https://en.wikipedia.org/wiki/Hawker_Hurricane_variants

Mk IIs were used in ground support, where it was quickly learned that destroying German tanks was difficult; the cannons did not have the performance needed, while bombing the tanks was almost impossible. The solution was to equip the aircraft with a 40 mm cannon in a pod under each wing, reducing the other armament to a single Browning in each wing loaded with tracers for aiming purposes. The Hurricanes No. 6 Squadron, the first squadron equipped with this armament, were so effective that the squadron was nicknamed the "Flying Can Openers".[9] A winged can-opener became an unofficial squadron emblem, and is painted on present-day aircraft of 6 Squadron.

The layout was originally tested on a converted Mk IIB and flew on 18 September 1941. A new-build version of what was known as the Mk IID started in 1942, including additional armour for the pilot, radiator and engine. The aircraft were initially supplied with a Rolls-Royce gun and carried 12 rounds, but soon changed to the 40 mm (1.57 in) Vickers S gun with 15 rounds. The weight of guns and armour protection had a marginal effect on the aircraft's performance.

The IID was used in anti-tank operations in limited numbers during the North African campaign where, provided enemy flak and fighters were absent, they proved accurate and highly effective against armoured vehicles and all motor transport.[10]