The biggest complaint was related to firepower; the Cromwell had originally been designed to carry the 57 mm Ordnance QF 6-pounder, also retrofitted to the Crusader tanks. In combat, these were found to be useful against other tanks but lacking any reasonable high explosive load they were ineffective against anti-tank guns or static emplacements. Prior to the Cromwell entering combat service, the Ordnance QF 75 mm was introduced which equipped the majority of Cromwells, an adapted version of the 6-pounder firing shells from the US 75 mm gun from the Sherman. This offered somewhat lower anti-tank performance than the 6-pounder but its much larger shell provided an effective high explosive load.