FN 509 Midsize Tactical 9mm 4.5″ Threaded — Matte Black
About this product
The FN 509 Midsize Tactical is a duty-capable, multi-role 9mm pistol engineered for shooters who demand suppressor compatibility and direct optic mounting without compromising concealment. It bridges the gap between a full-size service pistol and a micro-compact, offering a 4.5-inch threaded barrel and a low-profile optic system in a polymer frame that still accepts a full-handed grip. This configuration makes it a serious contender for both holster carry and home defense where modularity is paramount.
What is the FN 509 Midsize Tactical used for?
The FN 509 Midsize Tactical is primarily used as a daily carry, home defense, or duty firearm where suppressor and optic capability are non-negotiable. Its 4.5-inch threaded barrel, with a ½×28 thread pitch, is suppressor-ready out of the box, making it an ideal host for compact 9mm suppressors. The suppressor-height night sights provide a usable cowitness through most micro red dot optics, ensuring you maintain a sight picture whether running suppressed or not.
How does the FN 509 Midsize Tactical compare to the Glock 19 Gen5?
The FN 509 Midsize Tactical offers superior modularity compared to the Glock 19 Gen5, specifically in optics and suppressor readiness. Where the Glock requires aftermarket plate systems or slide milling for most red dots, the FN's Low-Profile Optics-Mounting System accepts multiple footprints directly, saving you 2-3 weeks for gunsmith work and $100-200. Conversely, the Glock's market dominance means magazine and holster availability is broader and often less expensive.
What does it weigh and what are the dimensions?
Unloaded, the FN 509 Midsize Tactical weighs 26.5 ounces, with a slide width of 1.35 inches and an overall length of 7.4 inches. The 4.5-inch cold hammer-forged barrel contributes to the forward balance, and the height of 5.7 inches to the top of the suppressor sights is critical for calculating holster fit. This dimensions profile is more akin to a standard full-size grip with a slightly shortened slide for easier concealment.
Who is this NOT for?
This pistol is not for the budget-conscious first-time buyer who isn't planning to immediately invest in a suppressor or optic. At this price point, you are paying a premium for capability you may not use. It's also a poor fit for those seeking the absolute lightest carry option; a micro-compact like the Sig Sauer P365 will save you nearly 10 ounces. For a purely traditional iron-sight range pistol, consider a simpler model like the Stevens 334 in .308 Win.
What's in the box?
The box includes the pistol, two magazines (one 15-round, one 17-round with grip extension), a soft-sided pistol case, and a threaded barrel protector. For a $784 firearm, the omission of a hard case is a noted cost-saving measure by FN. You will need to purchase your own optic plate specific to your red dot's footprint, as these are sold separately, a common point of end-user frustration.
Is the FN 509 Midsize Tactical worth it at $784?
At $784, the FN 509 Midsize Tactical is worth it specifically for the shooter who needs a suppressor-ready, optics-capable pistol in a mid-size format and does not want to pay for aftermarket gunsmithing. The value is in the integrated, factory-backed system. If your use case is purely iron-sight target shooting, that money is better spent on ammunition and range time with a more affordable platform, like many of our Stevens 555 shotguns designed for clay sports.
Specs at a glance
Video review
Pros & cons
What works
- Integral low-profile optic mount saves $150-250 vs. aftermarket slide milling
- 4.5-inch cold hammer-forged barrel provides a 15% longer sight radius than compact 3.8-inch models
- Includes both a flush 15-round and extended 17-round magazine for grip flexibility
- Suppressor-height night sights provide immediate cowitness with mounted red dots
Trade-offs
- Requires a separate, proprietary optic plate ($30-50) for each red dot footprint
- Aggressive grip texturing can be uncomfortable against bare skin for all-day carry
- Matte black finish on the slide is prone to holster wear marks within the first 500 draws
- No hard case included at this price point
Expert review
Key attributes
| upc | 845737015169 |
| manufacturer | FN America / FN Herstal |
| manufacturer part number | 66-100837 |
| action | Striker Fired |
| atf type | Pistol |
| barrel length | 4.50" |
| caliber/gauge | 9mm |
| capacity | 15 + 1 |
| color | Black |
| length | 12.1000 |
| model | FN509M |
| number of magazines | 2 |
| package height | 3.4 |
| package width | 11.2 |
| product type | Striker Fired |
| safety | No |
| shipping weight | 3.7 |
| sights | Suppressor-Height 3-Dot NS |
| sights type | 3-Dot Night/Suppressor Height |
| slide description | Optic Ready/Serrated |
| state restriction (ca) | NO DIRECT SHIP TO CALIFORNIA |
| state restriction (il) | NO SALE TO ILLINOIS PICA |
| state restriction (or) | NO SALE TO OREGON |
| state restriction (ri) | NO DIRECT SHIP TO RHODE ISLAND |
| state restriction (wa) | NO DIRECT SHIP TO WASHINGTON |
| units per box | 1 |
Frequently asked questions
- Is it compatible with Trijicon RMR optics?
- Yes, the FN 509 Midsize Tactical slide is compatible with the Trijicon RMR footprint using FN's specific RMR adapter plate, which is a separate purchase (part # FNS-794000079). The mounting system uses four screws, not three, and requires proper torque at 15 in-lbs to ensure zero retention.
- Does it fit Glock 19 holsters?
- No, the FN 509 Midsize Tactical will not reliably fit most Glock 19 holsters due to differences in slide geometry and accessory rail dimensions. You must use a holster specifically molded for the FN 509 series, such as those from Tier 1 Concealed or Vedder Holsters, for proper retention and safety.
- How long does shipping to an FFL take?
- Shipping to your selected FFL typically takes 2-4 business days after order processing, with most deliveries executed via UPS 2nd Day Air. Delivery date is subject to your FFL's hours for receiving shipments, so contact them directly to coordinate transfer timing once you receive tracking.
- Is the threaded barrel compatible with 9mm suppressors?
- Yes, the ½×28 threaded muzzle is the standard pitch for 9mm suppressors from manufacturers like SilencerCo, Dead Air, and Rugged. You must ensure the suppressor's outer diameter clears the raised suppressor-height sights, which typically requires a bore diameter of 1.375 inches or greater.