20 ITK 40 VKT 20 ItK 40 VKT or " 20 mm dual anti - aircraft cannon model 1940 manufactured by VKT " was a Finnish light anti - aircraft gun designed by the Finnish gunsmith Aimo Lahti . As the only multi - barrel 20 mm anti - aircraft gun 20 ItK 40 VKT was the most effective 20 mm air defence weapon used by the Finnish Army during World War II . A total of 174 guns were built , used in training until 1970s and kept in reserve until 1988 . The gun received the nickname " Vekotin " ( gadget ) from Finnish soldiers . The nickname was reached by adding to the abbreviation of manufacturer , VKT . Background . 20 ItK 40 VKT is dual anti - aircraft gun designed by Aimo Lahti . The gun barrels and mechanisms are based on the L - 39 anti - tank rifle converted from semi - automatic to full automatic fire and with the stock and barrel shroud removed . A prototype L - 39 anti - aircraft gun was completed just before Winter War , but Lahti made some improvements to the design and the mass - production version was designated L - 40 . Airforce headquarters ordered a series of 50 guns from Valtion Kivääritehdas ( VKT , State Rifle Factory ) in January 1940 and a further 120 guns in June 1941 . Production was delayed , however , and the first guns were finished only in 1943 . Of the total number of 174 guns , 155 were produced in 1943 and 19 in 1944 . The guns were distributed to units in small batches soon after they were completed . Design . Unlike the L - 39 anti - tank rifle , weapons in the 20 ItK 40 VKT are designed for full - automatic fire and so do not suffer from the similar structural weaknesses as the full - automatic conversion L - 39 / 44 anti - aircraft rifles . The rate of fire for the gun is adjustable , with a maximum cyclic rate of 2x700 rounds per minute , and a more commonly used rate of 2x360 rounds per minute . The gun is loaded from 20 round magazines , with an empty weight of 5 . 6 kg and 11 – 12 kg full , depending on the type of ammunition . The 20x138B Long Solothurn cartridge used in 20 ItK 40 VKT was also used in the L - 39 anti - tank rifle as well as the other 20 mm anti - aircraft guns , the 20 ITK 30 and 20 ITK 35 , used by field army units . The gun sight , designed by Osmo Niskanen and manufactured by Strömberg company , was not entirely satisfactory and was more complicated to use than the sight in the German 20 ITK 30 . The gun trailer was also problematic , as it was rather frail and offered a ground clearance of only 20 cm . Thus the towing speed was limited to 30 – 40 km / h and the mobility of the gun was limited . Equipment used with the gun included spare magazines with a transport case , gun tarpaulin , a transport case for the gun sight and a toolkit . Service use . 20 ItK 40 VKT was used by Finnish light anti - aircraft batteries in Continuation War and Lapland War along with other 20 mm guns . At the end of the war 20 ItK 40 VKT was the most numerous field army 20 mm anti - aircraft gun ( 20 mm Madsen was more numerous , but used primarily by navy and coastal artillery or at the home front ) . The guns made through the war mostly intact . After the war 20 ItK 40 VKT was considered to be the only still satisfactory 20 mm anti - aircraft gun , although it was recommended to re - design the gun sight . The re - design was materialized in 1955 when a new m / 55 pendulum ring sight was accepted to service . The same sight was also later used on 20 ITK 30 . 20 ItK 40 VKT was used in training until 1970s and they were kept in storage as reserve weapons until 1988 .