Mitrailleuse d'Avion Browning - F.N. Calibre 13,2 mm

Due to the above-mentioned features, the 13.2 mm FN Browning drew a lot of interest from a number of nations when it entered the export market in 1939.[2] Some interested countries of note were: the Finnish Air Force,[7] the Royal Romanian Air Force,[6] the Swedish Air Force,[8] the Royal Netherlands Army Aviation Brigade[12] and the Royal Belgian Military Aviation themselves.[13] The Dutch planned to use the 13.2 mm FN Browning in their in-development Fokker D.XXIII fighter aircraft,[12] while the Belgians had plans on using it in their in-development Renard R.36 fighter aircraft and its subsequent variants R.37,[14] R.38[13] and R.42.[15] However with the start of WW2, and the subsequent invasion and occupation of Belgium by Nazi Germany in the summer of 1940, the 13.2 mm FN Browning was, in that limited time, only exported to Romania[6] and Sweden.[8]

The few weapons that were sold to Romania were at first used on their SM.79 bombers but later saw use on their own indigenous IAR 80B fighter plane. In Romania the weapons saw combat and were considered equal to the 20 mm weapons used in the Romanian air force such as the MG 151/20.

Sweden gained interest in the 13.2 mm FN Browning in 1938 and ordered it from FN in 1939, as well as a license to produce the weapon in Sweden.[8] The order was ready for delivery by the summer of 1940, just prior to the German invasion of Belgium. Delivery of the guns, munition and documentation was initially meant to be sent by train to Sweden, but due to the German invasion the delivery had to be rushed by way of ship.[8] In Sweden the Belgian produced weapons received the designation 13,2 mm automatkanon m/39, abbreviated as 13,2 mm akan m/39, meaning "13.2 mm autocannon m/39".[3] Swedish license production of the 13.2 mm FN Browning was handled by LM Ericsson (LME) and production took place in a basement complex in central Stockholm.[8] Due to insufficient documentation and construction quality, a number of changes had to be made to the weapon design for Swedish production to begin, leading to a new variant being produced.[8] The Swedish produced variant therefore got the designation 13,2 mm automatkanon m/39A (13,2 mm akan m/39A).[3] In Sweden the 13,2 mm akan m/39 became their main aircraft weapon of WW2, playing a similar role to what the .50 in (12.7 mm) AN-M2 Browning did for the Americans during World War II where basically all warplanes were armed with it as their main armament. While the weapon never saw combat in the Swedish Air Force, it remained in use for an extended period.[3]

After the war it became apparent that 13.2×99mm ammunition would be too expensive to come by and with the purchase of surplus P-51D Mustangs (in Sweden designated J 26) armed with 12.7×99mm AN-M2 Browning guns in 1945, it was decided in 1947 to re-chamber the 13.2 mm akan m/39 guns for the readily available 12.7×99mm Browning (.50 BMG) cartridge.[8] Conversion to the new cartridge only required a barrel swap due to the similarities between the 13.2×99mm and 12.7×99mm cartridges, and both types of barrels (12.7 mm and 13.2 mm) was available simultaneously for a few years to allow the existing 13.2 mm stock to be used up in live fire exercise.[8] The 13.2 mm cartridge was written off from manuals around 1950. Even though the 12.7 mm cartridge was considered a downgrade from the 13.2 mm cartridge with its high-explosive ammunition,[8] it did not matter, as Sweden's main fighter fleet by then had been upgraded to Vampire fighter planes armed with 20 mm cannons.[16] The last frontline military aircraft to use the 12.7 mm akan m/39s was the SAAB T 18B coastal attacker aircraft which left service in 1959.

From the early 1950s onward however, the 12 mm akan m/39 started being used as a training weapon for jet fighters, such as the de Havilland J 28 Vampire[17] and the SAAB J 29 Tunnan,[18] were it could be mounted in place of their main cannon armament by the use of a small add-on. This use continued all the way to the early 2000s[19] when its last training carrier, the Saab 37 Viggen, left service in 2007.

Finland never formally got the chance to buy the Belgian design before the invasion of Belgium, however through their connections with Sweden they managed to get hold of the manufacturing blueprints for the weapon which allowed them to produce it in Finland.[8][9] Since Finland already was producing 12.7×99mm Browning ammunition it was decided to produce the weapon chambered for that cartridge.[8][9] The Finnish variant was produced by the Finnish State Rifle Factory Valtion Kivääritehdas (VKT) and received the designation 12,70 mm LentoKoneKivääri m/42, abbreviated as 12,70 LKk/42, meaning 12.7 mm (0.50 in) aircraft machine gun m/42.[8][9]

In Finland the weapon was used to rearm many of Finland's fighter aircraft as many of them were older pre-war designs armed with weak or unreliable weapons. The LKk/42 guns were mainly fitted to Finnish Curtiss 75 Hawk[20] and Brewster B-239 Buffalo[21] planes, but also to the indigenous Finnish VL Myrsky fighter aircraft.[21] The weapon was also planned to be used on the VL Humu and VL Pyörremyrsky fighter aircraft if they were to enter production. It was occasionally fitted as a field modification, such as on Finnish Arado 196s, to increase firepower.

After WWII the Finnish would use the 12,70 LKk/42 as training weaponry in aircraft such as the Saab 35 Draken and BAE Hawk.[21]

• "XII. Les munitions F.N. calibre 13,2 mm". La mitrailleuse Browning FN (in French). Belgium: Fabrique Nationale Herstal. 1939. pp. 24, 25.

• Brînzan, Radu (2014). Vânător – Romanian Hunter, The I.A.R.80 and I.A.R.81 in Ultimate Detail. Mushroom Model Publications. p. 285. ISBN 9788363678401.

• Källqvist, Lennart; Norrbohm, Gösta; Skogsberg, Bertil; Karlström, Björn (1986). Det bevingade verket, Svensk militär flygteknik och materiel under 50 år (in Swedish). Försvarets materielverk, Huvudavdelningen för flygmateriel. Stockholm, Sweden: Försvarets materielverk, Huvudavdelningen för flygmateriel. p. 32. ISBN 9178105439.

• Thunberg, L.; Björkstrand, N. (1948). Flygvapnets eldvapenammunition, fastställd 1948 (in Swedish) (1949 ed.). Stockholm, Sweden: Royal Swedish Air Force Materiel Administration & Victor Pettersons Bokindustriaktiebolag Stockholm.

• Söderberg, N.; Björkstand, N. (1949). Beskrivning över 12,7 mm akan m/39, 12,7 mm akan m/45, 13,2 mm akan m/39, 13,2 mm akan m/39A, 1949 års upplaga (in Swedish) (1955 ed.). Stockholm, Sweden: Royal Swedish Air Force Materiel Administration, Kungliga boktryckeriet, P. A. Norstedt & Söner.

• Thorsson, Nils (1975). Historik och kartläggning av vapenmateriel för flygplan. Arboga, Sweden. pp. 0–14.{{cite book}}: CS1 maint: location missing publisher (link)

• Fredriksson, Urban (2006-05-17). "Automatic cannon used by the Swedish air force". x-plane.org. Archived from the original on 2019-12-23. Retrieved 2021-11-18.

• "FN 13.2mm production in 1940". forum.cartridgecollectors.org. 7 December 2016. Retrieved 2021-11-18.

• Ford, Dan (2014-05-01). "Browning machine gun?". tapatalk.com. Archived from the original on 2018-01-23. Retrieved 2021-11-18.

• "Ksp m/22 (Akan m/39)". airwar.ru. Retrieved 2021-11-18.