HMS Benbow, last and most formidable of the Admiral class, in a handsome rendering shown courtesy of Digital Navy.com, highly recommended for a visit by anyone interested in the ships of this era. The derivation of the hull shape and deck layout from Devastation is quite obvious.
Collingwood served as the model for a class of five battleships, the Admiral class: Howe, Rodney, Anson, Camperdown, and Benbow (shown above). The last of the class, the 10,600-ton Benbow, mounted a single monster 16.25" gun in each barbette, anteing up in the Monster Gun competition popular among naval powers in the 1870s and 1880s -- principally a contest between Britain and Italy, but with participation by France as well. The Benbow's main guns, manufactured at the Royal Arsenal at Woolwich, did not perform as well as the 13.5" weapons in the other Admirals: they were slow loading, prone to muzzle droop after a few firings, and as originally installed, their rifling was insufficiently deep to impart the desired degree of spin to shells departing the barrels. In fact, these 110-ton weapons were simply too big and clumsy for the ships they were fitted on.
But more to the point, the technology of gun manufacture had not yet caught up to producing effective breech-loaders in such huge sizes. Inside of 35 years Armstrongs would be turning out 15" battleship guns for the Grand Fleet, among the best and most powerful naval weapons ever engineered. In the interim, with advances in metallurgy and manufacturing technique, British battleships fell back to 13.5" guns in twin barbettes for the Royal Sovereigns of the early 1890s, then to greatly improved Mark VII 12"/40 guns in the Majestic class and its successors, from 1895, through the early dreadnoughts (c. 1906 - 1911). The savings in weight, horsepower to rotate the guns (a hydraulic system in the Admirals), and time to load between rounds -- not to mention the advantages of standardization -- proved persuasive arguments to adopt the 12" gun, which became the standard calibre throughout the pre-dreadnought era. In turn, the experience gained designing, manufacturing, using, and improving 12" ordnance led to the technical solutions needed to tackle larger weapons when the time came.
All 5 of the Admiral class vessels were held up by delays in completing their guns. They were considered quite successful once they hit the waves. And whatever the technical deficiencies of those burly 16.25-inchers, they certainly LOOKED impressive. And in the relatively placid afternoon of the Pax Britannica, when immaculate paintwork and brilliantly polished brass counted for more than accurate marksmanship, looking formidable was at least half the game.
Plan of 16.25" Barbette Mounting - HMS Benbow