Debut: April 2016

 




   

.: Bob Williams' Bofors AA Battery and Crew - for "The Rob McCallum Collection"

Brand &
No. :

Italeri
6458

Scale:

1/35

Modelling Time:

~ hrs

PE/Resin Detail:

none

Comments:

"A Bofors A.A. Battery with crew, in sand bags and rubble reinforced emplacement.
S.W. Germany late 1944 "

Bofors 40 mm gun

From Wikipedia, the free encyclopedia
Bofors 40 mm gun
Bofors-p004596.jpg
Bofors 40 mm/L60. This example includes the British-designed Stiffkey Sight, being operated by the aimer standing to the right of the loader (turned sideways). It operates the trapeze seen above the sights, moving the sights to adjust for lead.
Type Autocannon
Place of origin Sweden
Service history
In service 1934–present
Used by See users
Wars World War II,
Indo-Pakistani wars and conflicts,
Arab-Israeli conflict,
Korean War,
Indonesia-Malaysia confrontation,
Vietnam War,
Yom Kippur War,
South African Border War,
Falklands War,
Lebanese Civil War,
Gulf War,
Yugoslav wars
Production history
Designer Bofors Defence
Designed 1930
Manufacturer Bofors Defence (1932–2000)
United Defense Industries(2000–2006)
BAE Systems AB (2006 onwards)
Produced 1932–present
Variants See variants
Specifications
Weight

L/60: 1,981 kg (4,367 lb)

L/70: 5,150 kg (11,350 lb)
Crew dependent on use

Shell Complete round: -
L/60 40×311mmR (1.57 in), L/70 40×364mmR
Caliber 40 mm L/60–70 (actual length varies from 56–70 calibers, based on model)
Carriage 522 kg (1,151 lb)
Elevation L/60: -5°/+90° (55°/s)
L/70: -20°/+80° (57°/s)
Traverse Full 360°
L/60: 50°/s
L/70: 92°/s
Rate of fire L/60: 120 round/min
L/70: 330 round/min
Muzzle velocity L/60: 881 m/s (2,890 ft/s)
L/70: 1,021 m/s (3,350 ft/s)
Maximum firing range L/60: 7,160 m (23,490 ft)
L/70: 12,500 m (41,000 ft)

The Bofors 40 mm gun, often referred to simply as the Bofors gun,[1] is an anti-aircraft/multi-purpose autocannon designed in the 1930s by the Swedish arms manufacturer AB Bofors. It was one of the most popular medium-weight anti-aircraft systems during World War II, used by most of the western Allies as well as by the Axis powers. A small number of these weapons remain in service to this day, and saw action as late as the Gulf War.

In the post-war era the original design was not suitable for action against jet powered aircraft, so Bofors introduced a new model of significantly more power, the 40 mm L/70. In spite of sharing almost nothing with the original design other than the calibre and the distinctive conical flash hider, this weapon is also widely known simply as "the Bofors". Although not as popular as the original L/60 model, the L/70 remains in service to this day, especially as a multi-purpose weapon for light armored vehicles, as on the CV 90.

Bofors itself has been part of BAE Systems AB since March 2005.

Development

The Swedish Navy purchased a number of 2 pounder Pom-Poms from Vickers as anti-aircraft guns in 1922. The Navy approached Bofors about the development of a more capable replacement. Bofors signed a contract in late 1928. Bofors produced a gun that was a smaller version of a 57 mm (6-pounder) semi-automatic gun developed as an anti-torpedo boat weapon in the late 19th century byFinspong. Their first test gun was a re-barreled Nordenfelt version of the Finspong gun, to which was added a semi-automatic loading mechanism.

Testing of this gun in 1929 demonstrated that a problem existed feeding the weapon in order to maintain a reasonable rate of fire. A mechanism that was strong enough to handle the stresses of moving the large round was too heavy to move quickly enough to fire rapidly. One attempt to solve this problem used zinc shell cases that burned up when fired. This proved to leave heavy zinc deposits in the barrel, and had to be abandoned. In the summer of 1930 experiments were made with a new test gun that did away with controlled feed and instead flicked the spent casing out the rear whereafter a second mechanism reloaded the gun by "throwing" a fresh round from the magazine into the open breech. This seemed to be the solution they needed, improving firing rates to an acceptable level, and the work on a prototype commenced soon after.

