Sergeant Charles Callistan looked through the sights of an antitank gun at an approaching enemy tank. His weapon, a six-pounder cannon, was in the perimeter of a surrounded British outpost named Snipe. The desert sun shone overhead and flies buzzed all around, but none of this mattered as much as the Axis artillery and machine-gun fire that sent hot metal flying through the air. Even worse was the force of nine Italian armored vehicles threatening to overrun the beleaguered English troops.
When the range had closed to only 600 yards, Callistan fired and knocked out his target. Five more armor-piercing rounds accounted for five more tanks in a row, but then the sergeant had a problem. Three enemy vehicles remained and he had only two rounds left.
Callistan’s lieutenant, J.E.B. Toms, came to the rescue. He ran under heavy fire to his jeep, which held four boxes of ammunition. As Toms drove the jeep over, it was hit and burst into flames. The fire didn’t stop Toms; the lieutenant got the boxes offloaded and replenished Callistan’s dwindling supply. Taking careful aim, the sergeant repeated his earlier feat: three rounds, three armored vehicles out of action.
Transitioning from the Two-Pounder
The six-pounder antitank gun was Great Britain’s premier tank killing weapon when it first appeared in the Western Desert, proving able to pierce the armor of any German tank the Afrika Korps could field. The technological arms race of World War II produced new tanks with ever thicker armor, however, and ultimately the six-pounder became ineffective well before war’s end. This obsolescence made little difference for many of the Allied soldiers who used it; since there was no comparable replacement that worked better, the cannon was still in wide use when the war ended.
The development of the six-pounder actually began before the war although the gun did not enter production until 1941. The standard British antitank gun of the late 1930s was the two-pounder, a 40mm weapon that could penetrate 42mm of armor at 1,000 yards. This made it one of the premier antitank guns in the world when it was adopted in 1936, but by 1940 tank development had left it behind. The British Army was forced to quite literally leave its two-pounders behind as well; over 500 of them had to be abandoned in France when the British Expeditionary Force evacuated at Dunkirk.
In the frantic days to follow, an invasion of the British Isles was expected. So the two-pounder production lines were kept open to re-equip the Army as quickly as possible. This desperate need led to a decision that kept the six-pounder on the drawing board until long after it was needed.
The original design work for the six-pounder began soon after the two-pounder’s adoption and was completed in 1938. The larger gun was a 57mm weapon, a caliber chosen largely as a logical matter of economics. Six-pounder weapons had been in British service since the 1880s, so manufacturing equipment and experience already existed. In 1939 a prototype, the Mk1, was completed and test fired. Testing was successful, but even with the rumblings of war on the horizon the perceived need was low so the design was shelved for the time being.
After the fall of France in June 1940, the call for the six-pounder was finally recognized. However, the need for any antitank gun, even a less effective one such as the two-pounder, was so great the British decided they could not afford to close the existing production lines down long enough to retool them for the six-pounder. There was also concern that the newer, bigger gun would require extensive retraining of gun crews already able to operate the two-pounder.
While an invasion of Great Britain never occurred, fighting did go on in the Mediterranean and North Africa with the increasingly ineffective two-pounder the only option against Germany’s panzers. The British Army was well aware of the need, yet unable to act on it immediately. While the first order for 400 six-pounder guns was made in June 1940, production could not begin until November 1941.
The Six Pounder: a Marked Improvement
The weapon the British Army eventually got was a marked improvement over its predecessor. The six-pounder Mk2 production model weighed in at 2,521 pounds, almost 800 pounds heavier than the two-pounder but still light enough for crews to manhandle it into position when necessary. It was mounted on a conventional two-wheeled carriage with “split” trails; that is, the two trailing arms that extended to the rear of the carriage could be separated to increase stability. The barrel on the six-pounder was 43-caliber, meaning the bore’s length was 43 times its diameter of 57mm. The weapon could traverse 45 degrees to either side and elevate from minus five to plus 15 degrees.
When firing the standard six-pound armorpiercing round, the six-pounder had a maximum range of 5,500 yards with a muzzle velocity of 2,693 feet per second and could penetrate 74mm of armor at 1,000 yards. Over time, improved ammunition was developed, culminating in June 1944 with an APDS (Armor Piercing Discarding Sabot) round that had a tungsten core. This increased penetration to 146mm at 1,000 yards. Tungsten was a valuable commodity in war production, so shortages meant there were never as many APDS rounds available as needed.
As Great Britain struggled to get the six-pounder into service, the United States was starting to rebuild its own war-making capacity. Woefully unprepared for a war many knew must eventually come, the U.S. Army began to search for a larger antitank gun to replace its standard M3 37mm weapon, whose performance was comparable to the ineffective two-pounder.
By February 1941, it was decided to adopt the British six-pounder design. This served a dual purpose; not only could the American Army improve its tank-killing capability, but using the British design meant the same gun could also be produced for the Lend-Lease program. To help the American effort, the British sent a pair of six-pounders with 100 rounds of ammunition. The six-pounder design was given final approval on May 15, 1941, becoming the 57mm Gun M1. Numbers were also supplied to the Soviet Union through Lend-Lease.
The American version initially had one major difference from that used by the British. The U.S.-built M1 had a barrel 16 inches longer; when the Mk2 entered production in England there was a shortage of suitable gun lathes for production of the longer barrels. The original Mk1 prototype had the longer barrel, but the Mk2s were made with shorter length. Since there was no shortage of the longer lathes in America, the M1 could be made with the longer tube from the start. The added 16 inches made the M1 a 50-caliber weapon and increased muzzle velocity by about 100 feet per second.
When the English lathe shortage was solved, British production shifted to the longer barrel, designated the Mk4. The only other major difference between the two versions was in the carriages, largely having to do with the wheels and tires used.
The Six-Pounder as a Tank Gun
While the Americans never mounted the 57mm on a tank, the six-pounder was also adapted as a tank gun. The turret rings in many early-war British tank designs limited the size of the cannon they could mount, but a few were able to accept a larger gun than the two-pounder, and these were fitted with the six-pounder Mk3 and later the longer barreled Mk5 version. Crusader, Valentine, and Churchill tanks were all up-gunned with six-pounders as quickly as possible.
Newer designs like the Cromwell began their service lives with a six-pounder before being upgraded to a 75mm cannon. The U.S. military did experiment with a few self-propelled mountings for the 57mm but only the halftracked T48 version was produced in any numbers. When the U.S. Army decided it no longer wanted them, the few hundred made were transferred to England where, in the words of the noted English military author Ian V. Hogg, “I cannot imagine what we did with them.” They were likely converted into something considered more useful.
The only British self-propelled six-pounder to see combat was the Deacon. This was a six-pounder encased in an armored shield mounted on the back of an AEC Matador truck. Some 175 were built and sent to North Africa. The vehicle was large and very easy to spot on the battlefield. After the defeat of the Axis in North Africa they were taken out of service.
50 Tanks Knocked Out
As a towed antitank gun, the six-pounder/57mm was a much greater success. Once issued to British antitank units in the Western Desert, the six-pounder quickly developed a solid reputation for effectiveness against German armored vehicles. More than 100 guns were available when the weapon was first fired in anger at Gazala in May 1942, where it took a heavy toll of Axis armor. Panzer crewmen began to get a taste of their own medicine as they were effectively engaged at ranges far beyond what they were previously accustomed to.