Apex Optic Mount for RMSc/507K – FN 509

If you’ve got an FN 509 with the factory Low Profile Optics Mounting System™, you know the struggle of trying to find a solid, no-wobble mount for your micro red dot. This steel optic mount solves that problem by giving you a dedicated, drop-in platform for the Shield Sights RMSc or Holosun 507K. No shims, no guesswork—just a secure fit that keeps your zero where you left it.

Will this fit my gun?

• FN 509 Tactical (with FN Low Profile Optics Mounting System™)
• FN 509 MRD (with FN Low Profile Optics Mounting System™)
• FN 509 Compact MRD (with FN Low Profile Optics Mounting System™)
• FN 509 LS Edge (with FN Low Profile Optics Mounting System™)
• FN 545 (with FN Low Profile Optics Mounting System™)
• Does NOT fit standard dovetail mounts or non-MRD slides

What you’re getting

• Machined from billet steel with a black oxide finish—holds up to holster wear and cleaning solvents
• Designed exclusively for the FN Low Profile Optics Mounting System™ (not a universal plate)
• For RMSc optics: use the “514” screws that came with your FN 509 Tactical or MRD
• For Holosun 507K: use the included screws from this mount
• Low-profile design keeps your optic close to the slide for a natural sight picture

Install difficulty: 2 out of 5

You’ll need a small flathead screwdriver or Torx bit (depending on your FN’s screw type), a dab of blue threadlocker, and about 10 minutes. Remove your factory optic cover, place the mount, and torque screws to manufacturer spec. No filing or fitting required. If you’ve ever mounted a red dot on a pistol, you’ve got this.

Quick answers

Can I use this mount with a different optic footprint?

This mount is specifically cut for the RMSc/507K footprint. If your optic uses a different pattern (like RMR or Docter), it won’t fit. Check your optic’s footprint before ordering.

Will this work on my FN 509 without the Low Profile Optics Mounting System?

No. This mount only fits slides that come from the factory with the FN Low Profile Optics Mounting System™. If your slide has a standard dovetail or a different cut, this won’t work.

Do I need to use the screws from my FN pistol or the ones in the box?

For RMSc optics, use the “514” screws that came with your FN 509. For the Holosun 507K, use the screws included with this mount. Mixing them up can cause the optic to sit too high or strip the threads.

Shipping & warranty

We ship from our shop in Texas, usually within one business day. This mount comes with Competition Trigger Works’ standard warranty against manufacturing defects—if something’s off, we’ll make it right. If you’re not sure about fit, give us a call. We’re shooters, not robots.