Rick, can you give us the low down on that old photo? It sure looks like one we saw in the Cold Spring, New York, West Point Foundry Museum of the West Point Foundry that Robert Parrott ran. The description was "Experimental Proving Battery" aimed at sheet-iron targets near the top of Storm King Mountain just north of the United States Military Academy at West Point, New York.
Using 1.25" as your bore size all the numbers work out at a 1:12.5 ratio. Example .125 X 40.0" = 5.0" I want to see a 300 Pdr. Parrott on an Iron, Front-Pintle, Seacoast, Barbette Carriage. Go Rick Go! You can do it, and you are correct, it would be big and pretty on the coffee table. If
you keep it dusted, maybe the better half will not yell at you after all.

Mike & Tracy