Bofors Anti Aircraft Gun

Bofors Anti Aircraft Gun - 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.

Bofors Anti Aircraft Gun

Most forces referred to it as the Bofors 40 mm L/60, although the barrel was actually 56.25 calibers in length, not the 60 calibers that the name implies. The first version of the 40 mm the Navy ordered was intended for use on submarines, where the larger caliber allowed the gun to be used for both AA and against smaller ships.

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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 waterproof cylinder.

The only known submarines that used this arrangement were the Sjölejonet class boats. The guns were later removed as the subs were modified with streamlined conning towers. 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 license was acquired and the gun was converted from metric 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. When a system gets it right, it becomes a classic. For anti-aircraft guns, the standard is arguably the 40mm Bofors. It packed a punch – about two and a half ounces of high explosives as used by the United States.

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But this was not an American-designed weapon. Bofors is actually a Swedish company, and Sweden was neutral in World War II. The gun is still produced today, and is still seeing action. 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 mounting Mark V (Mark VC for Canadian built examples) for the 20 mm Oerlikon and QF 2 pounder guns was also adopted initially as an interim mount for the Bofors.

It was a single barreled mounting with hydraulic power, and was known as the Boffin. 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 by Finspong.

The Big Breakthrough

Their first test gun was a re-barreled Nordenfelt version of the Finspong gun, to which was added a semi-automatic loading mechanism. Foreign sales started, as they had in the past, with the Netherlands and the United Kingdom.

In November 1953 it was accepted as the NATO standard anti-aircraft gun, and was soon produced in the thousands. The L/70 was also used as the basis for a number of SPAAGs, notably the U.S. Army's proposed M247 Sergeant York.

Breda (now Oto Melara) of Italy uses Bofors 40 mm L/70 gun in its anti-aircraft weapon systems Type 64, Type 106, Type 107, Type 564 and Type 520. Also they have developed a CIWS system named DARDO for the Italian

Army and Navy. A newer development from Breda, the Fast Forty (essentially a DARDO gun mount with twin 40mm/L70 guns), has nearly doubled the rate of fire to 450 rpm (7.5 rounds per second) (2 × 450 in twin mount), normally equipped

Mm L/

with a 736 round magazine and a dual feed mechanism for naval use. The Bofors 40mm saw action from land and sea mounts. The land versions were usually single mounts, but twin mounts were also used in vehicles like the M42 Duster and the failed M247 Sergeant York.

On sea, the primary mount – and most effective version – was the quad 40mm mount, but twin and single mounts were also used. 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 defense 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. 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. The demonstrations in Belgium took place in the presence of representatives from the French War Ministry.

It soon resulted in an order from the French Army, which was quite remarkable. Traditionally, France bought no guns from abroad. The gun fired a 31.75 oz (900 g) HE 40 × 311R (rimmed) shell at 2,787 ft (850 m) per second.

The nominal rate of fire was in the order of 120 rounds per minute, increased slightly when the barrels were closer to the horizontal as gravity assisted the feeding from the top-mounted magazine. In practice the rate of fire was nearer 80 to 100 rpm as the rounds were fed into the breech from four-round clips that had to be replaced by hand.

The maximum attainable ceiling was 23,625 ft (7200 m), but the practical maximum was about 12,470 ft (3800 m). The new 40 mm design used a larger 40 × 364R round firing a slightly lighter 870g shell at a much higher 1,030 m/s (3,379fps) muzzle velocity.

The rate of fire was increased to 240 rounds per minute (4.0 rounds per second), similar to the German Flak 43. Additionally the carriage was modified to be power-laid, the power being supplied by a generator placed on the front of the carriage.

. The first version was produced in 1947, accepted in 1948 as the 40 mm lvakan m/48, and entered Swedish service in 1951. Additional changes over the years have improved the firing rate first to 300 rpm (5.0 rounds per second), and later

to 330 rpm (5.5 rps). The Bofors 40mm was barely enough to handle the kamikazes that the United States was facing in 1945, but the end of World War II meant its replacement by a new three-inch gun was only a partial one.

The mounts hung around through parts of the 1980s with the United States Navy. 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).

By the end of World War II, jet aircraft had so increased the speed of attack that the Bofors simply could not get enough rounds into the air to counter the aircraft before it had already flown out of range.

In order to counter these threats, the gun would have to have a longer range and a higher rate of fire, thereby increasing the number of rounds fired over the period of an engagement. Bofors considered either updating the 40 mm, or alternatively making a much more powerful 57 mm design, and in the end did both.

In the Swedish Army Combat Vehicle 90 there is a cartridge fed, automatic version of the L/70 gun installed. In order to fit inside the vehicle, the gun is mounted upside down. New armor piercing and programmable ammunition have also been developed.

Germany has used L/70 guns on its Class 352 / Class 333 and Class 332 mine hunting vessels, although these will be replaced by Rheinmetall MLG 27 remote-controlled gun systems until 2008. Until the early 80s L/70 guns guided by D7B radars

were in widespread use in the AAA role in the German Navy and Air Force until replaced by Roland SAMs. The L/70 is also chosen as the default main gun for the K21 IFV for the Republic of Korea military.

