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FN 503 9mm Review

FN challenges the subcompact, single-stack 9mm pistol market and enters new territory with the 503.

FN 503 9mm Review
Photos by Michael Anschuetz

Since 1889, FN has been recognized as one of the world’s most-­respected firearms manufacturers. Despite its long and storied history, you have to think back the the FN Model 1910 and 1910/22 for a single-­stack carry pistol branded with the initials of the name “Fabrique Nationale.”

The first striker-­fired, subcompact single-­stack 9mm from FN is now shipping from FN America’s U.S.-­manufacturing operations in Columbia, South Carolina. Dubbed the “503”, it borrows mechanical influence and design architecture from the company’s 509 series. The 509 began as an entry for the U.S. Army’s Modular Handgun System (MHS) solicitation in 2015. The 509 didn’t win, but it proved itself as a formidable sidearm that was extremely accurate and reliable.

FN claims it tested the 509 to more than a million rounds during its development. That reputation for dependability is expected to carry over to the 503. The striker design between the 509 and 503 are similar, and like the 509, the 503 doesn’t feature a manual safety. There are three passive safeties including a striker block, a trigger-­safety lever, and a trigger disconnect. The striker block eliminates the risk of the striker contacting the primer without the trigger being pulled, the trigger disconnect prevents the gun from firing out of battery, and the trigger safety eliminates the risk of the trigger moving rearward by inertia if the gun were dropped.

Other features from the 509 have also been carried over to the 503. The new subcompact comes with a semicircular witness hole at the rear of the barrel hood to serve as a loaded chamber indicator. A beefy external extractor sits below to the right side of the slide to ensure reliable extraction in all conditions. This style extractor did not appear on the FNX or FNS series prior to the 509.


FN 503
The barrel hood features a witness hole that serves as a loaded-chamber indicator. It’s clearly marked for caliber, also.

Like the 509, the 503’s metalwork receives a salt-­bath, ferritic nitrocarburizing treatment that protects against metallic corrosion and scuffing. It also hardens the metal, so the 503 is well-­equipped to resist exposure to moisture and perspiration. Both guns also feature a modular platform and the 503 allows the shooter to change grip assemblies.


Size & Performance

The most pronounced difference between the FN 503 and the 509 is, of course, size. The 503 is a true subcompact. The slide measures .9-­inch wide. At its widest point across the slide-­lock lever, it measures 1.04 inches. The grip is slightly narrower than the slide at .89 inch, and the depth of the grip is roughly 2.2 inches. With a barrel measuring 3.1 inches, the 503’s overall length is 5.9 inches. It measures 4.4 inches from the toe of the flush-­fit magazine to the top of the slide.

FN 503
The 503 series is FN’s first sub-compact, striker-fired semiautomatic pistol. With its 3.1-inch barrel, 4.4 inches in height and measuring 5.9 inches in overall length, it is considerably smaller than the full-size FN 509.

How does the 503 compare to other similar-­size guns in this category? The Glock 43 has a 3.41 -­inch barrel and measures .4-­inch longer than the 503. However, the Glock is lighter. With a full six-­round magazine, the G43 weighs as much as the FN 503 with an empty magazine. Smith & Wesson’s M&P Shield and SIG Sauer’s P365 both have the same 3.1-­inch barrel length as the 503, but the P365 is .1-­inch shorter than the FN, while the S&W is .2-­inch longer. The Shield weighs about the same as the 503, while the P365 is lighter than both by about .3 ounces.

In terms of cost, the G43, P365, Springfield Armory’s Hellcat, and the 503 are within $50 of each other. You can expect to pay around $500 for each, while the 503 is advertised at $549. The Shield is the least expensive of these with a suggested retail price of $374.

Ultimately, the FN 503 is dimensionally on-­par with competing subcompact pistols, and odds are that you won’t notice an extra ounce or .1 inch in overall size. The 503 will be as easy to conceal as other comparable guns, which is to say that you can wear it under light clothing without printing, as a backup or a deep-­cover hideout.


What does the FN 503 offer that sets it apart in this crowded segment? I’d suggest build quality and material selection. Building subcompact guns is the ultimate compromise. It’s a perpetual trade-­off between shootability and concealability. In the process of shrinking guns, some cut corners.

Does a subcompact carry gun need metal sights? We at Guns & Ammo think so. The FN 503 features metal three-­dot luminescent sights dovetailed into the slide. The sights, too, are pretty snag-­free. They are firmly pressed in and are easy to see in all but dark conditions.

FN 503
Three white dots appear on metallic sights, which are dovetailed to the slide. These can be drifted for windage adjustments.

Do carry guns need great triggers? With so many shooters remarking that striker-­fired pistols only have spongy, heavy draws, I encourage you to try the 503’s the next time you're in a gun store. FN gave the 503 one of the best triggers in this class, without a doubt. It is metal, has a predictable, smooth take-­up and it fires after 5½ pounds of pressure each time.


From the magazine springs to the metal’s finish, and the grip texturing to the muzzle’s recessed target-­like crown, I find that every aspect of the FN 503 is well ­designed for serious shooters. With the slide locked back, you can inspect the chamber where you’ll see the feed ramp is polished. The metal magazines lock positively in place. Press the magazine release button, which is reversible, and even an empty one drops free of the gun.

FN 503
The short, 3.1-inch barrel is crowned to guard accuracy potential. The nitride finish protects against corrosion.

