The launcher was mounted atop 75mm variants of the M4 Sherman, and fired a barrage of 7.2 in (180 mm) rockets from 20 launch tubes.

These doors protected the rockets from enemy fire, reflecting that it was designed to be used at a close range.

After expending all the rockets, the operator could easily jettison the empty launcher by turning the turret towards the side of the tank, fully elevating the gun, disconnecting the cables, and then pulling two handles.

This operation was eventually cancelled due to the German counter-offensive in the Ardennes on 16 December, prompting the U.S. Army to remove the T40s from the battlefield.

[4] In Italy, the Whizbang's range proved dissatisfactory, prompting the 760th Tank Battalion to rearm at least one of theirs with 54 4.5-inch M10 aircraft rocket launch tubes.