A disappearing gun, which is a gun mounted on a disappearing carriage, is an obsolete type of artillery which enabled a gun to be hidden from direct fire and observation. The overwhelming majority of such carriage designs enabled the gun to retract backwards and down after it was fired, thus placing it behind a parapet or into a pit protected by a wall. A small number were simply barbette mounts on a retractable platform. Either way, retraction lowered the gun from view and protected it from direct fire by the enemy while it was being reloaded.
This design also made reloading easier, since it lowered the breech to a level just above the loading platform; shells could be rolled right up to the open breech for loading and ramming. Other benefits over non-disappearing types were a higher rate of repetitive fire and less fatigue for the gun crew.
Some disappearing carriages were complicated mechanisms, protection from aircraft observation and attack was difficult, and almost all restricted the elevation of the gun. With a few exceptions, construction of new disappearing gun installations ceased by 1918. The last new disappearing gun installation was a solo 16-inch gun M1919 at Fort Michie on Great Gull Island, New York, completed in 1923. In the U.S., due to lack of funding for sufficient replacements, the disappearing gun remained the most numerous type of coast defense weapon until replaced by improved weapons in World War II.Complete list of US forts and batteries at CDSG websiteBerhow, pp. 200-228
Although some early designs were intended as field siege guns, over time the design became associated with fixed fortifications, most of which were coastal artillery. A late exception was the use in mountain fortifications in Switzerland, where six 120 mm guns on rail-mounted Saint Chamond disappearing carriages remained at Fort de Dailly until replaced in 1940.
The disappearing gun was usually moved down behind the parapet or into its protective housing by the force of its own recoil, but some also used compressed airDisappearing Guns (from the Royal New Zealand Artillery Old Comrades Association) while a few were built to be raised by steam.The Defenses of Sandy Hook (from a Sandy Hook, Gateway National Recreation Area, U.S. National Park Service information pamphlet. Accessed 2008-02-22.)
History
As a result of his observations of artillery during the Crimean War, Captain (later Colonel Sir) Alexander Moncrieff improved on existing designs for a gun carriage capable of rising over a parapet before being reloaded from behind cover. His design was widely adopted, and used in many forts of the British Empire. The earlier experimental carriages of the type were wheeled.Hydro-pneumatic carriages at Victorian Forts and Artillery His key innovation was a practical counterweight system that raised the gun as well as controlled the recoil. Moncrieff promoted his system as an inexpensive and quickly constructed alternative to a more traditional gun emplacement."Moncrieff's method of mounting guns with counterweights, of using them in gun-pits, and of laying them with reflecting sights : a paper read at the Royal United Service Institution (1866)" (from archive.org. Accessed 2009-06-25.)
The usefulness of such a system had been noted earlier, and experimental designs with raisable platforms or eccentric wheels, with built-in counterweights, were built or proposed. Some used paired guns, in which one cannon acted as the other's counterweight, or counterpoise. An unsuccessful attempt at a disappearing carriage was King's Depression Carriage, designed by William Rice King of the United States Army Corps of Engineers in the late 1860s. This used a counterweight to allow a 15-inch (381 mm) Rodman gun to be moved up and down a swiveling ramp, so the weapon could be reloaded, elevated, and traversed behind cover. The carriage was subjected to six trials in 1869–1873. It was not adopted; an 1881 letter to the Chief of Engineers by Lt. Col. Quincy A. Gillmore stated that it "still leaves a great deal of heavy work to the slow and uncertain process of manual labor". Part of a test installation at Fort Foote, Maryland remains.King's Depression Carriage at the Historical Marker Database King's design was better suited for breech-loaders; had the US not had a plethora of new muzzle-loaders just after the Civil War it may have seen wider use.
Buffington and Crozier further refined the concept in the late 1880s by allowing the counterweight fulcrum to slide, giving the gun a more elliptical recoil path. The Buffington–Crozier Disappearing Carriage (1893) represented the zenith of disappearing gun carriages, and guns of up to 16-inch size were eventually mounted on such carriages. Disappearing guns were highly popular for a while in the British Empire, the United States and other countries. In the United States, they were the primary armament of the Endicott- and Taft-era fortifications, constructed 1898–1917. Simpler carriages with a limited disappearing function were initially provided for smaller weapons, the balanced pillar for the 5-inch gun M1897 and the Driggs-Seabury masking parapet for the manufacturer's 3-inch gun M1898. However, they could only be retracted at a specific traverse angle (90° off the emplacement's axis), so could not be used in action. Due to the mount's undesired flexibility when fired interfering with aiming, both types were disabled beginning in 1913 in the "up" position, with installations circa 1903 and later having received pedestal mounts. Both carriage types and their associated guns were removed from service in the 1920s; in the 3-inch gun's case a tendency for the piston rod to break was a factor in their removal.Berhow, pp. 70-71, 88-89
Several mobile disappearing mounts appeared in France and Germany circa 1893. These included both road-mobile and rail-mobile designs. In France, Schneider and St. Chamond produced road-mobile design and rail-mobile designs, in 120 mm (4.7 inch) and 155 mm weapons. The 0.6 meter rail affût-truck system was used tactically for 120mm and 155mm guns in WWI. Six 120 mm Modèle 1882 guns on St. Chamond mounts were deployed at Fort de Dailly in Switzerland from 1894 to 1939.La Mechanique a l'Exposition de 1900, Vol. 3, No. 15, p. 87 (in French) Krupp produced a rail-mobile 120 mm disappearing gun in 1900.Dillard, Col. James B., "Railway Artillery", Mechanical Engineering, Vol. 41, Issue 1, January 1919, p. 44
Though effective against ships, the guns were vulnerable to aerial observation and attack. After World War I coastal guns were usually casemated for protection or covered with camouflage for concealment. By 1912, disappearing guns were declared obsolete in the British Army, with only a few other countries, particularly the United States, still producing them up to World War I and retaining them in service until replaced by casemated batteries in World War II.
