Hi Jeroen,
Unfortunately, gun control device is not part of the JAMMA standard. JAMMA is just one joystick + 3 buttons per player. Every game that uses another control method (especially analog) does it in a non standard way. Most of the time, guns are not plugged to the JAMMA interface but to another connector on the game PCB or to a dedicated interface PCB. Do you have a particular game in mind?
Suzo-Happ sells pretty standard guns:
- http://eu.suzohapp.com/products/page/1/category_id/338/category/optical-guns
- http://eu.suzohapp.com/products/page/2/category_id/338/category/optical-guns
but they work for a dedicated range of games only.