Here is what Wikipedia says:
These new revolvers were chambered for a new more powerful type of .38 Special ammunition capable of firing a 158-grain (10.2 g) metal-penetrating copper-tipped lead-alloy bullet at 1,125 feet (343 m) per second.[5] In comparison, conventional .38 Special ammunition fires a 158-grain (10.2 g) bullets at 755 feet (230 m) per second.[1] It was easily capable of penetrating the automobile bodies and body armor of that era.
footnote {5}
Western Ammunition Handbook (3rd ed.). East Alton, Illinois: Western Cartridge Company. pp. 54–63
The .38/44 high-speed cartridge came in three bullet weights: 158 grains (10.2 g), 150 grains (9.7 g), and 110 grains (7.1 g), with either coated lead or steel jacket, metal-piercing bullets.[16] The media attention gathered by the .38/44 and its ammunition eventually led Smith & Wesson to develop a completely new cartridge with a longer case length in 1934, this was the .357 Magnum.
footnote says: The metal-penetrating bullets were often described as
Highway Patrol loads.