After the end of the First World War, many countries were armed with 37-mm automatic anti-aircraft guns Maxim-Nordenfeldt and 40-mm automatic anti-aircraft guns Vickers.
Both systems had a similar scheme of automatic operation based on the principle of using recoil energy with a short barrel stroke.
The world's first 37-mm automatic cannon was created by the American H. S. Maxim in 1883. In general, by design, it was an oversized, well-known machine gun.
All mechanisms of a 37-mm machine gun were mounted in a casing and a box. The casing guided the barrel when firing and was a reservoir for the coolant, and the spring knurler was also in the same fluid. The excess recoil energy was absorbed by the hydropneumatic buffer.
For food, a cloth tape for 25 shells was used. The weight of the projectile was about 500 g. The shells used were a cast iron grenade with a bottom shock tube, buckshot with 31 bullets or a remote grenade with an 8-second tube. The rate of fire is 250-300 rds / min.
The Vickers assault rifle was a lightweight and somewhat simplified Maxim assault rifle with a water-cooled barrel. The changes made it possible to reduce the size of the box and the weight of the machine in comparison with the Maxim.
40-mm Vickers automatic cannon
Both types of guns were used mainly in the fleet, which was due to the need for weapons in clean water to cool the barrels, their significant weight (400-600 kg) and the complexity of the design.
These assault rifles proved to be very effective air defense systems. A relatively powerful projectile had a good destructive effect, often the affected aircraft fell apart in the air. Automatic fire made it possible to create a sufficient density of fire and sharply increased the likelihood of hitting a target.
The general disadvantages of the machines were: the complexity and high cost of manufacturing, difficult cleaning and preparation for firing, the use of cloth tape and the long path of the cartridge when fed from the tape, low reliability.
Soon, due to the rapid development of aviation, these guns ceased to meet the demands of the military. A more reliable and long-range weapon was required for firing at air targets.
In the summer of 1930, Sweden began testing a new 40-mm automatic gun, which was developed by Victor Hammar and Emmanuel Jansson, designers of the Bofors plant.
The automatic gun is based on the use of the recoil force according to the scheme with a short recoil of the barrel. All actions necessary for firing a shot (opening the bolt after a shot with extracting the sleeve, cocking the striker, feeding cartridges into the chamber, closing the bolt and releasing the striker) are performed automatically. Aiming, aiming of the gun and the supply of clips with cartridges to the store are carried out manually.
The Swedish Navy has shown interest in the new system. Official trials for the Swedish Navy began on March 21, 1932. At the end of the tests, it received the name Bofors 40-mm L / 60, although the barrel was actually 56, 25 calibers, and not 60, as the name suggests. A high-explosive 900g projectile (40x311R) left the barrel at a speed of 850 m / s. The rate of fire is about 120 rds / min, which increased slightly when the gun did not have large elevation angles. This was due to the fact that gravity helped the ammunition supply mechanism. Those. the own weight of the shells helped in the work of the reloading mechanism.
The practical rate of fire was 80-100 rds / min. The shells were loaded with 4-round clips, which were inserted manually. The gun had a practical ceiling of about 3800m, with a range of more than 7000m.
The automatic cannon was equipped with an aiming system that was modern for those times. The horizontal and vertical gunners had reflex sights, the third member of the crew was behind them and worked with a mechanical computing device. The sight was powered by a 6V battery.
However, the recognition of the new system, as is often the case, did not take place at home. Swedish sailors believed that the optimal calibers for anti-aircraft guns were 20-25 mm, so they were in no hurry to order less rapid-fire 40-mm anti-aircraft guns.
The first customer of the L60 anti-aircraft guns was the Dutch fleet, which installed 5 twin installations of this type on the light cruiser De Ruyter.
Light cruiser "De Ruyter"
In the future, the Dutch fleet purchased several more consignments of anti-aircraft guns to arm the ships. The guns were mounted on a special stabilized installation developed by the Dutch company Hazemeyer. In the late 1930s, this installation was the world's most advanced short-range anti-aircraft weapon.
