The Collaborative International Dictionary of English v.0.48:

Firelock \Fire"lock`\, n.
   An old form of gunlock, as the flintlock, which ignites the
   priming by a spark; perhaps originally, a matchlock. Hence, a
   gun having such a lock.
   [1913 Webster]

WordNet (r) 3.0 (2006):

firelock
    n 1: a muzzle loader that had a flintlock type of gunlock [syn:
         flintlock, firelock]