Apex 5.00” Slide for FN 509 – RMR Slide Cut

This is a stripped, purpose-built 5.00” slide for the FN 509 platform, designed to extend the sight radius and reduce muzzle rise when paired with a ported barrel. The slide accepts all factory FN 509 internals, allowing you to transfer your existing components or source new ones. The integrated slide ports are cut to match the Apex ported barrel profile, venting propellant gasses upward to counteract muzzle flip. This is not a complete upper assembly — you must supply your own barrel and all internal slide parts.

Compatibility

• FN 509 (full-size)
• FN 509 Compact (requires barrel/slide overhang — confirm holster fit)
• FN 509 Midsize (same as Compact for slide fit)
• Factory 5” FN barrel or Apex 5” drop-in barrel (standard, threaded, or ported)
• All factory FN 509 slide internals (extractor, ejector, firing pin, spring, etc.)
• Apex FN 509 trigger components (all models)

Key Features

• Length: 5.00” (extends factory 4” slide by 1”)
• Black PVD finish — corrosion-resistant, low-glare
• Front and rear cocking serrations (choose Classic or Lightning Bolt pattern)
• Suppressor-height black-on-black steel sights, installed at factory
• Two forward slide ports — indexed to Apex 5” ported barrel gas ports
• Weight: approximately 9.2 oz stripped (no barrel, no internals)

Install Difficulty: 3/5

Requires full slide disassembly of your existing FN 509 slide, transfer of all internals to this slide, and installation of a barrel. Tools needed: punch set, non-marring hammer, slide vise (or clamp), and armorer’s block. If you lack experience with FN 509 slide assembly, order the Slide Completion Kit from Apex (available only with slide purchase) and have Apex install it prior to shipping.

Frequently Asked Questions

Will this slide work with my factory FN 509 barrel?

Yes — a factory 5” FN 509 barrel drops in. If you are using a 4” barrel, the slide will not function. The slide ports are non-functional unless an Apex ported barrel is used.

Do I need to buy new internals?

No. You can transfer the extractor, firing pin, spring cups, and ejector from your current FN 509 slide. If you prefer a fresh build, purchase factory FN parts from Midwestgunworks.com or Brownells.com, or order the Apex Slide Completion Kit (installed by Apex only).

Will the slide fit a holster made for a 4” FN 509?

Not reliably. The 5” slide adds 1” of length, so holsters must be open-ended or specifically designed for the 5” configuration. Confirm with your holster manufacturer before ordering.

Shipping: Ships within 3 business days. Warranty: Apex covers manufacturer defects in materials and workmanship for the lifetime of the product. No warranty on finish damage from improper installation or use of non-Apex ported barrels with the ported slide.