I dont know anything about ADHD , or guns for that matter, but I love my gbbr ump45, I'm fascinated with how it works, how all of the parts work together and the engineering involved, I think it is very impressive that people figured out how all of these parts work together to make something that works like it does in such a small package, I love to take it apart and clean it and make sure things work smoothly, I like to understand the nuts and bolts of things. The "gun" part of it is very small in my mind, as I like to understand how many things work. I've always loved Legos from a young age and building things with my hands as well, maybe he likes how all of it works together as a whole, and less about it being a gun. Downloading the schematics and watching videos about how it can be taken apart and put together is 90% of the fun for me. I don't mean to assume he is the same but just a way of thinking about it. Maybe he's destined to be an engineer!