The development and failure of the quadruple two-story turret

[disc]

The classic "quick-firing" (QF) gun evolved in the 1880s from machine-guns meant to defend against torpedo boats. These guns used brass cartridge cases to form a gas seal, such that the breech-block could be simplified. With their simple fixed or semi-fixed ammunition, quick-operating breech, and reduced need for bore clearance, these guns fired fast compared to conventional bag-loading screw-breech guns.

A 105mm M119 "QF"-type howitzer firing. Note the unitary fixed ammunition, as well as the rapid reload. The breech uses a sliding block rather than a screw interlock.

 

While conventional big guns were needed to fire armor-piercing solid shots, so as to penetrate the thickest armor on enemy battleships, QF guns could fire great volumes of high-explosive shells at attacking torpedo boats. Crucially, they could also wreck the unarmored upper works of enemy battleships. Battleships of the 1880s often only had armor to protect their vitals from heavy shots (compare with the later all-or-nothing concept), so much of their sides were vulnerable to even small explosive shells. New vessels in the 1890s thus had regions of medium armor to protect against QF guns.

The US Navy did not have the technology to make big QF guns when designing the battleships Indiana, Iowa, and Kearsarge. To compensate for a lack of 6in QF guns, the Americans instead implemented 8in bag-loading screw-breech guns. It was reasoned that these big guns, though they might only fire once every two minutes, would be able to penetrate medium armor meant to keep out the shells of 6in QF guns.

The battleship Indiana. Two of the four wing 8in turrets can be clearly seen, one deck above the main 13in guns.

 

Unfortunately, these guns would tend to produce a lot of blast effect, and themselves would be vulnerable to the blast effect of the main battery. This made their placement awkward.

An ensign, Joseph Strauss, came up with a solution for Kearsarge. The 8in guns would be mounted in a two-story turret, atop the 13in main guns. This made a quadruple turret, one each fore and aft. This would neatly save on centerline space and reduce the effects of blast. The 8in guns would have separate elevation but would not have a separate traverse. Rather, they would train with the 13in main guns. At the short ranges envisioned, any difference in lead between the guns would be negligible if firing at the same target. The slow-loading 13in guns would fire only about once every five minutes, so the turret could turn to let the 8in guns fire at other targets if needed. As all four superimposed 8in guns would would contribute to a broadside, four 8in guns could be eliminated compared to the Indiana and Iowa.

The battleship Kearsarge. Both quadruple turrets are visible. Note the lack of wing turrets.

A diagram of Kearsarge. Note how the hoists for the 8in guns descend through the 13in segment.

 

However, after the Kearsarge class (begun 1896, completed 1900), the 8in gun was dropped. It could after all penetrate medium armor only with AP shells, and with the development of US QF 6in guns these weapons were no longer considered useful. The complex, untried two-story turret was also dropped. Partially, it seems, there were fears that damage could kill the single trainer or the training engine and thus knock out all four guns. As consequence, the Illinois and Maine II classes had 6in secondary batteries.

The experience of the 1898 Spanish-American War changed things again. 8in guns made several hits on Spanish ships and were admired for their range and flat trajectory (and, as Friedman points out, probably their decent rate of fire). However, new QF 6in guns were evidently not present in any quantity, and the 8in gun had an accuracy of only ~4%. Though new gun technology was being implemented, new guns were not put in action: the Kearsarges were not finished until 1900, and the Illinois and Maine II classes had some years yet to completion.

The Virginia class was therefore constructed with a new model of quadruple two-story turret, incorporating 8in guns atop 12in guns. The 8in guns again had no separate traverse. However, dissatisfaction with the two-story turret soon flared. Though superposed turrets were again considered, the Connecticut/Vermont class was built instead with four twin 8in wing turrets instead. The small Mississippi class likewise lacked two-story turrets.

USS Virginia. Both quadruple turrets are visible, as is one of the two wing 8in turrets.

A closeup of one of Virginia's quadruple turrets.

 

Advances in propellants and ammunition handling and loading in the years since the Kearsarge design drastically increased the rate of fire of bag-loading screw-breech guns. Indeed, US 6in bag-loading guns attained nearly the same rate of fire as QF fixed-ammunition guns. This had severe effects on the superposed turret.

Friedman thus quotes Admiral Schroeder, a commander of Virginia: "by a strange paradox, the great increase in the rapidity of fire of our heavy guns from, say, one shot in three minutes to three shots in one minute, virtually neutralized the advantage of having 8-inch guns where thy could be fired without interfering with the 12-inch. Whenever a gun is fired in a turret there is a certain amount of concussion which precludes firing another for a few seconds; and, even with smokeless powder, the heated gasses linger for an appreciable time in front after each discharge, making it impossible to point for the next shot until they have been wafted away. With the two 12 inch in a turret firing alternately, and each able to fire every twenty seconds, there would be only about ten seconds between 12-inch shots; and if the 8 inch were to 'butt in,' they would probably interfere with the next 12in shot--the last thing to be thought of. As that problem gradually developed, and the rapidity of fire increased, each ship tried different combinations of fire to obtain maximum opportunities for fire--single-barrelled salvos, double-barrelled salvos, double-barrelled 8-inch salvos combined with single-barrelled 12 inch, and so on. But the ultimate conclusion was that rapidity of fire had knocked out the superposed turret."

By the time the Virginia class was completed, Dreadnought was already under construction. New battleships had no purpose for intermediate batteries: Big guns would be needed for long-range combat, and smaller, handy guns would be needed against torpedo boats and destroyers. At long ranges, the different trajectories of 8in and 12in+ guns guns would require different leads, so a single traverse would no longer be sufficient.

Seven battleships carried these weapons: the Kearsarge and Kentucky, and the Virginia, Nebraska, Georgia, New Jersey, and Rhode Island. All were completed after the Spanish-American War, and all served through WWI. Several were also involved in actions to quell war and regional unrest in Mexico and the Caribbean. To my limited knowledge none ever fired a shot in anger. Kearsarge had its weapons removed in 1920 and was converted to a crane ship, serving many years until being scrapped in 1955. Virginia and New Jersey were sunk as targets in Billy Mitchell's famous 1923 demonstration. The rest were scrapped in 1923.

Though many later ships would be fitted with small anti-torpedo-boat guns and AA guns atop their main gun turrets, these weapons were not intended to be manned for combat in fleet actions against other battleships. Neither were they truly integrated with the turret as the 8in guns had been.

 

It would be interesting to see superposed turrets in the game. I am not sure it would be productive to spend much (or any) time on implementing them, but as a early tech it would be cool to have.

Edited December 10, 2019 by disc