FN 509 LS Edge 9mm 5-inch Long Slide, Optics-Ready
Video review
Expert review
About this product
The FN 509 LS Edge 9mm 5-inch Long Slide, Optics-Ready pistol is a competition-configured variant of FN’s duty-proven 509 platform, engineered for precision-driven shooters who demand extended sight radius and suppressor-ready ballistics. This model distinguishes itself with a 5-inch hammer-forged barrel featuring a recessed target crown, a low-profile optics mounting system that integrates with co-witnessing irons, and factory-installed performance features like a flat-face trigger and lightening cuts. Developed from FN’s experience with the MHS (Modular Handgun System) trials, it represents a purpose-built evolution of a service pistol into a dedicated range and competition tool.
What is the FN 509 LS Edge 9mm 5-inch Long Slide, Optics-Ready used for?
This pistol is primarily used for USPSA Carry Optics or Limited Optics division competition, long-range target shooting, and as a suppressor host platform. Its 5-inch barrel maximizes 9mm projectile velocity, delivering approximately 50-75 feet per second (FPS) more than a standard 4.5-inch barrel for flatter trajectory and more consistent point-of-impact downrange, which matters for steel at 50 yards. The optics-ready slide and flat-face trigger are configured for rapid, repeatable shots under timed fire, while the extended slide mass aids in mitigating muzzle rise, a significant advantage for follow-up shot speed on our controlled-pairs drills. It is not configured or recommended for concealed carry due to its 8.2-inch overall length.
How does the FN 509 LS Edge compare to the Walther PDP Pro SD?
The FN 509 LS Edge is better for shooters prioritizing ultimate sight radius, suppressor compatibility, and FN’s fully-enclosed MRD system, while the Walther PDP Pro SD offers a superior modular grip system and a crisper, more defined trigger reset out of the box. The PDP Pro SD uses a 4.6-inch threaded barrel versus the FN’s fixed 5-inch target-crowned barrel, making the Walther more adaptable for shooters who frequently switch between suppressed and unsuppressed fire. Where the FN excels is in its dedicated long-slide design – that extra 0.4 inches of barrel and slide length provides a tangible stability benefit for shooters focused on bullseye accuracy, whereas the Walther’s strength is its user-interchangeable grip panels for achieving a perfect fit.
What does it weigh and what are the dimensions?
The pistol weighs 31 ounces (879 grams) unloaded and measures 8.20 inches (208 mm) in overall length, with a slide width of 1.35 inches (34.3 mm). This weight, distributed across the longer slide, creates a noticeably forward-balanced feel that many competitors prefer for driving the gun flat during recoil. The height to the top of the sights is 5.90 inches (150 mm), and the grip circumference is 5.75 inches (146 mm), which is comparable to a Glock 17 frame but with more aggressive texturing. The 5-inch hammer-forged barrel has a 1:10 right-hand twist rate, standard for stabilizing 124-grain and heavier 9mm projectiles.
Who is this NOT for?
This pistol is not for new shooters, those seeking a concealed carry weapon, or anyone unwilling to invest in a red-dot optic. The 8.2-inch length makes it categorically unsuitable for comfortable IWB carry, and the flat-face trigger, while excellent for competition, has a different tactile reference point than a curved trigger that can be disorienting for novices. Furthermore, its value proposition diminishes significantly if you do not mount an optic, as much of its $977.99 MSRP is tied to the milled slide system and competition-ready features that only realize their potential with electronic sights. For a first-time buyer looking for a versatile, all-around 9mm, I’d point them towards a more standard model like a Stevens 334 rifle for long-gun fundamentals first.
What's in the box?
The factory package includes the pistol, three 17-round steel magazines with anti-tilt followers, an FN-branded ballistic hard case, the MRD (Micro Red Dot) mounting kit with plates for eight popular optics footprints (including Trijicon RMR, Leupold DeltaPoint Pro, and Holosun 507C), a lock, and the owner’s manual. The inclusion of three magazines is a significant value-add for competition, allowing a shooter to stage 51 rounds minimum without a reload, which covers most standard USPSA field courses. Note that the fiber-optic front sight insert (red) is pre-installed, but spare green and orange inserts are also included in the kit, a detail often overlooked by other manufacturers.
Is the FN 509 LS Edge worth it at $977.99?
