Apex Optic Mount for RMSc/507K – FN 509

Description

The Apex Optic Mount for RMSc/507K – FN 509 bridges the gap between your FN 509 Low Profile Optics Mounting System slide and compact red dot sights like the Shield RMSc or Holosun 507K. Machined from billet steel with a black oxide finish, this mount gives you a rock-solid, zero-shifting platform for carry or competition. No adapters, no guesswork—just a direct fit that keeps your optic low and your co-witness intact.

Manufacturer	Apex Tactical Specialties
Model	Apex Optic Mount for RMSc/507K – FN 509
Material	Billet steel
Compatibility	FN 509 models with FN Low Profile Optics Mounting System (Tactical, MRD, standard cut slides)
Finish	Black oxide
Weight	0.6 oz (per manufacturer specs)
Condition	New

Key Features

• Billet Steel Construction – Why it matters: Steel beats aluminum for durability under recoil and heat. This mount won’t warp or strip threads, even after thousands of rounds.
• FN Low Profile Mounting System Specific – Why it matters: Designed exclusively for FN 509 slides with the factory LPM cut, so you don’t need a new slide or adapter plate.
• Direct Fit for RMSc and 507K – Why it matters: Uses the 514 screws from your FN 509 Tactical/MRD for the RMSc, or the included screws for the 507K. No filing, no fitting.
• Black Oxide Finish – Why it matters: Reduces glare and resists corrosion, keeping your setup low-vis and ready for all weather conditions.

Who It’s For

This mount is built for FN 509 owners who want to run a compact enclosed or open emitter dot without buying a whole new slide. If you carry an FN 509 Tactical or MRD and prefer the smaller footprint of the RMSc or 507K, this is your drop-in solution. It’s also a solid choice for competitors who need a repeatable zero and don’t want to chase screws after a match.

Pros & Cons

• Pros: Direct fit for two popular optics; steel construction; maintains low bore axis; uses factory screws where possible; backed by Apex Tactical’s warranty.
• Cons: Not compatible with full-size RMR or DPP footprint optics—you’re limited to RMSc/507K pattern. Also, the black oxide finish can show wear faster than nitride if you’re hard on gear.

Comparison

Feature	Apex Optic Mount	Zev Technologies FN 509 Optic Plate	Lone Wolf Distributors FN 509 Adapter
Material	Billet steel	7075 aluminum	6061 aluminum
Optic Footprint	RMSc / 507K only	RMR / DPP / RMSc	RMR / Docter / RMSc
Finish	Black oxide	Type III hardcoat anodized	Black anodized
Weight	0.6 oz	0.4 oz	0.5 oz
Price	$65	$85	$55
Installation	Drop-in with included screws	May require filing for some optics	Drop-in with included screws

According to Apex Tactical specs, the steel construction here gives you a weight penalty over aluminum plates, but the rigidity pays off in zero retention. Per industry surveys, over 60% of FN 509 owners who mount a dot use the RMSc or 507K footprint, making this a targeted solution.

FAQ

What optics fit the FN 509?

The FN 509 Low Profile Mounting System accepts optics with the RMSc footprint (Shield RMSc, Swampfox Sentinel, Sig Romeo Zero) and the Holosun 507K/407K. This Apex mount is specifically designed for those two patterns.

What sights fit the FN 509?

Standard-height iron sights from FN, Trijicon, and Dawson Precision work with the factory slide. For co-witness with an optic, you’ll want suppressor-height sights like the Apex FN 509 Tactical Sights or Trijicon HD XR.

What optics fit on the FN 509 Tactical?

The FN 509 Tactical ships with the LPM cut and includes 514 screws for RMSc optics. This Apex mount expands compatibility to the Holosun 507K, while still supporting the RMSc. You can also run RMR or DPP optics with a separate adapter plate, but that raises the dot height.

Secure Your Zero

The Apex Optic Mount for RMSc/507K – FN 509 gives you a steel foundation for your dot without breaking the bank or adding bulk. Grab one for your FN 509 Tactical or MRD and get back to shooting.

✔ Nationwide delivery (all 50 states)
✔ Ships 1-2 business days
✔ 30-day returns
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Browse more FN 509 Parts or check out FN 545 Parts and Optic Mounts.

Last updated: April 2026