FN 509 9mm
Model: 66-100002
FN 509 9mm
Model: 66-100002
Full Specifications
About This Firearm
FN built the 509 from the platform it submitted for the U.S. Army's Modular Handgun System trials. The military heritage shows in the materials: a cold hammer-forged stainless steel barrel and FNC-coated stainless slide that resist corrosion and wear better than the carbon steel found in most polymer 9mms. The gun holds 17 rounds, weighs 26.9 oz, and runs a 4" barrel in a 7.4" frame. Two magazines and interchangeable backstraps ship in the box.
The base 509 lacks an optic cut, which puts it behind the Walther PDP and Springfield Echelon that ship optic-ready. The 5.5 lb trigger is functional but unremarkable among striker-fired guns. Where the 509 earns its place is longevity. The stainless barrel will outlast carbon steel barrels by thousands of rounds, and the FNC slide coating handles sweat, holster wear, and neglect better than standard nitride finishes. For shooters who keep a gun for a decade or more and put serious round counts through it, the material advantage compounds over time.
Best For
Strengths & Limitations
- Cold hammer-forged stainless steel barrel and FNC-coated stainless slide provide better corrosion and wear resistance than the carbon steel used in most competitors. Owners in humid climates report virtually no surface rust even with minimal maintenance.
- MIL-STD-1913 rail, 3-dot luminescent sights, and 17-round capacity make it home-defense ready straight from the box
- The 5.79" sight radius is longer than most 4"-barreled guns, giving a slight accuracy advantage with iron sights at distance
- No optic cut on the base model. The Walther PDP and HK VP9 both ship optic-ready, and the 509 Tactical or 509 MRD are required if you want factory optic mounting from FN.
- The 5.5 lb trigger is competent but unremarkable. The Canik METE SFT breaks at 3.8 lbs, and the CZ P-10 F sits around 4.5 lbs. Both feel noticeably crisper.
Category Rankings
How the FN 509 9mm ranks among full-size 9mm Luger handguns.
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Frequently Asked Questions
Does the FN 509 accept magazines from other FN pistols?
No. The 509 uses proprietary FN magazines that are not cross-compatible with Glock, Sig, or any other platform. It ships with two 17-round magazines. The 24-round extended magazines from the 509 Tactical also fit the base 509 and extend below the grip. The aftermarket magazine ecosystem is smaller than for more popular platforms, so stock up when you find them available.
What is the difference between the FN 509 and FN 509 Tactical?
The 509 Tactical adds an optic-ready slide, 1/2x28 threaded barrel, suppressor-height night sights, FDE finish, and three 24-round magazines. The barrel grows from 4" to 4.5" and overall length increases from 7.4" to 7.9". Weight goes up about 1 oz to 27.9 oz. If you want a suppressor host or a red dot, the Tactical is the version to buy.
How does the FNC slide coating compare to standard nitride?
Ferritic Nitrocarburizing (FNC) is a surface hardening process that penetrates deeper than standard nitride coatings. It creates a harder, more corrosion-resistant surface layer. In practical terms, the FNC slide handles holster wear, sweat, and cleaning solvent exposure better than standard finishes. Owners who carry daily in humid environments report the FNC finish holds up well over years of use.