The gun entered service with the Swedish Navy after testing and trial operation only in 1936. The first versions of 40 mm guns were used on submarines. The barrel was shortened to 42 calibers, which reduced the muzzle velocity to 700 m / s. When this gun was not in use, the barrel was lifted up, and the gun was retracted into a waterproof cylindrical case. The shortened gun was used on submarines of the Sjölejonet type, on which it was the only deck gun powerful enough to provide effective fire on small ships.
In 1935, a land version of this gun appeared. It was installed on a four-wheel towed "cart". In case of urgent need, the shooting could be conducted directly from the gun carriage, i.e. "Off the wheels" without additional procedures, but with less accuracy. In the normal mode, the carriage frame was lowered to the ground for greater stability. The transition from the "traveling" position to the "combat" position took about 1 minute.
With a unit weight of about 2000 kg, its towing was possible with an ordinary truck. The calculation and ammunition were located in the back.
The gun was popular with foreign customers. Belgium became the first buyer of anti-aircraft guns. Countries that purchased Bofors L60 anti-aircraft guns in the late 1930s included Argentina, Belgium, China, Denmark, Egypt, Estonia, Finland, France, Greece, Norway, Latvia, Netherlands, Portugal, Great Britain, Thailand and Yugoslavia.
The Bofors L60 was produced under license in Belgium, Finland, France, Hungary, Norway, Poland and the UK. Bofors L60 was produced in very significant quantities in Canada and the USA. More than 100 thousand 40-mm Bofors anti-aircraft guns were manufactured all over the world by the end of World War II.
Anti-aircraft 40-mm guns produced in different countries were adapted to local conditions of production and use. Components and parts of guns of different "nationalities" were often not interchangeable.
The greatest difference from the "original" had anti-aircraft guns of British manufacture. The British did a tremendous job of simplifying and cheapening the guns. To speed up guidance on fast-moving and diving aircraft, the British used a mechanical analog computer Major Kerrison (A. V. Kerrison), which became the first automatic anti-aircraft fire control system.
Mechanical analog computer Kerrison
Kerrison's device was a mechanical calculating and deciding device that allows you to determine the gun pointing angles based on data on the position and movement of the target, the ballistic parameters of the gun and ammunition, as well as wind speed and other external conditions. The resulting guidance angles were automatically transmitted to the weapon guidance mechanisms using servomotors.
A crew of three people, receiving data from this device, aimed the weapon quite easily and with good accuracy. When using this device, the computer controlled the aiming of the gun, and the crew could only load the gun and fire. The original reflex sights were replaced by simpler circular anti-aircraft sights, which were used as backups.
In this modification, the QF 40 mm Mark III cannon became the army standard for light anti-aircraft guns. This British 40mm anti-aircraft gun had the most advanced sights of the entire Bofors family.
However, in battles, it was found that the use of the Kerrison device in some situations was not always possible, and in addition, a supply of fuel was required, which was used to power the generator. Because of this, in most cases, when shooting, they most often used only conventional ring sights, without using any target designation and calculating lead corrections, which greatly reduced the accuracy of shooting. Based on combat experience, a simple trapezoidal Stiffkey device was developed in 1943, which moved the ring sights to introduce corrections when firing and was controlled by one of the anti-aircraft gunners.
The British and Americans, using the Bofors L60, have created a number of SPAAGs. Anti-aircraft guns with an open turret were mounted on the chassis of the Crusader tank. This self-propelled anti-aircraft gun was named Crusader III AA Mark I.
ZSU Crusader III AA Mark I
However, the most common British 40mm SPAAG was the "Carrier, SP, 4x4 40mm, AA 30cwt", created by mounting an anti-aircraft gun on the chassis of a conventional four-wheeled Morris truck.
ZSU "Carrier, SP, 4x4 40-mm, AA 30cwt"
In the USA "Bofors" were mounted on modified 2, 5 t chassis of GMC CCKW-353 trucks.
