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Bofors M/50

Creusot-Loire Modèle 54 | Mitsubishi Type 71


Bofors B4 launcher

Two Bofors B4 quadruple launchers for 375mm rockets on a Halland class destroyer.
Source: Marcusroos - © GNU Attribution Share Alike license

Naval ASW system
Entered service
In service
1948 - 1954
1956 - mid 1980's
Sweden - Bofors, later Saab Underwater Systems
France - Creusot-Loire
Japan - Mitsubishi Heavy Industries
Type 71 (B4 launcher in Japanese service)
SR-375A (alternative name for Bofors B2)
Notable users



The Bofors M/50 is a naval anti-submarine warfare rocket depth charge system of Swedish origin. It was developed after World War 2 and entered service in the early 1950's. Several types of launchers and and a selection of 375mm rockets were developed over time. During the Cold War the Bofors M/50 was used in many European ships and was exported to various nations. Although over the last decades usage has declined in favor of lightweight torpedoes, many of these systems remain in service today.


The Bofors M/50 was one of the first operational anti-submarine depth charge systems combining accurate fire control using sonar input and rocket powered depth charges. Over time the launchers, fire control systems and ammunition were continuously improved. The general layout of these systems is identical. The unmanned multi-barrel launcher is the visible component of the system. Underneath the launcher there is an ammunition handling room. In the reloading position the barrels are raised and loaded from the rear.

Fire control

All Bofors M/50 launchers are unmanned and use a fire control systems. Early models introduced in the 1950's used and electro-mechanical predictor. Later at least four types of digital fire control systems were developed in Sweden and abroad. In all cases sonar input is used to determine traverse, range and depth. Range is controlled by elevation of the launcher in combination with the weight and velocity of the selected ammunition type.


Several types of 375mm rockets can be used in the Bofors M/50. Most have a warhead with over 100 kg of explosive filler. Early rocket had a measly 0.8 km range, which was doubled in the Erika, the most common type of rocket. Early rocket types used impact and time fuses. The Nelli rocket introduced in the 1970's introduced a proximity fuse. The Nelli also has a longer 3.6 km range and a lighter 80 kg warhead.


The Bofors M/50 was first acquired by Sweden and the Netherlands, both using the quadruple B4 launcher on their detroyers. France developed the six tube variant in the 1960's and used it in various classes of frigates. In the early 1970's Japan acquired a local production license and used the B4 launcher on various classes of frigates. The introduction of the lightweight B2 launcher allows installation on corvettes and smaller frigates, leading to various export sales around the world.


Bofors B4

Quadruple launcher introduced by Bofors in 1956. Known as M/50 at first and later designated B4. Produced under license in Japan as the Type 71. Nominal ammunition storage is 48 rockets per launcher. The semi-automatic loading system loads one round at a time, with four tubes being reloaded in 3 minutes.

Modèle 54

Sextuple launcher developed by French company Creusot-Loire, first introduced in 1967. The sextuple launcher was designed to approximate the firepower of two quadruple B4 launchers in a single mount. Ammunition varies per class and is between 30 and 72 rockets.

Bofors B2

Twin launcher introduced by Bofors in 1972. Most compact version of the launchers, while not sacrificing effective firepower. This is achieved by an improved reloading system that loads two rounds simultaneously in 30 seconds.


Facts Bofors B4 Bofors B2
Naval ASW rocket launcher
375mm Bofors rocket anti-submarine depth charge
Launch tubes
4 tubes
Tube length
3.6 m
Rate of fire
1 rocket per second
Depends on type of rocket:
0.65 to 1.6 km for Erika
1.4 to 2.2 km for Flora
0.4 to 0.9 km for Mimmi
1.6 to 3.6 km for Nelli
Feed mechanism
Semi-automatic loader below deck
48 rounds
130° left to 130° right
Traverse rate
-15 to +90°
Elevation rate
4 ammunition handlers below deck
Fire control
Electro-mechanical predictor in early systems
Digital fire control in later systems
7.5 t
Deck penetration
Ammunition handling room below deck
Power consumption
6 kW

Ammunition types

Bofors 375mm M/50

The Bofors M/50 series of launchers can fire several ammunition types. These are described in a seperate article.



List of ships with B4 / Type 71 launcher

Akizuki class
Japanese class of destroyer. Weapon Alpha replaced by 1x Type 71 during refit in 1972.
Almirante Pereira da Silva class
Portuguese class of frigate with 2x Bofors B4.
Deutchland class
German class of training ship with 2x Bofors B4.
Friesland class
Dutch class of destroyer with 2x Bofors B4.
Swedish class of destroyer with 2x Bofors B4.
Hamburg class
German class of destroyer with 2x Bofors B4.
Dutch class of destroyer with 2x Bofors B4.
Ishakari class
Japanese class of destroyer with 1x Type 71.
Isuzu class
Kitakami class subtype (3rd and 3th in class) with 1x Type 71.
Katori class
Japanese class of training ship with 1x Type 71.
Köln class
German class of frigate with 2x Bofors B4.
Minegumo class
Japanese class of destroyer with 1x Type 71.
Takatsuki class
Japanese class of destroyer with 1x Type 71.
Thetis class
German class of corvette with 1x Bofors B4.
Yamagumo class
Japanese class of destroyer with 1x Type 71.
Yubari class
Japanese class of destroyer with 1x Type 71.

List of ships with Modèle 54 sextuple launcher

D'Estienne d'Orves class
French class of corvette with 1x Mle 54 with 30 rockets. Removed in the 1990's. Not on export versions of class.
Dupre class
French class of destroyer with 1x Mle 54.
Le Corse class
French class of frigate with 1x Mle 54.
Le Normand class
French class of frigate with 1x Mle 54.
Surcouf class
French class of destroyer. 1x Mle 54 after refit of four ships converted for air defense and five ships for anti-submarine warfare.
Belgian class of frigate with 1x Mle 54.

List of ships with Bofors B2 twin launcher

Descubierta class
Spanish class of frigate with 1x Bofors B2.
Erinomi class
Nigerian class of corvette of British Vosper Mk 9 design with 1x Bofors B2.
Fatahillah class
Indonesian class of frigate with 1x Bofors B2.
Kasturi class
Malaysian class of corvette of German FS 1500 design with 1x Bofors B2.
Niterói class
Brazilian class of frigate of UK design with 1x Bofors B2.
Nilgiri class
Indian class of frigate, updated versions of British Leander class. The 5th and 6th ship in class are fitted with 1x Bofors B2.