The "gun" if you can call it that is a confederate vandenberg volley gun.
It was designed in 1860, by New York State Militia General Origen Vandenburgh & manufactured by Robinson & Cottam of London, England . The gun was rejected by the U S Army, interested the Royal Navy, but ultimately was purchased by North Carolina and possibly a few other Confederate States.
The Vandenburg Volley gun was not very effective due to the difficulties encountered in the firing and reloading of the weapon. The gun had from#45 to 451 barrels (depending on the model) on parallel chambers clustered, row upon row, in a cylindrical container. #
When the Vandenburg Volley gun’s breechblock was opened, a container with all the charges was inserted and the breechblock closed again.#
#A single percussion hammer set off the whole conglomeration. #It was a painfully time consuming job for re-firing and only effective if several magazines#were pre-loaded and ready for insertion.
The gun’s pattern of fire did not spread out like a shotgun’s but instead held a very close pattern. #It was accurate, and at 100 yards could group more#than 90 % of its bullets in a 6’square. #In battle it was certain death for hapless men who found themselves within that square footage.
The magazine for the Vandenburg Volley gun was a rectangular piece of metal with a hexagonal area that contained the 45 to 451 chambers containing the#bullet and powder charge. #It could be fed into the firing chamber of the gun. The bullet used is referred to as the double – ended Whitworth. It looks like a pill capsule.#
The model pictured in the book was made by robinson and cottam, london and is 50 caliber. Also all the barrels are rifled. It is only 36" long but weighs in at 400lbs.#
Originally it would have been on a wheeled carriage much like your standard artillery.# It was captured by Union cavalry near salisbury, North Carolina in april 1865
Thats very cool about your family, I would say its safe to assume that atleast later in the war he woul have carried a springfield. Although I would research both those units and perhaps you will know. The book lists what regiments the uniforms are from and some have the dates they were issued or used in.