Bofors 57 mm Naval Automatic Gun L/60
Swedish Bofors 57 mm SAK 60 (57 mm akan m/50) on the destroyer HSwMS Småland
Type	Naval Gun
Place of origin	Sweden
Service history
In service	1952 – 1990
Used by	Dutch Navy Swedish Navy French Navy
Production history
Designed	1950
Manufacturer	Bofors
Produced	1950
Specifications
Mass	Traversing mass: 24 t (53,000 lb)
Barrel length	60 calibres (3.420 m)
Crew	8
Shell	57 × 438 mm R (m/50)
Shell weight	2.6 kg
Calibre	57 mm
Elevation	-9°/+90°, 30°/s
Traverse	-360°, 30°/s
Rate of fire	2 × 130 rounds/min
Muzzle velocity	850 – 920 m/s
Effective firing range	13000 metres (max) 5000 metres (practical) 5500 meters AA ceiling

Bofors 57 mm Naval Automatic Gun L/60 (Swedish: 57 mm sjöautomatkanon L/60 (57 mm SAK 60)),^[1][2] also known as 57 mm/60 (2.25") SAK Model 1950^[3] and the like (full English product name: Bofors 57 mm Automatic A.A. Gun L/60 In Stabilized Twin Turret),^[4] was a twin-barreled 57 mm (2.2 in) caliber fully automatic dual purpose naval artillery piece designed by the Swedish arms manufacturer Bofors from the early of the 1940s to the early 1950s to meet a request from the Dutch Navy.^[1] Besides the Dutch Navy, the weapon was also adopted by the Swedish and the French Navy, most predominantly by the latter.^[3]

Design

The Bofors 57 mm Naval Automatic Gun L/60 is at its core a scaled up version of the famous Bofors 40 mm Automatic Gun L/70, but constructed as a twin-gun system sharing the same receiver/mantle with ammunition feeding from the sides into each gun.^[1] The guns were water-cooled and fed by large 80-cartridge magazines that allowed several long bursts to be fired without reloading.^[3]

• 
  French "57mm/60 modèle 1951" on display at Port-Louis naval museum.
• 
  French "57mm/60 modèle 1951" on display at Port-Louis naval museum.

Use in the Dutch Navy

The Dutch were the initial users of the Bofors 57 mm Naval Automatic Gun L/60. As part of rebuilding the Dutch Navy post World War II, the Dutch Navy had requested several naval gun systems to be developed by Bofors for their next generation of naval-vessels,^[5] one being a twin-barreled 57 mm dual-purpose gun for the planned De Zeven Provinciën-class cruisers HNLMS De Ruyter and De Zeven Provinciën.^[1] This request led to the creation of the Bofors 57 mm Naval Automatic Gun L/60, which entered active service with the Dutch Navy in 1953 mounted on the cruisers De Ruyter and De Zeven Provinciën.

Use in the Swedish Navy

Following the Dutch example, the Swedish navy decided to acquire the new 57 mm system for a new generation of destroyers in 1950. In Swedish service the weapon was fitted to the Halland-class destroyers HSwMS Halland and Småland, both of which entered service in 1956.^[1] The weapon was initially designated 57 mm automatkanon m/50 (57 mm akan m/50),^[6] meaning "57 mm autocannon m/50", but around 1970 the weapon was redesignated to 57 mm torndubbelautomatpjäs m/50 (57 mm tdblapjäs m/50),^[7][8] meaning "57 mm turret double automatic piece m/50" (literal).

The gun was in use until the Halland-class destroyers were taken out of service.

Use in the French Navy

The Bofors 57 mm L/60 naval gun was also purchased by the French Navy and came to serve on a number of naval-vessels under the designation 57mm/60 modèle 1951 (57mm/60 mle 51) from 1952 onward, although primarily post 1956.^[3] The French navy version of the system featured a French designed naval mount that maintained the system in mechanical equilibrium, even when firing.^[3] The French mounting was some 8 tons lighter than the Dutch/Swedish version.^{[citation needed]}

In French service the gun notably armed light escorts as main guns and larger ships as secondary guns. The following French ships were armed with the 57mm/60 mle 51 system:^[3]

• The battleship Jean Bart (1952 retrofit)
• The anti-aircraft cruiser De Grasse
• The anti-aircraft cruiser Colbert
• Le Normand-class frigates
• T 47-class fleet escorts (also known as the Surcouf class)
• T 53-class fleet escorts