Mitrailleuse d'Avion Browning - F.N. Calibre 13,2 mm
The Mitrailleuse d'Avion Browning - F.N. Calibre 13,2 mm (Browning Aircraft Machine Gun - F.N. Caliber 13.2mm), more commonly known as the FN Browning M.1939 or the Browning FN (as a nickname) was a heavy airplane machine gun built for export the year prior to WW2 by Fabrique Nationale "FN herstal" in Belgium.
|Mitrailleuse d'Avion Browning - F.N. Calibre 13,2 mm|
|Type||Heavy machine gun in Romania and Finland|
Autocannon in Sweden
|Place of origin||Belgium|
|In service||1939-1957 Swedish air force|
(used as training weapons on the Saab 29 to 37)
|Used by|| Finland|
|Wars||World War II|
|Variants||13,2 mm FN M.1939|
13,2 mm Akan m/39A
12,7 mm Akan m/39
12,7 mm Akan m/39A
12,7 mm VKT 12,70 LKk/42
|Mass||Cannon weight: 24.3 kg (54 lb)|
Barrel weight: 3.3 kg (7.3 lb)
Link weight: 0.017 kg (0.037 lb)
|Length||1,415 mm (55.7 in)|
(1,450 mm (57 in) with flash hider)
|Barrel length||816.5 mm (32.15 in)|
(919 mm (36.2 in) with flash hider)
13.2 x 99 Hotchkiss
(Patron m/39 in the SAF)
12.7 x 99 Browning
(Patron m/45 in the SAF)
|Cartridge weight||on average 120 g (0.26 lb) (13.2 x 99 Hotchkiss)|
|Caliber||13.2 mm (0.52 in) (original)|
12.7 mm (0.50 in) (later)
|Barrels||The barrel had eight constantly rising grooves going right.|
400 mm (16 in)/revolution
Groove depth was 0.16 mm (0.0063 in)
|Rate of fire||1 080 rpm (standard)|
600 rpm (lowest)
1 500 rpm (highest)
|Muzzle velocity||810–900 m/s (13.2 x 99 Hotchkiss)|
|Effective firing range||Tracer to 1,000 m (1,100 yd)|
|Maximum firing range||ca 7,000 m (7,700 yd)|
|Feed system||Belt fed (able to feed from both left and right)|
|Sights||Reflexsikte m/37 (Saab 18 & 21)|
Reflexsikte m/42B (FFVS J 22)
Gyroreflexsikte K-14 (Saab 21A-3)
The weapon was originally based on the M2 Browning but was heavily modified with a high rate of fire and the ability to fire high-explosive bullets, just designed, for the Browning FN. The cartridge used was the 13.2 x 99 mm Hotchkiss round, based on the 13.2 x 99 mm ammunition originally designed for use in the Hotchkiss M1929 machine gun. While basically a machine gun, the invention of exploding bullets in this caliber allows this weapon to be called a "cannon" when firing such ammunition. Normally, the smallest size explosive rounds in general use start at 20 mm.
Due to the above-mentioned improvements the gun drew a lot of interest from a number of nations when it entered the export market in 1939. With the start of WW2, and the subsequent invasion and occupation of Belgium in the summer of 1940, the Browning FN was, in that limited time, only exported to Romania and Sweden. Sweden was able to buy the majority of the weapons and even got the blueprints to produce the weapon on their own without paying for a license. Sweden then gave the blueprints to Finland so they could also produce the weapon.
Since Finland was already producing 12.7 mm ammunition the Finnish variant was rechambered to 12.7 mm. The Finnish variant was designated VKT 12,70 LKk/42 and was produced directly by the State of Finland.
In Finland the weapon in 12.7 mm was used to rearm many of Finland's fighter aircraft as many of them were older pre-war designs which used rifle-caliber armament. They were mainly used on their P-36 Hawk planes and their indigenous VL Myrsky fighter aircraft. The prototype fighter VL Pyörremyrsky was also intended to utilize twin LKk/42s in the cowling.
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.
In Sweden the weapon became their main aircraft weapon of WW2, playing a similar role to what the M2 Browning did for the Americans during WW2 where basically all US warplanes were armed with it as their main armament. While they never saw combat, they remained in use for an extended period.
The weapons were later re-chambered as well, since Sweden adopted the 12.7 mm M2 Browning after WW2 when they bought surplus P-51D's. Since 12.7 mm ammunition was cheaper to buy than the cost to produce new 13.2 mm ammunition, all 13.2 mm weapons were re-chambered during the post-war era, and after 1950 basically all Swedish weapons fired the new cartridge. Even though the 12.7 mm cartridge was considered a downgrade it did not matter as Sweden's main fighter fleet had by then been upgraded to Vampire fighter planes armed with 20 mm cannons.
In Sweden the weapon got the designation Automatkanon m/39, short Akan m/39, meaning Autocannon m/39 and was later produced by Ericsson as the Akan m/39A.
- Automatkanon m/39, Akan m/39 - Original Browning FN weapons built in Belgium.
- Automatkanon m/39A, Akan m/39A - Weapons built by Ericsson in Sweden.
Printed sources are in French and Swedish.
- Flygvapnets Eldvapenammunition 1949.
- (Swedish air force's ammunition 1949)
- Flygvapnets Eldvapenammunition Serie 2.
- (Swedish air force's ammunition serie 2)
- La mitrailleuse Browning FN, kapitel XII. Les munitions F.N. calibre 13,2 mm
- (The FN Browning machine gun, chapter 12. The 13.2 mm FN ammunition types)
- 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 fastställd 1949
- (Description on 12.7 mm akan m/39, m/45, 13.2 mm akan m/39, m/39A established 1949)