PICTURE: 40-mm Bofors anti-aircraft gun on its towed mount. (Photo taken in Ilmatorjuntamuseo). CLICK THUMBNAIL TO SEE LARGER PIC (146 KB).

distance	hitting angle	penetration
100 m	70 degrees	60 mm
200 m	70 degrees	57 mm
300 m	70 degrees	55 mm
400 m	70 degrees	53 mm
500 m	70 degrees	51 mm
600 m	70 degrees	50 mm
800 m	70 degrees	48 mm
1000 m	70 degrees	45 mm
1500 m	70 degrees	38 mm
2000 m	70 degrees	32 mm
2500 m	70 degrees	26 mm

This excellent anti-aircraft gun was designed by Victor Hammar and Emanuel Jansson for Bofors factory and T. Wennerstrom designed ammunition for it. Story of this legendary weapon started from request made by Swedish Navy in year 1925 for Bofors to develop 20-mm automatic-cannon for shipboard use. Year 1928 doubts about sufficiency of 20-mm calibre surfaced (The basic idea was that single hit had to be capable reliably destroying aircraft), so development goal was changed to 40-mm automatic cannon. The first prototypes were finished in 1930 and first gun was delivered to Swedish Navy in year 1932 (and named M/32). That same year developing of country based towed version started, that version named M/34 had two-axle carriage with 4 wheels. The weapon was recoil-action cannon with vertical breech combined to loading done with 4-round clips. As clips could be feed in one after another constant fire low firing-rate could be maintained. The gun could fire both single-shots and semiautomatic fire, in automatic-mode the gun kept firing as long as foot-pedal was hold down and ammunition was fed in.

M/32 had already been sold to four navies and M/34 to three armies, but it was slightly improvised version of M/34 named M/36 that really hit the jackpot. Countries that bought Bofors M/36 anti-aircraft guns in 1930's included: Argentina, Belgium, China, Denmark, Egypt, Estonia, Finland, France, Greece, Latvia, Netherlands, Norway, Portugal, Sweden, UK, Thailand and Yugoslavia. As production line of Bofors factory clearly was unable to satisfy such demand the company made deals for license production with Belgium, Finland, France, Hungary, Norway, Poland and UK. During World War 2 both Germany and Japan used captured 40-mm Bofors antiaircraft-guns and Soviet 37-mm antiaircraft-gun M/39 was obviously based to Bofors design. Over 100,000 40-mm Bofors antiaircraft-guns were manufactured world-wide by end of World War 2. During the war Bofors M/36 and its versions become the legendary classic weapon from which the company is still internationally known. The huge majority of Bofors 40-mm manufactured during World War 2 were made in United States, even if US had not acquired license for manufacturing it. Other World War 2 era manufacturers included Australia and Canada. The gun was not only ahead of its time in many areas, but it appeared in right place at the right time - in 1930's there was a gap in between effective range and firepower of existing 20-mm automatic guns and heavy antiaircraft-guns. 40-mm Bofors was just the weapon needed for filling that gap. The guns (especially M/36 variations) have remained in use in many countries to this day and variations of newer L/70 guns are still in production even today.

PICTURE: New 40-mm Bofors anti-aircraft gun being tested by factory personnel in State Artillery Factory after being assembled there. Photographed by Turo Kartto in May of 1942. (SA-kuva.fi photo archive, photo number 88334). CLICK THUMBNAIL TO SEE LARGER PIC (96 KB).

