The FN FNS-40 represents FN America's full-size striker-fired entry into the .40 S&W duty pistol market, featuring a 4" barrel, 14-round double-stack capacity, and ambidextrous controls housed in a polymer frame designed to compete directly with Glock and M&P service pistols.
The FNS-40L variant extends barrel length to 5" for enhanced accuracy and reduced muzzle flip, while maintaining the same magazine compatibility and control layout. Though superseded by the FN 509 family, the FNS-40 remains a proven duty platform common in law enforcement trade-ins and among shooters who standardize on FN's legacy striker-fired ecosystem.
This guide covers holsters, magazines, optics mounting, lights, grips, triggers, and essential support gear that maximize the FNS-40's capabilities across duty applications, home defense, and competitive shooting where .40 S&W performance matters.
Holsters for FNH FNS 40
Proper holster selection for the FNS-40 requires accounting for the pistol's full-size dimensions, 4" or 5" barrel length, and whether you've added weapon lights or slide-mounted optics via aftermarket milling.
Quality holsters provide secure trigger coverage, positive retention through friction or active mechanisms, and accommodate both standard duty configurations and modernized setups with lights or red dots. The FNS-40's service pistol dimensions favor OWB duty carry and home defense applications over deep concealment roles.
IWB Holsters
Inside-the-waistband carry suits off-duty law enforcement officers and civilians carrying the FNS-40 for personal defense, though the full-size dimensions make deep concealment more challenging than subcompact alternatives. Alien Gear Holsters produces IWB configurations specifically molded for the FNS-40, using reinforced Kydex shells that prevent collapse during one-handed reholstering while providing adjustable cant angles.
OWB Belt Holsters
Outside-the-waistband belt holsters represent the dominant carry method for the FNS-40 in duty, range, and home defense applications. Alien Gear's OWB belt holsters distribute the pistol's weight across belt surfaces, maintaining faster draw speeds compared to IWB positions while providing superior comfort during extended wear.
OWB Paddle Holsters
Paddle holsters eliminate belt threading via wide paddle inserts that slide inside the waistband, making them ideal for range sessions or situations requiring frequent holster removal. Alien Gear's paddle configurations distribute the FNS-40's weight across a larger waistband area than standard belt clips, though retention security may decrease compared to traditional belt holsters during vigorous movement or defensive training.
Drop Leg Holsters
Thigh-mounted drop-leg rigs position the FNS-40 lower on the body, clearing bulky tactical gear while maintaining accessibility during outdoor or duty applications. Alien Gear's drop leg holsters use adjustable leg straps to distribute weight across the thigh, though proper adjustment remains critical to prevent holster migration during movement. These configurations suit users wearing heavy duty belts, plate carriers, or outdoor gear where hip-mounted holsters would interfere.
Chest Holsters
Chest rigs keep the FNS-40 accessible during ATV riding, hiking, or activities where belt carry would interfere with backpack hip belts. Alien Gear's chest holsters use padded, adjustable harness systems to distribute weight across shoulders and prevent bouncing through rough terrain. These configurations particularly suit outdoor applications where the FNS-40 serves as wildlife defense or general field carry.
Lights for FNH FNS 40
Weapon-mounted lights enable positive target identification in low-light defensive scenarios, addressing the reality that most defensive encounters occur during reduced lighting when threats cannot be reliably identified with ambient illumination alone.
The FNS-40's integral accessory rail accepts standard 1913 Picatinny weapon lights from Streamlight, SureFire, and Olight. Light selection balances output, durability, and holster compatibility, with most duty users selecting proven systems that maintain function through thousands of cycles.
Streamlight TLR-1 HL
The TLR-1 HL provides 1000 lumens of output in a proven package that has become the de facto standard for duty pistol illumination.
This light's robust construction withstands impacts and environmental exposure through years of service, while ambidextrous paddle switches enable activation from either hand. The TLR-1 HL's widespread adoption ensures extensive holster compatibility across manufacturers.
