pistol grip vs gunstock

pistol grip and gunstock both are nouns.

Word	Noun	Adjective	Verb	Adverb
pistol grip	Yes	No	No	No
gunstock	Yes	No	No	No

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

pistol grip: a handle (as of a gun or saw) shaped like the butt of a pistol
gunstock: the handle of a handgun or the butt end of a rifle or shotgun or part of the support of a machine gun or artillery gun

Other hypernyms of pistol grip include stock.

pistol grip (noun)	gunstock (noun)
a handle (as of a gun or saw) shaped like the butt of a pistol	the handle of a handgun or the butt end of a rifle or shotgun or part of the support of a machine gun or artillery gun