User:Blockhaj/Sandbox2

Bofors 40 mm gun
Type	Autocannon
Place of origin	Sweden
Service history
In service	1934–present
Used by	See Users
Wars	See Wars
Production history
Designer	AB Bofors
Designed	1930
Manufacturer	Bofors Defence (1932–2000) Zastava Arms (1970–present) Gun Carriage Factory Jabalpur(1960-present) United Defense Industries (2000–2006) BAE Systems AB (2006–present)
Produced	1932–present
No. built	>60,000 (L/60)[1]
Variants	See variants
Specifications
Mass	L/60: 1,981 kg (4,367 lb)
Length	L/60: 6.5 m (21 ft 4 in)
Barrel length	L/60: 2,400 mm (7 ft 10 in) gun & breach
Width	L/60: 1.8 m (5 ft 11 in)
Height	L/60: 1.9 m (6 ft 3 in)
Crew	4[2] (dependent on use)
Shell	40×311mmR
Shell weight	0.9 kg (2 lb 0 oz)
Caliber	40 mm L/43 or L/60 (barrel + breach)
Barrels	1 or 2[2]
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	120 – 140 round/min
Muzzle velocity	L/43: 700–730 m/s (2,300–2,400 ft/s) L/60: 850–880 m/s (2,800–2,900 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 Automatic Gun L/60 (Bofors 40 mm L/60, Bofors 40 mm/60, Bofors 40/60 and the like), often referred to simply as the Bofors 40 mm gun or the Bofors gun,^[3] is an anti-aircraft 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 the majority of the western Allies, and some Axis powers such as Nazi Germany and Hungary. A small number of the weapons remain in service today, and saw action as late as the Gulf War.

In the post-war era, the Bofors 40 mm L/60 design was not suitable for action against jet-powered aircraft, so Bofors developed a new 40 mm gun with significantly more power — the Bofors 40 mm Automatic Gun L/70. In spite of being a separate development, although based on the same core action and looking visually similar (comparable to the AK-47 vs the AK-74), the Bofors 40 mm L/70 gun is also widely known simply as "the Bofors" or the "Bofors 40 mm gun". The L/70 design never achieved the same popularity and historical status as the original L/60 model but has still seen great export and popularity to this day, having been adopted by around 40 different nations and even being accepted as NATO-standard in November 1953.^[4]l

In 1922, the Swedish Navy purchased a number of 2-pounder Pom-Poms from Vickers as anti-aircraft guns. The navy approached Bofors about the development of a more capable replacement, and Bofors signed a contract in late 1928. The company 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 Finspång. Bofors' first test gun was a re-barreled Nordenfelt version of the Finspång gun, to which was added a semi-automatic loading mechanism.

Testing of the gun in 1929 showed that a problem existed with feeding the weapon 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 operate quickly enough to fire rapidly. One attempt to solve the problem used zinc shell cases that burned up when fired. However, that left heavy zinc deposits in the barrel and had to be abandoned. In the summer of 1930, experiments were conducted with a new test gun that did away with controlled feed and instead flicked the spent casing out the rear, after which a second mechanism reloaded the gun by "throwing" a fresh round into the open breech from the magazine. That improved firing rates to an acceptable level, so work on a prototype commenced soon after.

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

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, the gun was operating at 130 rounds per minute. The development needed to turn it into a weapon suitable for production was completed in October 1933. Because acceptance trials had been passed the year before, it 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 implied.^{[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).^[5] The rate of fire was normally about 120 rounds per minute (2 rounds per second), which increased slightly when the barrels were closer to the horizon, because 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), because 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.

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

The first version of the 40 mm the Swedish Navy ordered was intended for use on submarines, because the larger calibre allowed the gun to be used both as an anti-aircraft gun, and against smaller ships. The barrel was shorter, at 42 calibers, which reduced 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 that arrangement were the Sjölejonet-class boats. The guns were later removed when the submarines were modified with streamlined conning towers.

The first order for the "real" L/60 was made by the Dutch Navy, which ordered five twin-gun mounts for the cruiser De Ruyter in August 1934. Those 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 was displayed at a show in Belgium in April 1935. That mount allowed the gun to be fired from the carriage with no set-up required, although it had limited accuracy. If time was available for set-up, the gunners used the tow-bar and muzzle lock as levers, raising the wheels off the ground and so lowering the gun onto supporting pads. Two additional legs folded out to the sides, and the platform was then levelled with hand cranks. The entire set-up process could be completed in under a minute.

