Abstract: Disclosed is apparatus for removeably mounting on small firearms to assist in marksmanship training. The apparatus includes a lamp and lamp firing circuit activated by a switch moveable between first and second positions by an elastic band coupled between the switch and the hammer of the firearm. The circuit is arranged to charge a capacitor when the hammer is cocked and uses the energy stored in the capacitor to switch a transistor to temporarily connect the lamp to a battery when the firearm is fired.