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The Unique FN P90 and How it Works

The FN P90 is a compact, lightweight, and highly efficient submachine gun designed and manufactured by FN Herstal in Belgium. It was first introduced in 1990 and has since become a popular choice for military and law enforcement agencies around the world. In this article, we will take a closer look at the unique features of the FN P90 and how it works.

Design and Features

The FN P90 has a distinctive bullpup design, meaning that the magazine is located behind the trigger, allowing for a shorter overall length without sacrificing barrel length. This makes it more compact and easier to maneuver in tight spaces. The P90 also features a top-mounted magazine, allowing for a low profile and better balance. It has a polymer frame and a metal receiver, making it lightweight yet durable.

One of the most unique features of the FN P90 is its use of the 5.7x28mm cartridge. This small, high-velocity round was specifically designed for the P90 and its companion pistol, the FN Five-seven. The P90 can hold 50 rounds in its magazine, giving it a high capacity for a submachine gun.

Check this video to see how the magazine functions.


The FN P90 operates on a straight blowback system, meaning that the force of the expanding gases from the fired round pushes the bolt back, ejecting the spent casing and loading a new round from the magazine. This system is simple and reliable, making it a popular choice for submachine guns.

To fire the P90, the user must first load the magazine into the top of the gun and pull back on the cocking handle to chamber a round. The P90 has a unique ambidextrous charging handle located on the left side of the gun, making it easy for both right and left-handed shooters to operate.

The P90 has a two-stage trigger, meaning that the first stage is a light pull to engage the sear and the second stage is a heavier pull to fire the gun in full auto. This allows for more control and accuracy when firing.


Disassembling the FN P90 is a simple process that can be done without any tools. First, the magazine and any rounds must be removed from the gun. Then, the user must pull back on the cocking handle to cock the gun. The barrel assemble can be removed from the gun by pushing the barrel release button. The shoulder pad is lifted out of the gun exposing the trigger mechanism. The trigger pack can be slid out by lifting the lever on the back of the trigger mechanism.

In conclusion, the FN P90 is a unique and highly efficient submachine gun with a distinctive design and features. Its use of the 5.7x28mm cartridge and straight blowback operation make it a popular choice for military and law enforcement agencies. Its compact size and high capacity make it a versatile and reliable weapon.


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