full metal jacket vs bullet

full metal jacket and bullet both are nouns.

Word	Noun	Adjective	Verb	Adverb
full metal jacket	Yes	No	No	No
bullet	Yes	No	No	No

As nouns, bullet is a hypernym of full metal jacket; that is, bullet is a word with a broader meaning than full metal jacket:

full metal jacket: a lead bullet that is covered with a jacket of a harder metal (usually copper)
bullet: a projectile that is fired from a gun

Other hypernyms of full metal jacket include slug.

full metal jacket (noun)	bullet (noun)
a lead bullet that is covered with a jacket of a harder metal (usually copper)	(baseball) a pitch thrown with maximum velocity
	a projectile that is fired from a gun
	a high-speed passenger train