Shell guns, which could be eight or 10 inches long, were introduced in 1824 for the Royal Navy. They were an imitation of a French design. They were used principally for throwing live spherical shells for long ranges. Their lighter construction was such that they could only fire hollow shot and shells with a small bursting charge.
Although used primarily in the Navy, they were also used in coastal fortifications (as at Fort Henry and the Halifax Citadel). The outward appearance of shell guns was similar to a shot gun except for the removal of some of the minor decorative parts — fillets, astragals, reinforced rings and breech mouldings. In particular, shell guns may be recognized by having one annular moulding (instead of two) between the swell of the muzzle and the mouth of the bore.
Because smooth-bore shell guns cannot be used to fire solid shot, they are designated by their calibre in inches, e.g., "8-inch SBML (Smooth Bore Muzzle Loading) shell gun of 65 cwt." The only shell guns in Fort Henry are the four 8-inch guns in the Advanced Battery.
