I would be afraid to use a device like that. IMO, there is too much to go wrong if you hurry your 2nd shot.
I used to hunt the fields of an old farmer who used a single shot Model 37 Winchester 12 gauge. When we got a rabbit up he would say "Der He Does!" and bang he would shoot quick. More often than not, he would kill the rabbit with his first shot.
Old Jim always carried a second shell in his left hand. If he missed, he could break open the '37, insert a shell and shoot in the blink of an eye. One day, he dropped the shell trying to insert it, stuck his thumb into the barrel and closed the action. He did not cut his thumb off but he cut it pretty bad. We wrapped the wound, which bled a lot, in a red bandana and went back to the farmhouse.
Jim washed his wound with water and applied a copious amount of Yellowstone 90 proof bourbon to it and then took a couple of long pulls on the bottle. We drove Jim to the hospital and they stitched him up. They also and put a protective splint around his thumb and gave him a tetanus shot. He recovered well but gave up on a quick second shot.
Love it. A perfect example of American ingenuity. Sad that not every invention works but certainly a great attempt at solving a problem.
The study of Gun manufacturing is a history of the American Industrial revolution.
While I would love to own one of these devices, I would be afraid the punch to the forehead would be intolerable.
I wonder if this was a 1 off. Maybe a Patent model. ????