FN PS90 In Depth Overview

The FN P90 was developed in the late 80's by FN Herstal as an attempt to satisfy a request from NATO to replace weapons, mainly handguns and submachine guns, chambered in 9x19mm Parabellum. The round that they came up with was the 5.7x28mm, a bottlenecked round designed to fire a light projectile at high velocities.

The P90 was an overall success, being adopted by numerous Special Forces groups and agencies that require a PDW (Personal Defense Weapon) including the US Secret Service. This is a PS90, which is essentially a semi auto P90 with a 16 inch barrel for sale to the US civilian market.

Looking down from the top you can see how the unique magazine lay horizontal across the top of the rifle, allowing a 50 round capacity.

This version of the PS90 includes a picatinny rail with rather terrible iron sights integrated with them.

Due to the rounds being situated horizontally in the magazine of a rifle, they have to be rotated to line up with the bore of the rifle. This is done with a ramp located at the rear of the magazine.

To disassemble, start by pressing in the button located under the magazine and push the upper receiver off of the stock.

Next the bolt and recoil spring assembly can be pulled out of the front of the stock.

The PS90 is a straight blowback gun so the bolt has to have fairly significant mass to operate safely.

Here is the extractor at the bottom and ejector at the top of the bolt face. The PS90 ejects downward through the stock of the weapon.

Here is the ejection port

There is also a dust cover which can be snapped into place to keep the weapon clean.

Next the buttpad can be pushed up and off the rear of the stock

Finally you can remove the trigger pack by lifting up on the black lever and pulling the pack out of the rear of the stock.

The trigger pack is made almost entirely made out of polymer. There are several generations of PS90 trigger packs, earlier generations included an inoperative auto sear that was removed in the later generations.

Here it is with the other FN firearms of my collection. It fits right in!