40mm/56 Bofors Medium Antiaircraft Gun

National Archives #80-G-413915. Via Wikipedia Commons.

Specifications:

The Bofors was the best medium antiaircraft gun of the war. A Swedish design, it was manufactured and used (at first illegally and later under license) by all the Allied powers. It was typically mounted in a quadruple mount with a single director and with water cooling. Although the shells could nominally reach out to 11,000 yards (10,000 meters), Campbell states that the shells were designed to self-destruct at 4000-5000 yards (3700-4600 meters.) This was probably to avoid friendly fire incidents.

The first twin mounts were produced in January 1942 and the first quad mounts in April 1942. The gun was highly praised for its performance at the Battle of Santa Cruz, but production did not begin to match demand until mid-1944. Large numbers were mounted on warships to counter the kamikaze, at which they were only modestly effective: The state of the art in electronics was insufficient to put a proximity fuse in the shell, and its explosive charge was insufficient to disintegrate an aircraft with just one or two contact hits. But they were the best weapons for close-in defense available at the time. Apparently the Gridleys were the only major warships in the U.S. Navy that had not shipped a Bofors mount by the end of the war.

The sustained rate of fire was reduced by the need to reload the small clips (4 rounds) by hand.

References

Frank (1990)

Campbell (1985)

The Pacific War Online Encyclopedia (c) 2007-2008 by Kent G. Budge. Index