So then you can explain how this works.
At the back end of the cylinder is a shield that, I presume, is to prevent the caps from falling off the nipples when the cylinder turns.
With a single action revolver - even, I suppose, with a single action peppeebox - you pull the hammer back to half cock and then you can rotate the cylinder and cap the nipples.
But with a double action only gun, that has no hammer spur, and has no half cock (right? It does not have a half cock?) how do you rotate the cylinder to put the new cap on the nipple? How do you prime that thing?