Self-propelled anit-aircraft systems have remained popular in Europe since World War II. Today we have the Tunguska in the CIS and from Germany, the resilient Flakpanzer Gepard. The United States flirted with a mobile anti-aircraft platform during the 1980s with the ill-fated M247 "Sgt.York."
However, going back to World War II the Canadian military came up with a system that effectively put four 20 mm auto-loading cannons into the turret of a tank. It was known as the Skink.
As the marriage of two off-the-shelf technologies- the M4A1 Grizzly tank (a Canadian version of the Sherman tank) and the Polsten automatic cannon, the Skink was a weapon system that saw little action but was a superb proof of concept.
As a system, the turret and its porcupine like array of 20mm barrels make the Skink particularly noteworthy.
The Polsten 20mm automatic-cannon is a remarkable version of lean reverse engineering and construction. During the late 1930s Polish engineers set out to recreate the ubiquitous Oerlikon automatic cannon, but build it lighter and cheaper. The Swiss made Oerlikon was reliable and coveted by militaries, but complicated and precise to manufacture; as well as expensive.
The Polsten (which was given new life when engineers and their plans arrived in Britain after the invasion of Poland,) recreated the Oerlikon 20mm cannon, but cut the number of parts by half. And when it came to price, the Oerlikon cost £320 to build, while the Polsten only cost as little as £60.
The cannon system also changed the feeding from a removable 60 round drum to a double stacked 30 round box magazine, while continuing to fire standard 20mm of the time from High Explosive to Incendiary.
When it came down to business of dealing death, the Polsten fired at a steady 450 rpm, with a muzzle velocity of over 2,200 fps. The typical 20mm round could reach an altitude of just about 6,600 ft. Four guns, firing as a group could lay down a barrage of devastating fire. Mated to the hull of a tank, the idea was to provide tactical air-defense, anywhere.
Reportedly by the time the Skink arrived in the European Theatre for combat testing, the German threat from the air had rapidly diminished, resulting in the Skink being employed briefly as very effective anti-personal cannon system.
The Polsten quad-gun system, minus the cast armor turret, was re-adapted and turned into a towed AA system by the British. The gun arrangement was also positioned in the back of a truck,creating added mobility. This version of the Polsten quad was used particularly in defense of V1"Buzzbomb"
This "copy" of a successful Swiss design would continue in British service until the 1950s.