Streamlight TLR-7X
The TLR-7X offers 500 lumens in a more compact profile compared to the TLR-1 HL, reducing overall pistol length while providing adequate output for most defensive applications.
This light suits users prioritizing reduced bulk over maximum illumination, particularly for off-duty or concealed carry applications where the FNS-40's dimensions already challenge concealability.
SureFire X300 Ultra
The X300 Ultra delivers 1000 lumens with SureFire's legendary durability and proven reliability through extreme environmental conditions.
This light represents the premium choice for duty applications where reliability outweighs cost considerations. The X300's widespread law enforcement adoption ensures extensive holster compatibility and parts availability.
Light-Bearing Holster Requirements
Adding weapon lights changes the FNS-40's dimensions, requiring light-specific holsters that accommodate both firearm and light profiles while maintaining proper retention and trigger coverage.
Users must verify holster compatibility with their specific light model before purchase, as dimensional differences between light systems prevent universal fitment.
Optics for FNH FNS 40
The FNS-40 lacks factory optics mounting provisions, requiring slide milling services from specialized gunsmiths to accommodate micro red dots or reflex sights.
Slide milling creates precision-cut mounting surfaces for popular footprints including Trijicon RMR, Holosun 507C, and similar micro dots. Optics-equipped slides dramatically improve target acquisition speed and precision, particularly for duty applications where electronic sights provide advantages over iron sights.
Slide Milling Services
Professional slide milling from established shops like Primary Machine, ATEi, or Jagerwerks creates direct-mount optics surfaces machined into the FNS-40 slide.
Quality milling maintains structural integrity while providing rock-solid micro dot platforms that withstand duty use and training. Milling services typically include sight dovetail retention for suppressor-height backup irons that cowitness with mounted optics.
Trijicon RMR
The Trijicon RMR represents the proven choice for duty pistol red dots, with Type 2 models addressing earlier durability concerns through strengthened housings and improved electronics.
The RMR's forged aluminum construction withstands impacts that destroy budget optics, while 3.25 MOA and 6.5 MOA dot options balance precision and target acquisition speed. Extensive law enforcement adoption ensures proven reliability through duty applications.
Holosun 507C
The Holosun 507C brings multiple reticle options and solar backup capability to milled FNS-40 slides, offering 2 MOA dot, 32 MOA circle, or combined configurations selectable via side buttons.
Solar panels preserve function even with dead batteries under bright ambient light, providing redundancy for defensive applications. The 507C's Shake Awake feature conserves battery by powering down during inactivity.
Backup Iron Sights
Optics installations should preserve backup iron sight capability through suppressor-height front and rear sights that cowitness with the mounted dot.
Lower-1/3 cowitness allows dot use while maintaining iron sight visibility in the lower sight picture, whereas absolute cowitness places dot and irons at identical heights. Duty applications typically prioritize iron sight retention for redundancy if optics fail.
Magazines and Extensions for FNH FNS 40
The FNS-40 ships with two 14-round factory magazines that share compatibility with FNX-40 models, providing interchangeability across FN's .40 S&W polymer pistol line.
Factory 10-round magazines address capacity restrictions in jurisdictions limiting magazine capacity, while grip extension base pads improve control and accommodate larger hands.
Magazine compatibility between FNS-40 and FNX-40 simplifies parts inventory for users maintaining both platforms.
Factory FN Magazines
FN factory FNS-40/FNX-40 magazines represent the reliability gold standard, using steel construction and quality followers that ensure consistent function across ammunition types.
These magazines maintain FN's reputation for reliability through thousands of cycles, making them the baseline for duty and defensive applications. The 14-round capacity provides adequate firepower for most defensive scenarios without excessive length.
10-Round Compliance Magazines
Factory 10-round FNS-40 magazines address capacity restrictions in states limiting magazine capacity to 10 rounds.
