Bofors 57 mm L/70 naval artillery gun

Bofors 57 mm L/70 naval artillery gun
Bofors 57 mm L/70 naval artillery gun
	A Mk 110 57 mm gun on the littoral combat ship USS Freedom
Type	Naval artillery
Place of origin	Sweden
Service history
In service	1966–present
Used by	See users
Production history
Designer	Bofors Defence
Designed	Mark 1: 1964; Mark 2: 1981; Mark 3: 1995;
Manufacturer	Bofors Defence (1966–2000); United Defense (2000–2005); BAE Systems AB (2005 onwards);
Produced	Mark 1: 1966; Mark 2: 1985; Mark 3: 2000;
Variants	See variants
Specifications
Mass	Mark 3: 14,000 kg (31,000 lb) (weight including 1,000 rounds onboard, each weighing 6.5 kg (14 lb) per complete round)
Barrel length	Bore length: 3,990 mm (157.09 in); Without flash hider: 4,045 mm (159.25 in); With flash hider: 4,345 mm (171.06 in);
Shell	57 × 438 mm ; 6.1 kg (13 lb) complete round ; 2.4 kg (5.3 lb) pre-fragmented shell
Caliber	57 mm/70 caliber
Barrels	Single barrel (progressive RH parabolic twist, 24 grooves)
Action	Electronic firing
Elevation	Mark 1: −10°/+78° (40°/s); Mark 2: −10°/+75° (40°/s); Mark 3: −10°/+77° (44°/s);
Traverse	Full 360°: Marks 1 & 2: 55°/s; Mark 3: 57°/s;
Rate of fire	Mark 1: 200 rounds/min; Marks 2 & 3: 220 rounds/min;
Muzzle velocity	1,035 m/s (3,400 ft/s) (HE round)
Effective firing range	8,500 m (9,300 yd) (HE round)
Maximum firing range	17,000 m (19,000 yd) (HE round at 45°)
Feed system	Magazine: Mark 1: 40 ready rounds, 128 rounds in ready racks in mount; Mark 2: 120 ready rounds, up to 40 rounds in dual hoists; Mark 3: 120 ready rounds, up to 40 rounds in dual hoists, 1,000 rounds in mounting;
Sights	Gyro-stabilized in local control.

The Bofors 57 mm L/70 naval guns are a series of dual-purpose naval guns designed and produced by the Swedish arms manufacturer AB Bofors (since March 2005 part of BAE Systems AB), designed in 1964 as a replacement design for the twin barreled Bofors 57 mm L/60 naval artillery gun. Production of the baseline 57 mm Mark 1 variant began in 1966 and was initially used to equip smaller coastal patrol craft and fast attack craft. The gun is remotely controlled by a fire-control computer; as a redundancy measure, however, the crew can also operate the gun using instrument panels that are either on or in direct contact with the gun.^[1] Although the Swedish Navy is the primary user of the gun, it has been exported widely by Bofors Defence for use by the navies of Brunei, Canada, Croatia, Finland, Indonesia, Ireland, Malaysia, Mexico, Montenegro, Singapore, Thailand, and the United States.

The gun was upgraded and improved several times, first the Mark 2 in 1981 which drastically lowered the weight as well as introduced new servo stabilizers. The Mark 3 came in 1995 with modifications made to enable the smart ammunition developed.^[1]

Design and development[]

The Bofors 40 mm L/60 anti air gun (1.6 inch) was one of the most popular naval anti-aircraft guns during World War II, used long after the war in a variety of roles. However, as jet aircraft became more prevalent in the post-war era, it was clear the gun did not have the rate of fire needed to effectively deal with these threats. Flying at speeds close to 1,000 kilometres per hour (620 mph), a jet aircraft flew through the effective range of the Bofors 40 mm gun in too short a time for the gun to fire enough rounds to ensure a hit.

Bofors' engineers considered two solutions to the problem. One was to greatly increase the firing speed of the 40 while also incorporating any minor changes that would improve its range. This produced the 40 mm L70, which remains popular to this day. The other was to design a larger weapon with much greater effective range and a larger explosive load that offset a lower firing rate. This was based on the existing 57 mm lvakan M/50 design, likewise upgraded for more range and higher firing rates. This design became the 57 mm L70 gun.

