 Like the U.S. M1 gun, the 17 pdr was also a 76 mm gun, but the British piece used a more voluminous cartridge case containing a much bigger propellant charge.This allowed it to penetrate of unsloped RHA at and at using APCBC ammunition.The 17-pounder still could not penetrate the steeply sloped glacis plate of the Panther but it was expected to be able to pierce its gun mantlet at over ; moreover it was estimated it would defeat the Tiger I's frontal armor from .