The Sturmgewehr 44 is the world first assault rifle. For those unfamiliar, basically an assault rifle is a fully automatic rifle. It gives you the accuracy and hitting power of a high powered rifle and the volume of fire from a machine gun.
That said, we all know that German war engineers were tasked with creating Vunderwaffen or wonder weapons. One of them was a Sturmgewehr 44 with a curved barrel.
Oddly the deadliest thing for a tank, is infantry. Obviously tankers have small portholes to look through and a sapper with explosives can walk up to a tank and destroy it. The idea here was to give tankers a weapon that they could aim out of the ports and keep infantry off.
GiIs came upon a few of them, many afraid to fire it. They just boxed them up and shipped them to Headquarters.
The gun didn’t work very well. It had to vent air through the barrels to allow the curved flight which in turn cut down muzzle velocity. Hitler took one look at it and asked that it not be developed further.
Sources: The History Channel