During this period Krupp purchased a one-third share of Bofors. Krupp engineers started the process of updating the Bofors factories to use modern equipment and metallurgy, but the 40 mm project was kept secret.

Finnish Bofors 40 mm. This gun mounts the original reflector sights, and lacks the armor found on British examples.

The prototype was completed and fired in November 1931, and by the middle of the month it was firing strings of two and three rounds. Changes to the feed mechanism were all that remained, and by the end of the year it was operating at 130 rounds per minute. Continued development was needed to turn it into a weapon suitable for production, which was completed in October 1933. Since acceptance trials had been passed the year before, this became known as the "40 mm akan M/32". Most forces referred to it as the "Bofors 40 mm L/60", although the barrel was actually 56.25 calibres in length, not the 60 calibres that the name implies.[citation needed]

The gun fired a 900 g (2.0 lb) high explosive 40 × 311R (rimmed) shell at 2,960 ft/s (900 m/s).[2]The rate of fire was normally about 120 rounds per minute (2.0 rounds per second), which improved slightly when the barrels were closer to the horizontal as gravity assisted the feeding from the top-mounted magazine. In practice firing rates were closer to 80–100 rpm (1.3–1.7 rounds per second), as the rounds were fed into the breech from four round clips which had to be replaced by hand. The maximum attainable ceiling was 7,200 m (23,600 ft), but the practical maximum was about 3,800 m (12,500 ft).

The gun was provided with an advanced sighting system. The trainer and layer were both provided with reflector sights for aiming, while a third crew-member standing behind them "adjusted" for lead using a simple mechanical computer. Power for the sights was supplied from a 6V battery.

Polish-made Bofors gun after theBattle of the Bzura. This gun also mounts the reflector sight that equipped the original Bofors versions.

In spite of the successful development, the Swedish Navy changed its mind and decided it needed a smaller hand-swung weapon of 13 mm-25 mm size, and tested various designs from foreign suppliers. With the 40 mm well along in development, Bofors offered a 25 mm version in 1932, which was eventually selected as the 25 mm akan M/32.

The first version of the 40 mm the Navy ordered was intended for use on submarines, where the larger calibre allowed the gun to be used for both AA and against smaller ships. The barrel was shorter at 42 calibers long, with the effect of reducing the muzzle velocity to about 700 m/s (2,300 ft/s). When not in use, the gun was pointed directly up and retracted into a watertight cylinder. The only known submarines that used this arrangement was the Sjölejonet-class boats. The guns were later removed as the subs were modified with streamlined conning towers.

The first order for the "real" L/60 was made by the Dutch Navy, who ordered five twin-gun mounts for the cruiser De Ruyter in August 1934. These guns were stabilized using the Hazemeyer mount, in which one set of layers aimed the gun, while a second manually stabilized the platform the gun sat on. All five mounts were operated by one fire control system.

Bofors also developed a towable carriage which they displayed in April 1935 at a show in Belgium. This mount allowed the gun to be fired from the carriage with no setup required, although with limited accuracy. If time was available for setup, the gunners used the tow-bar and muzzle lock as levers, raising the wheels off the ground and thereby lowering the gun onto supporting pads. Two additional legs folded out to the sides, and the platform was then leveled with hand cranks. The entire setup process could be completed in under a minute.

Orders for the land based versions were immediate, starting with an order for eight weapons from Belgium in August 1935, and followed by a flood of orders from other forces including Poland, Norway, and Finland. It was accepted into the Swedish Army the next year, known as the "40 mm lvakan m/36", the lower-case "m" indicating an Army model as opposed to the capital "M" for Navy.

Because of the labour shortages some of the Bofors 40mm factories were opened in Poland.

