Staff Writer (Updated: 7/15/2016):
One of the key identifying elements of the P90 is its translucent, swiveling 50-round magazine made of polycarbonate and mounted over the receiver. Individual cartridges rest within the magazine at a 90-degree angle to the receiver. Due to this seating, each cartridge is repositioned automatically prior to chambering and firing. Ejection of spent shell casings is through a port at the base of the pistol grip. Couple this feature with an ambidextrous charging handle (and magazine catch) and the weapon can be utilized by left- and right-handed shooters with no modification necessary. The barrel is of forged steel and capped by a flash suppressor. Overall body construction of the P90 remains mostly high-tolerance alloy and polymers.
Unlike other Western-originated submachine gun-type weapons that center on the German 9mm Parabellum pistol cartridge, the P90 is engineered to fire the specialized, high-velocity 5.7x28mm cartridge (SS190 Ball). The pistol grip, optical sight (low light and daylight use, non-magnifying) and trigger guard are all built into the P90 standard design with field-stripping breaking the system down into four major components. The oversized stock also aids the shooter with improved stability when firing from the shoulder with a two-hand hold in place. Recoil is reportedly very low with engagement ranges out to 656 feet. Since the stock is fixed in place, the P90 is made essentially "ready to fire".
The P90 supports use of a sound suppressor and this can be coupled with subsonic ammunition for quieter, "silenced" operation by clandestine operatives. The weapon also features select-firing, covering single-shot and full-automatic fire. The including rail system can adapt a variety of optics and aimers as needed.
The P90 is used in various forms the world over, appearing in military, security and civilian sporting forms. Design is attributed to Stephane Ferrard, begun in 1986, with serial production forthcoming in 1990 through the storied concern of Fabrique Nationale de Herstal of Belgium.
The P90 has been released in two major variants, the P90 Standard and the P90 Tactical. Subvariants with subtle changes and additions have also been identified.