100 56 TK 100 56 TK or 100 TK ( " 100 mm , 56 length caliber , turret gun " ) is a Finnish stationary coastal artillery gun that utilizes the tank turret from the Soviet T - 55 tank with its 100 mm D - 10 tank gun . 100 56 TK was the main light weapon of the Finnish coastal artillery and complemented the medium gun 130 TK in the coastal artillery role until its decommissioning in 2012 . Background . After World War II the primary fixed light coastal guns in Finland were older heavy anti - aircraft gun s on fortification mounts that were obsolete in air defence duties and had been transferred to coastal artillery , primarily 76 ItK 16 V and 76 ItK 31 ss . These guns were inadequate for their role in firepower , range and survivability . The idea of using tank turrets as coastal guns was first raised regarding Charioteer and Comet turrets . In 1966 yliluutnantti Juhani Niska submitted a proposal to use modified 100 mm T - 54 tank turret as coastal gun . The proposal compared also Swedish 75 mm Bofors turret gun and 76 ItK 31 ss as other possibilities . 100 mm T - 54 turret was considered the most suitable solution , and after a T - 54 turret was tested in Katajaluoto it was decided to purchase 56 T - 55 turrets from Soviet Union and modify them as 100 56 TK coastal gun . As a cost - saving measure the turrets were ordered without stabilisers . This caused later some criticism from the Finnish Army , since while stabilisers are not needed in a fixed fortification , the Finnish Armoured Brigade could have used them as spare parts . Design . The total barrel length of the 100 TK is . The maximum range is about . The sustained fire rate is 6 rounds per minute and the muzzle velocity is with HE - FRAG shells . The breech block weighs . The breech mechanism is semi - automatic and the gun is loaded manually . Guns were modified for a higher maximum elevation and necessary equipment for indirect fire was added . Since the turrets were intended for coastal fortifications the turret insides were coated with asbestos - cork mixture to prevent moisture from condensing into gun position . Messaging , electric and ventilation systems were left mostly intact . A fully automatic loading system would have taken too much space , and simple counterweight operated shell hoisting mechanism was developed to transfer ammunition up to the turret . Operation and modifications . The first battery was built in 1968 – 1969 . After these batteries were built in 14 sea fortresses , each one equipped with 4 such turrets . The Russians , who had been informed by this program , seemed surprised . At first only gun positions were built , but since 1970s a second construction phase began to create integrated positions with command - and storage facilities and to improve air - and close defence positions . One turret was built on a wooden platform for testing and training purposes . In 1980s planning for a major maintenance and modernization program began . The largest modifications were the electrical system in the turrets and the gun periscope . New periscopes were ordered from Yugoslavia , but the break - up of the nation and the resulting Yugoslav wars caused delays . The guns were equipped with gun computers and laser range - finders , and some of the turrets also with night - vision systems . The electrical systems were replaced using western components and the guns and gun positions were overhauled . Externally the most visible change was new thermal insulation dome on top the turrets that also gives them a more rock - like appearance for camouflage . The ammunition for the guns has not fulfilled all the expectation . The most serious shortcoming was the lack dedicated anti - ship shells . In addition to normal tank gun ammunition and air burst shells with mechanical time - delay fuse , semi - armour piercing shells from Riga class frigate s ( Finnish Navy had two such ships ) were available . As attempts to purchase suitable munitions from Russia did not succeed , it was also considered to purchase them from China . However , in the end a domestic development work began in the beginning of the 1990s on shells suitable for naval engagements . Decommissioning . Most 100 TK batteries were deactivated in 2006 – 2007 because of closure of the coastal forts due to budgetary reasons as well as the obsolescence of the stationary coastal artillery . The second phase of the deactivation was completed in 2012 after the last live firings in Upinniemi . Most of the turrets have since been transported away for scrapping or resale . The 100 TK battery in Kuivasaari will be preserved as a museum battery .