Finland bought license for manufacturing 40-Bofors guns in year 1937. In fact the Finns intended 40-mm Bofors as one of the main products of newly established VTT (= Valtion Tykkitehdas = State Artillery Factory) already before World War 2 broke out. Even the first order was sent to VTT already year 1938. However, as VTT's production failed to start as fast as had been earlier planned and as the international situation developed more serious the Finns decided to order guns from Sweden (Bofors) and Hungary (MAVAG) already before Winter War. First delivery of 9 guns came from Sweden and arrived in spring of 1939. From Hungary 42 guns were ordered, 24 of them arrived via Sweden during December of 1939, just barely getting past Germany before the Germans stopped weapon transports through their territory to Finland. The next shipment of 12 guns from Hungary was not so lucky - the Germans stopped it. After secret negotiations (for details see 20 ItK/30 negotiations and "Ab Svenska Castra" dummy company arrangement in previous page) the Germans released the 12-gun shipment and it arrived to Finland in January of 1940. The last 6 guns ordered from MAVAG never arrived. All in all the Finns managed to get 53 guns total before starting of Winter War. During Winter War Sweden was the largest supplier of these guns and most of the guns it delivered were in fact loaned from Swedish Army. By 13^th of March 1940 (the day Winter War ended) the total number of 40-mm Bofors guns in Finnish use had climbed to about 100. Next large purchase happened when during Interim Peace Finland managed to buy 92 guns from Germany, these probably originated from Poland, Netherlands and Austria, they arrived in November of 1940. From these 92 guns coming from Germany 56 arrived with S/S Lutjehörn 9th of November 1940 and 36 with the same ship 20^th of November 1940. Finnish license production did not produce its first guns until year 1941 and produced only 77 guns. As usual Finnish guns Lokomo manufactured barrel blanks while Crichton-Vulcan manufactured much of the parts needed for the gun carriages. Finnish license manufacturer VTT (Valtion Tykkitehdas = State Artillery Factory) manufactured rest of the parts and built the guns. VTT delivered 12 guns in 1941, 45 guns in 1942, 14 guns in 1944 and 6 guns in 1945. The total number of 40-mm Bofors guns in Finnish use during World War 2 reached about 300 or so.

Some of the deliveries of 40-mm Bofors guns to Finland:

(Notice: This chart might be missing delivery or two, however the total it gives seems to be pretty close to real number and most data is double or triple verified. The total is 306, from which 300 delivered during the war as the last 6 guns of license production were not finished until only after it).

PICTURE: 40-mm Bofors anti-aircraft gun equipped with gun shield near shore of River Syväri / Svir in June of 1942. Finnish troops used 40-mm Bofors sometimes also for direct-fire against surface targets and probably mainly due to it some of the guns were equipped with gun shields. Photographed by Military Official A. Viitasalo. (SA-kuva.fi photo archive, photo number 95920). CLICK THUMBNAIL TO SEE LARGER PIC (132 KB).

As usual Finnish military ended up with collection of 40-mm Bofors guns manufactured in variety of countries. During World War 2 the Finnish Army naming system used to separate these various models seems to have been quite mixed. "40 ItK/38" seems to have been used as a name for Finnish license-made version already during the war, but otherwise the information looks quite sketchy. In wartime naming system the letter "B" (like "40 ItK/36 B") meaning "Bofors" seems to have been commonly used to separate these guns from 2-pound pom-pom AA-guns. Letters "BK" were used in similar manner with to indicate fixed version of the gun and "BK 2" for fixed twin-barrel version. The chart below shows Finnish Army post-war naming system.

40-mm Bofors guns used in Finland according Finnish Army post-WW2 naming system:

(Notice: 40 ItK/Bofors was not really how Finns called these guns, but instead guns were called with exact models listed in this chart as guns had small differences, mainly in gun-counters and sights).

(*) It seems that these guns were actually made by Bofors. They had been ordered by United Kingdom, but had not been delivered before starting of World War 2. Since Great Britain was in war with Germany the neutral Sweden refused to deliver these guns to UK. In this situation at October of 1939 Finland succeeded securing license of Great Britain for these guns to be delivered to Finland instead. It seems that at least 12 of the 44 guns delivered from Sweden in October and December 1939 were these guns originally ordered by Great Britain. Finnish military named the 12 guns as 40 ItK/39. Exceptionally these guns had no predictor sights.

