and elevation, additionally he could disengage the traverse mechanism and the gun commander could rotate the gun be pushing against the gunners shoulders aided by a simple ring and bead sight on the top of the shield. The gunner had a 1.9x magnification telescopic sight with a 21 degree field of view, graduated from to at 300 yd intervals. The gunner also had a notch and bead sight above the telescopic With the Vickers carriage, the gun could also be fired from its wheels, at the expense of limited traverse. The shield was 5/16 inch armour plate. Typically it was towed by a 15-cwt (3/4-ton) truck with 68 rounds on the truck with a further 14 on the carriage itself. It could also be carried "portee" on a 30-cwt truck. The 40 mm 2-pounder could outperform a typical 37 mm piece, such as the German 3.7 cm PaK 36 or the Bofors 37 mm, and significantly outclassed 25mm and 20mm weapons of that era. A drawback of the 2-pounder was that it was nearly twice as heavy as the PaK 36 and had a higher profile. The gun was first put into use on a tank as the main armament of the Vickers-designed Cruiser Tank Mk I. A late-war project was the Canadian David High Velocity to allow 2-pdr ammunition to be fired from the larger-calibre 6-pdr. This was intended to improve the muzzle velocity of the shot. Initial trials carried out in Canada and the U.K. were promising; however the system was still being developed when the war ended, and the program was subsequently ended along with it. Another development was the 2-pdr HV 'Pipsqueak', a postwar gun using a 40x438R cartridge originally intended as the main armament for the Saladin armoured car that was to replace the AEC Armoured Car. This was designed to fire Armour-Piercing Discarding Sabot (APDS) rounds, which would match the penetration of the 'Littlejohn' shot while still allowing high-explosive (HE) shells to be fired. In fact, the claimed performance was better, the 1,295 m/s shot penetrating 85mm of armour at 60 degrees at . Development of this gun was also abandoned when the role of the Saladin shifted towards infantry fire support, and a low-velocity 76 mm gun was selected for it instead. Initially one of the most serious shortcomings of the 2-pdr was the lack of a high-explosive shell, especially when the 2-pdr