Description
The FN 66100797 509 Compact Tactical 9mm Luger 4.32″ Threaded Barrel, 12+1/24+1, FDE Polymer Frame w/Mounting Rail, Optic Cut FDE Stainless Steel Slide, Includes Viper Red Dot bridges the gap between a duty-sized handgun and an everyday carry piece. This pistol ships with a Vortex Viper red dot pre-installed on the FN Low-Profile Optics Mounting System, giving you a ready-to-run suppressed or compensated setup right out of the box. The compact slide and grip keep it concealable, while the included 24-round magazine gives you full-size firepower when you need it.
| Manufacturer | FN America |
|---|---|
| Model | 509 Compact Tactical |
| Material | FDE Polymer Frame, FDE Stainless Steel Slide |
| Compatibility | 9mm Luger; accepts most miniature red dots (RMSc, Docter, Shield, etc.) |
| Finish | Flat Dark Earth (FDE) polymer frame; FDE PVD-coated stainless steel slide |
| Weight | 24.5 oz (unloaded, with 12-round magazine per manufacturer specs) |
| Condition | New |
Key Features
- FN Low-Profile Optics Mounting System — Why it matters: The included Viper red dot sits low enough to co-witness with the blackout iron sights, so your point of impact stays consistent whether the dot is on or off. No adapter plates needed for most miniature red dots.
- 4.32″ Cold Hammer-Forged Threaded Barrel — Why it matters: 1/2×28 threads let you run a suppressor or compensator without swapping barrels, and the hammer-forged construction outlasts cut-rifled barrels by thousands of rounds.
- Two Magazine Capacity Options (12+1 / 24+1) — Why it matters: Flush-fit 12-rounders keep the grip short for concealed carry; the 24-round extended mag gives you a full grip and extra capacity for range or home defense.
- Fully Ambidextrous Controls — Why it matters: Slide stop and magazine release are mirrored on both sides, making this pistol genuinely lefty-friendly without aftermarket parts.
- Interchangeable Backstraps — Why it matters: Three included backstraps let you dial in palm swell and trigger reach, improving grip consistency shot to shot.
Who It’s For
Shooters who want one gun for EDC, home defense, and suppressed range use. The FN 509 Compact Tactical suits anyone who needs an optic-ready 9mm with a threaded barrel but doesn’t want the bulk of a full-size pistol. If you carry appendix or strong-side and value the ability to run a can or comp, this is your sweet spot.
Pros / Cons
- Pro: Ships with a Vortex Viper red dot — saves you $150+ over buying the optic separately.
- Pro: 24-round magazine for extended capacity without a separate purchase.
- Con: The Viper red dot has a non-replaceable battery and requires removal to change it, which can shift zero if you’re not careful. Plan to re-zero after battery swaps or invest in a dot with a top-load battery.
Comparison vs. Competitors
| Feature | FN 509 Compact Tactical | Zev Technologies OZ9 Compact | Agency Arms AOS G19 |
|---|---|---|---|
| Optic System | FN Low-Profile Mount (included Viper) | Zev RMR-cut slide (no optic included) | AOS plate system (no optic included) |
| Barrel | 4.32″ threaded, cold hammer-forged | 4.0″ threaded, match-grade | 4.0″ threaded, match-grade |
| Capacity | 12+1 / 24+1 | 15+1 (Glock mags) | 15+1 (Glock mags) |
| Frame | FDE polymer, interchangeable backstraps | Serrated polymer, modular grip | Polymer, no backstraps |
| Price | $758.87 | $1,299+ | $1,100+ |
| Best For | Value-driven EDC with suppressor | Competition / custom builds | High-end carry with Agency parts |
FAQ
What is the thread pitch on the FN 66100797 barrel?
The barrel is 1/2×28 threaded, which is the standard for 9mm suppressors and compensators. It works with most popular aftermarket muzzle devices.
Does the Viper red dot co-witness with the iron sights?
Yes. The FN Low-Profile Mounting System positions the Viper so the blackout rear and front sights align through the lower third of the optic window. You can use the irons if the battery dies.
Can I use Glock 19 holsters with the FN 509 Compact Tactical?
No. The 509 Compact Tactical has a different trigger guard shape and slide profile than a Glock 19. You need holsters made specifically for the FN 509 Compact or 509 Compact Tactical.
How long does it take to swap the Viper battery?
You must remove the optic from the slide using a T6 Torx driver, replace the CR1632 battery, reattach the optic, and re-zero. Plan on 10–15 minutes and a trip to the range.
Ready to Buy?
Order the FN 66100797 509 Compact Tactical 9mm Luger 4.32″ Threaded Barrel, 12+1/24+1, FDE Polymer Frame w/Mounting Rail, Optic Cut FDE Stainless Steel Slide, Includes Viper Red Dot today. According to the 2024 NSSF industry report, compact pistols account for 42% of new handgun sales — this is the category that sells fastest.
✓ Nationwide delivery (all 50 states) ✓ Ships 1-2 business days ✓ 30-day returns ✓ Secure checkout
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Last updated: April 2026
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