Bofors 57 mm Naval Automatic Gun L/70

Bofors 57 mm Naval Automatic Gun L/70
A Mk 110 57 mm gun on the littoral combat ship USS Freedom
Type	Naval artillery
Place of origin	Sweden
Service history
In service	1971–present
Used by	See users
Production history
Designer	Bofors Defence
Designed	Mark 1: 1970 Mark 2: 1981 Mark 3: 1995
Manufacturer	Bofors Defence (1970–2000) United Defense (2000–2005) BAE Systems AB (2005 onwards)
Produced	Mark 1: 1970 Mark 2: 1985 Mark 3: 2000
Variants	See variants
Specifications
Mass	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 × 438 mm R (m/70) 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°: Mark 1: 55°/s Mark 2: 55°/s Mark 3: 57°/s
Rate of fire	Mark 1: 200 rounds/min Mark 2: 220 rounds/min Mark 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.

The Bofors 57 mm Naval Automatic Gun L/70 (Swedish: 57 mm sjöautomatkanon L/70 (57 mm SAK 70)),^[1][2] among other names, is 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 the late 1960s as a replacement design for the twin barreled Bofors 57 mm Naval Automatic Gun L/60. The gun is remotely controlled by a fire-control computer but can as a redundancy measure also be operated manually by crew using instrument panels either on or in direct contact with the gun.^[3]

The gun has been upgraded and improved several times:

• Mk1 – The baseline Mark 1 variant began production in 1970 and was initially used to equip smaller coastal patrol craft and fast attack craft.
• Mk2 – The improved Mark 2 variant came in 1981 and drastically lowered the weight as well as introduced new servo stabilizers.
• Mk3 – The improved Mark 3 variant came in 1995 and primarily features the ability to use programmable ammunition.^[3]

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.^[4]

Although the Swedish Navy has been 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.