Orders for the land-based versions were immediate, starting with an one for eight weapons from Belgium in August 1935, followed by a flood of orders from other forces including Poland, Norway, and Finland.^[6] It was accepted into the Swedish Army the next year, and known as the "40 mm lvakan m/36", the lower-case "m" indicating an army model as opposed to the capital "M" for the navy.

The Swedish navy adopted the weapon as the m/36 in two versions: hand-worked single air-cooled, and power-operated twin water-cooled. 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.

The British Army had first examined the weapon in 1937, when it received a number of Polish-built examples for testing. They were 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 from metric to imperial measurements. Numerous changes were made to the design so that it more suitable for mass production, because the original Bofors design was intended to be hand-assembled. Many parts were labeled "file to fit on assembly", requiring many man-hours of work to complete.

Testing showed that there was a serious problem with aiming the gun at high-speed aircraft. Although it could be trained quickly, aiming accurately while doing so proved difficult. In order to deal with that, the British introduced a complex mechanical analogue computer, the Kerrison Director, which drove the laying electrically. A three-man team operated the director by pointing it at the target whilst dialing in estimates for speed, range, and various atmospheric conditions. The director then aimed the gun using powered mounts, while a gunner loaded the clips. That eliminated the need for the lead-correcting reflector sights, which were replaced with a backup system consisting of a simple ring-and-post sight, known as a "pancake".

In that 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 ad 3.7-inch heavy weapons. Following the fall of France in 1940, the gun was considered so important to the defence of Britain that a movie, The Gun, was produced to encourage machinists to work harder and complete more of them. British production started slowly and, by September 1939only 233 equipments had been produced. However, by the end of the war, the total production of British, Canadian and Australian factories numbered over 19,000. The peak production year was 1942, when British factories produced 5,025 and Canadian factories produced 1,311.^[7]

In combat, it was found that the Kerrison was difficult to set up 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". A much lighter, two-wheeled carriage was also developed for airborne use.

The army experimented with various self-propelled anti-aircraft systems based on various tank chassis. Changes to the breech for that role created the "QF 40 mm Mark VI", which was used on the Crusader tank to produce the Crusader III AA Mark I. The main self-propelled version of the Bofors used the gun mounted on the chassis of a Morris Commercial four-wheel drive lorry, which was known as the "Carrier, SP, 4x4 40mm, AA (Bofors) 30cwt". Such guns were used in support of army divisions, to provide swift protection against air attack without the need to unlimber. 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 Division on Sword Beach on D-Day, to protect the vital bridges over the Caen Canal and the 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 tracer horizontally to mark safe paths for units through the German minefields. That 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 different formations in large-scale night attacks.

An RAF Regiment was formed in February 1942, in response to the army's failure to defend airfields on Crete, which resulted in strategic defeat on the island by numerically inferior German forces. That signalled the transfer of responsibility for defending airfields from the army to the RAF, and included low-level air defence, in which the Bofors L60 — the same design as the Army version — was the principal weapon for the RAF Regiment's Light Anti-Aircraft squadrons in North Africa, Malta, Italy, the Balkans, the UK (including the allocation of fifty-two squadrons to Operation Diver), and north-western Europe (from D-Day through to the cessation of hostilities).

No 2875 Squadron RAF Regiment, employing the L60, became the first unit to shoot down a jet aircraft, a Me 262, with ground-based anti-aircraft fire, at Helmond in the Netherlands on 28 November 1944. Although the Allied air forces had achieved air superiority after D-Day, forward airfields continued to be high-priority targets for the Luftwaffe when the opportunity presented, and that ensured that the RAF Regiment's L60s continued to be heavily used. For example, on New Year's Day 1945, during the Battle of the Bulge, RAF Regiment Light Anti-Aircraft squadrons shot down 43 German aircraft and damaged 28 others during the Operation Bodenplatte attacks on eleven RAF forward airfields. After World War II, the RAF Regiment continued to employ the L60 as its principal anti-aircraft weapon until it was replaced by the L70 gun in 1957. The guns were deployed in the UK, Germany, Cyprus, the Middle East, and the Far East. There had been insufficient L60s available to equip the RAF Regiment's squadrons in the Far East during the war, and they had to make do mostly with Hispano and Oerlikon guns).

