automatic pistol vs handgun

automatic pistol and handgun both are nouns.

Word	Noun	Adjective	Verb	Adverb
automatic pistol	Yes	No	No	No
handgun	Yes	No	No	No

As nouns, handgun is a hypernym of automatic pistol; that is, handgun is a word with a broader meaning than automatic pistol:

automatic pistol: a pistol that will keep firing until the ammunition is gone or the trigger is released
handgun: a firearm that is held and fired with one hand

Other hypernyms of automatic pistol include automatic firearm, automatic gun, automatic weapon, pistol, shooting iron, side arm.

automatic pistol (noun)	handgun (noun)
a pistol that will keep firing until the ammunition is gone or the trigger is released	a firearm that is held and fired with one hand