Which American manufactured submachine gun was informally known by the American soldiers that used it as "Grease Gun"?

The American-manufactured submachine gun that was informally known as the "grease gun" by the American soldiers who used it is the M3. This nickname was given due to its resemblance to a mechanic's tool, specifically a grease gun. The M3 submachine gun was widely used during World War II and the Korean War, known for its reliability and distinctive design.