FN 509 Red Dot Sights

Adding a red dot to your FN 509 should make the gun faster, not fussier. Below you’ll find the best optic options for carry, duty, or competition, plus the plate and sight-height notes that keep everything reliable and repeatable — pick your optic first, then match the footprint plate and co-witness height.

Top picks for the FN 509

• Compact, concealed carry: Trijicon RMRcc, Holosun EPS Carry, Holosun EPS

• Duty/competition speed: Trijicon RMR or SRO, Holosun 507C, 507Comp, 508T

• Enclosed emitter (weather, hard use): Holosun 509T, Aimpoint ACRO P-2, Steiner MPS

• Budget-friendly performers: Holosun 407C, Olight Osight X

Will it fit? Footprints & plates

• RMR footprint: Trijicon RMR/SRO/RCR and most Holosun “C/T” bodies (507C, 508T, 507Comp).

• 509T clamp style: Holosun 509T uses a dedicated plate that clamps the optic body.

• ACRO pattern: Aimpoint ACRO and Steiner MPS use ACRO-style plates.

• Micro carry footprints: RMRcc and EPS Carry require their specific plates/adapters.
  Rule of thumb: match pistol cut → FN 509 plate → optic footprint → correct screw length/torque.

Co-witness & sight height

• Irons-only height: Lowest profile if you’re running backup irons only.

• Lower 1/3 or absolute: Choose suppressor-height sights that pair with your plate + optic stack.

• Threaded/suppressed builds: Go taller; enclosed emitters sit higher and cans add visual bulk.

Why these red dots work on the FN 509

• Window you can track: Larger windows (SRO, 507Comp) speed transitions; compact windows carry easier.

• Battery access: Top/side-load makes swaps simple without re-zeroing.

• Durability: Sealed or titanium housings (508T, ACRO, MPS, 509T) shrug off weather and impact.

• Mature footprints: RMR and ACRO ecosystems have the widest plate support and accessory options.

Mounting notes

• Degrease screws and plate pockets before install.

• Use medium-strength (blue) threadlocker on clean threads.

• Torque to the optic and plate manufacturer specs with an inch-pound driver.

• Re-torque after cure time and verify zero at the range.

Recommended add-ons

• FN 509 optic plate matched to your footprint (RMR, 509T, ACRO/MPS, RMRcc, EPS/EPS Carry)

• Suppressor-height sights for co-witness builds

• Replacement screw kit sized for your plate/optic

• Torque driver and spare battery

---

FAQ

Do I need a plate to mount a red dot on the FN 509?
Yes. The FN 509 uses model-specific plates that match each optic footprint. Pick the plate that matches your dot (RMR, 509T, ACRO/MPS, RMRcc, EPS/EPS Carry).

Which red dots fit the FN 509 most easily?
RMR-pattern optics (Trijicon RMR/SRO/RCR and Holosun 507C/508T/507Comp) have the broadest plate support and straightforward installs.

I want an enclosed emitter—what should I choose?
Holosun 509T (clamp-style plate), Aimpoint ACRO P-2, and Steiner MPS (ACRO plates) are proven sealed options for rain, dust, and heavy use.

Will my iron sights co-witness with the dot?
Yes, if you install suppressor-height sights appropriate to your plate and optic. The exact height depends on optic body and plate thickness.

What torque and threadlocker should I use?
Follow the plate and optic maker’s numbers. As a general practice: blue threadlocker on clean threads and a calibrated inch-pound wrench.

My optic won’t hold zero. What should I check first?
Confirm correct screw length (not bottoming out), use the locating pins if provided, degrease/Loctite properly, torque to spec, and re-check after cure.

Does the same plate work for FN 509, 510, and 545?
Some plates share the V4-style interface, but you should verify the exact cut and plate specification for your model before ordering.