This optic mount is a direct-fit steel adapter plate for mounting Shield Sights RMSc or Holosun 507K footprint optics to FN 509 pistols equipped with the FN Low Profile Optics Mounting System™. It solves the gap, shear, and zero-hold issues common when using polymer or aluminum plates with micro red dots on a reciprocating slide. Machined from billet steel with a black oxide finish, this component provides a rigid, corrosion-resistant interface that maintains optic height and returns to zero after disassembly.
Compatibility
- FN 509 Tactical (MRD-cut slide)
- FN 509 Compact Tactical (MRD-cut slide)
- FN 509 Mid-Size (MRD-cut slide)
- FN 509 Full-Size (MRD-cut slide)
- Does not fit standard (non-MRD) FN 509 slides without optic cut
- Optics: Shield Sights RMSc, Holosun 507K, Holosun 407K, and other RMSc/507K footprint optics
Key Features
- Material: Billet steel, black oxide finish
- Designed specifically for FN Low Profile Optics Mounting System™ – no adapter required for factory MRD slides
- Uses factory FN mounting screws: “514” screws (included with FN 509 Tactical/MRD) for RMSc optics; included screws for Holosun 507K
- Maintains factory iron sight co-witness height when using standard-height suppressor sights
- Drop-in fit – no slide milling or permanent modification
Install Difficulty: 2 out of 5
Tools required: #6 Torx (T6) driver, small flathead screwdriver (for screw alignment), Blue Loctite (recommended for thread lock). Remove factory optics cover plate, clean screw holes, apply Loctite to screws, mount plate, mount optic to plate. Torque to 12-15 in-lbs. Estimated install time: 10 minutes.
FAQ
Will this work on an FN 509 Compact without an MRD cut?
No. This mount is designed exclusively for FN 509 pistols with the factory Low Profile Optics Mounting System™ (MRD-cut slide). Standard slides require slide milling before this plate can be used.
Can I use this with a Holosun 407K?
Yes. The 407K shares the same RMSc/507K footprint as the 507K. Use the included screws provided with this mount.
Does the mount require permanent modification to the slide?
No. This is a direct replacement for the factory optic cover plate. No drilling, tapping, or slide modification is required. Returns to factory configuration by reinstalling the cover plate.
Shipping: Ships same business day if ordered by 2:00 PM ET. Warranty: This component carries a limited lifetime warranty against manufacturing defects. Does not cover improper installation, use of incorrect screws, or damage from thread-locker contamination.
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