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 a revision of the 57 mm lvakan M/50 used on the Halland class destroyers. 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 stabilizers. 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).
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.