Littlejohn adaptor

This was coupled with a round formed from a hard core (tungsten) inside a softer metal casing - the armour-piercing, composite non-rigid (APCNR) design.

Together with the higher driving pressure developed in a barrel of diminishing cross-section compared to a standard cylindrical bore, the APCNR round, called APSV (from armour-piercing super velocity), travelled faster, over a flatter trajectory.

[3] The adaptor was chiefly used on British armoured cars, e.g. the Daimler, which had been designed and built earlier in the war and could not be readily fitted with a larger gun.

When crews discovered the special 'squeeze bore' ammunition was more effective than the standard 2-pounder anti-tank round even when not 'squeezed', the usual practice was to store the adaptors rather than have them fitted.

Attacks with HE were twice as accurate as with AP, possibly because the ballistics were a closer match to the .303" Browning machine guns used for sighting... the gun/ammunition combination did not function with sufficient reliability...