So while I was trying to find the best place for the solenoid it became apparent that the further back the better. I redesigned the bracket to be a simple strip with a hole to hold the solenoid.

And the solenoid core is simply held in by a screw, here is the final design in place, notice the screw at the bottom:

The electronics for controling the solenoid is simple. I used the example at Arduino's own site (LINK). But before I would hook the targets up to the Arduino I wrote a test program to turn each of 5 outputs on and off. I tested this with an LED hookup:

Once that was tested I could replace the LED's with the transistor circuit as described in the Link above, and hook up the outputs to the targets. (Which were now held together on a strip of 1x2 wood.



Next I would have to add something to detect when the target was down.