ordnance vs heavy weapon

ordnance and heavy weapon both are nouns.

Word	Noun	Adjective	Verb	Adverb
ordnance	Yes	No	No	No
heavy weapon	Yes	No	No	No

As nouns, ordnance and heavy weapon are synonyms defined as:

Other synonyms of ordnance include artillery, gun.

ordnance (noun)	heavy weapon (noun)
military supplies	large but transportable armament
large but transportable armament