automatic gun vs self-loader

automatic gun and self-loader both are nouns.

Word	Noun	Adjective	Verb	Adverb
automatic gun	Yes	No	No	No
self-loader	Yes	No	No	No

As nouns, self-loader is a hypernym of automatic gun; that is, self-loader is a word with a broader meaning than automatic gun:

automatic gun: a firearm that reloads itself and keeps firing until the trigger is released
self-loader: a firearm that reloads itself

Other hypernyms of automatic gun include autoloader.

automatic gun (noun)	self-loader (noun)
a firearm that reloads itself and keeps firing until the trigger is released	a firearm that reloads itself