robtillaart:
Sounds like fun!
the arduino can generate random sequences of targets but you could also have build in practice sequences. As you only use the numbers 1..5 you can store one target in one byte (in fact you can compress and store 3 in one byte)
I expect it can even register how long it took to shoot a target.
If someone is shooting good and fast it can decrease the time from 5 seconds to 4 to 3 to ....
it can store high score in EEPROM
Could not resist to dump some code to get you started, still leaves a lot todo
...
4 ) get started with an UNO
Awesome, thanks for that 
As I said in my post, I'm inclined to make the targets as dumb and electrical as possible. I'd been planning on using card targets in a lightweight frame (lighter for the servos to snap up), but if you had a smart target unit with an arduino at the pointy end of the range (or pinged back data to the control box) you could totally do steel plates with a rotation sensor to detect shots and modify the sequence on the fly if someone was doing rather too well!
You could do a speed test like those infernal bleep tests in gym where you have to run 20-metre lengths in shorter and shorter periods, but giving shorter and shorter exposures till the shooter fails to hit three targets in a row or something.