In December 1943 the first Wirbelwind appeared. It was on an unaltered PzKpfw IV Ausf J chassis with a 16 mm all around turret.
Turret traverse was slow, and thus restricted the vehicle when combating ground-attack aircraft. Rate of fire was 800 rpm/450 rpm.
The HE round weighed 0.3 lbs and was fired at a muzzle velocity of 2,953'/sec.