Buffalo:
The Rohrbaugh R9 is chambered for the 9mm Luger, sometimes referred to as 9mm Parabellum or 9X19mm. Use only standard pressure ammunition in the R9 -- not +P or +P+.
Other "9mm" rounds are:
9mm Makarov, sometimes referred to as 9X18mm. It is not interchangeable with the 9mm Luger. It was a standard military pistol cartridge of the Soviet Union and the Eastern Bloc in the latter half of the 20th Century.
9mm Kurz, sometimes referred to as 9X17mm and most commonly known in the United States as the .380ACP. It is not interchangeable with either of the above rounds and cannot be used in the Rohrbaugh R9. It is, however, the round for which the Rohrbaugh K380 is chambered.
9x21mm, also known as the 9×21mm IMI or 9mm IMI, reflecting its having been designed by Israel Military Industries . As it is a rimless round, the 9×21mm is often used in USPSA/IPSC competition in Open class firearms.
9x23 Winchester, a cartridge developed as a joint venture by Winchester Ammunition and Colt's Manufacturing Company and intended primarily for competition shooters as a replacement for .38 Super.
9x25mm Dillon, a "wildcat" cartridge developed by employees working at Dillon Precision for use in USPSA/IPSC Open guns. It is made by necking down a 10mm Auto case to 9 mm.
There are still other 9mm cartridges that have been developed over the years, but the 9mm Luger (9mm Parabellum, or 9X19mm) is the round for the R9 and the .380ACP (9mm Kurz or 9X17mm) is the round for the K380.
