I learned of this gun while researching for the firs tbook and contacted the Royal Armouries whose staff confessed at the tyme that they knew nothing about the action. Well, they've corrected that deficiency and here's their video on the Belton Repeating rifle that was offered to the American Congress during the American Revolution.
https://youtu.be/E2kIPmuXMWU?si=_LOcY84T_EUwWiny
https://youtu.be/E2kIPmuXMWU?si=_LOcY84T_EUwWiny