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  • Post last modified:April 14, 2024

The FN P90 is a very special 5.7mm PDW (Personal Defense Weapon), and it's even selected as one of the primary Secret Service weapons for its low profile, lightweight, high round capacity, and rate of fire capabilities.

Finding a quality optic for the P90 isn't as hard now compared to many years back. So here are some of the best red dot sights for FN P90 and low profile mounts.

Read More: Best Red Dot Sights

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Best Red Dot Sights for FN P90

Trijicon RMR - Best Overall

Holosun 507C - Best For The Money

Aimpoint ACRO P2 - Best Enclosed

CHPWS ACRO - Best Value For Enclosed 

What To Look For In An Optic for FN P90

The FN P90 is designed for close-quarter combat in the 1980s with its effective 5.7mm cartridge. Its 50 rd magazine and fast rate of fire make it a perfect PDW (Personal Defense Weapon).

Low Profile Design Machine P90 red dot sight mount

Using the PS90 iron sight isn't a practical way to shoot this gun, so having a red dot sight is the way to go for faster target acquisition and wider situational awareness.

Here are a few things you should consider when purchasing an optic for P90.

  • Keep the optic size small
  • Find a secure & compatible low mount
  • Lightweight
  • Large field of view as much as possible

Recommended Optic Mounts

Generally speaking by default, the P90 optic is mounted very high over the bore, and that's the problem we have to deal with based on its original design.

hbi p90 optic mount

The plan is to remove the original Picatinny rail adapter and replaces it with one of the Design Machine Inc's mounts or HBI

Reticle Size Selection for P90

You got the P90 because you value its close-quarter capability, therefore a 2 to 5 MOA dot size is perfect for the P90 for close-range shooting.

Usually, a super-fine 1 MOA size dot is great for long distance precision.

A big 5 MOA size red dot from the Trijicon SRO gives you about a 5" shot group at 100 yards, and this can also be beneficial for acquiring the sight much faster.

Does The P90 Sight Sit Too High Over The Bore?

The average sight-over-height distance is approximately 3 inches, and it is beneficial to reduce this distance as much as possible.

Popular P90 RDS configurations involve aftermarket optic adapters that fit inside the top section of the gun, significantly lowering the optic height.

FN P90 Design Machine INC low optic mounts

We prefer configurations where the optic sits low on the gun. Design Machine Inc or HB Industries offer excellent mounts for various optics, including the Aimpoint ACRO P-2 and other ACRO footprint optics.

Even with the lowest profile red dot sight, the height-over-bore distance is about 4 to 5 inches, which is quite significant!

By default, the optic on the P90 sits very high on the gun, necessitating the mastery of new holdover techniques for this firearm.

Additionally, ensure you choose an optic with a wide range of windage and elevation adjustments, ideally something with 100 MOA or more in total travel. Without this, you may max out your adjustments and still find it inadequate for zeroing.

What Distance Should I Zero My Optic on The P90?

The optimal distance to zero a gun for close-quarter shooting is between 20 and 50 yards. Using a standard NATO SS197 5.7 x 28mm 40-grain bullet, the weapon can achieve an effective muzzle velocity of up to 2350 ft/s, with a range of 150 to 200 meters.

Whether you are using the standard 16" barrel or a shorter barrel, this distance is ideal for zeroing.

The P90 has a notable height-over-bore issue; therefore, zeroing at 50 yards, where the point of aim coincides with the point of impact, is advisable. The holdover at this distance is approximately 3-4 inches for targets within 10 yards.

For close-range targets, simply aim higher. It is crucial to use a PS90 low-profile red dot mount to minimize holdover as much as possible.

By using the lowest mount, such as the Design Machine Inc RMR fixed mount, you can reduce the sight height by almost 2 inches, thereby decreasing the holdover distance.

Minimizing the need to measure or compensate for holdover enables faster and easier target acquisition when shooting at close range.