unit of ammunition vs one shot

unit of ammunition and one shot both are nouns.

Word	Noun	Adjective	Verb	Adverb
unit of ammunition	Yes	No	No	No
one shot	Yes	No	No	No

As nouns, unit of ammunition and one shot are synonyms defined as:

unit of ammunition and one shot: a charge of ammunition for a single shot

Other synonyms of unit of ammunition include round.

unit of ammunition (noun)	one shot (noun)
a charge of ammunition for a single shot	a charge of ammunition for a single shot