OVERVIEW: The 20-pounder High-Explosive (HE) round is an 84mm explosive-filled shell developed for use with the British Ordnance QF 20-pounder tank gun. It was intended to engage soft targets, infantry, and field fortifications using blast and fragmentation effects.

DETAILS: The HE round for the 20-pounder gun featured a forged steel casing filled with high explosive, typically TNT or a similar compound, and was fitted with a nose or base fuze to control detonation upon impact or with delay. Fired at lower velocity than armor-piercing ammunition, it provided British tanks like the Centurion Mk 3 and Mk 5 with a general-purpose munition effective against enemy positions, unarmored vehicles, and dismounted personnel. The 84mm HE shell produced a lethal fragmentation radius, making it effective in support roles during infantry engagements. While not intended for use against armored vehicles, it could damage lightly protected assets and was often carried alongside AP or APDS rounds for mission flexibility.

ROLE SUMMARY:
Category: Tank Gun Ammunition
Primary Use: Anti-personnel and anti-material (soft targets)
Function: Blast and fragmentation via high-explosive payload
Strong Against: Infantry, light vehicles, bunkers, unarmored infrastructure
Weak Against: Armored vehicles, hardened structures, reactive armor
Platform: Centurion Mk 3, Mk 5, and other vehicles equipped with the QF 20-pounder (84mm) gun
Integration: Standard HE round for the 84mm QF 20-pounder; later replaced by 105mm HE shells with the L7 gun

SOURCE: 
Janes Ammunition Handbook ; British Army Gunnery Training Documents ; Tank Museum (Bovington) Archives ; https://en.wikipedia.org/wiki/Ordnance_QF_20-pounder