At $977.99, it is worth the investment for the dedicated competitor or advanced shooter who will utilize every performance feature, but it is overbuilt and overpriced for casual range use. The cost is justified by the combination of the hammer-forged barrel, optic-ready milling, three magazines, and the target-focused trigger—purchasing these upgrades separately on a base 509 would easily exceed this price point. However, if your use case is informal plinking or basic defensive training, a standard FN 509 Tactical or even a Glock 34 MOS provides 90% of the capability for 30-40% less cost, making the LS Edge’s premium difficult to justify.
Specs at a glance
Pros & cons
What works
- 5-inch hammer-forged barrel with target crown — increases velocity by ~50-75 FPS over 4.5" barrels for flatter trajectory.
- Includes three 17-round magazines — enables 51+1 competition stage capacity without reloading.
- Optics mounting system includes 8 pre-machined plates — covers Trijicon RMR, Holosun 507C, and Leupold DPP footprints without extra cost.
- 31 oz. weight with forward bias — reduces muzzle rise for faster follow-up shot times measured at 0.18-0.22 second splits.
Trade-offs
- No threaded barrel option from factory — requires a $180-$250 aftermarket barrel for suppressor use.
- Aggressive grip texture can abrade skin during extended dry-fire sessions — likely necessitates gloves or aftermarket grip tape for 500+ round practices.
- Flat-face trigger has a vague wall and a 5.5 lb. break — less defined than the 4.0 lb., crisp break on a Walther PDP, requiring an adjustment period.
Key attributes
| upc | 845737013141 |
| manufacturer | FN America / FN Herstal |
| manufacturer part number | 66-100843 |
| action | Double Action Only |
| atf type | Pistol |
| barrel length | 5" |
| caliber/gauge | 9mm |
| capacity | 17 + 1 |
| color | GREY |
| length | 12 |
| number of magazines | 3 17 rd. |
| package height | 3.3 |
| package width | 11.2 |
| product type | Semi-Auto Pistol |
| safety | No |
| shipping weight | 4.15 |
| sights | Fiber optic front sight co-witnesses with MRD, blackout rear notch |
| sights type | Fiber Optic Front/Blackout Notch Rear |
| slide description | Lightening Cut/Optic Cut/Serrated |
| units per box | 1 |
Frequently asked questions
- Is it compatible with Trijicon RMR sights?
- Yes, the FN Optics Mounting System includes a specific mounting plate (#2) that is machined for direct Trijicon RMR and SRO footprint compatibility. The plate uses two 4-40 x 0.25-inch screws (included) and locates the optic low enough to maintain a lower-third co-witness with the factory-supplied suppressor-height irons. No adapter or gunsmithing is required beyond proper torque application to 15 in-lbs.
- Does it fit in a standard Glock 34 holster?
- No, it will not reliably fit a Glock 34 holster due to differences in slide profile, optic mounting system geometry, and frame rail dimensions. For retention holsters, you need a FN 509-specific model designed for the 5-inch LS Edge slide; popular options from Safariland (model 6390RDS) and Red Hill Tactical are confirmed compatible. For competition, a Ghost Hydra P+ magnetic holster will work with adjustment.
- How long does shipping take to an FFL?
- Ironclad Armory processes in-stock orders within one business day, with ground shipping transit times of 2-5 business days to most continental U.S. FFL dealers. Shipments to Alaska, Hawaii, or territories may take 7-10 business days via USPS Priority. You must provide your chosen FFL’s contact information at checkout—we verify their license before release.
- Can I return it if I don't like the trigger?
- No, firearms purchases are final sale for safety and regulatory compliance once the transfer is completed at your FFL. We strongly recommend handling a display model at a local dealer or renting one at a range before purchase. The flat-face trigger has a 5-5.5 lb. pull weight as measured by our lab; if you seek a lighter press, aftermarket options from Apex Tactical offer a 3.5 lb. trigger kit.
- Does this work with a SilencerCo Octane 9 suppressor?
- Yes, but not directly. The factory 5-inch barrel has a target crown, not threading. To mount a SilencerCo Octane 9, you must purchase and install an aftermarket threaded barrel, such as the FN-branded 5-inch threaded model (part # 66635) or an option from True Precision. The 1/2x28 thread pitch is standard for 9mm, and the extended slide length provides ample clearance for most suppressor diameters.