Overview
Upgrade your FN PS90 with the Haga Defense Gen 4 Front Handguard — a lightweight, receiver-mounted M-LOK platform made from high-strength nylon. It converts the exposed barrel area into functional accessory space, adds forward grip options, improves handling, and gives your rifle a modern profile without unnecessary weight.
Choose Your Version
Standard (Narrow)
- M-LOK slots on top, sides, and bottom for lights, lasers, and grips.
- 4.6 oz (approx.) — ultra-light yet durable.
- Best for non-suppressed PS90s — no suppressor clearance under the handguard.
- Attaches directly to the receiver with included hardware; does not contact the barrel.
Suppressor-Compatible (Wide)
- Suppressor clearance up to 1.7" diameter (fits most PS90 suppressors).
- M-LOK slots on top and sides for flexible accessory mounting.
- 3.7 oz (approx.) with a compact ~4.2" profile.
- Also works great on PS90s with a standard 16" barrel and no suppressor.
Shared Features
- Lightweight nylon construction designed for strength and reliability.
- Easy installation with included hardware — no permanent modifications.
- Compatible with all PS90 receiver widths (older ~31mm and newer ~33mm).
- Allows tool-less field stripping once installed.
- Made in the USA
Important Notes
- M-LOK rails and accessories are sold separately (no longer pre-installed).
- Some side-mounted accessories may require shorter screws due to barrel proximity.
Feature Comparison
Standard (Narrow)
- M-LOK slots on top, sides & bottom
- 4.6 oz (approx.)
- Best for non-suppressed PS90s
- Receiver-mounted; does not contact barrel
- Tool-less field strip once installed
- Fits older (~31 mm) & newer (~33 mm) receivers
- M-LOK rails sold separately
- Made in the USA
Suppressor-Compatible (Wide)
- Suppressor clearance up to 1.7" diameter
- M-LOK slots on top & sides
- 3.7 oz (approx.), ~4.2" long
- Works with or without a suppressor
- Receiver-mounted; does not contact barrel
- Tool-less field strip once installed
- Fits older (~31 mm) & newer (~33 mm) receivers
- M-LOK rails sold separately
- Made in the USA
Installation Instructions
- Set the fire selector to “S” (safe).
- Remove the magazine by pulling the catch rearward and lifting the magazine free.
- Pull the cocking handle fully rearward and visually check the chamber through the magazine well to confirm it is empty. Release the handle if clear.
- Remove the forward-most screw and nut with a 3mm hex tool.
- Test-fit the included mounting blocks into the front receiver cavity:
- On newer PS90s, blocks fit snugly.
- On older PS90s, adjust the pre-installed nylon set screws with a 1/8" hex key until snug. If stripped, use a T20 Torx bit.
- Hold the blocks in place and slide the handguard onto the receiver until the lower hole aligns with the screw hole.
- Reinstall the lower screw and tighten the thumb nut by hand.
- Install the upper handguard screws with a 4mm hex tool.
- If using an older PS90, place the included washers between mounting tabs and blocks before tightening to prevent stress or breakage.
Installation Notes
- If there is play in the handguard, re-adjust the mounting blocks for a tighter fit. Adhesive may be used for a more solid installation.
- Slight handguard movement may also result from play between the upper and lower receiver itself.
- For field stripping, remove only the lower screw and thumb nut — the handguard can remain attached to the upper receiver.
Why Choose the Gen 4 Handguard?
Refined over nearly a decade, the Haga Defense Gen 4 handguard turns unused barrel space into a modular, ergonomic platform. Whether you select the Standard or Suppressor-Compatible model, your PS90 gains modern styling, improved control, and flexible accessory mounting for tactical use or range performance.
