Limitations of the existing 2-pounders were apparent even as the gun entered service and an effort was made to replace it with a much more capable weapon starting as early as 1938.

Guns of this calibre had been employed by the Royal Navy from the late 19th century and manufacturing equipment was available.

The loss of equipment – most of the heavy equipment of the British Expeditionary Force (BEF) was left behind in France during Operation Dynamo – and the prospect of a German invasion made re-equipping the army with anti-tank weapons an urgent task, so a decision was made to carry on the production of the 2-pounder, avoiding the period of adaptation to production and also of re-training and acclimatisation with the new weapon.

Unlike the 2-pounder, the new gun was mounted on a conventional two-wheeled split trail carriage on pneumatic tyres but without a spring suspension.

A second attempt was made with a shorter 48 calibre barrel but this proved to have only marginally better performance than the 6-pounder and the program was cancelled in January 1943.

As a smaller and more manoeuvrable gun, the 6-pounder continued to be used by the British Army for the rest of World War II and for about 20 years afterwards.

The US version, classified as substitute standard as 57 mm gun M1, was based on the 6-pounder Mark II, two units of which were received from the UK.

American shell designs and production lagged behind the introduction of the gun once it was accepted for service and so, at first, only AP shot was available.

The North Irish Horse disabled and captured Tiger 131 after the crew had abandoned it after it received several hits, most seriously a shot which struck the turret ring, making traverse impossible.

The 6-pounder was initially chosen for the A24 Cavalier, A27M Cromwell and A27L Centaur, all similar designs in competition to replace the Crusader.

In 1943 a program was initiated to replace the 6-pounder with the Ordnance QF 75 mm, a dual role weapon with better HE performance.

The Royal Navy used the 6-pounder extensively in Motor Gun Boats during World War II (especially the Fairmile D).

The guns were all the early short-barrel (43 calibre) type and fired exclusively HE (high-explosive) ammunition, at much lower muzzle velocities than for AP (armour-piercing), because of the use of flashless propellant for night operations.

Officially the QF 6-pdr Class M Mark I with Auto Loader Mk III, it was based on the long-barrelled (50 calibre) gun.

[9] In spring 1943, following the experience of the North African Campaign, the Infantry branch of the US Army recognised the need to field a heavier antitank gun than the 37 mm M3.

The Ordnance Board, on the other hand, felt that a more powerful weapon should be introduced; the Airborne and Cavalry rejected it.

[11] The squad leader and driver were issued M1 Garands, the gunner and cannoneers M1911 pistols, and the ammunition bearers M1 carbines.

The British 6-pounder with the MK III carriage was also used by the Antitank Company of the 442nd Infantry Regiment as part of the glider-borne invasion force assigned at that time to the 517th Parachute Infantry Regiment, First Airborne Task Force, during Operation Dragoon, the invasion of Southern France.

Only after the Normandy Campaign did the HE round reach the battlefield, although before then US units were sometimes able to get a limited amount of HE ammunition from the British Army.

[13] Towards the end of the war, towed anti-tank units had gone out of favour due to their lack of mobility compared to self-propelled guns.

Armor-piercing (AP) ammunitions did not have enough firepower to penetrate North Korean tanks, and nearly 70 % of the 35,000 shells were anti-personnel high-explosives (HE).

The South Korean military tried to overcome the disadvantage by firing at close range or concentrating on weak parts, but it did not have a significant impact on the war situation.

[15] The South Korean military operated the M1 anti-tank gun as an infantry-assisted firearm from 1950 to 1951, and gradually retired it by replacing it with a M20 Super Bazooka and M20 recoilless rifle.

The US 57 mm M1 gun is popular with modern-day cannoneers, as there is a relatively good supply of shell casings and projectiles.

The gun is also reportedly still in active military use with some South American countries, and in coastal defence emplacements of outlying island garrisons of the Republic of China Army.

The production of the T18E2 armored car, known as Boarhound in its limited British service, was stopped after 30 units were built.

A project for a tank destroyer armed with the M1—the 57 mm gun motor carriage T49—was cancelled after a single pilot vehicle was built.

Similarly, the wheeled 57 mm Gun Motor Carriage T44, based on Ford 4×4 ¾ ton cargo carrier chassis, was cancelled after brief testing.

[19] Ammunition was of the fixed type made up of projectile with a tracer in the base, a charge in a brass cartridge, and a percussion primer.