Many countries used somewhat simple sight arrangements (like annular sights) with 40-mm Bofors during World War 2. Finland however was somewhat exception in this, as the large majority of Finnish guns were equipped with Bofors made "Bofors course and speed corrector", which was small mechanical computer connected to sight and could be used against targets which had speed up to 563 km/hour. Also guns manufactured under license in Finland were equipped with m/38 version of "Bofors course and speed corrector" predictor gun sights. From all Finnish used 40-mm Bofors guns without "Bofors course and speed corrector" both Hungarian and Austrian made guns had other type of predictor gun sights. The Austrian made guns had Goertz system while Hungarian made guns had "34/38M Johasz-Gamma Loelemkepzo" on-carriage predictor sight. From these three simple mechanical computers Goertz was least effective, while Bofors and Johanz-Gamma were about equally effective, but Hungarian Johanz-Gamma was the easiest to use. Only very few guns in Finnish use did not have any of these three predictor sights. The influence of these sight systems was very clear: They demanded well-trained crews, but as the Finns managed to train their AA-gun crews well they made 40-mm Bofors guns in Finnish use more effective and accurate than what was average internationally during World War 2.

PICTURE: 40-mm Bofors anti-aircraft gun being used against Soviet bunkers in Lotinanpelto (River Syväri / Svir) in July of 1942. Photographed by Military official A. Viitasalo (SA-kuva.fi photo archive, photo number 96780). CLICK THUMBNAIL TO SEE LARGER PIC (95 KB).

The guns came with several gun mount versions, but they can be roughly divided to mobile ones (two-axle arrangement with four wheels attached to guns mount) and fixed naval versions. The fixed naval guns were water-cooled and very rare in Finnish use - only two twin barrel guns and four single barrel naval guns existed in Finnish use and they were used on Väinämöinen and Ilmarinen. Both Väinämöinen and Ilmarinen each had one twin-barrel gun and two single-barrel guns of naval version - all manufactured by Bofors in Sweden and acquired after Winter War. On its other ships Finnish Navy was using normal mobile 40-mm Bofors guns with their undercarriage removed and rest of gun mount bolted on ship deck. Fixed guns created in this manner were also used on armoured trains during Continuation War, while all six Landsverk II anti-aircraft tanks used by Finnish Army were equipped with guns license-manufactured by VTT.

Bofors 40-mm was the gun with which Finnish soldiers were very happy. It had good shooting accuracy, enough range, firepower and very good reliability. During Winter War Finnish 40-mm Bofors guns shot down 128 planes while spending only 392 shots per downed aircraft. As World War 2 progressed Soviets introduced Sturmovik ground attack aircraft, which was practically almost immune to high explosive shells of 20-mm guns. This made 40-mm Bofors even more important weapon for Finnish air-defence during late part of Continuation War. In Finnish use 40-mm Bofors antiaircraft-guns downed over 500 enemy aircraft during World War 2. Wartime use included also being used as direct-fire support weapon and (however very rarely) also in antitank role.

PICTURE: 40-mm Bofors AA-gun without undercarriage. With undercarriage removed rest of the gun could be easily bolted to ship deck. Most of the 40-mm Bofors guns used by Finnish Navy were in this configuration. (Photo taken in Ilmatorjuntamuseo). CLICK THUMBNAIL TO SEE LARGER PIC (205 KB).

Finnish military used variety of ammunition with its 40-mm Bofors guns. High-explosive tracer (HE-T) ammunition (ammunition-type used against aircraft) was naturally the most commonly used. This also seem to have been the only ammunition type in use when Winter War started. During that war Finnish military bought also armour-piercing (AP) and armour-piercing capped tracer (APC-T) rounds, which became widely available. Several HE-T versions existed in Finnish use, the one with longest burning tracer version had 10-second tracer, which burn up to 4,500 meter distance.

Finnish military continued using 40-mm Bofors anti-aircraft guns also after World War 2. Circa year 1947 Bofors introduced L/70 version, which had both longer gun barrel and more powerful ammunition. The old version became known as L/60 (name coming from rough barrel length of each version). Finnish military had the wartime 40-mm Bofors L/60 anti-aircraft guns in training-use for a long time and then storage them for possible wartime use until 1990's. Galileo P 36 counter equipped more modern version of L/60 called "40 ItK/36-59" was introduced in late 1950's and remained in Finnish use until late 1990's.