These magazines maintain the same steel construction and reliability as 14-round variants while providing legal compliance. Users in restricted jurisdictions should verify local laws before purchasing higher-capacity magazines.
FNS Compact Grip Extension Base Pads
FN's compact grip extension base pads add approximately 0.75" of frontstrap grip space, benefiting shooters with larger hands who find standard magazine bases too short for proper purchase.
These extensions fit any FNS 9mm or .40 S&W magazine, providing universal compatibility across the FNS family. The extensions maintain magazine capacity while improving control during rapid fire or recoil management.
Magazine Sleeves
FNS magazine sleeves smooth the transition between compact magazine bases and full-size grip frames, eliminating gaps that can pinch hands during recoil. These sleeves suit users running compact magazines as backups in full-size guns or those preferring flush-fit appearance.
The polymer construction maintains durability through repeated magazine changes and handling.
Grips for FNH FNS 40
Factory FNS-40 grips provide adequate texture through molded checkering, but aftermarket enhancements address recoil management and trigger reach through varied textures and materials.
Talon Grips offers adhesive panels that dramatically improve traction compared to factory surfaces, while professional stippling creates permanent texture modifications. Grip selection balances improved control against comfort during extended shooting sessions and daily carry.
Talon Grips
Talon adhesive grip panels attach directly to FNS-40 frames via 3M adhesive backing, providing granulate or rubber texture options that dramatically improve traction compared to factory checkering.
Granulate texture mimics skateboard tape with aggressive surface grip, while rubber variants offer softer touch with excellent moisture resistance. These grips install in minutes and remove cleanly if users prefer returning to factory configuration.
Professional Stippling
Professional stippling services create permanent texture modifications using soldering tools that alter frame surface patterns.
Custom stippling allows precise texture placement matching individual hand dimensions, creating aggressive traction where hands naturally grip while leaving other areas smooth for comfortable carry. Quality stippling maintains structural integrity without compromising frame strength or voiding warranties.
Triggers for FNH FNS 40
The FNS-40 ships with a striker-fired trigger providing consistent 5.5-6 pound pull weights suitable for duty applications without creating liability concerns.
Factory trigger geometry delivers adequate performance for most users after break-in periods of 500-1000 rounds.
Aftermarket trigger modifications remain limited compared to Glock or other established platforms, with most users finding factory triggers acceptable for duty and defensive roles after proper familiarization.
Factory Trigger Performance
The FNS-40's factory trigger represents FN's duty-oriented design philosophy, balancing reliable operation with acceptable feel.
Break-in periods smooth trigger action considerably, with many users finding no modification necessary after familiarization. The consistent pull weight maintains safe operation during defensive carry without excessive heaviness that degrades accuracy.
Lower Parts Kits
Recovered lower parts kits from specialty suppliers like JSD Supply provide internal components including springs, pins, and small parts essential for maintaining discontinued FNS-40 pistols.
These kits enable users to replace worn components and maintain reliability as the platform ages. Quality lower parts kits ensure continued function as factory support diminishes with the platform's discontinuation.
Sights for FNH FNS 40
Factory FNS-40 models include three-dot sights that provide adequate target acquisition for general use, though aftermarket sight upgrades dramatically improve low-light performance and precision.
Night sights from Trijicon and AmeriGlo provide self-luminous aiming points in complete darkness, while fiber-optic fronts gather ambient light for faster daylight acquisition. Sight selection balances defensive requirements, shooting conditions, and personal preferences regarding sight picture and alignment speed.
Trijicon Night Sights
Trijicon produces FNS-specific night sight sets with tritium inserts in front and rear positions, providing complete low-light visibility for duty and home defense applications.
The tritium lamps remain visible in complete darkness for approximately 12 years before requiring replacement. Trijicon's proven durability suits duty applications where reliability matters most.
AmeriGlo Night Sights
AmeriGlo offers multiple night sight configurations for the FNS platform, including blacked-out rear/bright front combinations that create front-sight-focused sight pictures preferred by many duty shooters.
