FN 509 Review — First-Time Buyers Guide

The FN 509 is a modern, duty-grade, striker-fired 9mm designed by FN Herstal (distributed by FN America) to compete in the service pistol space.

Built on a polymer frame with a cold-hammer-forged barrel and fully ambidextrous controls, the 509 family (Standard, Midsize, Compact MRD, Tactical, Fullsize MRD) offers optics-ready slides, high-capacity magazines and features tuned for reliability and real-world defensive use.

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The FN 509 arrived explicitly to challenge entrenched duty pistols — it’s a no-nonsense 9mm intended for first responders, IC/LE procurement, and civilians who want a rugged, feature-rich defensive handgun. FN Herstal brings a long history of military and law-enforcement firearms to the table; the 509 draws on that lineage while adopting the modular ergonomics and optics readiness modern shooters expect.

Where older FN pistols emphasized unique mechanical systems, the 509 goes pragmatic: proven striker-fire operation, robust frame, and straightforward controls.

The result is a pistol designed for consistent service use, easy maintenance, and broad aftermarket support — a platform aimed squarely at duty, carry, and competition shooters who want reliability plus modern features.

FN 509 Specifications

Below are the core specs across the 509 family (note: exact numbers vary by variant):

• Caliber: 9×19mm Luger

• Action: Striker-fired, short recoil (double-action style trigger engagement)

• Barrel length: 3.7" (Compact MRD) to 4.5" (Tactical/Fullsize MRD); Standard ~4.0"

• Overall length: ~6.8" (Compact MRD) to 7.9" (Tactical/Fullsize)

• Height: ~4.8" (Compact MRD) to 5.75" (Tactical)

• Width: ~1.35"

• Weight (unloaded): ~25.5–27.9 oz depending on model

• Capacity: 17+1 standard (full-size); magazines available in 10, 12, 15, 17, and 24+1 for some variants

• Frame: Glass-filled polymer with interchangeable backstraps and aggressive texture

• Slide: Steel slide with FN Low Profile Optics Mounting System™ on MRD and Tactical models; stippled serrations; sight-protecting slide caps on some versions

• Sights: Flush sight options on base models; Tactical and MRD variants include suppressor-height night sights (Trijicon style on some packages)

• Rail: Integrated 1913 Picatinny for lights/lasers

• Notable features: Ambidextrous slide stop and mag release, optics-ready slides (MRD/Tactical), 1913 rail, recessed target-crowned barrels, optional manual safety variants

These specs explain why the 509 competes in the duty pistol market: it pairs capacity and modular ergonomics with practical features (optics readiness, suppressor height sights, threaded barrel options on Tactical models).

FN 509 Design & Build Quality

Frame and slide

The 509’s polymer frame is stiff, well-scaled, and treated with a textured pattern meant to bite into the hand for secure purchase without shredding clothing. Interchangeable backstraps let shooters tune grip circumference and feel — a critical feature for deputies and shooters who must share firearms or run a fixed-size platform across different hand sizes.

Slides are steel, machined with crisp serrations, and the MRD/Tactical slides accept common red-dot mini sights without milling by the end user.

FN’s Low-Profile Optics Mounting System is a robust implementation: it provides a low-line of sight co-witness with suppressor-height irons and maintains slide integrity better than some plates or adapter systems.

Controls

Controls are intentionally ambidextrous: slide stops on both sides and reversible magazine releases make the 509 friendly to left-handed shooters and adaptable for tactical immediate action.

The magazine well isn’t aggressively flared on standard models (the Tactical variants have more pronounced geometry), but FN’s factory mags are easy to seat and extraction is positive.

Fit & finish

Fit and finish are consistent with FN’s manufacturing standards: tight slide-to-frame tolerances, corrosion-resistant finishes on steel parts, and durable polymer frames.

Out-of-the-box reliability and finish longevity are recurring praise points in user reports; FN’s QC catches fewer cosmetic and functional errors than many budget makers.