37/30 Ma (37-mm Naval gun Maxim) (1-pound pom-pom): This water-cooled and belt-fed automatic cannon was real granddad of automatic-cannons and first gained its popularity in Boer War. In Britain the gun was rather well known as 1-pound pom-pom gun. Imperial Russia bought small number of these guns from Maxim-Nordenfelt factory in 1890's and during World War 1 Russian Navy ordered additional 120 guns from Russian Obuhov factory. Also Finnish company Ab H. Ahlberg & Co Oy built about 60 guns during World War 1 and when Civil War of 1918 ended about half of these were still unfinished so they remained in Finland. Finnish White Army captured total of 50 - 60 guns in Civil War of 1918. The gun mount for these guns was column mount designed for naval use. It offered 360-degree traverse and about 70-degree elevation, so in theory these guns could be used as antiaircraft-guns. The Finns managed to get bit over 30 guns of the captured guns to working order and they were used in warships and coastal artillery fortifications. Two of these guns also saw service in automatic-cannon wagons of armoured trains from 1918 to late 1930's. 37-mm Maxim automatic gun was never popular in Finnish use as it was unreliable and had quite a short range. Main reason for the short range was in 37 mm x 94R ammunition (with moderate muzzle velocity of only about 440 m/sec), which did not really have the ballistics needed for proper antiaircraft-use. As this would not have been enough the reliability of old fuses used in their high explosive shells also proved questionable. During World War 2 some of these guns were used in coastal artillery forts, where their unsuitability for anti-aircraft use became painfully obvious. However they were not totally useless - the guns proved somewhat reliable when fired with only low elevation. This was likely because shooting with low elevation did not stress their fabric ammunition belts as much as shooting with higher elevation. Their theoretical rate of fire was around 200 - 250 rounds per minute and maximum range around 4,400 meters. In either case, Finnish coastal defence decided to use them mainly as close range defence weapons of its coastal forts against surface targets and these old guns proved somewhat successful in this role. Still, since the coastal forts had rather limited number of anti-aircraft weapons, when needed these guns were also used against enemy aircraft. At least once this produced also results - Humaljoki Coastal Artillery Battery in Karelian Isthmus downed Soviet bomber with 37-mm Maxim automatic cannon in 25th of December 1939. Anyway, by end of World War 2 they were terribly outdated. So the last remaining 16 guns were ordered to be scrapped soon after Continuation War ended in 1944.

37 ItK/37 (3,7 cm Flak 37) (37 mm antiaircraft gun model 1937): This German anti-aircraft gun was based to earlier 3,7 cm Flak 18 and 3,7 cm Flak 36 anti-aircraft guns. Basically it was earlier 3,7 cm Flak 36 gun adopted to use new Flakvisier 40 sight. Transporting equipment for mobile version was two-wheeled trailer quite similar to one used with German mobile 20-mm antiaircraft-guns. The gun was otherwise good, but the projectiles it fired were not as powerful as the ones used in it number one competitor 40-mm Bofors. Finnish military acquired four of these guns and 3,200 (37 mm x 263B calibre) shells for them in September of 1944. Usually German antiaircraft-guns bought in Finland were new, but exceptionally these four guns were used. The guns were fixed version and had clearly seen a lot of use. As the guns were in very poor shape they required repairs before they could be issued, but the war ended before completion of repairs. When the Continuation War ended, so did the interest of Finnish military towards these guns, which had their own ammunition, that was not used in any other guns used by Finnish military. Organising maintenance and spare-parts for only four guns did not make any sense during peacetime. Hence the guns were never repaired or issued to military use.

PICTURE: One of the four Finnish bought 37 ItK/37 anti-aircraft guns with fixed mount. This gun was never taken in use in Finland. (Photo taken in Ilmatorjuntamuseo). CLICK THUMBNAIL TO SEE LARGER PIC (166 KB).