The baseline version of the Bofors 57 mm (2.2 in) gun was the Mark 1, first introduced into service with the Spica-class fast attack craft of the Swedish Navy in 1966, it has a rate of fire of 200 rounds per minute and a 40-round magazine in the gun mount with a further 128 rounds stowed inside. With minor modifications, the Mark 1 guns could use ammunition developed for the Mark 2 gun.^[1]

The Mark 2 was designed in 1981 but introduced into service with the Stockholm-class corvette—HSwMS Stockholm in 1985 (sister ship HSwMS Malmö was built in 1984 but armed with the older Mk 1, subsequently retrofitted with the Mk 2 in 2009), the rate of fire was slightly increased to 220 rounds per minute. Also, it featured a new light weight gun mount with a new gun barrel that was forged from monobloc steel (this eliminated the need to use a water jacket for gun barrel cooling during firing) and a new servo drive/servomechanism system (for faster reaction time and better gun aiming and control). According to Bofors, the new servo system allowed the Mk 2 to be both accurate and agile enough for use against sea skimming anti-ship missiles and that it could put more explosives into a surface target within a thirty-second window than any naval gun with a calibre smaller than 100 mm (3.9 in).^[1]

The latest development is the Mark 3, which was designed in 1995 but introduced into service with the Visby-class corvette—fitted on HSwMS Visby in 2000. This new design retained the Mark 2 gun mount, rate of fire and ammunition capacity and has another 1,000 rounds stowed in the standby rack beneath deck. A small radome has been added above the gun barrel and is used for measuring the muzzle velocity of the departing projectiles for fire-control purposes, usually but not necessarily with the new Bofors 57 mm 3P all-target programmable ammunition. Also, a new optional low radar profile (also known as low radar cross-section, or RCS) stealth mounting was developed, this allows the gun to be hidden from radar and plain sight when not in use.^[1]

In American service, the United States Navy has designated the Mark 3 as the Mark 110 Mod 0 57mm gun. According to a BAE Systems press release dated 1 August 2005, the Mark 110 would be manufactured at the BAE Systems facility in Louisville, Kentucky.^[1] BAE Systems has been awarded a contract by General Dynamics to provide two additional Mk110 Naval Gun Systems for the Independence variant of the US Navy's (USN's) Littoral Combat Ship (LCS).^[2]

While the 57 mm cannon may not seem as powerful as larger naval guns, such as the OTO Melara 76 mm, some of its performances are comparable; given its rate of fire and amount of explosive per shell, the Bofors gun actually achieves a higher amount of "explosive fired per second" than the 76 mm.^[3]

Ammunition[]

Sailors load ammunition aboard USS Gabrielle Giffords

Ammunition for the Bofors 57 mm gun is produced by Bofors, Sako Limited in Finland, SME Ordnance in Malaysia and Nammo in Norway.^[1]

In 2006, BAE Systems AB began to offer the Bofors 57 mm 3P all-target programmable ammunition, this allows three proximity fuzing modes as well as settings for time, impact, and armor-piercing functions. This increases the flexibility and effectiveness of the gun system, which has further reduced the reaction time of the gun and it is possible to choose ammunition mode at the moment of firing, giving it the ability to switch rapidly between surface targets, air targets, and ground targets.^[4]

In April 2015, BAE Systems unveiled a new round for the Mk 110 in the design stage called the Mk 295 Mod 1 Ordnance for Rapid Kill of Attack Craft (ORKA), made to achieve one shot kills of surface and air threats. Answering a U.S. Navy requirement for increasing the accuracy and efficiency of naval rounds, the ORKA leverages technology BAE Systems developed for larger 127 mm and 155 mm guided rounds, using a 4-canard actuation systems to guide the round. It is fitted with a multi-mode imaging semi-active seeker that can be guided through laser designation or autonomous targeting by downloading image of the target prior to firing; ORKA retains the 3P multiple fuzing modes.^[5]

In December 2015, the U.S. Navy revealed they were working on developing a guided 57 mm round for its Mk 110 guns on the Littoral Combat Ship and other Navy and Coast Guard ships.^[6]

