I contacted the people that manage HMS Warrior about possibly getting drawings or plans of the main deck gun carriages (they had to replicate them from something, right?) They got back to me saying that department was closed down for a while because their systems were hacked.

I found a rough PDF of the 1875 Navy Ordnance & Gunnery Manual, and a little more looking turned up a much better scan which contained this bit of info on the XI Dahlgren on the wrought iron pivot mount.
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File comment: Page 336
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I had been working from a very nice drawing I found on Deviant Art, but it turns out at wasn't a real gun, but a movie-prop used in the 1960's 40,000 Leagues Under the Sea (I was wondering how that compressor was supposed to function...
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File comment: Drawing of the movie-prop IX gun on an iron pivot mount
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File comment: Movie still with Abe Lincoln gun
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I rearranged, replaced, and rebuilt my 3D model of the XI pivot based on the 1875 manual and some photos. I'm working toward an early version of this gun mount. They got a lot of modifications going into the 1880s, dampers, gears, the gun's trunnions got cut off so they wouldn't poke out past the cap squares, etc.
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File comment: XI Dahlgren on iron pivot
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File comment: Existing iron pivot without the slide
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There was also a drawing of a later version of the "Iron Marsilly" There's some shape problems with my model I need to fix with this new data. I may also make one with the later elevation screw shown in the drawing.
The drawing says it's an 8 inch Dahlgren rifle, which is a 9" smoothbore sleeved and rifled.
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