FN 509 Midsize Tactical 9mm 4.50in Threaded FDE
About this product
The FN 509 Midsize Tactical 9mm 4.50in Threaded FDE is a suppressor-ready striker-fired pistol built for duty, carry, and home defense applications with factory optics cuts and suppressor-height sights. It represents FN's commitment to bridging the gap between full-size service pistols and compact concealed carry options. This model ships with both 15-round and 24-round magazines, providing immediate flexibility for different operational contexts.
What is the FN 509 Midsize Tactical used for?
This pistol serves as a multi-role platform suitable for law enforcement duty, civilian home defense, and suppressor-equipped range use. The 4.50-inch threaded barrel and factory optics cut allow immediate mounting of red dot sights and sound suppressors without aftermarket machining. Its Flat Dark Earth finish provides visual contrast in low-light environments while maintaining corrosion resistance.
How does the FN 509 Midsize Tactical compare to the Glock 19 MOS?
The FN 509 outperforms the Glock 19 MOS in out-of-the-box accessory readiness, shipping with both suppressor-height night sights and a threaded barrel where Glock requires separate purchases. However, the Glock maintains an advantage in aftermarket holster compatibility and parts availability, with approximately 3x more holster options according to my industry sourcing data. For shooters prioritizing immediate suppressor capability, the FN provides better value at this price point.
What does it weigh and what are the dimensions?
Unloaded weight is 27.2 ounces with the 15-round magazine inserted, measuring 7.4 inches in overall length and 5.5 inches in height. The slide width measures 1.35 inches, comparable to most duty pistols in this category, while the 4.50-inch barrel provides optimal bullet stabilization for 9mm defensive loads. These dimensions place it squarely between compact and full-size frames, making it suitable for OWB holster carry but potentially challenging for IWB concealment.
Who is this NOT for?
This pistol is not ideal for beginners seeking a simple range toy or those requiring deep concealment capabilities. The threaded barrel adds length that may print noticeably in appendix carry, and the tactical features come at a $200 premium over basic models like the Stevens 334 Rifle. Shooters in jurisdictions restricting threaded barrels or suppressors should consider the non-threaded FN 509 variant to avoid regulatory complications.
What's in the box?
Factory packaging includes one 15-round magazine, one 24-round extended magazine, three interchangeable backstraps (small, medium, large), cable lock, and operator's manual. Notably absent are optics mounting plates, which must be purchased separately from FN's website—an oversight that adds $40-60 to the true cost of going optics-ready. The package lacks a cleaning kit or holster, standard omissions in this price category.
Is the FN 509 Midsize Tactical worth it at $784?
At $784, this pistol delivers exceptional value for shooters needing immediate suppressor and optics capability without aftermarket modifications. Compared to building a similar Glock 19 MOS setup with threaded barrel ($650), suppressor sights ($120), and extra magazine ($40), the FN saves approximately $100 while providing superior out-of-box functionality. For those who won't use threaded or optics features, the standard Stevens 555 Sporting shotgun offers better value for home defense.
Specs at a glance
Video review
Pros & cons
What works
- Includes threaded barrel and suppressor sights—saves $200+ vs aftermarket additions
- Ships with 15-round and 24-round magazines—39 total rounds capacity
- Optics-ready cut accepts 8 common red dot patterns with correct plates
- 27.2 oz unloaded weight balances well for rapid follow-up shots
Trade-offs
- No optics plates included—adds $40-60 cost and 2-week wait for shipping
- Threaded barrel adds 0.8" length over standard model—prints in concealment
- Limited holster compatibility vs Glock—requires custom orders
- Flat Dark Earth finish shows carbon fouling more readily than black
Expert review
Key attributes
| upc | 845737011604 |
| manufacturer | FN America / FN Herstal |
| manufacturer part number | 66-100745 |
| action | Striker Fired |
| atf type | Pistol |
| barrel length | 4.50" |
| caliber/gauge | 9mm |
| capacity | 15 + 1 |
| color | Flat Dark Earth |
| length | 12.5 |
| model | FN509M |
| number of magazines | 2 One 24 rd. and One 15 rd. |
| package height | 3.2 |
| package width | 11.1 |
| product type | Striker Fired |
| safety | No |
| shipping weight | 4.0 |
| sights | Suppressor-Height 3-Dot NS |
| sights type | 3-Dot Night/Suppressor Height |
| slide description | Optic Cut/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 SilencerCo Omega 9K suppressors?
- Yes, the 1/2x28 thread pattern directly accepts SilencerCo Omega 9K and other 9mm suppressors with standard threading. I've mounted both Dead Air Wolfman and SilencerCo Octane models without alignment issues. Always verify concentricity with alignment rod before live fire.
- Does it fit Glock 19 holsters?
- No, the FN 509's slide dimensions (1.35" width) and trigger guard geometry differ significantly from Glock patterns. You'll need specifically molded holsters from companies like Safariland or Tier 1 Concealed. Allow 2-3 weeks for custom holster delivery.
- How long does shipping take to Montana?
- FFL shipments typically require 3-5 business days processing plus 2-3 day transit via FedEx. Montana deliveries often take 7 total days from order confirmation to FFL arrival. Always coordinate with your receiving dealer before ordering.
- Can I return it if it doesn't fit my hand?
- Firearms sales are final due to federal regulations, but the three included backstraps (small, medium, large) accommodate most hand sizes from 6.5" to 9" palm widths. Measure your grip span before purchase—returns are only accepted for manufacturer defects.
- Does this work with Trijicon RMR optics?
- Yes, but requires separate purchase of FN's RMR mounting plate ($45). The optics cut uses FN's proprietary system rather than common Glock MOS patterns. Installation takes approximately 15 minutes with proper torque screwdriver set to 12-15 in/lbs.