Well, the lightgun microswitch mod I came up with originally for saturn guns is just as easy and equally effective on playstation 1 namco Guncon guns. before and after photos above
See my original topic on saturn guns http://www.racketboy.com/forum/viewtopic.php?t=3406 for more detailed instructions. Doing the mod on one of these guncon guns is almost exactly the same, its just a little harder to mount the switch securely. the only real difference here is instead of soldering wire to the old switch, it (the old switch) has its own board which can be removed. the wires that go to this board can be snipped, stripped, and soldered directly to the new microswitch using the NO and COM posts.
Enjoy!