The Swedish Navy adopted the weapon as the m/36 in hand-worked single air-cooled, and power operated twin water-cooled version. A twin air-cooled mounting, probably hand-worked was also used by the navies of Sweden and Argentina and a twin air-cooled wet mounting was developed for Polish submarines.

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Click on each image for a closer look

Box art:

 

British versions

Army versions

Q.F. 40 mm Mk. 1 displayed at CFB Borden. This example mounts a Stiffkey Sight, and displays the additional armor protecting the gunners.
Bofors gun on the Ley-class minehunter HMS Isis (M2010) (1978)

The British Army had first examined the weapon when they received a number of Polish-built examples in 1937 for testing, known as the "QF 40 mm Mark I" (QF standing for "quick firing"), or "Mark I/2" after a minor change to the flash hider. A licence was acquired and the gun was converted frommetric to imperial measurements. They also made numerous changes to the design to make it more suitable for mass production, as the original Bofors design was intended to be hand-assembled, and many parts were labeled "file to fit on assembly", requiring many man-hours of work to complete.

Testing showed that aiming the guns against high-speed aircraft was a serious problem. Although the gun could be trained quickly, aiming accurately while doing so proved difficult. In order to address this, the British introduced a complex mechanical analogue computer, the Kerrison Director, which drove the laying electrically. A three-man team operated the director simply by pointing it at the target whilst dialing in estimates for range and various atmospheric conditions. The director then aimed the guns directly through powered mounts, as the gunners loaded the clips. Backup sights were fitted to the individual guns, replacing the former reflector sight and lead-calculator with a ring-and-post sight known as a "pancake".

In this form, the "QF 40 mm Mark III" (Mk II was a designation used for a Vickers "pom-pom"), became the Army's standard light AA (anti-aircraft) weapon, operating alongside their 3-inch and 3.7-inch heavy weapons. The gun was considered so important to the defence of England after the fall of France in 1940 that a movie, The Gun, was produced to encourage machinists to work harder and complete more of them. By the end of the war total production from British, Canadian, and Australian factories was over 2,100, while U.S. lend-lease examples added about 150.

In combat it was found that the Kerrison was difficult to set up to use in many situations, as well as making logistics more complex due to the need to keep its electrical generator supplied with fuel. In most engagements only the pancake sights were used, without any form of correction, making the British versions less capable than those used by other forces. Eventually an anti-aircraft gunnery school on the range at Stiffkey on the Norfolk coast delivered a workable solution, a trapeze-like arrangement that moved the pancake sights to offer lead correction, operated by a new crew-member standing behind the left-hand layer. The "Stiffkey Sight" was sent out to units in 1943, arriving in Canadian units in the midst of the Battle of the Aleutian Islands. A final wartime change to the elevation mechanism resulted in the "QF 40 mm Mark XII". They also designed a much lighter two-wheeled carriage for airborne use.

The Army also experimented with various self-propelled anti-aircraft systems based on various tank chassis. Changes to the breech for this role created the "QF 40 mm Mark VI", which was used on the Crusader to produce the Crusader III AA Mark I. The main self-propelled version of the Bofors used the gun set on the chassis of a Morris Commercial four-wheel drive lorry. Such guns were used in support of Army divisions to provide swift protection against air attack without the need to unlimber. this was known as the "Carrier, SP, 4x4 40mm, AA (Bofors) 30cwt". They saw service in North West Europe, where six SP Bofors of 92nd (Loyals) Light Anti-Aircraft Regiment, Royal Artillery, landed with the British 3rd Infantry Divisionon Sword Beach on D-Day to protect the vital bridges over the Caen Canal and Orne River (Pegasus Bridge and Horsa Bridge), shooting down 17 German planes. Later in the campaign, SP Bofors were used extensively for ground shoots as well as in an anti-aircraft role. In British army service the Bofors found a highly specialised role: during the North Africa Campaign at the Second Battle of El Alamein, they were used to fire tracerhorizontally to mark safe paths for units through the German minefields. This practice was further developed during operations in North-West Europe, where bursts of colour-coded tracer were used to define the axis of advance of the different formations in large-scale night attacks.

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