How A Gun Upgrade Made The Hurricane A ‘Can Opener’

In the years before World War II, the British Air Ministry explored the best way to bring down enemy aircraft. Their answer was simple in theory: one 40mm shell should be enough to destroy a bomber. Vickers developed the Class S 40mm cannon, complete with a 15-round magazine firing two rounds per second. In practice, that gave just seven to eight seconds of firepower—impressive on paper but difficult to use effectively in aerial combat.

From Bomber Defense to Tank Killer

Hitting fast-moving aircraft with a heavy shell proved far more difficult than anticipated. As a result, the gun shifted roles when German armored spearheads rolled into France in 1940. Suddenly, the RAF needed weapons capable of stopping tanks.

The solution was to mount the Vickers 40mm under the wings of Hawker Hurricanes, first the Mk IID and later the Mk IV. With one cannon on each wing, the aircraft earned a fearsome reputation in North Africa, where the gun’s power gave rise to No. 6 Squadron’s “can opener” emblem—a nod to its ability to slice through German armor.

A Limited but Memorable Service

Only about 100 of these weapons were produced, and just a handful of squadrons ever operated them. Still, they left an indelible mark. Hurricanes equipped with the Class S gun became true tank busters, though their limited ammunition and weight penalties restricted performance.

The Rolls-Royce Rival

Vickers wasn’t the only company to attempt a 40mm aircraft cannon. Rolls-Royce designed its own, but it suffered catastrophic problems: shells occasionally detonated before chambering. While eventually adapted for naval use, it never entered RAF service.

Legacy of the “Can Opener”

Today, one of the few surviving Vickers 40mm guns sits in the RAF Museum collection. Its legacy is remembered not only through history displays but also through the enduring insignia of 6 Squadron, reminding us of the ingenuity—and limitations—of wartime weapons development.