Bofors 40 mm Gun

Origins

In the late 1920s the Swedish navy asked the armaments firm AB Bofors for a new automatic anti-aircraft gun. Aircraft were becoming faster and stronger, and the small machine guns and slow single-shot guns then used against them were no longer enough. Bofors engineers, led by Victor Hammar and Emanuel Jansson, developed a 40 mm gun with a long barrel, sixty calibers in length, which gave it the name L/60. It was ready in the early 1930s and was soon adopted by the Swedish armed forces. The gun was offered for export, and orders came from Poland, Belgium, the Netherlands, Norway and other countries. Britain ordered guns and a license in 1937, and the United States adopted it in 1941.

Design & Construction

The Bofors was a recoil-operated automatic gun. Rounds were loaded from the top in clips of four, and a loader dropped fresh clips into the feed guides while the gun was firing, so it could keep up a steady rate of about 120 rounds a minute. Each shell weighed about two pounds (0.9 kg) and was fitted with a sensitive nose fuze and a self-destroying tracer, so that shells which missed would burst in the air rather than fall on friendly ground. The gun was aimed by two layers, one turning it left and right and one raising it, and it was served by a crew of about six. The British Army version rode on a four-wheeled carriage that could be towed by a truck and brought into action quickly. From 1940 the British added the Kerrison predictor, a mechanical computer that worked out the aim-off needed to hit a moving target. At sea the Americans and British fitted it in twin and quadruple water-cooled mounts.

Combat Use

In the summer of 1940 Anti-Aircraft Command, under General Sir Frederick Pile, had far fewer light guns than it had planned for. The Bofors guns it did have were placed around airfields, radar stations, ports and aircraft factories, where German aircraft were most likely to attack at low level. During the Battle of Britain they fired at dive bombers and at low-level raiders, such as the Dornier bombers that attacked the fighter station at Kenley on 18 August 1940, together with older weapons such as the Lewis Gun. Through the rest of World War II the Bofors served in almost every theater. It defended the Malta harbors, the Normandy beachhead and Antwerp, where it helped against the V-1 flying bomb. In the Pacific, American and British warships carried thousands of them against Japanese aircraft, including kamikazes. British and Commonwealth gunners also used it against ground targets when no aircraft were about.

Legacy

The Bofors was made in Sweden, Britain, Canada, the United States, Australia, Hungary and elsewhere, and more than 100,000 may have been built during the war, though estimates vary. American Army versions fought again in Korea and Vietnam, where the twin-gun M42 Duster was used mostly against ground attacks. In 1947 Bofors introduced a new model with a longer barrel and a higher rate of fire, the L/70, which was adopted by NATO and is still made today. The 40 mm caliber remains in service on warships and armored vehicles, and the name Bofors became a general term for light anti-aircraft guns in the English-speaking world.