Actually, here's a nicer image of a stripped action, and instead a short video showing and explaining the beautiful and clever simplicity of these things:
https://www.youtube.com/watch?v=GadzX6vPl8YMoving from a muzzle loading musket, or even a breech-loading musket, this would not just be a tremendous increase in rate of fire, it would be much easier to load, much easier to unload, much easier to clean.
I've heard it argued that the US Army was supposed to have adopted the Remington Rolling-Block rifle, as it did the best in trials (and I fully believe that), but I still think that the Springfield Trapdoor rifle was the right choice in the end, as it was by far the most economical option (unusually so, even), and it was still pretty good, even if the Remington rifle was better.