If you’ve got an FN MRD pistol running an Apex mount for an RMR-footprint optic, you already know how important it is to keep that red dot locked down tight. This Apex Optic Mount Screw Set is a simple, direct replacement for the screws that came with your mount — perfect for when you’ve stripped a head, lost one during installation, or just want a spare set on hand. It solves the “will this screw actually fit” headache by being purpose-made for this specific combo, so you can get back to shooting without wondering if your optic is going to shake loose.
Compatibility
- FN 509 series (all MRD variants) with an Apex mount for RMR-footprint optics
- FN 509 Compact / 509 Midsize / 509 Tactical with Apex mount
- FN 510 MRD (10mm) with Apex mount
- FN 545 MRD (.45 ACP) with Apex mount
- Fits only Apex-brand mounts for RMR footprint — not for factory mounting plates or other aftermarket mounts
- Does not fit non-MRD FN pistols or models without the Apex optic mount
Key Features
- Precision-machined to match the thread pitch and length required by the Apex mount for FN MRD pistols
- Includes four screws (two for optic, two for mount-to-slide) — check your installation to confirm you’re using the right ones
- Steel construction with a black oxide finish for corrosion resistance and a clean, low-profile look
- Straightforward swap: remove old screws, install new ones with a dab of blue Loctite (not included), and torque to spec
- Sold as a complete set — no guessing which screw goes where
Install Difficulty: 2 out of 5
Easy job if you’ve mounted an optic before. You’ll need a small flathead or hex driver (size depends on your mount’s screw heads — typically T10 or 1/16” hex), a torque wrench or driver (recommended 12-15 in-lbs for the optic screws), and blue threadlocker. Watch our install video linked on the product page for a walkthrough. Total time: about 10 minutes.
Frequently Asked Questions
Will these screws work with my factory FN mounting plate?
No. These are designed specifically for the Apex mount on FN MRD pistols. Factory FN plates use different thread sizes and lengths. If you’re using the factory plate, you’ll need the screws that came with your pistol.
Can I use these screws with a Holosun or other RMR-pattern optic?
Yes, as long as your optic has the same RMR footprint (e.g., Holosun 507C, 508T, Trijicon RMR Type 2, etc.). The screws are cut for the Apex mount’s depth and thread pattern, not for the optic brand itself. Double-check that your optic’s screw holes align with the mount before installing.
Do I need to use threadlocker?
Absolutely. We recommend a small drop of blue Loctite (medium strength) on each screw before torquing to spec. This keeps everything from backing out under recoil. Red Loctite is overkill and will make future removal a pain.
Shipping & Warranty: We ship these screw sets same business day if you order by 2 PM Central. Like all Apex parts we carry, this set is backed by Apex’s limited lifetime warranty against defects in materials or workmanship. If you run into an issue, just give us a call — we’re a family shop and we stand behind what we sell.
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