FN P90

The FN P90 is a selective fire personal defense weapon (PDW) designed and manufactured by FN Herstal in Belgium.^[4] The P90's name is taken from 1990, the year it was introduced.^[3] The P90 was created in response to NATO requests for a replacement for 9×19mm Parabellum firearms; it was designed as a compact but powerful firearm for vehicle crews, operators of crew-served weapons, support personnel, special forces and counter-terrorist groups.^[4][8]
The P90 was designed by FN in conjunction with the FN Five-seven pistol and 5.7×28mm ammunition.^[3] Development of the P90 began in 1986, and production commenced in 1990, whereupon the 5.7×28mm ammunition was redesigned and shortened.^[1] A modified version of the P90 with a magazine adapted to use the new ammunition was introduced in 1993, and the Five-seven pistol was subsequently introduced as a companion weapon using the same 5.7×28mm ammunition.^[9]
The P90 was developed and initially marketed as a personal defense weapon, but it could also be considered a submachine gun or compact assault rifle.^[10] Featuring a compact bullpup design with an integrated reflex sight and fully ambidextrous controls, the P90 is an unconventional weapon with a futuristic appearance.^[10] Its design incorporates several innovations such as a unique top-mounted magazine and FN's small caliber, high velocity 5.7×28mm ammunition.^[10]
The P90 is currently in service with military and police forces in over 40 countries throughout the world.^[11] In the United States, the P90 is in use with over 200 law enforcement agencies, including the U.S. Secret Service.^[12] The standard P90 is restricted to military and law enforcement customers, but since 2005, a semi-automatic carbine version has been offered to civilian shooters as the PS90.^[13]

The P90 was developed by FN between 1986 and 1990 in conjunction with the 5.7×28mm cartridge. FN's goal was to replace the pistol-caliber submachine guns which were in use at the time by military and law enforcement personnel, as it had become evident that such weapons were ineffective against body armor.^[5][14]
Initially the weapon was designed to use a 5.7×28mm cartridge called the SS90, which propelled a 1.5-g (23 grain) plastic-core projectile from the P90 at a muzzle velocity of roughly 850 m/s (2,800 ft/s).^[5] The first P90 prototypes firing this ammunition were created in 1987, and over 3,000 submachine guns were produced in this configuration until 1993, in a low-rate trial production mode.^[15][16] Shortly after its introduction, the P90 was adopted and used in service with the Belgian special forces group in the 1991 Gulf War.^[1]
Following the P90's introduction, FN revised the 5.7×28mm ammunition.^[9] The new variation, designated the SS190, used a projectile 2.7 mm (0.11 in) shorter in length than that of the SS90.^[5] This allowed it to be used more conveniently in the 5.7×28mm FN Five-seven pistol, which was under development at that time.^[9] The SS190 projectile also had a heavier weight, and a more conventional construction with an aluminum and steel core.^[5][9] The first prototypes of the SS190 were created in 1992, and the design was finalized in 1993, replacing the SS90.^[9] A modified version of the P90, with a magazine adapted to use the shortened ammunition, was then introduced in the same year.^[9] Several special cartridge variations were also developed, such as the L191 tracer round and the SB193 subsonic round for use with a sound-suppressed P90.^[6]
Further development of the P90 platform led to the creation of the P90 TR variant, which has a MIL-STD-1913 triple rail interface for mounting accessories. This variant was introduced in late 1999 and continues to be offered alongside the standard P90.^[17] More recently, the P90 has been offered to civilian shooters as the PS90, a semi-automatic carbine intended for personal protection and sporting use.^{[18]
(Sources from Wikipedia)}