New member here, so forgive me if I am stepping on anything. Concerning the right side butt forward holster for revolver users during the ACW. It is correct that the revolver was intended for the left hand as the saber was still considered the primary weapon at the time and it was used right handed. Hence the holster design.
So, consider this. Take any single action (Model P, 1851 Navy, 1860 Army, Remington, etc) and hold it your left hand and raise it into your "workspace" (to borrow a modern tactical term) with the muzzle held to the sky and the right side facing you. Notice that now on C&B revolvers the frame's loading window is easily accessible when inserting paper cartridges. You can operate the loading lever with your right hand without losing your firing grip. The cut for placing caps is also easily accessible to the right hand. On the Model P (1873 Colt SA) when you are ejecting spent shells using your right hand to operate the ejector they slide right out the ejector cut, across the frame, and drop to the ground. Try operating a single action while holding it in your left hand and performing the reload with your right, it will all make sense.
IMO, the single action pistol was designed from the ground up to be reloaded and fired while holding it in your left hand. Once you do it it's obvious and might encourage you to shoot your SA left handed. I do now.
Just my possibly useless 2 cents worth.
DAve
