For Holoson – Apex Optic Mount Screw Set for FN MRD Pistols with an Apex mount for RMR Footprint Optics

If you’ve got an FN MRD pistol with an Apex optic mount and a Holosun red dot that uses the RMR footprint, you might have run into the classic headache: the screws that came with the mount don’t quite play nice with your optic. Too long, too short, or the wrong thread pitch can leave your zero shaky or your dot sitting loose. This Apex Optic Mount Screw Set is the fix — a simple, drop-in set of screws specifically sized to pair your Holosun optic with an Apex mount on FN’s MRD slide lineup. No more guessing, no more shims, no more stripped threads.

Compatibility

• FN 509 MRD series (all generations)
• FN 509 Compact MRD
• FN 509 Tactical MRD
• FN 509 Edge
• FN 545 MRD
• FN 510 MRD
• Holosun optics with RMR footprint (e.g., 507C, 508T, 407C, 509T with adapter plate)
• Fits only with Apex Tactical optic mounts for FN MRD pistols
• Does NOT fit factory FN optic mounts or other aftermarket mounts

Key Features

• Precision-machined screws matched to Holosun thread specs (typically #6-32 or M3, depending on mount iteration)
• Correct length to avoid bottoming out in the slide or interfering with the extractor
• Includes both screws needed for a standard RMR-footprint Holosun optic
• Black oxide finish for corrosion resistance and low glare
• Sold as a set — no need to buy extras or hunt for hardware at the hardware store

Install Difficulty: 2 out of 5

Easy job if you’ve got a small screwdriver (Torx or hex, depending on screw head) and a drop of blue Loctite. Remove the old screws, clean the threads, apply Loctite, torque to spec (around 15-18 in-lbs). No gunsmithing required. We’ve got a quick install video on the product page if you want to watch it first.

Frequently Asked Questions

Will these screws work with my FN 509 Compact MRD?

Yes, if you’re using an Apex mount. The MRD cut on the Compact is the same footprint as the full-size, so this set is a direct fit.

Do I need to use Loctite with these screws?

Absolutely. We recommend a medium-strength thread locker (blue Loctite) to keep the screws from backing out under recoil. Don’t use red — you’ll never get them out again.

Can I use these screws with a Trijicon RMR or other non-Holosun optic?

These are optimized for Holosun optics with the RMR footprint. Trijicon RMRs use a different thread pitch (usually #6-32 vs. M3), so they may not fit. Check your optic’s thread spec before ordering.

All orders ship within one business day from our shop in central Texas. Every Apex screw set is covered by Apex’s lifetime warranty against manufacturing defects — if it breaks or strips, we’ll get you a replacement, no questions asked.