I don't think inertia would propel the firing pin forward from a blow to the hammer, but the transmitted impulse would. Think about croquet, or billiards, or those swinging ball executive toys where an immobile ball abuting another ball is struck, and the transmitted impulse propels the ball. Put a pencil in the barrel of your unloaded pistol with the hammer down, and strike the hammer a sharp blow, see if the pencil is "shot" out.
[This message has been edited by stanmog (edited September 13, 2000).]