The Cromwell's armament was changed from the 6-pounder to the dual purpose 75mm. This gave a significant reduction in armour penetration compared to newer 6-pounder APDS ammunition, which was becoming available, but added the ability to fire High Explosive shells, which were more capable against other targets, such as anti-tank guns. The High Velocity 75mm gun was developed in an attempt to give both good anti-tank and HE performance, but in May 1943 proved too big to be fitted to the Cromwell. This issue led to the development of the A34 Comet, while the gun bore was increased to 76.2mm to gain compatibility with the 17-pounder ammunition albeit with smaller shell casings with less propellant. The lack of a high-velocity weapon proved to be a significant limitation against opponents such as the Tiger, and Cromwell had to rely on mobility.