The Royal Navy also made extensive use of the Bofors. Its first examples were air-cooled versions quickly adapted for ships during the withdrawal from Norway. After the fall of western Europe in 1940, the Dutch mine-layer, Willem van der Zaan, gave the navy its first example of a water-cooled gun on its Hazemeyer tri-axially stabilized mounting. Locally produced examples started arriving in 1942, known as the "QF 40 mm Mark IV" with twin-mounts, or the "QF 40 mm Mark V" with single mounts. The navy ran through a variety of versions of the basic Bofors gun over the war, including the Mark VII to Mark XI. The Royal Navy's home-grown light anti-aircraft weapon, the QF 2-pounder gun, also had a caliber of 40 mm, but was referred to as the QF 2-pdr.

The designation of models in Royal Navy service can be confusing bcause the gun and its mounting received separate mark numbers. The following mountings were used:

• Mark I: twin mounting based on American design and using American-built guns, not widely fitted. Fitted for remote fire control.
• Mark II: quadruple version similar to the Mark I
• Mark III: a navalized version of the Army single mounting, hand worked elevation and training.
• Mark IV: a tri-axially stabilized twin mounting, copied from, and usually known as, the "Hazemeyer". It had on-mounting fire control, and was usually fitted with Radar Type 282 to provide target range information.
• Mark V: twin mounting, which superseded, and eventually replaced, the Mark IV, often referred to as the "utility" mounting. It was a simplified, unstabilised mounting based on the American twin mounting Mark I, and was designed for remote fire control.
• Mark VI: a six-barreled weapon, feeding from large trays instead of clips, and designed for remote control from a dedicated radar-equipped director.
• Mark VII: a single-barreled, hydraulically-powered mounting, that superseded the Mark III and entered service in 1945.
• Mark IX: Mark VII mount modified for electrical power, as the Mounting Mark IX and, in that form, saw service in the Falklands War.

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 final British Bofors mounting to see service was the "stabilized tachymetric anti-aircraft gun" (STAAG), which was twin-barrelled, stabilised, and carried its own tachymetric (i.e. predictive) fire control system, based around the centimetre Radar Type 262, capable of "locking on" to a target. The mounting was heavy (17.5 tons) and the high-vibration of the gun mounting made it a poor location for sensitive valve electronics and mechanical computers. The STAAG Mark I carried the radar dish over the gun barrels, where it was subject to damage during firing so, on the STAAG Mark II, the set was shifted to the roof of the control cabin. STAAG was ultimately too difficult to maintain in the harsh environment of a warship and was replaced by the Mounting Mark V, with the fire control equipment located remotely, then by the single Mark VII and, ultimately, with the Sea Cat missile. The final version of STAAG was fitted to the RN Type 12 Whitby anti-submarine frigates and the Type 41/Type 61 diesel frigates, completed from 1956 to 1958. HMNZS Royalist was also fitted with the STAAG Mk 2 during modernisation, completed in 1956. Initially, it had three STAAG CIWS, the STAAG in Q position was removed in 1960, but it carried two mounts until the end of its service in Southeast Asian waters, in 1965. In 1956, the crew of Royalist seemed to find the STAAG a reasonably effective anti-aircraft weapon during Operation Musketeer, off Egypt.

In order to supply both the U.S. Army and U.S. Navy with much greater numbers of the guns, Chrysler built 60,000 of the guns and 120,000 barrels through the war,^[1] at half the original projected cost, and filling the Army's needs by 1943.^[9] Over the lifetime of the production, their engineers introduced numerous changes to improve mass production, eventually halving the overall time needed to build a gun. Most of the changes were in production methods rather than the design of the gun itself.^[9][10] York Safe & Lock also produced the weapons, though its attempts to coordinate drawings across the program were unsuccessful, and this responsibility was transferred to the Naval Gun Factory in July 1943.^[11]

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. 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.^[9]

The United States Navy's Bureau of Ordnance purchased a twin-mount air-cooled example, spare parts and 3,000 rounds of ammunition directly from Bofors, which arrived in New York on 28 August 1940 aboard the Army transport USAT American Legion, which had evacuated 897 people, including members of the Norwegian royal family, through the Finnish port of Petsamo.^[12] During that month another Dutch ship, the Van Kinsbergen, demonstrated the Hazemeyer mount to Navy observers. The gun was quickly chosen as the Navy's standard anti-aircraft weapon over the British 40mm calibre, 2-pounder pom-pom; however, negotiations with Bofors for licensed production stalled when the Swedes requested airplane export and manufacturing licenses in return.^[11] Reportedly, the Navy secretly imported a set of imperial designs from Britain and started production illegally. A formal contract with Bofors was reached in June 1941. The resulting Mark 1 and Mark 2 weapons were intended for the left and right side of a twin mount, respectively, and were adapted by Chrysler for water cooling.^[9]

