Apex 5.00” Slide for FN 509 – RMR Slide Cut

If you’re looking to stretch the legs on your FN 509 and get a little more sight radius without buying a whole new gun, this stripped 5” slide from the kit is exactly what you need. It takes your factory slide internals and barrel, and gives you a longer, port-ready platform that’s cut for an RMR red dot. No need to send your slide off for machining – this is a drop-in swap that gets you a competition-ready setup in an afternoon.

Will this fit my gun?

This slide is designed for full-size FN 509 pistols. It will not fit the 509 Compact, 509 Midsize, or 509 LS Edge models. Here’s what you need to know:

• Fits: FN 509 (full-size / standard frame)
• Requires: Your factory FN 509 slide internals (extractor, firing pin, spring, etc.)
• Requires: A 5” barrel – factory FN 5” barrel or an aftermarket 5” barrel (including the Apex ported barrel)
• RMR cut accepts Trijicon RMR and similar footprint red dots
• Suppressor-height sights (black on black) are pre-installed by the kit

What makes this slide different?

• 5” length gives you a longer sight radius and more weight out front for softer recoil
• Front and rear cocking serrations – classic or lightning bolt pattern available
• Black PVD finish for durable, low-glare protection
• Ports in the slide match the Apex ported barrel, letting gas escape upward to reduce muzzle rise (requires Apex ported barrel for port function)
• All factory FN internal parts drop right in – no fitting required

Install difficulty: 2 out of 5

You’ll need a set of pin punches, a small hammer, and about 20 minutes. If you’ve ever field-stripped your 509, you can swap the slide. We recommend watching the install video on our site – it walks you through transferring your factory parts step by step. If you’d rather not mess with it, you can order a slide completion kit from the manufacturer and they’ll assemble it for you before shipping (that kit must be purchased with the slide and installed by them).

Frequently asked questions

Do I need a new barrel for this slide?

Yes – you need a 5” barrel. You can use a factory FN 509 5” barrel, or one of the Apex drop-in barrels (standard, threaded, or ported). The slide ports will only work with the Apex ported barrel.

Will my factory FN 509 slide parts work in this slide?

Yes. All spaces in this slide accept factory FN 509 internal components. You’ll just transfer your extractor, firing pin, spring, and other small parts from your original slide.

What about the sights?

Suppressor-height black-on-black sights come installed from the factory. They co-witness with most red dots mounted in the RMR cut. If you prefer fiber optic or tritium sights, those can be swapped out – but these are ready to go out of the box.

Shipping & warranty

We ship this slide free to the lower 48, and it’s covered by the manufacturer’s warranty against defects in materials and workmanship. If you have any fitment questions, give us a call – we’re shooters, not a call center.