For many years a universal light gun interface was talked about and one was even marketed but I do not think anyone here has seen it working. The UGLI from nanotec was talked about for a couple of years but I do not know if anyone ever saw one. There was another one but I have forgotten its name and it is also has not been seen in the real world.
The other one was the USB2GUN. It is an actual arcade part used in a few Global VR machines like America's Army.
It can still be ordered from the Global VR parts department for $300.
http://parts.globalvr.com/The guns will show up as joysticks, so a good working knowledge of how analog controls work in MAME is necessary.
Settings in MAME for things like dead zone, saturation & sensitivity will affect how well they work.
With Howard Casto's Troubleshooter2 program, they should work in Model 2 Emulator also.
Only one person on this board has ever bought one and couldn't get it working to their satisfaction.
IIRC, they were using Namco guns instead of the Happ guns it was designed to work with.
I still think it's possible, but I'm not laying out the money for the interface and the guns to test it.
Not a lot is understood about how it works. It could be that the color pallet & brightness of the arcade games it was originally used in were designed to work with the device and other games might not work as well.
Search USB2GUN in the main forum and you'll find a couple threads concerning it.
The nanotech product was just a repackaged USB2GUN.
I have an Aim Trak in a Happ recoil shell. It's not too big of a project to squeeze the Aim Trak into it, although some grinding away at plastic is necessary.
You'll need the recoil firmware, a resistor, a transistor and a 24v power supply to get the recoil kicking. I built it just to experiment with and check out the Aim Trak.
I still prefer the old true pixel perfect lightguns over the IR guns. I use old S-Video Act Labs TV Guns when I play.