Bofors 40 mm Anti-Aircraft Auto Cannon
Bofors 40 mm Anti-Aircraft Auto Cannon
Bofors 40 mm Anti-Aircraft Auto Cannon


Caliber: 57 mm
Weight: 2,500 pounds including cartridge
Range: 10,250 yards
Shell Types: Armor-piercing,
APC from Sep '42
APCBC from Jan '43
APCR from Oct '43
APDS from Mar '44
Muzzle Velocity: 3,000 ft second APDS Round
Penetration: 64-140 mm @1,000 yards
depending upon shell/gun combination
Crew: 6
Traverse: 45 degrees left and right of center
Status: Static display
Owner: Estrella Warbirds Museum


The 57 mm anti tank gun was the primary allied anti tank gun during the middle of World War II, and it was also the main gun for a number of tanks. The M1 is an almost exact copy of the British six-pounder anti-tank gun. The British design was first modified to American manufacturing practices and standards in order to produce the weapon for Great Britain under Lend-Lease. Production of the U.S. M1 anti-tank gun began in May 1941, and approximately 16,000 were made through 1945. The gun was light, easy to maneuver on the battlefield, and fired both armor-piercing ammunition and a high-explosive shell. Compared to American designed artillery, it had a horrendous recoil that was not popular with troops. The weapon was retired at the end of World War II.

At the beginning of WWII, the existing anti tank guns, called two pounders, were very limited in terms of power. The British set out to create a more powerful anti tank weapon starting as early as 1938. The 57mm, or six pounder, was completed in 1940, and the gun's carriage design was completed in 1941. Having a need for anti tank guns, the British continued the production of the two pounder and built a new assembly line for the 57mm. This delayed the the 57mm's entry into service until May of 1942. The US Army adopted the 57mm as its own anti tank gun as the "M1".

In spring 1943, following the experience of the North African Campaign, the Infantry branch of the U.S. Army recognized the need to field a heavier antitank gun than the 37 mm M3. The goal was to get improved performance, but keep the wieght and dimensions of the 57mm. The first attempt was the 8 pound 59 caliber, but it proved to be too heavy. The second attempt was a shorter 48 caliber, but it only had a slight performance boost over the 57mm gun.The 57mm was very effective against enemy tanks, so over time the Germans introduced heavier tank designs with stronger front armor. The 57mm was not effective against this frontal armor, but it was very effective against these improved tanks at other angles.

The program was scrapped in January 1943. A 17 pounder was delevoped in small numbers to combat German Tiger tanks.According to the Table of Organization and equipment from 26 May 1943, a regimental antitank company included nine 57 mm guns and each battalion had an antitank platoon with three guns giving a total of 18 guns per regiment. Dodge WC-62 / WC-63 6x6 1 1/2 ton trucks were issued as prime movers. By mid-1944 the M1 was the standard antitank gun of the U.S. infantry in the Western Front and outnumbered the M3 in Italy.

Because of the unexpected adoption for service, the only ammunition type in production in the U.S. by mid-1943 was the AP ammunition. New ammunition was developed for the 57mm, giving it a performance boost. The first was a "core" design APCR shot. This was followed up with the "Armor pierceing, discarding sabot", or "APDS" which greatly improved the armor penetrating ability. An HE shot was also developed for unarmored targets. Only after the Normandy Campaign did the HE round reach battlefield (U.S. units were sometimes able to get a limited amount of HE ammunition from the British Army), and the canister shot was not seen in significant numbers until the end of the war. This limited the efficiency of the gun in the infantry support role. Also, APCR or APDS rounds were never developed.

The U.S. Army also employed a limited number of British-built 6-pounders on carriage Mk 3, designed to fit into the Horsa glider. These guns were used to replace 37 mm pieces in the 82nd and the 101st airborne divisions before the Normandy airdrops.

The M1 went out of service in the U.S. soon after the end of the World War II.

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