Bofors 57 mm gun

Bofors 57 mm
A Bofors 57 mm Mk 1 live-firing on the Swedish Spica-II Class FAC
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
Weight	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 mm × 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.

Full 360°:

Magazine:

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. 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 stabilizers. The Mark 3 came in 1995 with modifications made to enable the smart ammunition developed.

The Bofors 40mm gun 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 weight 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 40 in too short a time for the gun to fire enough rounds to ensure a hit.