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 destroyer 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 , 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 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 ammunition s developed for the Mark 2 gun . The Mark 2 was designed in 1981 but introduced into service with the — 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 missile s 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 . The latest development is the Mark 3 , which was designed in 1995 but introduced into service with the — fitted on 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 . 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 . 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 . 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 . Variants . The Bofors 57 mm 3P ammunitions are designated as " Mark 295 Mod 0 " in US service .