The Pro-Operator series provides tritium in all three positions for complete low-light visibility. AmeriGlo's extensive catalog allows precise sight picture customization matching shooting style and preferences.
Fiber-Optic Sights
Fiber-optic front sights gather ambient light into brilliant aiming points that drastically accelerate sight acquisition under daylight conditions.
These sights particularly suit competition and range applications where lighting remains controlled, though fiber rods can break through impacts. Many competitive shooters combine fiber-optic fronts with blacked-out rears for high-contrast sight pictures.
Barrels for FNH FNS 40
The FNS-40L variant features a factory 5" stainless steel barrel that extends overall length while reducing perceived recoil and improving sight radius for precision applications.
FN offers the FNS-40L barrel as a standalone component through their accessories catalog, enabling standard FNS-40 owners to convert to long-slide configurations. Barrel swaps require compatible slides and recoil spring assemblies, making complete upper assemblies more practical than barrel-only conversions for most users.
FNS-40L 5" Barrel
The factory FNS-40L 5" stainless steel barrel provides enhanced accuracy and reduced muzzle flip compared to standard 4" barrels, benefiting competitive shooters and precision enthusiasts.
The increased barrel length generates higher velocities that improve .40 S&W ballistic performance. This barrel suits users building dedicated competition or precision FNS-40 platforms where concealment isn't a consideration.
Maintenance Tools and Cleaning Supplies for FNH FNS 40
.40 S&W generates significant fouling and carbon buildup that accumulates in the chamber, feed ramp, and bore, requiring regular cleaning to maintain reliability and accuracy.
FNS-40 maintenance demands proper-length cleaning rods that avoid crown damage, chamber brushes sized for .40 S&W chambers, and appropriate solvents for carbon removal without damaging finishes.
High-volume shooters benefit from ultrasonic cleaners that remove fouling from hard-to-reach areas including trigger assemblies and magazine wells.
Essential Cleaning Tools
Quality cleaning kits include bronze or nylon bore brushes sized for .40 S&W, chamber brushes that reach fully into chambers removing stuck cases and carbon rings, and proper-length cleaning rods that won't damage barrel crowns.
The FNS-40's striker-fired mechanism requires periodic detail stripping and cleaning to maintain reliable function through thousands of cycles. FN recommends cleaning every 500-1000 rounds for duty pistols.
Lubrication Requirements
FNS-40 reliability demands proper lubrication at slide rails, barrel hood, and striker channel interfaces using quality gun oils from manufacturers like Slip 2000 or Break-Free.
The striker-fired design requires light oil application rather than heavy greases that can accumulate debris or impede function in cold conditions. Proper lubrication reduces friction and wear while preventing corrosion during storage through humid environments.
Maintenance Schedule
Duty FNS-40 pistols require cleaning every 500-1000 rounds or annually if carried but not fired, while training guns demand cleaning after every range session to maintain peak performance.
High round counts accelerate wear on recoil spring assemblies and firing pin springs that require periodic replacement to maintain reliability. Factory springs typically last 3000-5000 rounds before replacement becomes advisable.
Conclusion: Best FNS 40 Accessories and Upgrades
Outfitting your FNH FNS-40 with appropriate accessories maximizes its potential as a duty pistol, home defense platform, or competitive shooting system. Quality holsters from manufacturers like Alien Gear Holsters ensure secure retention and consistent accessibility across carry positions from duty OWB to off-duty concealment.
Factory FN magazines and grip extensions provide reliable feeding and improved control. Weapon-mounted lights enable positive target identification during low-light defensive encounters. Slide milling services bring micro red dot capability to the legacy platform without factory optics provisions.
Whether you're running a standard FNS-40 for duty applications, an FNS-40L for competition, or maintaining a legacy platform for home defense, these accessories transform the FNS-40 from a capable factory pistol into a fully optimized system matched to your specific requirements across duty, defensive, and competitive shooting applications.