The artillery was called KARL" because of the involvement of the artillery General Karl Baker in the development. The prototype was manufactured in 1939. The prototype has 8 pairs of road wheels, while the production model has 11 pairs. The "KARL" gun uses two types of shells, the s Be shell weighs 2.17 tons, and the le Be shell weighs 1.70 tons. Cars 1-4 went to the front line with the 628th Heavy Artillery Battalion in July 1941, and were later assigned to the 883th Heavy Artillery Battalion.