<P> Featuring a compact bullpup design with an integrated reflex sight and fully ambidextrous controls, the P90 is an unconventional weapon with a futuristic appearance . Its design incorporates several innovations such as a unique top - mounted magazine and FN's small - caliber, high - velocity 5.7 × 28mm ammunition . </P> <P> The P90 is currently in service with military and police forces in over 40 nations, such as Austria, Brazil, Canada, France, Greece, India, Malaysia, Poland, and the United States . In the United States, the P90 is in use with over 200 law enforcement agencies, including the U.S. Secret Service . While developed and initially marketed as a PDW, it can also be considered a submachine gun or compact assault rifle . The standard selective fire P90 is restricted to military and law enforcement customers, but since 2005, a semi-automatic version has been offered to civilian shooters as the PS90 . </P> <P> The P90 and its 5.7 × 28mm ammunition were developed by FN Herstal in response to NATO requests for a replacement for the 9 × 19mm Parabellum cartridge and associated pistols and submachine guns . NATO called for two types of weapons chambered for a new cartridge--one a shoulder - fired weapon, and the other a handheld weapon . According to NATO, these new weapons, termed personal defense weapons (PDWs), were to provide "personal protection in last - resort situations when the user is directly endangered by the enemy (...)." In 1989, NATO published document D / 296, outlining a number of preliminary specifications for these weapons: </P> <Ul> <Li> The new cartridge was to have greater range, accuracy, and terminal performance than the 9 × 19mm cartridge . Additionally, it was to be capable of penetrating body armor . </Li> <Li> The shoulder - fired personal defense weapon was to weigh less than 3 kg (6.6 lb), with a magazine capacity of at least 20 rounds . </Li> <Li> The handheld personal defense weapon (pistol) was to weigh less than 1 kg (2.2 lb), although a weight of 700 g (1.5 lb) was deemed desirable; it was to have a magazine capacity of at least 20 rounds . </Li> <Li> Both weapons were to be sufficiently compact to be carried hands - free on the user's person at all times, whether in the cab of a vehicle or the cockpit of an aircraft, and were to perform effectively in all environments and weather conditions . </Li> </Ul>

What kind of ammo does a p90 use