firing pin

from WordNet (r) 3.0 (2006)

firing pin
    n 1: striker that ignites the charge by striking the primer

from The Collaborative International Dictionary of English v.0.48

Firing pin \Fir"ing pin`\
   In the breech mechanism of a firearm, the pin which strikes
   the head of the cartridge and explodes it.
   [Webster 1913 Suppl.]