The Whizbang was originally intended for use in the allied invasion of France, where it would be used to breach shoreline defenses. No T40s were ultimately deployed during the landings, despite some tanks already being fitted with the mounting brackets. Later the U.S. Army planned to equip a total of 30 Shermans, belonging to the 743rd Tank Battalion, with the system, to be used in a planned operation in Belgium in December 1944. This operation was eventually cancelled due to the German counter-offensive in the Ardennes on December 16, prompting the U.S. Army to remove the T40s from the battlefield. The launcher ended up not being reinstalled on their intended Shermans, instead, 8 of the launchers were sent to Italy, to be used for artillery fire support. 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.
