When I first went to an 8 1/2# hammerspring with a short reset disco in my 75 Shadow, I did it twice in a period of two weeks(?).
I ride the trigger forward when shooting fast. If your applying slight pressure to the trigger right at the reset point, it CAN go bang again. It's so fast, the target had snake-bite holes.
Any well tuned pistol can do it, if all the variables fall together.
I took some slack out of a High Standard .22 trigger linkage many years ago. It fired two rounds EVERY trigger pull, and it just sounded slightly strange. Riding the reset can do the same thing if the sear engagement is short and light.