The .38 ACP cartridge, is an American round designed by legendary arms inventor John Browning. It is also known as .38 Automatic. Its metric designation is 9x23mm SR (Semi-Rimmed).
This cartridge was manufactured by Colt in 1900 to be chambered in it’s .38 Automatic pistol, otherwise known as the ‘Colt M1900’, with the intention of military use. While Colt’s Manufacturing Company produced both the round and the pistol, Browning was responsible for their design.
It never found favour with the military, but did have some success as a sporting and hunting round. In 1929 it’s power was increased and it was redesignated as .38 Super.
The .38 ACP cartridge didn’t find great success, but only some small use in the US and UK. It is now long since obsolete.