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Littlejohn adaptor

 
Littlejohn Adaptor

 
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The Littlejohn adaptor was a device that could be added to the British QF 2 pounder
Ordnance QF 2 pounder

The Ordnance QF 2-pounder was a 40 mm United Kingdom anti-tank gun and vehicle-mounted gun, employed in the Second World War. It was actively used in the Battle of France, and during the North Africa campaign....
 (40 mm) anti-tank gun. It was used to extend the service life of the 2-pounder during the Second World War by converting it to squeeze bore operation.






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Iwm Kid 4781 Tetrarch With Littlejohn Adaptor
The Littlejohn adaptor was a device that could be added to the British QF 2 pounder
Ordnance QF 2 pounder

The Ordnance QF 2-pounder was a 40 mm United Kingdom anti-tank gun and vehicle-mounted gun, employed in the Second World War. It was actively used in the Battle of France, and during the North Africa campaign....
 (40 mm) anti-tank gun. It was used to extend the service life of the 2-pounder during the Second World War by converting it to squeeze bore operation. "Littlejohn" came from the literal anglicization of the name of Mr. Janecek, the Czech designer who had been working on the squeeze-bore principle in the 1930s and who had brought his know-how to Britain after he fled from the Nazi-occupied Czechoslovakia.

Design

The adaptor took the form of a reducing bore that was screwed onto the end of the gun. This was coupled with a round formed from a hard core (tungsten
Tungsten

Tungsten , also known as wolfram , is a chemical element that has the symbol W and atomic number 74.A steel-gray metal, tungsten is found in several ores, including wolframite and scheelite....
) inside a softer metal casing - the Armour-Piercing, Composite Non-Rigid
Shell (projectile)

A shell is a payload-carrying projectile, which, as opposed to Round shot, contains an explosive or other filling, though modern usage includes large solid projectiles previously termed shot ....
 (APCNR) design. The round upon firing travelled the first part of the bore as normal. On entering the tapering portion the softer and malleable metal of the outer shell of the round was compressed - from 40 mm to around 30 mm. The round when it emerged from the adaptor now had a smaller cross-section compared to its weight. Together with the higher pressure developed in the barrel of diminishing internal volume compared to standard cylindrical bore, the APCNR round, called APSV (from armour-piercing super velocity), travelled faster, over a flatter trajectory. The higher velocity at impact was concentrated in the hard core alone. The Littlejohn adaptor/APCNR combination gave the 2 pounder a similar enhancing effect as the APDS
Shell (projectile)

A shell is a payload-carrying projectile, which, as opposed to Round shot, contains an explosive or other filling, though modern usage includes large solid projectiles previously termed shot ....
 round gave to the larger QF 6 pounder
Ordnance QF 6 pounder

The Ordnance QF 6-pounder 7 cwt, or just 6 pdr, was a United Kingdom 57 mm gun, their primary anti-tank gun during the middle of World War II, as well as the main armament for a number of armoured fighting vehicles....
 gun.

The muzzle velocity of the APSV Mark II shell was 1,143 m/s compared to the 792 m/s of the normal 1.2 kg APCBC shell. The lighter Mark I APSV shell was capable of penetrating 88 mm of armour.

In 1942 US Ordnance
Ordnance Corps

The mission of the Ordnance Corps is to "support the development, production, acquisition and sustainment of weapons systems and munitions, and to provide explosive ordnance disposal, during peace and war, to provide superior combat power to current and future forces of the United States Army."...
 tested the Littlejohn adaptor in an attempt to develop taper bore adaptor for the 37 mm Gun M3
M3 37 mm gun

The 37mm Gun M3 was the first dedicated anti-tank gun fielded by United States forces. Introduced in 1940, it became the standard anti-tank gun of the U.S....
. The adaptor distorted after a few shots.

Combat Use

The adaptor was chiefly used on British armoured cars e.g. the Daimler
Daimler Armoured Car

The Daimler Armoured Car was a United Kingdom Armored car of the Second World War....
 which had been designed and built earlier in the war and could not be readily fitted with a larger gun. As an adaptor to the existing gun it could be removed at any time so that normal rounds could be fired.

See also

  • 2.8 cm sPzB 41
    2.8 cm sPzB 41

    2.8 cm sPzB 41 was a Nazi Germany anti-tank weapon working on the squeeze bore principle. Officially classified as heavy anti-tank rifle , it would be better described, and is widely referred to, as a light anti-tank gun....
     - German anti-tank weapon working on the squeeze bore principle.
  • 7.5 cm PaK 41
    7.5 cm PaK 41

    The PaK 41 was one of the last Nazi Germany anti-tank guns brought into service and used in World War II. It was built on the squeeze-bore principle to deliver a higher muzzle velocity and there greater penetration in relation to its size....
     - Another German anti-tank weapon working on the squeeze bore principle.