Following the attack on Pearl Harbor on 7 December 1941, the existing 1.1" (28 mm) quad mount and .50 caliber machine guns were determined to be inadequate against modern aircraft, and their replacement by 40 mm Bofors and 20 mm Oerlikon weapons was accelerated. The water-cooled version was used almost exclusively by the U.S. Navy and Coast Guard. The 40 mm quadruple mount was developed by essentially mounting two twin mounts side by side.^[11] A major improvement was the addition of power operation to both twin and quadruple mounts. Essentially all US naval mountings were twin or quadruple. 40 mm weapons were eventually mounted on virtually every naval and armed auxiliary vessel larger than a small landing craft.^[11] After the war, the 3"/50 caliber gun Mark 27 twin mount began to replace the Bofors, because the "VT" proximity fuse would not fit a 40mm projectile, and the 40 mm weapon was considered inadequate against the emerging anti-ship missile threat. The twin 3" mount was intended to be the same weight as the 40mm quad mount, but was somewhat heavier in practice, which had to be compensated for. Except on destroyers and new construction, the Navy was slow in phasing out the 40 mm gun, and it continued in active Navy service through the Korean War. It remained on inactive Reserve fleet ships at least through the early 1970s.^[13]

The Navy's satisfaction with the weapons was demonstrated by their practice of telegraphing Chrysler Corporation with the serial numbers of guns when they shot down an aircraft.^[9]

In 1938 the United States Army introduced a 37 mm gun of their own design, but found it to be of limited performance. In early World War II, six British Bofors were imported for testing, along with Kerrison Predictor directors, and they proved to be superior in all areas. By the middle part of the war, most of the 37 mm guns had been replaced by the 40 mm.

In U.S. Army and Marine Corps service, the single mount Bofors was known as the 40 mm Automatic Gun M1.^[14] 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 Army, each Anti-Aircraft Artillery (AAA) auto-weapons battalion was authorized a total of thirty-two 40 mm guns in its four firing batteries.^[15][16] Each U.S. Marine division had a "special weapons battalion" that included sixteen 40 mm guns; in early 1944 these were replaced with anti-aircraft battalions with twelve 40 mm guns. Marine defense battalions also used the 40 mm gun.^[17] All of these unit types also included other AA weapons.

During World War II, the twin mount version of the gun was mounted on an M24 Chaffee tank chassis as the M19 Gun Motor Carriage. In the 1950s, the M41 Walker Bulldog tank was heavily modified into the M42 Duster with the same twin 40 mm mounting. After being largely withdrawn from service in the early 1960s, the M42 was re-introduced beginning in 1966 for the Vietnam War, where it was mostly used for ground fire support. Following the withdrawal from Vietnam in the early 1970s, the M42 was retained in National Guard service until finally retired in 1988.

See Bofors 40 mm gun § AC-130 Gunship

In World War II Germany, the Wehrmacht used a number of Bofors guns which had been captured in Poland and France. The Kriegsmarine also operated some guns obtained from Norway. In German naval use, the gun was designated the "4 cm Flak 28", and was used aboard the cruisers Admiral Hipper and Prinz Eugen toward the end of the war.^[18] Beginning in 1942, several E-boats were equipped with the Flak 28 to enable them to fight against British MGBs and MTBs on equal terms.

Germany also purchased a large number (200+) of Hungarian-made Bofors guns. In return, Hungary received a 75 mm PAK gun for every 4-5 Bofors. The Wehrmacht used Hungarian guns after German occupation of Hungary from late 1944. Most of them were lost during the fights in Budapest and Transdanubia.^[19]

Japan captured a number of Bofors guns in Singapore and put them into production as the Type 5.^{[citation needed]}

After the Continuation war the Soviet Union took possession of the Finnish coastal defence ship Väinämöinen, which was armed with four M/36 Bofors guns.^{[citation needed]}

Bofors L/43 is a submarine variant of L/60 with retractable mounting, and using low propellant charge ammunition.^[20][21][22]

L/60 is an autocannon using 40x311mmR ammunition. Although the L/60 was later replaced in production by the L/70, it remained in front-line service well into the 1980s and 1990s. In most cases, these were the ground anti-aircraft versions, as a suitable replacement in this role did not come along until the introduction of truly effective MANPADS missiles in the 1980s and 1990s.

