flintlock vs firing mechanism

flintlock and firing mechanism both are nouns.

Word	Noun	Adjective	Verb	Adverb
flintlock	Yes	No	No	No
firing mechanism	Yes	No	No	No

As nouns, firing mechanism is a hypernym of flintlock; that is, firing mechanism is a word with a broader meaning than flintlock:

flintlock: an obsolete gunlock that has flint embedded in the hammer; the flint makes a spark that ignites the charge
firing mechanism: the action that ignites the charge in a firearm

Other hypernyms of flintlock include gunlock.

flintlock (noun)	firing mechanism (noun)
an obsolete gunlock that has flint embedded in the hammer; the flint makes a spark that ignites the charge	the action that ignites the charge in a firearm
a muzzle loader that had a flintlock type of gunlock