37 ItK/39 ss (37 mm antiaircraft gun model 1939) (37 m/m Zenitnaja Puska obr. 1939 g.): This Soviet antiaircraft-gun was based to Bofors design and its calculator was probably based to German designs, otherwise its aiming devices were Soviet designed. Even if the design was heavily based to Bofors, the Soviets decided to build it in 37-mm calibre. Reducing calibre allowed Soviets to increase rate or fire up to 160 shots per minute. However the benefit of this was questionable, as their 37-mm ammunition (based to 37-mm Colt-Browning) was less effective than 40 mm x 311R used in Bofors guns. Soviets manufactured about 18,000 guns of this model during World War 2. The Finns captured only few of these guns intact. As almost no ammunition was captured with them and ammunition type was not used or manufactured by the Finns, only one of the captured guns saw ever use with Finnish military. That one gun captured near Karhumäki - Poventsa road in year 1941 served shortly in Finnish use, as troops capturing it took it immediately to own use. The gun was so close copy of 40-mm Bofors, that Finnish soldiers familiar with Bofors gun could easily use it. However as only 110 rounds were captured with the particular gun its career in Finnish use was very short. The abbreviation "ss" in name of this gun is abbreviation of term "sotasaalis" (captured). After World War 2 also China manufactured copy of the gun in very large numbers.

PICTURE: 37 ItK/39 anti-aircraft gun. (Photo taken in Museum of Sappers, Artillery and Signal Corps in St. Petersburg, Russia). CLICK THUMBNAIL TO SEE LARGER PIC (221 KB).

This belt-fed 40-mm automatic manufactured under license by Vickers. In Britain it was rather commonly known as 2-pound pom-pom gun. The gun was based to the older 1-pound (37-mm) version, which in turn was basically enlarged version of Maxim machinegun. Subsidiary company of Vickers in Italy was Vickers-Terni, which introduced the 40-mm version year 1915. Besides calibre and size these automatic guns shared working principle of 37-mm Maxim automatic cannon. Unfortunately these shared characteristics included also unreliability and short range (caused by weak ballistics of 40 mm x 158 R ammunition). The unreliability was partly due to fabric ammunition belts used with these guns. After World War 1 development of 40-mm Vickers automatic gun continued and they saw large-scale use with British Navy during World War 2.

PICTURE: 40/40 V15 Vickers naval gun with its fixed column mount used for beach defense in Hanko / Hango / Gangut Coastal Defense Sector in year 1941. Photographed by 2^nd Lieutenant Pentti Nikulainen. (SA-kuva.fi photo archive, photo number 32756). CLICK THUMBNAIL TO SEE LARGER PIC (188 KB).

During World War 1 Russian Army and Air Force ordered number of , which were also used in ships of Russian Navy. The Finns captured few in Civil War of 1918. Finnish military had two names for these guns - 40 ItK/15 V (40 mm antiaircraft gun model 1915 Vickers) and 40/40 V15 (40-mm naval gun with 40 caliber barrel, model 1915 Vickers). During World War 2 Finnish military had four of these captured guns, for which Crichton-Vulcan had manufactured new column mounts year 1934. Vickers continued to further developing the guns and was selling them actively in 1920's and 1930's. Year 1932 Finnish Navy bought eight of these improved guns. They were called 40 ItK/34 V (40 mm antiaircraft gun model 1934 Vickers) and 40/40 V34 (40-mm naval gun with 40 caliber barrel, model 1934 Vickers). The new 40/40 V34 guns were installed to then brand new Finnish coastal defence ships Väinämöinen and Ilmarinen, which were the largest and most heavily armed ships of Finnish Navy. Finnish soldiers found the original trigger system complicated to use, so it was replaced with pedal-like trigger. Finnish military bought additional four 40/40 V34 guns from Swedish Naval Administration in October of 1939. This increased the total number of 40-mm Vickers guns in Finnish use during Winter War to 16 guns. Finnish Navy has such a shortage of weapons it found use to all of these 16 guns during Winter War. Besides the eight guns already installed to Ilmarinen and Väinämöinen the other six guns were used to arm three Finnish ice-breakers (Jääkarhu, Voima and Sisu) and the remaining two guns were installed to gunboats Uusimaa and Hämeenmaa. The guns proved as poor in wartime use that the peacetime experiences had already earlier suggested. So after Winter War the eight guns on Ilmarinen and Väinämöinen were replaced with 40-mm Bofors guns. During Continuation War 40-mm Vickers automatic guns were mostly used in coastal fortifications. But two were also in auxiliary ships Ääninen and Laatokka. In coastal fortifications they were mostly intended to be used mainly against surface targets, but when needed they also served as antiaircraft-guns. After 2^ndWorld War 14 guns still remained, but they were so outdated, that they do not seem to have seen any post-war use. Apparently at least some of the Finnish-used 40/40 V34 guns had been manufactured by Terni in Italy. Improvements made by Vickers to this gun type after World War 1 included introducing new ammunition type, which gave somewhat better ballistics. While the old ammunition had projectiles, which weight about 900 grams and had muzzle velocity around 600 meters/second the projectiles of new ammunition weight only about 760 grams and had muzzle velocity around 730 meters/second. However all of the 40-mm Vickers Naval guns acquired to Finland seem to have used old type ammunition.

