sentences:  Early cartridge firearms had to be cocked and caught by the "sear", which holds the hammer back, before each shot.Pulling the trigger allows the hammer or striker to fly forward, striking the "firing pin," which then strikes the "primer," igniting an impact-sensitive chemical compound (historically, first fulminate of mercury, then potassium chlorate, now lead styphnate) which shoots a flame through the "flash hole" into the cartridge's propellant chamber, igniting the propellant.The Springfield Armory in Springfield, Massachusetts became important to the history of firearms during the 1850s, when it debuted the Springfield rifle.