Apex 5.00” Slide for FN 509 – RMR Slide Cut

This is a stripped 5.00” slide assembly for the FN 509, designed to replace the factory slide with an extended, optics-ready platform. It accepts an RMR footprint red dot directly, eliminating the need for an adapter plate. The slide is supplied without internal components — you must transfer your factory FN 509 parts or purchase a separate slide completion kit. For shooters who want a longer sight radius, a ported option to match Apex ported barrels, or a dedicated RMR mounting surface without modifying the original slide.

Compatibility

• FN 509 (all standard models)
• FN 509 Compact (not recommended without barrel/slide length verification)
• FN 509 LS Edge (frame compatible, but barrel length must match 5”)
• Requires factory or aftermarket 5” barrel (see barrel options below)
• Accepts all factory FN 509 slide internals (extractor, firing pin, spring cups, etc.)
• All Apex FN 509 aftermarket parts (trigger kits, barrels) fit this slide

Key Features

• 5.00” length — extended sight radius and barrel support
• RMR cut — direct mount for Trijicon RMR / SRO footprint optics
• Suppressor-height black-on-black sights installed at build
• Black PVD finish — corrosion-resistant, low-glare
• Choice of Classic or Lightning Bolt serration patterns (front and rear)
• Ported slide option available — barrel ports must align with Apex ported barrel (105-073 variant)
• Stripped — no internals, no barrel included

Install Difficulty: 3 / 5

Requires detail strip of factory slide to transfer extractor, firing pin, spring cups, and sights. You will also need a 5” barrel (factory or Apex). Tools needed: roll pin punch set, non-marring hammer, bench block, and a sight pusher or punch for front sight if reusing factory sights. If you cannot perform a full slide assembly, Apex offers a Slide Completion Kit (purchased with slide only) that is assembled before shipping.

FAQ

Can I use my factory FN 509 barrel with this slide?

Yes — a standard 5” FN 509 barrel works. The slide is machined to factory barrel lockup dimensions. If you choose the ported slide option, you must use the Apex ported barrel for gas port alignment.

What internals do I need to supply?

You must transfer the extractor, extractor spring & plunger, firing pin, firing pin spring, firing pin spring cup, firing pin safety & spring, and the rear sight from your factory slide. The slide comes with suppressor-height front and rear sights installed. If you purchase a Slide Completion Kit from Apex, they will fully assemble the slide with all new internals before shipping (kit must be ordered with this slide).

Does this slide fit the FN 509 Compact?

The slide is 5” long. The Compact frame will accept it, but the barrel must be 5” and the dust cover may not fully cover the barrel extension. For standard 509 and LS Edge frames, fit is direct.

All slides ship with a black PVD finish and suppressor-height sights installed. Shipping via insured carrier. Warranty covers manufacturing defects — normal wear, improper installation, or use of non-compatible barrels/internals is not covered. Contact Apex customer service for Slide Completion Kit availability before ordering if you want a fully assembled slide.