The 17 pounder mounted on the Achilles was able to penetrate some 140 mm of armour at  and 131 mm at  using standard Armour Piercing, Capped, Ballistic Capped (APCBC) ammunition impacting at a 30-degree angle. When supplied, Armour-piercing discarding sabot (APDS) ammunition could penetrate some 209  mm (8 inches) of armor at 500 meters and 192  mm at 1,000 meters at a 30-degree angle, though the accuracy of the APDS round was poor during the war.  In comparison, the M7 gun on the standard M10 using the same type of ammunition (APCBC) would penetrate 98  mm of armor at 500 m at a 30-degree angle, and 88  mm of armor at 1,000 meters at a 30-degree angle. Only with High-Velocity Armour Piercing (HVAP) ammunition did that gun compare with the 17 pounder, the ammunition being able to penetrate 140  mm at 500 m at a 30-degree angle, and 127  mm at 1,000 m at a 30-degree angle. However, HVAP ammunition was in very short supply, whereas the standard 17 pounder ammunition was available in huge quantities for the British.