Bofors 57 mm L/70 naval artillery gun

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 revision of the 57 mm lvakan M/50 used on the s. 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. 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.

Design and development
The Bofors 40 mm L/60 AA 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 1000 km/h, 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 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.

The Mark 2 was designed in 1981 but introduced into service with the —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.

The latest development is the Mark 3, which was designed in 1995 but introduced into service with the —fitted on HSWMS Visby (K31) 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.

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. 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).

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.

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.

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.

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.

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's intend for use on the LCS and the new fast Frigate, and the US Coast Guard's Legend and Heritage class cutters.

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 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. 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. Gun can also be operated/fired manually without the FC system using a joystick and video camera (mounted on gun).
 * Bofors 57 mm Mk 2
 * Bofors 57 mm Mk 3

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. The Bofors 57 mm programmable 3P ammunition is designated as Mark 295 Mod 0 in US service.
 * Mk 110 57 mm gun

Users

 * Mark 1
 * Madumati class
 * Meghna class
 * Pohjanmaa 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 )
 * Eithne class
 * Perdana class
 * Sea Wolf class (Lurssen TNC 45 )
 * Hugin class
 * HSWMS Carlskrona (P04)
 * Prabbrorapak class (derivative of Singapore's Sea Wolf class, which was based on the Lurssen TNC 45 )
 * 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 )
 * Eithne class
 * Perdana class
 * Sea Wolf class (Lurssen TNC 45 )
 * Hugin class
 * HSWMS Carlskrona (P04)
 * Prabbrorapak class (derivative of Singapore's Sea Wolf class, which was based on the Lurssen TNC 45 )
 * Sea Wolf class (Lurssen TNC 45 )
 * Hugin class
 * HSWMS Carlskrona (P04)
 * Prabbrorapak class (derivative of Singapore's Sea Wolf class, which was based on the Lurssen TNC 45 )
 * Sea Wolf class (Lurssen TNC 45 )
 * Hugin class
 * HSWMS Carlskrona (P04)
 * Prabbrorapak class (derivative of Singapore's Sea Wolf class, which was based on the Lurssen TNC 45 )
 * HSWMS Carlskrona (P04)
 * 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 )
 * Prabbrorapak class (derivative of Singapore's Sea Wolf class, which was based on the Lurssen TNC 45 )


 * Mark 2
 * Pandrong class/Todak class (two and four ships respectively) (Lürssen FPB 57-II )
 * Pandrong class/Todak class (two and four ships respectively) (Lürssen FPB 57-II )
 * Pandrong class/Todak class (two and four ships respectively) (Lürssen FPB 57-II )
 * Pandrong class/Todak class (two and four ships respectively) (Lürssen FPB 57-II )


 * Mark 3/Mk 110 57 mm gun


 * (Post HCM/FELEX Refit / 2x MK3 operational prior to Halifax Class Modernization (HCM) refit)
 * NOCGV Svalbard
 * Legend class
 * Future Heritage-class cutter
 * NOCGV Svalbard
 * Legend class
 * Future Heritage-class cutter
 * NOCGV Svalbard
 * Legend class
 * Future Heritage-class cutter
 * NOCGV Svalbard
 * Legend class
 * Future Heritage-class cutter
 * NOCGV Svalbard
 * Legend class
 * Future Heritage-class cutter
 * NOCGV Svalbard
 * Legend class
 * Future Heritage-class cutter
 * Future Heritage-class cutter