automatic firearm vs automatic weapon

automatic firearm and automatic weapon both are nouns.

Word	Noun	Adjective	Verb	Adverb
automatic firearm	Yes	No	No	No
automatic weapon	Yes	No	No	No

As nouns, automatic firearm and automatic weapon are synonyms defined as:

automatic firearm and automatic weapon: a firearm that reloads itself and keeps firing until the trigger is released

Other synonyms of automatic firearm include automatic gun.

automatic firearm (noun)	automatic weapon (noun)
a firearm that reloads itself and keeps firing until the trigger is released	a firearm that reloads itself and keeps firing until the trigger is released