There were many difficulties in producing the guns within the United States, beyond their complexity (illustrated by the use of 2,000 subcontractors in 330 cities and 12 Chrysler factories to make and assemble the parts). The drawings were metric, in Swedish and read from the first angle of projection, with lower precision than needed for mass production.

Chrysler had to translate to English, fix absolute dimensions, and switch to the third angle of projection. Chrysler engineers also tried to simplify the gun, unsuccessfully, and to take high speed movies to find possible improvements, but this was not possible until near the end of the war.[4]

Bofors also developed a towable carriage which they displayed in April 1935 at a show in Belgium. This mound 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 the 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. 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 they began experimenting 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 began soon after. In the United States, Chrysler Corp. produced 60,000 guns and 120,000 barrels during the war.

Emplaced on Dutch-designed Hazemeyer twin mounts, the Bofors became a mainstay of anti-aircraft defense aboard the U.S. Navy warships. The Army mounted twin Bofors on its M-24 tank chassis, dubbing the new weapon the M19 gun motor carriage.

Although Bofors later developed a lighter, higher-velocity AA weapon (the 40mm L/70), L/60s remain in use by armed forces worldwide. Few products developed in Sweden have received so much publicity and have been of such historical significance as the Bofors 40 mm gun.

It has been portrayed as one of the weapons that came to determine the outcome of the Second World War. In the U.S. In Army service, the single mount Bofors was known as the 40 mm Automatic Gun M1.

The U.S. version of the gun fired three variants of the British Mk. II high-explosive shell as well as the M81A1 armor-piercing round, which was capable of penetrating some 50 mm of homogeneous armor plate at a range of 500 yards.

In the USA the Bofors gun became an integral part of the US air defenses and production of the gun began under license, mainly at the Chrysler Corporation in Detroit. Chrysler is said to have manufactured around 60,000 guns and more than 120,000 gun barrels in all.

However, Bofors was not satisfied with the payment they received for subcontracting and it was only well into the 1950s that a final financial agreement was reached. The Bofors gun was particularly widely used in the US armed forces and the name of Bofors came to be equated with high quality.

The USA had for some time been investing in the development of a 37 mm gun, but US officers became curious about the Bofors 40 mm gun after the UK and France had purchased it. Initial contacts between Bofors and the USA took place in 1938. The business discussions were complicated by the outbreak of World War II in 1939, but in July 1940 a gun was ordered through the US Embassy in Stockholm.

It was delivered along with test ammunition in the utmost secrecy by truck from Bofors to Petsamo in northern Finland. From there it was taken on board a ship that was evacuating US citizens from Scandinavia.

As of August 2006, the French navy uses L/60s on more than twenty ships (patrols and auxiliaries). Ships of the Norwegian and Icelandic Coast Guards continue to use the 40mm Bofors gun. The L/60 continued in use in the Irish Army until recent years, when it was retired in favor of the radar controlled L/70.

Three P20 class patrol vessels of the Irish Naval Service retained L/60s on board as their main weapon until the 1990's but have now been rearmed with L/70's. Two retired L/60s can be seen adjacent to the square in Sarsfield Barracks, Limerick.

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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The final British Bofors mounting that saw service was the STAAG (Stabilized Tachymetric Anti Aircraft Gun') which was twin-barrelled, stabilized, and carried its own tachymetric (i.e. predictive) fire control system, based around the centimeter Radar Type 262, capable of

"locking on" to a target. This mounting was heavy (17.5 tons) and the high-vibration environment of the gun mounting was poor location for sensitive valve electronics and mechanical computers. STAAG Mark I carried the radar dish over the gun barrels where it was subject to damage during firing, therefore STAAG Mark II shifted the set to the roof of the control cabin.

STAAG was ultimately too difficult to maintain in the harsh environment of a warship and was later replaced by the mounting Mark V with the fire control equipment located remotely, the single Mark VII and ultimately, with the Sea Cat missile.

The Bofors had a maximum range of 11,133 yards and could hit targets just over 22,000 feet high. It could fire as many as two rounds a second, but given the need to manually reload with five-round clips, it was more likely to fire about 90 rounds a minute tops.

The big breakthrough came at firing tests in Belgium in 1935 against a British competitor. It was found that the Bofors gun could be moved more than twice as quickly as the competitor's gun and that it scored three times as many hits when firing on aerial targets.

The Belgian officers were amazed. On 25 November 1928 Bofors was commissioned by the Royal Swedish Naval Materiel Administration to develop a special new anti-aircraft weapon: a 40 mm gun. The prototype was a British gun which had been tested in Sweden for some time.

Most of the design work took place in 1929, a year that marked the end of the 'Roaring 20s' with the Wall Street Crash being the most talked-about event. The bridges were to be defended at any price.

The German aircraft attacked over the next few days. Daredevil pilots circled level with the treetops and were met with powerful fire from the Bofors guns, which were famous for their precision.

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