On 22 August 2017 L3 Mustang Technology announced the completion of the Critical Design Review (CDR) phase for the U.S. Navy's MK 332 Mod 0 High-Explosive, 4-Bolt Guided (HE-4G) projectile. The round was developed from the Advanced Low Cost Munitions Ordnance program. It is intended for use on the LCS and the new fast Frigate, and the US Coast Guard's Legend and Heritage class cutters.^[7]

Variants[]

Bofors 57 mm Mk 1[]

Bofors developed the Mark 1 as an replacement design for the Bofors 57 mm L/60 naval artillery gun in 1962. Improvements included: going from a twin gun design to a single gun design, higher rate of fire, the use of new munitions (including an improved proximity fuse) and a new electro-hydraulic system for rapid training and elevation. Finland, Malaysia, Norway, Indonesia, Singapore and (the former) Yugoslavia are among the countries that adopted the Mark 1.

Bofors 57 mm Mk 2[]

The Mark 2 was a lighter weight version, which utilized a new servo system. Bofors designed the gun in 1981 and it entered active service on the Stockholm-class corvette in 1985. The gun was partly dual-purpose in the sense that it is accurate and agile enough to destroy sea-skimming missiles.^{[citation needed]} Bofors manufactured a total of about 25 Mk 2 guns.^[1]

Bofors 57 mm Mk 3 on Finnish missile boat Hanko

Bofors 57 mm Mk 3[]

The Mark 3 is the latest version of the gun. Bofors designed it in 1996 and it entered service in 2000. The gun uses smart ammunition but can also fire the same ammunition as the Mk 2. The stealth variant has a reduced radar profile, in part by hiding the gun barrel when it is not firing. Also, the gun has a small radar mounted on the gun barrel to measure muzzle velocity for fire control purposes and can change ammunition types instantly due to a dual-feed system.^[8] The gun can also be operated/fired manually without the FC system using a joystick and video camera (mounted on the gun).

Mk 110 57 mm gun[]

Essentially a slightly modified Mark 3, it was offered for use by the United States Coast Guard in 2004 and the United States Navy in 2006.^[8] The Bofors 57 mm programmable 3P ammunition^[9] is designated as Mark 295 Mod 0 in US service.^[1]

Users[]

Mark 1[]

Swedish Spica-II-class fast attack craft firing its 57 mm Mk 1 (57 mm APJ 7101)

RSS Sea Dragon with its 57 mm Mk 1

Bangladesh:

Croatia:

Kralj class
Končar class

Finland:

Indonesia:

Mandau class (modified version of the South Korean Navy's Bae Ku class, which was based on the U.S. Navy's Asheville-class gunboat)

Ireland

Eithne class

Malaysia:

Montenegro:

Končar class

Singapore:

Sea Wolf class (Lurssen TNC 45^[10])

Sweden:

Swedish designations:

57 mm automatpjäs 7101 (57 mm apj 7101)
57 mm automatpjäs 7102 (57 mm apj 7102)

Swedish usage:

Thailand

Prabbrorapak class (derivative of Singapore's Sea Wolf class, which was based on the Lurssen TNC 45^[10])

West Germany:

Begleitpanzer 57 AIFSV prototype

Mark 2[]

A 57 mm Mk 2 firing from a Halifax-class frigate

Canada:

Halifax class

Indonesia:

Singa class (Lürssen FPB 57 Nav II, Fast Attack Craft - Torpedo)
Pandrong class (Lürssen FPB 57 Nav IV, Fast Attack Craft - Missile/Fast Patrol Boat)
Todak class (Lürssen FPB 57 Nav V, Fast Attack Craft - Missile/Fast Patrol Boat)^[10]

Malaysia:

Lekiu class

Sweden:

Swedish designations:

57 mm automatpjäs 7103 (57 mm apj 7103), later changed to 57 mm allmålspjäs Mk2

Swedish usage:

Mark 3[]

Comparisons between the Mark 3 guns

The 57 mm Mk 3 on the bow of a Hamina-class missile boat; note the prominent but small radome above the gun barrel which is used for measuring muzzle velocity of the departing projectile