heavy weapon vs armament

heavy weapon and armament both are nouns.

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

As nouns, armament is a hypernym of heavy weapon; that is, armament is a word with a broader meaning than heavy weapon:

heavy weapon (noun)	armament (noun)
large but transportable armament	the act of equipping with weapons in preparation for war
	weaponry used by military or naval force