10 . 5 cm tornautomatpjäs m / 50 The 10 . 5 cm tornautomatpjäs m / 50 ( 105 mm automatic turret gun model 1950 ) was the first modern weapon system designed for the Swedish coastal artillery . Development started in the late 1940s , and construction of 6 gun installations based on this system was offered by Bofors in 1950 . Various problems plagued the design and construction process and the last gun installation was not finished and ready for operational use until 1968 , 12 years behind schedule . History . In 1949 the Inspector of the Coastal Artillery ( IKA ) ordered an investigation concerning the replacement of numerous older , and for the most part , completely obsolete artillery system with model years stretching as far back as the late 1800s . Most of these had been hastily built during World War II using old naval guns in very simple emplacements which were not designed with endurance and high survivability in mind . Protection from nuclear weapons was non - existing and collective BC protection was very limited usually requiring most of the gun crews to wear gas masks . Finally , most of the older guns were 57 mm designs and lacked the firepower to be an effective defense against an invasion . < br > In 1950 Bofors offered 6 fully automatic 105 mm guns ( probably based on an earlier naval dual - purpose gun design ) in armored turrets , to be delivered in 1953 - 54 . However , various problems at Bofors caused the delivery to be delayed until late 1957 . One of the guns ( which ended up becoming Gun # 2 at Nåttarö ) also had its breech damaged somewhere in the process . This was repaired and the gun delivered anyway . < br > All of the guns went to the Stockholm area where the need to replace older systems was deemed the most urgent . System description . The 6 guns were split into 3 batteries consisting of 2 guns each . They were built in such a way that each gun in a battery could be targeted individually , that is , the battery ' s fire could be split between two targets . Each gun emplacement was designed to be completely self - sufficient and in the case of Battery Arholma they were spread across 2 islands . Turret and gun system . The 10 . 5 / 50 system consists of an armored turret which is unmanned above ground , and an automatic magazine . The gun is a fully automatic , water - cooled sliding wedge design which is automatically laid in both traverse and elevation . It uses fixed ammunition which is fed from a magazine several meters below the gun turret . Spent cartridges are ejected from a hatch on the turret ' s rear face . 10 . 5 / 50 is known for a switch located in the magazine which is marked " war - peace " ( krig - fred ) . This selected between half and full rate of fire and was normally locked in the " peace " position using a padlock . The lower rate of fire was normally used in peacetime because it meant less wear on the various mechanical systems . Supporting installation . Each gun is supported by an installation built in a tunnel connected to the gun turret and magazine . This installation provides fire control , power supply and accommodation for the gun crew and is designed to provide power , food and water for weeks despite being sealed of from the outside world . < br > It uses an older construction technique , pioneered in the 1920s and common in the 1950s , which involved blasting a large tunnel inside of which a concrete building was erected . A non - military but very visible example of this construction technique are the older stations of the Stockholm Metro . This technique proved inadequate when better research on the effects of nuclear weapons became available . It is debated that the concrete structures which were rigidly built on the tunnel floor could collapse from the ground shockwave of a nearby nuclear detonation . Starting in the 1960s , all newer installations were built with steel - framed structures isolated from the surrounding rock with some type of elastic dampers ( springs , rubber blocks , etc . ) . Fire Control . As built , the 10 . 5 / 50 system used a mechanical fire control computer called Ci 709 built by the Dutch company Hollandse Signaalapparaten ( HoSa ) . This occupied 2 floors in the fire control section of the installation . For surveillance and ranging , a periscope and radar was installed which fed into the computer . Modifications and final disposal . When the 10 . 5 / 50 system was first designed and built its nuclear protection was thought to be pretty good , based on the knowledge concerning the effects of nuclear weapons available at the time . However , as more research became available , the protection of most parts of the system had to be downrated quite a bit . Nevertheless , 10 . 5 / 50 was a highly effective weapon system mainly owing to its very high rate of fire which meant a large volume of ammunition could be placed on a target . < br > In the 1980s , when the coastal artillery decided not to use the option to order more 12 / 70 systems the fire control systems meant for those installations were redirected to replace older systems . This meant that all 10 . 5 / 50 installations received a modern ArtE 724 digital fire control system , complete with the new HSRR fortified radar system and AML 702 laser rangefinder and low - light TV system . The installations were also updated with new communications including the STRIKA 85 computerized command and control system , as well as a general renovation of the accommodation spaces . < br > A decision in 1999 meant that all coastal artillery systems would be disbanded in line with the Swedish government ' s new take on defense . The 10 . 5 / 50 installations were dismantled in the early 2000s , with only Arholma 1 being retained as a State Construction Memorial . It opened as a museum for the 2008 season and is mostly open during the summer , but may be visited any time of the year by groups if booked in advance .