PICTURE: 40/40 V34 Vickers naval gun as anti-aircraft gun in Finnish use in coast of Lake Laatokka / Ladoga. Photographed by Senior Sergeant Arvo Häkönen on Kuhavuori Hill in town of Sortavala in April of 1942. (SA-kuva.fi photo archive, photo number 83272). CLICK THUMBNAIL TO SEE LARGER PIC (61 KB).

• 45/47 N (Captured 45-mm naval/coastal gun with 47 caliber barrel, Soviet): Finnish military captured small number (at least 16) of these Soviet semi-automatic guns with L/47 barrels during Continuation War. They used same ammunition as Soviet 45-mm antitank guns and were known as "21-K" in Soviet use. Just like the antitank-gun it was likely based the gun has semi-automatic (in that sense that after firing a shot it removed cartridge case and remained open for another round to be inserted) breech system with vertical sliding breech-block. Finnish Navy and coastal artillery used the guns both against aircraft and surface targets. The (original Soviet) gun mounts used in them offered elevation from -15 degrees to +85 degrees and among captured ammunition was also ammunition intended for antiaircraft-use, so the gun was quite suitable for this sort of dual role. Maximum rate of fire was around 20 - 25 shots per minute. Finnish Navy used these guns (one gun per ship) in minesweepers Narvi and Jurmo and support ships Pansio, Porkkala and Pukkio. At least at some point while in Finnish use, these guns were equipped with flash hiders. Most if not all of the 14 guns were refurbished and equipped with new sights in 1950's. Most of the remaining guns were scrapped in 1980's.



PICTURE: Captured Soviet 45/47 N gun in Helsinki Naval Station. Photographed by Military official Esko Salmela in January of 1944. (SA-kuva.fi photo archive, photo number 145178). CLICK THUMBNAIL TO SEE LARGER PIC (92 KB).

 

• 47/40 H (47-mm Hotchkiss naval/coastal gun with 40 caliber barrel, model Hotchkiss) and 47/40 O (47-mm Obuhov naval/coastal gun with 40 caliber barrel, model Obuhov): Both of these guns were simple naval/coastal guns, which Russian military had started acquiring already in 1880's. Both guns had 47-mm calibre L/40 long barrel and breech system with vertical sliding breech-block. Great majority of these guns had gun mounts, which did not allow enough elevation for them to be used as antiaircraft-weapons, but a few had. The Finns captured 22 47-mm Hotchkiss guns and bit over twenty 47-mm Obuhov guns in year 1918. The Russians has equipped four of the Hotchkiss guns with antiaircraft-gun mounts, which offered about 85-degree elevation and during World War 2 Finnish Navy used two of these four guns. In addition Finnish company Kone- and Siltaosakeyhtiö equipped one of the guns (presumably Obuhov one, but it may have also been Hotchkiss gun) with fixed gun mount suitable to antiaircraft use, but there does not seem to be certainty if this one gun saw any actual use during the war or not.

