Forward Controls Design Fn 509 Optic Mounting Plate

The Forward Controls Design FN 509 optic mounting plate is a precision steel solution for shooters looking to run a Trijicon RMR or SRO-pattern red dot on their FN 509 Tactical or FN 509 MRD. Built from solid steel and machined as a one-piece unit, this mount is engineered to handle the demands of duty, competition, and defensive carry without the flex or movement you'll get from polymers. FCD designed this plate to work seamlessly with FN's factory irons, delivering a lower 1/3 co-witness that keeps your backup sights in frame while your dot sits high enough for rapid target acquisition.

Installation is straightforward if you have the right tools. The plate comes complete with two 6-40 x 1/2 T10 screws (the same spec as FN's factory hardware, so you can use those too), a packet of VC-3 thread locker to keep things locked in, and the T10 hex key you'll need for assembly. The critical detail: you'll want a proper torque wrench to tighten those screws to 12–13 in-lbs. Get sloppy here, and you're asking for zero shift or, worse, a loose optic downrange. This isn't a component where eyeballing it works.

FCD manufactures this plate in the USA using billet steel, so you're getting the kind of durability that doesn't give up features for weight savings. It's the kind of detail that separates a mount you forget about from one that becomes a liability. If you're running a 509 Tactical and want a rock-solid red dot platform that respects your irons, this is the straightforward path.

Key Features

• One-piece billet steel construction for rigidity and durability
• Compatible with Trijicon RMR and SRO-pattern optics
• Works with FN 509 Tactical and FN 509 MRD platforms
• Lower 1/3 co-witness with factory FN iron sights
• Includes mounting screws, thread locker, and T10 hex key
• Made in the USA

Specifications

Frequently Asked Questions

Will this mount work with non-Trijicon RMR clones?

FCD specifically designs this plate for Trijicon RMR and SRO-pattern optics. While other red dots may share the RMR footprint, FCD does not guarantee compatibility with non-Trijicon sights. If you're running an RMR or SRO, you're good. If it's a different optic, contact FCD or check the manufacturer's compatibility list first.

Do I need special tools to install this mount?

You'll need a proper torque wrench to tighten the mounting screws to the correct spec (12–13 in-lbs). The plate includes the T10 hex key for screw installation. A torque wrench is non-negotiable—guessing on screw tension can result in zero shift or a loose optic, both of which are safety issues.

What's included in the package?

The FN 509 optic mounting plate comes with the adapter plate itself, two 6-40 x 1/2 T10 mounting screws, a packet of VC-3 thread locker, and a T10 hex key. You'll supply the torque wrench.

Will my factory FN iron sights still work with this mount?

Yes. Factory FN 509 Tactical sights remain fully compatible and will co-witness at lower 1/3 height, so your irons stay visible and usable while your red dot sits up high for primary aiming.