FN 509 Variants & Model Differences

FN intentionally built the 509 family to cover multiple niches without fragmenting the platform:

• Standard FN 509: Full-feature duty pistol with 4.0" barrel, 17-round magazines, and proven configuration for general duty or carry.

• Midsize: Slightly reduced grip height and overall profile for easier concealment while retaining a 15–17 round feel.

• Compact MRD: Smaller footprint (3.7" barrel, 6.8" length) and optics-ready slide for concealed carry with modern red-dot compatibility.

• Tactical / Fullsize MRD: 4.5" threaded barrels, suppressor-height sights, and heavy-duty features for duty or suppressed use; these often ship with higher-visibility sights and extended controls.

• Manual safety options: Some configurations add a manual thumb safety for agencies or shooters who prefer it.

What are Direct Competitors to the FN 509?

Direct competitors to the FN 509 include the Glock 17 and Glock 19, SIG Sauer P320 Full Size and P320 Carry, Smith & Wesson M&P9 M2.0 Full Size, Walther PDP Full Size, CZ P-10 F, HK VP9, and Canik TP9SF.

These pistols closely match the FN 509 in barrel length around 4–4.5 inches, double-stack capacity, intended service/EDC roles, and availability of tactical or MRD configurations, and they compete directly on ergonomics, trigger quality, suppressor and optics support, and aftermarket ecosystem for duty, home defense, and range use.

Performance

Accuracy

Out of the box the FN 509 typically groups very well for a service pistol. Users routinely report 2" groups at 25 yards from supported positions with good ammunition — performance on par or slightly better than many polymer service pistols due to the recessed, target-crowned barrel and consistent lockup.

Recoil & control

Recoil is what you'd expect from a polymer 9mm: manageable but not absent. Some shooters note a bit more perceived muzzle impulse than on a Glock 17, likely due to frame geometry and slide mass.

Interchangeable backstraps and the grip texture mitigate muzzle flip by delivering a firm purchase; follow-up shots are fast and controllable for trained shooters.

Reliability

Reliability is the 509’s headline claim. Field reports and range testing repeatedly show the 509 cycling a wide variety of 9mm defensive and training ammo with very low malfunction rates — that’s why it was adopted in some law enforcement evaluations.

Users report thousands of rounds with no major stoppages when using factory magazines and standard defensive/full-metal-jacket loads.

Trigger quality

Factory trigger feel is widely discussed: it’s serviceable and safe, but reviewers often call it “service-grade” rather than “match.”

Many shooters find the take-up somewhat long and the break a little gritty compared to premium aftermarket triggers; that said, trigger feel often improves with break-in and is acceptable for duty use. Upgraded triggers and springs are available for those who want a crisper break and a shorter reset.

Ammunition Compatibility

The FN 509 is tolerant of a wide spectrum of 9mm loads — from standard 115–124 gr FMJ practice rounds to modern 124–147 gr hollow points and +P defensive loads.

FN’s cold hammered barrel and robust feed ramp geometry help feed hollow points reliably; practice with your chosen defensive ammo is still mandatory because every pistol + ammo pairing can differ.

For target work, standard 115–124 gr FMJ or match-grade 124–147 gr loads produce best grouping. For defensive use, contemporary JHPs from major makers cycle reliably. Users have reported that high-quality magazines and run-in with at least a few hundred rounds improves consistency.

FN 509 Use Case Suitability

Concealed / Self-Defense

The Compact MRD variant is aimed at CCW users who want a red-dot capable micro-compact with serious capacity. It’s a little thicker than ultra-slim single stacks, but it trades a slimmer carry profile for more capacity and features.

For deep concealment, the Midsize or Compact models work well; full-size 509s are better for open carry or duty.

Home defense

Full-size and Tactical 509s make excellent home defense guns: threaded barrels and suppressor-height irons are useful if you run a can, and the higher capacity magazines reduce the need for immediate reloads. The frame rail accepts lights easily, which is essential for household defense.

Competition (IDPA/USPSA)

The 509 is configurable enough for production and limited divisions; optics-ready MRD variants then compete in optics divisions.

