Maybe I missed it, but have you considered the PT Rocker? I would think you could tweak the visual element (how much it rocks) by the simple addition of counter weights. Of course, that would be dependent on the ammo/loads, but perhaps a compromise counter weight could be found that would work for all your ammo. You could also attach to the counter weight one of those motion detector lights, and set it for as short a reset as possible. Target is hit, moves, light flashes. That would be a pretty good visual indicator. If you wanted to do an audio mod, you could use a similar motion detector light, but hack to run to a buzzer instead of the light.
I'm not sure if any of those ideas would work with available materials at a reasonable price, just thought I'd throw out some.
I'm not sure if any of those ideas would work with available materials at a reasonable price, just thought I'd throw out some.
