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FN 503 Slim 9mm Review

The new FN 503, a slim 9mm concealed carry pistol, combines shooter-friendly features with battle-proven reliability to create the most rugged, reliable EDC handgun on the market.

FN 503 Slim 9mm Review
Photo by Brad Fitzpatrick

A couple years ago, FN launched their modular, striker-fired FN 509 9mm pistol, a gun that was met with instant praise and which has developed a large and growing fanbase. One of the primary reasons FN owners remain so loyal to their chosen brand is reliability: FN guns are, after all, the world’s most battle-proven firearms, and the company fired more than a million rounds during development of the 509. From back alleys to the battlefield, shooters know they can rely on their FN when their life is on the line.

Though the FN 509 remains a popular choice among shooters and law enforcement professionals, its double-stack design makes it wider than some competing carry pistols. Thin is in for EDC, and almost since the 509’s inception, shooters have been asking FN to develop a single-stack version of the pistol. New for 2020, for all those who wanted a trimmed-down carry version of the 509, FN has launched its first slim 9mm carry gun.

Photo by Brad Fitzpatrick

Meet the New FN 503 Slim 9mm

The FN 503 shares similar design heritage with the 509, so that extreme high reliability carries over into this new pistol. But the new 503 is much trimmer than its larger cousin. Measuring just under an inch across the controls, the 503 is the slimmest semiauto FN has ever built and one of the narrowest single stack pistols in the marketplace.

The barrel measures 3.1 inches long, and the overall length of the pistol is just 5.9 inches. That’s nearly 0.4 inches shorter overall than a Glock 43 and 0.2 inches shorter than Smith & Wesson’s M&P Shield. The 503’s overall weight is just 21 ounces, which is light enough for everyday carry (EDC) yet heavy enough to balance properly and manage recoil and muzzle flip.

Photo by Brad Fitzpatrick

The FN 503 comes standard with two metal magazines: a flush-fit 6-round and an extended 8-round. The 6-round magazine is designed for maximum concealability for no-print concealed carry while the 8-round magazine increases capacity and grip size and is perfect for practicing at the range or home defense situations.

The 503’s ergonomic grips are among the best in this class. Texturing on the side panels and front and back straps provides a secure hold on the gun even with wet hands and the grip angle promotes a high hand hold on the pistol for maximum control. FN also offers interchangeable accessory grip options if you want to customize your pistol.

Photo by Brad Fitzpatrick

The 503’s mass, grip angle and low bore axis allow for faster follow-up shots. One of the features that sets the 503 apart in the crowded carry gun market is a best-in-class metal-blade trigger that breaks cleanly around five pounds. It’s clear that trigger quality was a point of emphasis when FN designed the pistol, and it’s far better than many competing triggers, which are sloppy and spongy. The 503’s trigger take-up is smooth, reliable, and predicable, and trigger reset is short.

Building a carry gun is a balancing act. The sights and controls should be useable and functional, but they shouldn’t be so large they impede draw or dig into the body while carrying. The FN 503 features low-profile three-dot dovetailed iron sights that won’t snag, yet they are large enough to allow you to quickly get on target and make accurate shots. The slide stop is large enough that it is easy to manipulate – even with gloved hands – yet it rides close to the frame, so the FN maintains a streamlined, narrow profile for concealed carry.

Photo by Brad Fitzpatrick

There’s a magazine release positioned just behind the trigger and rides in a molded oval that virtually eliminates any risk of accidental mag drops (both left- and right-handed mag release buttons are included). And while the 503 doesn’t feature a manual safety, it does come with passive trigger disconnect lever, striker block, and trigger safety lever. There’s also a visual loaded chamber indicator.

FN’s attention to detail is apparent throughout the 503. The chamber and feed ramp are polished for reliable function and the barrel features a recessed target crown. Ferritic nitrocarburizing and PVD on the steel slide and barrel offer the highest level of protection against wear and corrosion and the 503 is well-equipped to withstand years of exposure to moisture and perspiration during regular carry without damage. Angled cuts machined into the front portion of the steel slide reduce weight and improve comfort while carrying the gun and robust slide serrations offer improved control when operating the gun.

Built in Columbia, South Carolina, the FN 503 carries an MSRP of $549, which is a great value for a pistol of this quality.

Photo by Brad Fitzpatrick

FN 503 Carry and Range Evaluation

The FN 503 9mm is small enough to be worn under light, warm-weather garments. Its narrow profile and compact size allow it to ride comfortable against the body without printing, and this gun functions well in minimalist IWB holsters and belly bands. Its small size and minimal weight make it ideal for strenuous activities like hiking, and it’s also an excellent backup or deep concealment gun.


There are a lot of light, small handguns that are easy to conceal, but very few can match the 503’s build quality. Fit and function were flawless, and the FN’s trigger sets a new standard in the class. While at the range I shot the gun both from a bench and offhand, and there were no issues with reliability or function.

The beefy external claw extractor is similar to the one found on FN’s other pistols and, not surprisingly, it functions flawlessly. While firing more than 400 rounds of test ammo (everything from lightweight target loads to hot defensive rounds) there wasn’t a single feeding, extraction, or ejection issue. The luminescent sights are easy to see and the 503’s grip design makes this one of the most manageable slim 9mm pistols on the market. The handgun never snagged when it was being drawn and delivering fast, accurate shots at defensive ranges is easy to do.

The wait is finally over for FN fans who wanted a single-stack carry pistol, and the 503 doesn’t disappoint. Its design, ergonomics, build quality and reliability make it one of the standard-bearers in the slim 9mm market, and it’s poised to be the next big thing in small pistols. If you’re shopping for an easy-to-conceal defense pistol, the FN 503 should be on your short list.

Photo by Brad Fitzpatrick

FN 503 Pistol Specs

Cartridge/Caliber: 9mm
Action: Striker fired semiauto
Capacity: 6+1, 8+1
Weight: 21 oz. (unloaded)
Sights: Three-dot dovetailed
Finish: Black nitride
Frame: Polymer
Trigger Pull: 5.5 lbs
MSRP: $549
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