The superimposed loading revolver was the Walch. There are a couple of versions.
As for the Grossman book mentioned as a source by P226, I haven't read it, but after perusing the table of contents, it appears to be another of one of those "psycho-babble" books that can neither be proved nor disproved. I do not believe that a "vast majority" of Civil War soldiers consciously and intentionally "mimed" shooting or "pulled" their shots. I think it was more of a case, as pointed out by gmatov, spray and pray. This held as true in the Civil War as lt does today. As much as we would like to think otherwise, a "Nation of Riflemen", we're not. If we were all Carlos Hathcocks, "one shot-one kill", "Reach out and touch someone", battles woudn't last long. Send out a thousand "riflemen" with one 20 rd. magazine each, that's 20,000 enemy casualities.
It's more of a case of pointing your rifle in the general direction of the enemy and letting the laws of chance take over. (These odds can be raised by putting more rounds downrange.) If you are being shot at and the only way to make it stop is to take out the shooter, you're not going to intentionally try to miss, or not return fire at all. You may not expose yourself to take careful aim, but you will do something, even if it is to panic. (see "buck-fever" above).
Besides, if everybody were "miming" it would be a pretty quiet battle. I would think the OIC might notice.
Dean