FN P90: An advanced personal defense weapon

Submachine gun FN P90 chambered in 5.7 mm
A shooter aiming with FN P90 submachine gun chambered in 5.7 mm caliber (Photo: Vickers)

The FN P90 submachine gun was developed in the late 1980s as an advanced personal defense weapon for the troops whose primary activities does not include small arms, such as vehicle and tank crew members, artillery crews, etc.

Standard pistols and submachine guns chambered for pistol rounds were proved ineffective against enemy soldiers, wearing body armor; Therefore, FN designers first developed a new round with enhanced penetration, initially known as SS90.


To achieve necessary high penetration while keeping recoil impulse low, FN used a small-bore approach, creating a round that looked much like the scaled-down 5,56 NATO round. It must be noted that similar concepts were tried in other countries, most notably in the USA, several decades before FN.

For example, US Army tested M1 carbines chambered for .221 Johnson Spitfire round back in the late 1950s; later on, Colt produced its .22 SCAMP and 5,6×30 MARS ammunition for special SCAMP machine pistol and MARS “mini assault rifle” (a scaled-down M16 rifle) respectively.

Belgium Fabrique Nationale (FN) created a FN P90 submachine gun
Belgium Fabrique Nationale (FN) created a P90 submachine gun as a personal defense weapon (Photo: Fabrique Nationale Belgium)

It must be noted that 5,6×30 MARS round was in a sense a direct predecessor to 5,7×28 FN SS90 round, although the latter featured slightly lighter and faster bullet. By the late 1980s, a concept of a small-bore, low-impulse “personal defense weapon” (PDW) with good accuracy and lethality at ranges of up to 200-250 meters was well established, although there were no weapons adopted for service yet.

FN decided to follow this concept and to create its own PDW using a clean sheet approach. Basic ideas used for this development, designated as “Project 9.0″, included the following: minimal size and weight of weapon; large magazine capacity; complete ambidexterity; ease of use and maintenance.

Bullpup layout

To save on size and weight, FN designers put a new weapon into the compact and lightweight stock of bullpup layout, made of impact-resistant polymer. The high-capacity magazine also was made from semi-translucent polymer and holds 50 rounds in two rows.

To made the loaded weapon as compact as possible, FN designers followed the idea of American designer Hall, and placed the magazine above the barrels, with cartridges stored in a horizontal position with bullets pointing to the left.  While the Hall system employed a rotary feed unit, operated by the bolt, to put a new cartridge in line with the barrel, FN designers incorporated a stationary helical ramp into each magazine, which rotates cartridge for 90 degrees prior to placing it on feed lips.

Complete ambidexterity was achieved by using ambidextrous controls (including dual charging handles and dual back-up open sights), and bottom ejection. Finally, the simplicity of aiming was achieved by the use of integral reflex type collimating sight and integral laser aiming module (LAM).

The resulting weapon appeared in around 1990 as FN P90 personal defense weapon, along with improved 5,7×28 SS190 ammunition, which replaced polymer-cored bullets with heavier dual-core (steel/aluminum) bullets with better penetration against body armor. Several other types of ammunition were developed for this weapon, including tracer, subsonic ball, and soft-core training ball.

Worldwide users of FN P90

First sales of P90 were made to Saudi Arabia in the early 1990s; today it is believed that FN sold more than 20 000 of P90’s to a wide variety of law enforcement agencies and military special operation units worldwide, including US Secret Service, Austrian Army Rangers, EKO Cobra, Dutch BBE special operations forces, Belgian Army and others.

The most interesting fact about the adoption of P90 is that so far it has been adopted for the role, directly opposite to its original niche of “personal defense weapon”.

A member of U.S. Secret Service armed with FN P90 submachine gun
A member of U.S. Secret Service armed with FN P90 submachine gun (Photo: XY)

In fact, most services and agencies that adopted P90 use it for offensive roles, as a specialist or even a primary weapon for various assault teams, and other “professional small-arms users”, as opposed to military personnel whose primary functions do not include the use of small arms.

In around 1995 FN supplemented the P90 with a pistol, firing the same 5,7×28 ammunition, designated as FN Five-seveN. Recently, FN also introduced a civilian version of P90, designated as PS90 carbine. This is a self-loading weapon with a longer barrel (408 mm / 16″).

FN P90 personal defense weapon is blowback operated, a selective-fired weapon which fires from a closed bolt. The firing is controlled by a removable trigger unit with a conventional hammer. Manual safety is located directly below the trigger. Magazine lies at the top of the weapon, feeding on front-to-back, with a spiral ramp built into the “rear” part of the magazine. Spent cartridges are ejected straight down through the chute, which exits just behind the pistol grip.

The standard sighting equipment includes a non-magnifying collimating sight with “ring and dots” illuminated aiming reticule.

Back-up open sights are provided on either side of the primary collimating sight. The so-called P90 USG version is provided with two additional Picatinny rails at either side of the collimating sight base; FN also offers a version with no standard sighting equipment; the user has to make its own choice of day and/or night sights and additional equipment, which can be installed on three Picatinny rails – top, left and right.

This version is designated as FN P90 TR (triple rail). The front part of the forward handgrip on FN P90 is shaped like a hand protector, and it can contain an integral laser aiming module, which sends either visible or IR laser beam to mark the intended target. For special missions, P90 can be fitted with a special silencer, which is used in conjunction with special subsonic ammunition.

Completely Ambidextrous Controls

The FN P90 is completely ambidextrous and as such is perfect for both shooters that are left-handed or right-handed. The P90 could be split down the middle and for all intents and purposes, both halves would be mirror images of each other. Talk about being inclusive.

Easy to Take Down and Assemble

Part of the basic design initiatives for the P90 was to be an easily maintainable PDW (Personal Defense Weapon or small personal select-fire weapon) as the originally proposed users of the P90 would be NATO military forces. A firearm is prone to malfunction or equally as problematic, one difficult to repair or fix while in the field, is to be avoided at all costs. The P90 was designed to be maintained easily, by its operator, in any environment.

Specifications: FN P90

Caliber: 5.7 x 28 mm SS190
Weight: 2.54 kg empty; 3 kg loaded with a magazine with 50 rounds
Length: 500 mm
Barrel length: 263 mm
Rate of fire: 900 rounds per minute
Magazine capacity: 50 rounds
Effective range: 200 meters
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