In United States Army service, the M19 Gun Motor Carriage was replaced by the M42 Duster, using the same turret but based on the chassis of the M41 Walker Bulldog tank.

The L/60 saw active service with the Argentinian and British navies in the 1982 Falklands War and continued to be used into the 1990s, when it was replaced by modern 20 mm and 30 mm artillery.

The Canadian Forces also used Bofors on their surface fleet, removed the guns in the late 1980s when they were considered to be outdated, only to re-use old Bofors guns as the main armament of the Kingston-class coastal defence vessel.^[8] The Bofors served as the main armament for almost 20 years.^[23] The decision to remove them was made in 2014, due to their maintenance burden, and their lack of stabilization.

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 favour of the radar-controlled L/70. The Irish Naval Service P20 class retained L/60s on board as their main weapon until the 1990s but were rearmed with L/70s. The last remaining P20-class patrol vessel, (LÉ Aisling) decommissioned in 2016, was the final vessel fitted with the L/70. Two retired L/60s can be seen adjacent the square in Sarsfield Barracks, Limerick.

The last 40 mm/60 Bofors in service with the Royal Australian Navy (RAN) were used as the main weapon aboard the Attack class and Fremantle class patrol boats and for training purposes at the West Head gunnery range at HMAS Cerberus.^[24] These were removed from service during 2007; Bofors were used aboard almost every RAN ship to operate between the 1940s and the 1990s, including the aircraft carriers Sydney and Melbourne.^[24]

As of 2012, the L/60 is still in use by the military of Brazil, Indonesia, Paraguay, Taiwan, and the United States.

Since the beginning of the 1970s Bofors L/60s have been used in the United States Air Force's AC-130 gunships in the air-to-ground role.^[25] Between 2006 and 2012, there were plans to remove these and the M61 Vulcans from newer AC-130U variants and replace them with 30 mm autocannons. However, these plans did not come to fruition at the time, and the Bofors and Vulcans remained in service as of 2009^[update],^[26] though the later W- and upcoming J-model variants have 30 mm Mk44 Bushmaster II autocannons instead.^[27][28]

When four additional AC-130Us were to be converted from 2002, the necessary 40 mm L/60 guns had to be salvaged from old M42 targets at the Nellis AFB range.^[29]

By the end of World War II, the speed of jet aircraft enabled them to withdraw quickly out of range of the Bofors; a longer range was necessary. A higher rate of fire was also required, 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. In the end they did both.

The new 40 mm design used a larger 40×365R round firing a slightly lighter 870 g shell at a much higher 1,030 m/s (3,379 fps) muzzle velocity. The rate of fire was increased to 240 rounds per minute^[1] (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 increased the firing rate first to 300 rpm (5.0 rounds per second), and later to 330 rpm (5.5 rps). The introduction of a 40mm proximity fuzed round in the early 1970s was another improvement.

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, including the U.S. Army's failed M247 Sergeant York. The UK's RAF Regiment adopted the L70 to replace its L60 guns in 1957, replacing its last examples in 1977 with the Rapier missile system.

In 1970s Zastava Arms acquired from Bofors a license to produce the L/70 together with laser-computer group.^[30] Ammunition for the L/70 is produced locally for both domestic and export use by Sloboda Čačak^[31]

In 1979 the Royal Netherlands Air Force acquired 25 KL/MSS-6720 Flycatcher radar system and upgraded 75 of their 40L70s to create 25 firing units for static air base defence. The improved guns had an increased rate of fire (300 rounds/min), and the loading mechanism was provided with extended guides so that it could hold 22 cartridges. A 220 volt diesel generator was mounted onto the undercarriage, powered by a Volkswagen diesel engine.

In 1989 the Royal Netherlands Army acquired 30 Flycatcher systems, each fielded with two modified Bofors 40L70G guns (the appended 'G' is for 'gemodificeerd', 'modified'). In the 40L70G version the loading mechanism was further improved and could be recognized by open rear guides. The 40L70G guns were also provided with muzzle velocity radars.

Early in the 1990s the Royal Netherlands Air Force 40L70s were upgraded to the 'G' version.