SOURCES:

Raimo Vehviläinen, Ahti Lappi and Markku Palokangas: Itsenäisen Suomen Ilmatorjuntatykit 1917 - 2000 / The Anti-aircraft Guns of Independent Finland 1917 - 2000.

Alex Buchner: Deutche and allieerte heereswaffen 1939 - 1945.

Heikki Tiilikainen and Ilmari Pusa: Talvisodan jäinen loppunäytös

Terry Gander: The 40 mm Bofors Gun.

Terry Gander and Peter Chamberlain: Small Arms, Artillery and Special Weapons of the third reich.

Ian Hogg: Twentieth-Century Artillery.

Chris Chant: Artillery of World War II.

Stig A. Fransson: Bofors 350 år.

Raimo Vehviläinen: Ilmatorjuntamuseo-opas.

Pekka Kiiskinen and Pasi Wahlman: Itsenäisen Suomen laivaston laivatykit 1918 - 2004.

Pentti Palmu: Yön yli päivään, Suomen Ilmatorjunnan vaiheita 1925 - 1990.

Ilmatorjuntajoukot 1925 - 1960 by E. Peura, Niilo A. A. Simojoki, J. Lapinleimu, O. Ranta, V. Rantalainen and L. Pamppunen.

Ahti Lappi: Ilmatorjunta ilmasodassa 1794 - 1945.

Talvisodan historia series, parts 1 and 4.

Jatkosodan historia series, parts 1 and 6.

Ove Enqvist: Itsenäisen Suomen rannikkotykit.

Koivisto ja Viipurinlahti by Lyytinen, Reponen, Pohjanvirta and Hukari.

Markku Palokangas: Sotilaskäsiaseet Suomessa 1918 - 1988.

Risto Erjola: Aseiden valmistus Suomessa vuosina 1939 - 1945

Military manual: Ilmatorjuntatykistön Ampumatarvikkeet by Ilmavoimien Esikunta, Ilmatorjunta Osasto (World War 2 era).

Military manual: Ilmatorjuntaohjesääntö VI3, Ilmatorjuntaerikoishuolto, Ilmatorjunta-ampumatarvikkkeet (II Painos) (introduced November of 1941).

Military manual: 40/ItK/38 Bofors-tykin kalusto-ohje.

Military manual: Ilmatorjuntatykkien 40 ItK/Bofors kalusto-opas (1960).

Military manual: 40 mm ilmatorjuntatykki (40 ItK Bofors), Kalusto-opas by Pääesikunta (1979).

Military manual: Ilmatorjuntamies 1950.

Military manual: Ampumatarvikenimikkeistö by Puolustusvoimien Pääesikunta Taisteluvälineosasto (printed 1941).

Military Manual: Ampumataulukko Konekivääritykille 40/39 1915 V by Taisteluvälineosasto T.1.

Military manual: Lyhennetty tykistön ampumatarvikenomenklatuuri (printed 1939).

Finnish military archives, archive reference T19043/20

Werner Müller: German medium flak in combat - 20mm-88mm FLAK.

Werner Müller: Die leichte und mittlere Flak 1906 - 1945, eingesetzt bei den Waffengattungen an allen Fronten.

Pentti Toivonen: Salpauselän ilmatorjuntapatteristo 1928 - 1988.

Military manual: It-joukkojen erikoisohjeita (30th of December 1939) by Ilmapuolustuksen Esikunta.

Article: Ilmatorjuntatykistömme 1925 - 45 by Jalmari Lapinleimu in Kansa Taisteli magazine vol. 11/1976.

Special thanks to Ilmatorjuntamuseo (Finnish Antiaircraft Museum), Tuusula.

Special thanks to Sotamuseo (Finnish Military Museum), Helsinki.

Special thanks to Bunkkerimuseo (Bunker Museum), Virolahti.