These self-propelled guns were used to support the ground forces and provided quick protection against air attacks without the need for a stationary installation on the ground and deploying the system into a combat position.
After the fall of Holland in 1940, part of the Dutch fleet went to Great Britain, and the British had the opportunity to get acquainted in detail with the Hazemeyer 40-mm naval installations. 40-mm Dutch naval anti-aircraft guns "Hasemeyer" favorably distinguished in combat and service-operational characteristics from the British 40-mm "pom-poms" of the firm "Vickers".
Firing from a 40-mm Vickers anti-aircraft gun
In 1942, the UK began its own production of such installations. In contrast to the "land" anti-aircraft guns, most of the naval guns were water-cooled.
For the American and British fleets, a large number of one, two, four and six-barreled anti-aircraft guns were developed, including those with radar guidance.
In the American navy, this gun is considered the best anti-aircraft machine gun of the Second World War, 40-mm anti-aircraft guns turned out to be the most effective against Japanese kamikaze aircraft. As a rule, one direct hit from a 40-mm fragmentation projectile was enough to destroy any Japanese aircraft used as a "flying bomb".
The effective fire range of 40-mm anti-aircraft guns was twice as high as that of 12, 7-mm machine guns and 20-mm anti-aircraft guns.
At the end of the war, the Bofors almost completely replaced the Oerlikon 20-mm automatic cannons on large warships.
Despite the fact that Germany had its own 37-mm Rheinmetall anti-aircraft machine gun, the 40-mm Bofors L60 was actively used in the armed forces of Germany and its allies.
The captured Bofors captured in Poland, Norway, Denmark and France were used by the Germans under the designation 4-cm / 56 Flak 28.
Abandoned Polish 40-mm anti-aircraft gun Bofors L60 against the background of a defeated column
A number of these Norwegian-made guns were used on submarines and on the Admiral Hipper and Prince Eugen cruisers.
In Finland and Hungary, these guns were produced under license and used throughout the war.
Finnish 40-mm automatic anti-aircraft gun "Bofors" L60 on an armored train
In Japan, an attempt was made to launch the Bofors L60 into series production after several British air-cooled units were captured in Singapore. The Japanese anti-aircraft gun received the designation 4 cm / 60 Type 5, but was not produced in significant quantities due to the weakness of the production base.
But the most massive copy of the Bofors L60 was the Soviet 37-mm automatic anti-aircraft gun mod. 1939 g. also known as 61-K.
After the failure of the attempt to launch into mass serial production at the plant near Moscow. Kalinin (No. 8) of the German 37-mm automatic anti-aircraft gun "Rheinmetall", due to the urgent need for such an anti-aircraft gun, at the highest level it was decided to create an anti-aircraft machine gun based on the Swedish system, which by that time had received worldwide recognition.
37-mm automatic anti-aircraft gun mod. 1939 g.
The gun was created under the leadership of M. N. Loginov and in 1939 it was put into service under the official designation “37-mm automatic anti-aircraft gun mod. 1939.
According to the leadership of the gun service, its main task was to combat air targets at ranges up to 4 km and at altitudes up to 3 km. If necessary, the cannon can also be used for firing at ground targets, including tanks and armored vehicles.
Mastering it in production went with great difficulties, the percentage of rejects was high. Before the start of the war, it was possible to release about 1,500 37-mm anti-aircraft guns. True, their quality left much to be desired, delays and refusals during shooting were very frequent.
On June 22, 1941, the Red Army had 1214 "37-mm automatic anti-aircraft guns mod. 1939 ". During the battles of 1941, anti-aircraft guns suffered significant losses - until September 1, 1941, 841 guns were lost, and in 1941 - 1204 guns. Huge losses were hardly compensated for by production - as of January 1, 1942, there were about 1600 37-mm 61-K anti-aircraft guns in stock.
