I can only argue about them based on what is shown at face-value. Anything that needs an explanation of "it just works" or "space magic!" is not valid. The hand cannons in Destiny are all shown to be double-action revolvers (meaning that pulling the trigger cocks the weapon and also fires it), with the exception of The Last Word, which is shown to be a single-action revolver. There is no indication that any of them have the same internal functionality of the Rhino, and given the animations and action displayed by the hammer in-game, there is no indication that it is meant to work any differently than a standard revolver. Given this deductive reasoning, it's safe to assume that the current configuration of Hand Cannons in Destiny would not work.