Bofors 40 mm Gun M2

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Summary

The Bofors 40 mm Gun is an autocannon developed by AB Bofors from Sweden. A very popular multi-purpose weapon, the autocannon as purchased and used by both sides in World War II, though mostly as an anti-aircraft armament. Despite no longer considered efficient against jet-powered aircrafts, the Bofors still see wide usage today in a variety of vehicles.

Users

Ammunition

Ammunition Penetration in mm @ 90° Type of
warhead
Velocity
in m/s
Projectile
Mass in kg
Fuse delay
in m:
Fuse sensitivity
in mm:
Normalization At 30°
from horizontal:
Ricochet:
10m 100m 500m 1000m 1500m 2000m 0% 50% 100%
Default 76 74 62 45 33 24 AP-T, HEFI-T N/A N/A N/A N/A N/A N/A N/A N/A
Mk.II 9 9 9 9 9 9 HEFI-T 874 0.86 0.2 0.1 28° 21° 17°
M81A1 76 74 62 45 33 24 AP-T 874 0.88 N/A N/A -1° 43° 30° 15°

History of creation and combat usage

Development

In late 1920s, the Swedish Navy approached AB Bofors for a development of a better anti-aircraft gun to replace the 2-pounder Pom-poms that was purchased from Britain. Bofors started production in 1928 with a smaller 57 mm semi-automatic gun, but trouble arise from a problematic feeding system. It wasn't until 1930 when a new design fixed the feeding system that development continued to a prototype. At the time, Krupp from Germany bought out a third of Bofors' shares. This had Krupp update the Bofors factories with better equipment, but the anti-aircraft gun project was kept a secret from them. The first test fire began in November 1931, which changes in the feed mechanism continued until the gun could reach a rate of 130 rounds per minute. The weapon was ready for production in October 1933, and the gun became known as the "40 mm akan M/32" officially, but most countries refer to the weapon as the "Bofors 40 mm L/60" (This name stuck despite the actual barrel length being 56.25 caliber long).

Procurement

Despite being developed for the Swedish Navy, they decided not to adopt it and favored a weapon with a caliber of 13 - 25 mm. The Bofors autocannon's first order was from the Dutch Navy who wanted a twin-gun mount on their De Ruyter cruiser in August 1934. Bofors advertised the Bofors gun in a show at Belgium in April 1935 which featured a towable carriage that allowed firing on land without setup, albeit with reduced accuracy. The carriage however could be set up in less than a minute for a more stable firing position. This version was ordered first by the Belgium in August 1935, then expanded rapidly as military forces from Poland, Norway, Finland, and even the Swedish Army.

The British Army soon picked it up after testing a few cannons from the Polish, but requested a manufacturing license instead to convert the measurements from metric to imperial. The British also simplified the Bofors construction so it could be more suitable for mass production. The British also introduced a new automated fire control system to improve the Bofors' accuracy against moving aircrafts. The Bofors then became the standard AA gun for the British, who used it in land mounts and in self-propelled systems like the Crusader AA Mk.I. The British navy also adopted the Bofors in twin mounts on their ships. The Americans also adopted the Bofors cannon and produced the guns in the states, with Chrysler producing 60,000 guns throughout World War II. The Americans also simplified the Bofors production method for mass production that resulted in fulfilling the U.S. Army's orders in 1943 at half of the original project cost. The Navy and Army adopted the gun for use in a single and twin mounted role. The Army also adapted the twin-mounted variant onto self-propelled vehicles, producing the Twin Gun Motor Carriage M19 from the M24 Chaffee.

The Axis forces also used Bofors cannon captured from the Allies, with the Germans capturing them from Poland and France and Japanese capturing them from Singapore.

Usage

The Bofors cannon saw usage in a variety of roles and were mounted on a single, twin, or quadruple mount. The autocannons proved very successful in their role as anti-aircraft guns. Their utility is proved in that after the end of World War II, the Bofors 40 mm cannon continued to be used on naval and ground mounts. However, the initial variants soon became outdated with the introduction of jet-powered aircraft, causing an upgrade in the cannon from Bofors 40 mm L/60 into the L/70, which improved firing range and rate of fire, but both variants continued to see service in the world. Today in 2012, the Bofors 40 mm L/60 cannons are still widely used in Brazil, Paraguay, and Taiwan; but in the United States, they still use on the AC-130 gun ships

Images

Additional information (links)