A guy on a swedish electronics forum made this:

the gun:
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the target w. a couple of minute old shots:
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the target w. new shots:
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The target with tracking switched on so that you can follow the gun movements:
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The targets are emergency exit signs with transparent laser printed overlays.
The gun control electronics is a constant current generator and some timers to simulate the mechanical delay in a real gun, control pulselenght and to generate an extra weaker pulse so that you can track your aim with a line.