The only major campaign in which US disappearing guns played a part was the Japanese invasion of the Philippines, which began shortly after the attack on Pearl Harbor on 7 December 1941 and ended with the surrender of US forces on 6 May 1942. The disappearing guns were the least useful of the coast defense assets, because they were positioned to defend against warships entering Manila Bay and Subic Bay and, in most cases, could not engage Japanese forces due to limited traverse. Despite attempts at camouflage, their emplacements were vulnerable to air and high-angle artillery attack.
Advantages
The disappearing carriage had several advantages: It afforded the gun crew protection from direct fire by raising the gun over the parapet (or wall in front of the gun) only when it was to be fired, otherwise leaving it at a lower level, where it was also able to be loaded easily. With its guns in a retracted position (down behind the parapet), the battery was much harder to spot from the sea, making it a much harder target for attacking ships. Flat trajectory fire tended simply to fly over the battery, without damaging it. Interposing of a moving fulcrum between the gun and its platform lessened the strain on the latter and allowed it to be of lighter construction while limiting recoil travel. Simple, well protected earthen and masonry gun pits were much more economical to construct than the previous practice of constructing the standing heavy walls and fortified casemates of a more traditional gun emplacement. The entire battery could be hidden from view in place when not in use, unlike a traditional fort, enabling ambuscade fire. Higher rate of repetitive fire over non-disappearing types. Less fatigue for the gun crew.
Disadvantages The disappearing gun had several drawbacks: Some British carriage designs restricted maximum elevation to under 20 degrees and thus lacked the necessary range to match newer naval guns entering service during the early part of the 20th century. (Buffington-Crozier carriages, at their final development, could manage 30 degrees on a 16-inch gun.Hogg, Ian V., "Illustrated Encyclopedia of Artillery," Chartwell House, Secaucus, NJ, 1978 p74) The additional elevation gained by mounting the same gun on a later non-disappearing carriage increased its range.The Six Inch Shield Gun (from a private website. Accessed 2009-02-28.) The time taken for the gun to swing up and down and be reloaded slowed the rate of fire of some designs. Surviving records indicate a rate of fire of one round per one to two minutes for a British eight-inch (20 cm) gun, significantly slower than less complicated guns. (By contrast, the Buffington-Crozier 16-inch mount could manage one round per minute; the barbette mount was only 20 percent faster, and was slower at some elevations.) The improvement in the speed of warships demanded an increased rate of firing. The disappearing gun was at a disadvantage compared with a gun that stayed in position as one could not aim or reposition a disappearing gun while it was in the lowered position. The gunner still had to climb atop the weapon via an elevated platform to sight and lay the weapon after it was returned to firing position, or receive fire control information (range and bearing) transmitted from a remote location. Their relative size and complexity also made them expensive compared with non-disappearing mounts, In 1918, the 12" DC gun cost $102,000, the barbette mounted gun $92,000. Fortifications Bill Congressional Hearings, 1916, p. 154 This was more than made up, for some designs, by the reduced cost of protection. From the above reference, the cost of a 16" DC emplacement was $605,000, while a turreted gun's proportional cost was $2,050,000.
Other applications
Gun lift battery One very uncommon and even more complex type of disappearing gun was Battery Potter at Fort Hancock in the Coast Defenses of Sandy Hook, New Jersey. This and a number of 12-inch barbette emplacements were constructed due to the inability of the early versions of the Buffington-Crozier carriage to accommodate a 12-inch gun. Built in 1892, the battery covered the approaches to New York Harbor. Instead of using recoil from the gun to lower the weapon, two 12-inch barbette carriages were placed on individual hydraulic elevators that would raise the 110-ton carriage and gun 14 feet to enable it fire over a parapet wall. After firing, the gun was lowered for reloading using hydraulic ramrods and a shell hoist. While the operation of the battery was slow, taking 3 minutes per shot, its design allowed a 360° field of fire. Since its design was not further pursued, Battery Potter was disarmed in 1907.Berhow, pp. 130-133