Lost World can use 2 type of gun hardware
-classic gun style
-CCD gun style
The classic one (unused by game made by Sega) flash the screen when you pull the trigger.
In this mode the "gun pcb" (the same used by Virtua Cop IIRC) is connected to the Model3 via the RS422 bus.
The new one just output the x-y coordinate as analog output. this "gun pcb" also output 2 digital bit
-offscreen
-trigger
I have just give SuperModel source a quick look, it seem you emulate the first (old) type of gun HW, where such effect are missing as the game didn't know where you are aiming at.
MAYBE if you don't use the FIFO (or reply the FIFO buffer is always empty) the game switch to the other mode
Hope it help