The primary anti-tank gun for British forces during the middle of World War II was the 57 mm Ordnance Quick-Firing 6-pounder, or just 6 pounder. First used in North Africa in the Spring of 1942, it replaced the 2 pounder in the anti-tank role. The United States Army also adopted the 6 pounder as our primary anti-tank gun under the designation 57 mm Gun M1. The 6-pounders were issued to the Royal Artillery anti-tank regiments of infantry and armored divisions in the western theaters, consisting of four batteries with 12 pieces each.
The anti-tank ammunition was a basic Armor-Piercing (AP) shot, but by January 1943 an Armor-Piercing, Capped (APC) shot and an Armor-Piercing, Capped, Ballistic Capped (APCBC) shot was supplied. Then by 1944, the Armor-Piercing, Composite Rigid (APCR) shot, and the Armor-Piercing, Discarding Sabot (APDS) shot were supplied. There was a considerable difference in effectiveness, as the APC shot could penetrate up to 92mm of armor, but the APDS could penetrate armor up to 142mm thick. Furthermore, a high explosive shell was produced so that the gun could be used against un-armored targets as well.