Over at Civil War Talk, there was an inquiry as to how the big, mounted artillery on ships like Alabama were moved about. When you look at a model or drawing of a CW-era ship, the deck often seems to be covered with metal arcs, obviously related to moving the gun, but in no clear pattern that’s easy to discern. (See this example on a model of U.S.S. Kearsarge.)Fortunately, Andrew Bowcock covers this procedure in some detail in his C.S.S. Alabama: Anatomy of a Confederate Raider. Although he described the procedure for a specific gun on that vessel, the process would be similar on other ships.
There are three basic components to the gun — the tube, the carriage on which the tube is mounted, and the slide in which the carriage was run forward and back (with recoil). It’s the arrangement of the slide here that’s important. The key to the whole process is that each end of the slide is fitted with a hole through which a brass pivot pin could be dropped, going through the carriage and into a matching, iron-reinforced hole in the deck. The key to shifting the gun from one position to another was to swing the slide on one pivot to line up the pivot hole at the other end with another point, put that pin in place, remove the first pin, and then swing the whole thing from the other end. It sounds complicated, but it is practical and (relatively) safe on a rolling deck, since the slide will (at worst) swing in an arc, rather than go barreling across the deck like a loose gun on trucks.
Here is a diagram of the eight pivot positions (marked in red) used for Alabama’s aft 8-inch smoothbore pivot — the one Captain Semmes was famously photographed with:
And this shows the pivot points on the slide for that gun:
And here is that process illustrated on the digital model:
Gun positioned on center-line of deck, normal stowed position.
Back end of slide is swung to an intermediate pivot point on the port side and pinned there.
Front end of the slide in unpinned and swung toward the port side.
The swing complete, the forward end of the slide in pinned at the ship’s side, and the back end in unpinned to allow the back end of the slide to swing freely.
The gun is now ready for action.
The model is simplified for clarity, and omits all the block-and-tackle, breeching ropes, and the dozen or more crew members required to provide the muscle power to do this. (Bowcock notes that the official complement to work this gun in action would be sixteen men.) Anyway, I hope this makes the process a little clearer.