 As it is a rimless round, the 9×21mm is used in USPSA/IPSC competition in Open class firearms.A rimless case is preferred because, unlike rimmed cartridges, it will not tend to lock together with other rounds in a double-column magazine, resulting in a malfunction.As other .38 Super–based rimless cartridges became available, the 9×21mm decreased in popularity in the United States for competition use, but it is still widely used in the rest of the world.