Many competitive shooters appreciate the platform for local matches, though dedicated competition pistols may offer lighter triggers or tuned recoil systems out of the box.

Outdoors / hunting

Not a hunting sidearm per se, but a 509 is rugged and capable in outdoor settings. The Tactical/MRD with threaded barrel can integrate suppressors for pest control in rural settings, and the robust construction stands up to wet and dusty environments.

Range toy or workhorse?

The 509 is primarily a workhorse — designed for daily carry, law-enforcement use, and trainers. It’s also a solid range gun: reliable, accurate, and comfortable for high round counts.

Best Holsters for FNH FN 509 Holsters

The FN 509 fits comfortably in a variety of holsters suitable for different carry styles. Pick a FN 509 holster that matches how you carry and what you need to access quickly.

IWB — Cloak Tuck 3.5

Slim inside-the-waistband holster for deep concealment and comfortable all-day carry. Adjustable cant and sweat guard keep the 509 tucked tight against your body.

Belt Holster

Strong-side belt holster offers quick access and excellent retention for range days or open carry. Durable polymer construction keeps the pistol secure and stable.

OWB Paddle Holster

Quick on and off the belt — great for instructors and range users who need to remove the holster frequently. The paddle spreads weight and rides comfortably during extended wear.

Swivel Drop Leg Holster

Designed for tactical or range scenarios where you need low-ride access and retention during movement. Swivel mounts allow a fast re-position without sacrificing security.

Chest Holster

A good option for vehicle use and outdoor activities where torso carry is practical. Keeps the pistol centered, accessible, and comfortable under outer garments.

Hook & Loop Holster

A modular, soft-surface option for off-body carry (packs, consoles, glove boxes). Velcro mounting allows quick retrieval from unconventional platforms.

FN 509 Pros & Cons

Pros

• Proven reliability in service and civilian testing — runs many ammo types with low malfunction rates.

• Wide family: Standard, Midsize, Compact MRD, Tactical and Fullsize MRD offer flexibility for duty, carry, and suppressed use.

• Optics-ready slides on MRD/Tactical models allow modern red-dot adoption without gunsmithing.

• Ambidextrous controls and interchangeable backstraps deliver excellent ergonomics for a broad user base.

• Strong out-of-box accuracy due to target-crowned barrel and consistent lockup.

• Robust feature set (1913 rail, suppressor-height sights, threaded barrels on Tactical models).

Cons

• Factory trigger is functional but not as crisp as some rival pistols — many buyers opt to tune or replace springs/trigger for a crisper break.

• Perceived recoil is slightly peppier than some competitors (subjective and dependent on variant).

• Tactical/MRD variants and accessories push price into the premium bracket compared with some mainstream competitors.

• Some shooters find the factory grip texture and aggressive stippling divisive — try before you buy if possible.

Final Verdict

The FN 509 is a mature, well-rounded platform that deserves consideration for anyone who needs a serviceable 9mm for duty, concealed carry (compact/midsize options), or a training platform. Its reliability record in agency and private testing makes it a legitimate duty candidate, and optics-ready slides put it in front of modern carry trends.

Who should buy it?

• Law enforcement and security agencies who need a proven, high-capacity, optics-ready pistol.

• Defensive shooters who want a robust full-feature handgun with modular grip options and strong out-of-box reliability.

• CCW users who prefer capacity and optic compatibility over ultra-slim concealment.

Value for money: Standard FN 509 models are competitively priced for the features offered; Tactical/MRD editions cost more but justify the premium if you’ll use optics, threaded barrels, or night sights.

Long-term ownership looks favorable: FN supports parts and service well, and the 509 platform is increasingly common in the aftermarket for sights, holsters, and upgrades.

Bottom line: the FN 509 is a serious, modern defensive pistol — not a novelty. It blends duty reliability with practical modern features, making it a strong option for shooters who value capability, modularity, and the ability to run optics and suppression without heavy modification.