#183mm

During the Berlin Victory Parade, the IS-3 was first observed by the western allies. Among the British, fear grew about its armour and the fact that only the 17-pounder, firing the scarce APDS (Armour Piercing Discarding Sabot) stood a chance at penetrating it. As a result, a British program began to develop a gun capable of accomplishing the feat of penetrating the IS-3 frontally. When doubts arose about the planned vehicle, FV215, coming into service before cold war hostilities in sufficient numbers, a stopgap order was issued in 1950. This utilised the Centurion MK3 hull and mounted a 183mm anti-tank gun. This was named the FV4005.