In the gun-armed versions of the Swedish Army Combat Vehicle 90 a cartridge-fed automatic version of the L/70 autocannon is fitted. In order to fit inside the vehicle, the gun is mounted upside down. New armour piercing and programmable ammunition have also been developed. Germany has used L/70 guns on its Type 352, Type 333 and Type 332 minesweeper vessels, although these will be replaced by Rheinmetall MLG 27 remote-controlled gun systems until 2008. Until the early 1980s L/70 guns guided by D7B radars were in widespread use in the anti-aircraft role in the German Navy and German Air Force, until replaced by Roland SAMs.^[32]

The L/70 is also used by the Indian Abhay IFV, which carries 210 APFSDS and high-explosive rounds.^[33] In 2014 Indian Army started upgrading its L/70 guns to modern standards electric turret drive system and digital fire control system with thermal imaging cameras ,laser range finder, muzzle velocity radar for accurate engagement of targets and has automatic target tracking capability under all weather conditions. The gun has the ability to be integrated with tactical and fire control radars to give more flexibility in its deployment.^[34]

The guns has been equipped with ZADS EW suite for detection and suppression of drones between 10-10,000 meters and has the ability to "soft-kill" the drones without using the gun. Upon detecting a drone the ZADS indicates the direction of the approaching drone, then the day and night camers aligns itself towards the target and locks on to it and auto tracks its,the system then passes the target coordinates on to the L-70 gun through a customised hardware interface. The gun received the coordinates in ‘remote’ mode and aligns itself towards the target allowing the operator to lock on and fire.^[35]

Breda (now Oto Melara) of Italy uses the 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, employs two modified Bofors 40, each with an improved rate of fire of 450 rpm, as opposed to 240-330 rpm for L/70 version. For naval use, it is normally equipped with a 736-round magazine and a dual feed mechanism.

• L/70 BOFI (Bofors Optronic Fire control Instrument) gun system:  Electro optic fire control system (with a computer and laser range finder) and proximity fused ammunition.  A "fair weather system".^{[citation needed]}
• L/70 BOFI-R  (All weather):   Multisensor fire control system with a J band radar.  Provides automatic acquisition and tracking with an effective range of 4 km without external radar input.
• L/70 REMO (Renovation and Modernisation): Package aimed at extending life span and increasing effectiveness.  Higher rate of fire, new fire control system/air burst programming, and ammunition.
• L/70 40mm Netherlands upgrade: New servo system, amplifiers, increased rate of fire (to 300 rds/min), ammo racks, and diesel power unit.
• L/70 40mm Spanish upgrade:  Felis electro optic automatic tracking system (HD TV set, automatic tracking, telemetry laser, portable target designator, and radar interface)
• AOS 40mm L70 FADM (Field Air Defense Mount): Singapore Technologies electric drive aiming system
• TRIDON 40mm L/70: Bofors installed Volvo 725 6x6 truck with fully enclosed, armour protected cab for a crew of five, with only two crew required.  Did not enter service.^[36]
• LVS 40mm L/70: Equipped with LVS modular fire-control system by Saab.  Entered service with the Swedish Army and Royal Thai Army in 1994 and 1997.^{[citation needed]}

• Bofors 40 mm Automatic Gun L/70
• Bofors 57 mm Naval Automatic Gun L/60
• Bofors 57 mm Naval Automatic Gun L/70
• Bofors 75 mm Model 1929
• List of anti-aircraft guns
• List of naval anti-aircraft guns
• The Bofors Gun – 1968 movie about British airmen in Germany (the gun serves as a framing device)

• Foss, Christopher (1977). Jane's pocket book of towed artillery. New York: Collier. pp. 231–233. ISBN 0020806000. OCLC 911907988.

• 1940 Popular Science cover illustration of twin 40mm Bofors in Swedish service
• "New Tools For Army Power", October 1941, Popular Science, pp. 73–74 on testing of U.S. version of 40mm Bofors
• 40 mm Automatic Gun M1 (AA) and 40 mm Antiaircraft Gun Carriages M2 and M2A1 TM 9-252
• 40 MM Antiaircraft Gun, OP 820, 1943 : Navy Service Manual placed online courtesy of maritime.org
• Data and spec comparison of various marks of Bofors 40mm L/60
• Data and Spec comparison of various marks of Bofors 40mm L/70
• Rae, CJE, Harris, A.L. & Bryant, R.K. 1987, On target: the story of the 2/3 Australian Light Anti-Aircraft Regiment from formation on 18 July 1940 until disbandment on 14 July 1943 and the subsequent service of 7th Battery, 8th Battery, and 9th Battery, until the end of World War II, 2/3rd Australian Light Anti-Aircraft Regiment Association, Melbourne