Bofors 57 mm gun

The Bofors 57 mm 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 an evolution of the 57 mm lvakan M/50 used on the Halland class destroyers, 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, usually by a fire-control computer but as a redundancy measure the crew can also train and aim the gun using instrument panels that are either on or in direct contact with the gun. 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 stabilisers. The Mark 3 came in 1995 with modifications made to enable the smart ammunition developed.

Design and development
The baseline version of the Bofors 57 mm L70 gun was the Mark 1, first introduced into service with the Spica-class fast attack craft (FAC) of Swedish Navy in 1966, it has a rate of fire of 200 rounds per minute and a 40-round magazine in the gun turret with a further 128 rounds stowed inside. With minor modifications, the Mark 1 guns could use ammunitions developed for the Mark 2 gun.

The Mark 2 was designed in 1981 but introduced into service with the Stockholm-class corvette—HMS Stockholm (K11) in 1985 (sister ship HMS Malmö (K12) 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 turret 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.

The latest development is the Mark 3, which was designed in 1995 but introduced into service with the Visby-class corvette—fitted on HMS Visby (K31) in 2000. This new design retained the Mark 2 gun turret, 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.

In American service, the United States Navy has designated the Mark 3 as the Mark 110 Mod 0 57mm gun. According to a BAE press release dated 1 August 2005, the Mark 110 would be manufactured at the BAE Systems facility in Louisville, Kentucky.

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

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.

Variants
Bofors developed the Mark 1 from the Bofors 57 mm/L60 in 1962. Improvements included a higher rate of fire, the use of new munitions including an improved proximity fuse, water cooling for the gun tubes 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 1

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. Bofors manufactured a total of about 25 Mk 2 guns.
 * Bofors 57 mm Mk 2

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.
 * Bofors 57 mm Mk 3

Mk 110 57 mm gun (essentially a slightly modified Mark 3) was offered for use by the United States Coast Guard in 2004 and the United States Navy in 2006. The Bofors 57 mm 3P ammunitions are designated as Mark 295 Mod 0 in US service.
 * Mk 110 57 mm gun

Users

 * Mark 1
 * BNS Madumati class
 * Kralj class
 * Končar class
 * Helsinki-class missile boat
 * Pohjanmaa class
 * Hämeenmaa class
 * Andau class (Lürssen FPB 57-I )
 * 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)
 * Eithne class
 * Kasturi-class frigate
 * Perdana class (Combattante-II 4AL ) missile boat
 * Handalan class (Spica-M)
 * Jerong class (Lurssen TNC 45 )
 * Končar class
 * Sea Wolf class (Lurssen TNC 45 )
 * Hugin class
 * Spica class
 * Spica II class
 * Prabbrorapak class (derivative of Singapore's Sea Wolf class, which was based on the Lurssen TNC 45 )
 * Končar class
 * Sea Wolf class (Lurssen TNC 45 )
 * Hugin class
 * Spica class
 * Spica II class
 * Prabbrorapak class (derivative of Singapore's Sea Wolf class, which was based on the Lurssen TNC 45 )
 * Spica class
 * Spica II class
 * Prabbrorapak class (derivative of Singapore's Sea Wolf class, which was based on the Lurssen TNC 45 )
 * Prabbrorapak class (derivative of Singapore's Sea Wolf class, which was based on the Lurssen TNC 45 )


 * Mark 2
 * Halifax-class frigate
 * Pandrong class/Todak class (two and four ships respectively) (Lürssen FPB 57-II )
 * Lekiu-class frigate
 * Stockholm-class corvette
 * Göteborg-class corvette
 * Lekiu-class frigate
 * Stockholm-class corvette
 * Göteborg-class corvette
 * Göteborg-class corvette


 * Mark 3/Mk 110 57 mm gun


 * Darussalam-class Offshore Patrol Vessel
 * Halifax-class frigate (Post HCM/FELEX Refit)
 * Hamina-class missile boat
 * Sierra-class corvette
 * Durango-class patrol vessel
 * Visby-class corvette
 * Legend-class cutter
 * Freedom-class littoral combat ship
 * Independence-class littoral combat ship
 * Zumwalt-class destroyer
 * Visby-class corvette
 * Legend-class cutter
 * Freedom-class littoral combat ship
 * Independence-class littoral combat ship
 * Zumwalt-class destroyer
 * Zumwalt-class destroyer