information that can be used to attack or defend a claim or argument or viewpoint
	any nuclear or chemical or biological material that can be used as a weapon of mass destruction