FN 509 Tactical 9mm 4.5″ Threaded Barrel Optic-Ready
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About this product
The FN 509 Tactical is a full-size, suppressor-ready 9mm duty pistol built on an optic-ready platform with a 4.5-inch threaded barrel. It ships from FN with a modular optic mounting system and suppressor-height night sights, representing a factory-configured path to a silenced or red-dot-equipped sidearm without aftermarket machining. This specific configuration weighs 27.9 ounces and carries a 10+1 capacity, designed to meet regulatory requirements while maintaining the mechanical overbuilt standards FN delivers for military contracts.
What is the FN 509 Tactical used for?
This pistol is used for duty carry, home defense, or as a dedicated host for a sound suppressor or miniature red-dot optic. The threaded barrel accepts 1/2x28 thread pitch muzzle devices like compensators or direct-thread suppressors, while the Low-Profile Optics Mounting System accepts a dozen common micro-dot footprints from Trijicon, Holosun, and Leupold. It's not a competition gun—its 6.5-pound double-action-only trigger pull is designed for deliberate, consistent duty use over raw speed.
How does the FN 509 Tactical compare to the Glock MOS series?
The FN 509 Tactical is a more mechanically robust and suppressor-focused alternative to a Glock 17 MOS. The FN's cold hammer-forged barrel and full 4.5-inch length provide a 50 fps velocity advantage over a standard Glock 17 barrel, and its factory co-witnessed suppressor-height sights are a $120 value over the standard-height sights on a Glock MOS. The Glock MOS system is more universally compatible and has a vastly larger aftermarket, but the FN 509 Tactical is better out of the box for immediate suppressed or red-dot use without additional parts purchases.
What does it weigh and what are the dimensions?
Unloaded weight is 27.9 ounces or 791 grams. Overall length is 7.9 inches with a 4.5-inch barrel, slide width is 1.35 inches, and height is 5.9 inches to the top of the suppressor-height sights. The grip circumference adjusts from 6.1 to 6.4 inches with the included medium and large backstraps, providing a 0.3-inch variation to fit most hand sizes. The Picatinny rail section is 1.8 inches long, accommodating lights and lasers up to the size of a Streamlight TLR-1 HL.
Who is this NOT for?
This pistol is not for first-time shooters, budget-minded buyers, or those in non-threaded-barrel jurisdictions. The $819 price point requires a significant investment, and the 10-round magazine capacity is a non-negotiable compliance feature in many states. If you want a simple, low-cost home defense pistol without plans for a suppressor or optic, consider a standard model like the Stevens 334 in .308 Win for a more straightforward long-gun solution.
What's in the box?
The box contains the pistol, one 10-round magazine, four optic mounting plates (for RMR, Doctor, DeltaPoint, and an uncovered plate), an O-ring sealed thread protector, three backstraps (small, medium, large), a cable lock, and the owner's manual. Notably absent is a hard case—FN ships these in a cardboard container with foam inserts. You'll need to supply your own red-dot optic, suppressor, and hearing protection; this is a tool-grade firearm, not an all-inclusive kit.
Is the FN 509 Tactical worth it at $819?
Yes, if you need a suppressor-ready, optic-ready platform from a factory with a proven military pedigree. The cost is justified by the cold hammer-forged barrel, suppressor-height tritium night sights, and the patented optics mounting system that requires no separate plate purchase. Compared to buying a standard pistol and adding those features piecemeal, you'd spend over $1,000. For a hunter needing a different type of ready-to-use platform, the Stevens 555 Sporting 20 Gauge offers similar out-of-the-box utility at a lower price point for a different application.
Specs at a glance
Pros & cons
What works
- Factory suppressor-height tritium night sights provide immediate co-witness – a $120+ value over standard sights
- Cold hammer-forged 4.5-inch threaded barrel adds 50 fps velocity over a standard 4-inch barrel
- Patented Low-Profile Optics Mounting System includes 4 plates – no additional $40-80 plate purchase required
- 27.9 oz unloaded weight balances well with a suppressor or micro red-dot attached
Trade-offs
- 10-round magazine capacity is fixed for compliance – no 17 or 24-round FN magazines included or compatible without modification
- Double-action-only trigger has a 6.5-pound pull weight – not ideal for precision shooting or competition
- Ships in cardboard packaging – no hard case included for the $819 price
- Slide serrations are moderately aggressive – may wear holsters faster than smoother-finished slides
Key attributes
| upc | 845737010195 |
| manufacturer | FN America / FN Herstal |
| manufacturer part number | 66-100527 |
| action | Double Action Only |
| atf type | Pistol |
| barrel length | 4.50" |
| caliber/gauge | 9mm |
| capacity | 10 + 1 |
| color | Black |
| length | 12 |
| number of magazines | 2 |
| package height | 3.5 |
| package width | 11.5 |
| product type | Pistol |
| safety | Loaded Chamber Indicator |
| shipping weight | 3.9 |
| sights | Suppressor Height Night Sights |
| sights type | 3-Dot Night/Suppressor Height |
| slide description | Optic Ready/Serrated |
| units per box | 1 |
Frequently asked questions
- Is it compatible with Trijicon RMR optics?
- Yes, the FN 509 Tactical is directly compatible with a Trijicon RMR using the included RMR-specific mounting plate. The plate uses two 4-40 screws, which are provided, and locates the optic correctly for a lower third co-witness with the suppressor-height sights. Installation requires a torque wrench set to 15 inch-pounds per FN's spec.
- Does it fit a Glock 19 holster?
- No, the FN 509 Tactical will not fit a standard Glock 19 holster. The slide and frame dimensions differ, specifically around the optic cut and rail section. You need a holster molded for the FN 509 series, available from manufacturers like Safariland, Blackhawk, or Tier 1 Concealed. Expect a lead time of 2-3 weeks for custom Kydex holsters.
- How long does shipping take to an FFL?
- Shipping to your selected Federal Firearms License (FFL) dealer typically takes 3-5 business days from our warehouse. Once the firearm arrives, you must complete the required 4473 background check at the dealer, which can add 1-7 days depending on state laws and NICS queue times. All shipments require an adult signature upon delivery.
- Can I return it if it doesn't fit my hand?
- No, firearms are non-returnable final sale items per federal regulations and our policy. You can handle display models at local dealers to check ergonomics before purchasing. The three included interchangeable backstraps provide a grip circumference range from 6.1 to 6.4 inches, which accommodates most adult hand sizes from small to XL.
- Does this work with a SilencerCo Octane 9 suppressor?
- Yes, the 1/2x28 threaded barrel is directly compatible with the SilencerCo Octane 9, Omega 9K, and most other 9mm pistol suppressors using a standard thread pitch. Use a piston assembly and fixed-barrel spacer if your suppressor requires it. The suppressor-height sights provide a clear sight picture over a can up to 1.5 inches in diameter.