In the initial period of the war, 37-mm anti-aircraft guns entered the anti-tank artillery brigades and anti-tank regiments as standard weapons for fighting tanks. In 1941, 320 37-mm anti-aircraft guns were sent to the anti-tank subunits. In 1942, anti-aircraft guns were removed from anti-tank artillery.
A significant number of 61-K were captured as trophies by German troops. In the Wehrmacht, these guns received the index 3, 7 cm Flak 39 (r) and were used in battles - so, by January 1944, the troops had 390 such guns.
37-mm automatic anti-aircraft gun 61-K captured by the Germans
During the war years in the USSR, the 40-mm Bofors L60 were massively supplied by the allies. In terms of its ballistic characteristics, the 40-mm Bofors cannon was somewhat superior to the 61-K - it fired a slightly heavier projectile at a close muzzle velocity. In 1940, comparative tests of the Bofors and 61-K were carried out in the USSR, according to their results, the commission noted the approximate equivalence of the guns.
61-K during the Great Patriotic War were the main means of air defense of the Soviet troops in the front line. The tactical and technical characteristics of the gun allowed it to effectively fight the enemy front-line aviation, but until 1944 the troops experienced an acute shortage of automatic anti-aircraft guns. Only at the end of the war were our troops adequately covered from air strikes. On January 1, 1945, there were about 19,800 61-K and Bofors L60 guns.
After the end of World War II, the 37-mm 61-K and 40-mm Bofors L60 anti-aircraft guns took part in many armed conflicts, in a number of countries they are still in service today.
In the United States, 40-mm Bofors L60 assault rifles are used on Lockheed AC-130 gunships for firing at ground targets.
Reloading the 40mm Bofors L60 gun aboard the AC-130
These anti-aircraft guns have become the most "belligerent" in all the years of their use, more aircraft were shot down than all other anti-aircraft guns combined.
A further development of the Bofors L60 system was the 40-mm Bofors L70 anti-aircraft gun, which uses a more powerful 40 × 364R ammunition with a projectile slightly lighter up to 870 g, which made it possible to increase the muzzle velocity to 1030 m / s.
40 mm Bofors L70
In addition, the gun carriage and recoil mechanism were redesigned. The first copy of the new gun was made in 1947. In November 1953, this weapon was adopted as the standard NATO anti-aircraft gun and soon it began to be produced in thousands of series.
Over the years of production, several versions of this anti-aircraft gun were created, which differed in the power supply scheme and sighting devices. The latest modifications of this gun had a rate of fire of 330 rounds per minute.
In addition to the Bofors L70 towed anti-aircraft gun itself, they were used in self-propelled anti-aircraft guns: VEAK-4062 and M247 Sergeant York.
Over the years of production, several versions of this anti-aircraft gun were created, which differed in the power supply scheme and sighting devices. The latest modifications of this gun had a rate of fire of 330 rounds per minute.
In addition to the actual towed anti-aircraft gun Bofors L70, they were used in self-propelled anti-aircraft guns: VEAK-4062 and M247 Sergeant York.
ZSU M247 Sergeant York
In the Swedish army, this gun is armed with the CV9040 BMP, in order to place it in the turret it was necessary to turn the gun upside down. New ammunition has been developed for this weapon, including: sub-caliber and fragmentation with remote detonation.
BMP CV9040
The Bofors L / 70 is used as the main gun on the South Korean K21 infantry fighting vehicle.
BMP K21
The Bofors L / 70 cannons are also still used in various naval installations to arm patrol and missile boats and small-displacement combat ships.
The most modern of those where the L / 70 artillery unit is used is the Italian ZAK "Dardo" (manufactured by "Oto Melara"), designed for the anti-missile and air defense of the ship.
For firing at anti-ship missiles, high-explosive fragmentation projectiles with ready-made striking elements in the form of 600 tungsten balls and a proximity fuse are used.
Over the years, the technical solutions implemented in the 40-mm guns of the Swedish company "Bofors" in the 30s of the last century are effectively used today. There is no doubt that this system will celebrate its centenary in the ranks.