The FN 503 comes with very few controls. There is a slide-­stop lever serrated at both the top and bottom for use as a slide release, also. This lever doubles as the pistol’s takedown pin. A great many of the subcompacts on the market have slide stops with poor ergonomics, but the FN 503’s lever is elongated and easy to reach with a purposeful sweep of the thumb. In my opinion, it’s a better approach than the short and stubby levers that appear on many other competing models including the 509 series. The FN 503’s lever is streamlined and won’t hang-­up.

FN 503
Controls are minimal. Besides the trigger and interchangeable magazine release, the widest part of the 503 is the slide lock.

The sense of quality is reinforced by the grip texturing. The slab-­sided grip presents micro-­texturing on the sides and pronounced square checkering molded to the front and backstraps for better recoil control. Shallow channels along the top of the grip offer a landing place for the shooting finger and thumb.

FN 503
The grip is less than an inch wide. The texturing combination is molded, but aggressive. It results in excellent control.

The frame offers plenty of room for a thumbs-­forward shooting position, and while the almost flush-­fit six-­round magazine will leave most shooters’ grip with a pinky finger unsupported, the eight-­round magazine has enough to maintain confident control. Control of the pistol is improved when shooting with the extended eight-­round magazine inserted.

Concealed Carry, Range Tests, & Maintenance

When carrying, the FN 503 is almost indistinguishable from the popular G43, P365 and XD-­S. I toted the 503 in a belly-­band holster, as well as a generic nylon IWB holster, for weeks.

If you’re looking for maximum concealment, the FN 503 is a good choice. No matter your body shape or clothing, you can conceal the 503. With a bit of forward cant, even the thinnest, smallest shooter can pack this gun in summer dress. I’m also a fan of the black nitride finish for carry. Guns that receive this treatment hold up well to the daily effects of perspiration in my experience. To end my notes on concealing the 503, nothing jabbed, stabbed or dug at my body.

I’ll offer a bit of advice: Don’t leave the eight-­round magazine behind when you take your 503 to the range. Not only does the added capacity reduce the frequency of reloads, but it also offers more real estate to grip. My wife, for example, has relatively small hands. Even she couldn’t get a full grip on the gun with the six-­round magazine in place. The FN has a relatively low bore-­axis.

FN 503
The 503 comes with two magazines. The smaller is a more concealable six-rounder, and the larger is an extended eight-rounder that’s more comfortable to grip while shooting.

While you may not notice a few extra ounces while carrying, you will notice the weight when firing hot defensive rounds. A little extra heft makes recoil and muzzle rise more manageable, and the added grip area that the 8-­round magazine provides offers help in controlling the gun during rapid fire. The longer magazine also reduces shooter fatigue when firing string after string.

In terms of accuracy, the FN 503 is a standout, and it has everything to do with the trigger. While it doesn’t sport target sights, the 503 managed consistent groups measuring between 2 and 3 inches at 25 yards — even with its 3.1-­inch barrel! A few five-­shot groups produced 1.8-­inch groups, but that number is still awesome for any subcompact. The key word is “consistent.” The FN’s trigger provided a level of repeatability that created confidence with the gun.

FN 503
The 503 offers one of the finest triggers of any subcompact striker-fired handgun. It also features a trigger safety lever.

Guns owners will argue about all the nuances of every gun design. From sights to grip texture, to the angle and position of slide serrations. However, the FN 503 impressed G&A’s staff for its build quality, materials and reliability. Sure, the gun’s accurate, but more importantly it’s built well and functions predictably. Throughout our test, I fired more than 400 rounds from it. The 503 didn’t falter. There was no need to determine whether a stovepipe malfunction was the fault of the gun or the ammo, and no reason to record failure-­to-­feeds because there were none. Not even a failure to lock open, even after the last round was fired. About half of this test took place in the midst of a steady rain. With water dripping off the frame and muzzle, the 503 just kept running and grouping holes on paper.

Field stripping the 503 required removing the magazine from the unloaded gun, retracting the slide and aligning the slide-­stop lug and disassembly notch. It is then possible to pull the slide stop free and release the striker by pulling the trigger. This allows the slide assembly to move forward on the frame rails. Once the slide is free, the barrel and spring can be removed. The process isn’t cumbersome either. It’s easy once you understand the procedure, but strong hands and a review of the owner’s manual make the task faster and simpler.

FN 503

There are a few design features that I would change about the 503, but those come down to personal taste. For example, I wish the triggerguard’s undercut was more pronounced, and the grip was a bit wider. If this gun served daily duty as my defense pistol, I’d swap out the utilitarian thee-­dot sights. That is a feature that you can determine whether you like or dislike for yourself.

What can’t be accomplished as quickly is whether or not this gun will run the distance, but I’ll attest that it will. The 503 is a worthy addition to the FN family and fills a sensible gap in the brand’s recent history. It is not the first single-stack subcompact carry pistol to market, but it’s positioned to challenge the slim 9mm market. If you like shooting the FN 509, you’re going to love carrying the FN 503.

FN 503
Notes: Accuracy results are average of five, five- shot groups fired from 25 yards on a fixed rest. Velocity is the average of 10 shots recorded by a Shooting Chrony digital chronograph placed 10 feet in front of the muzzle.

FN 503

  • Type: Striker fired, recoil operated, semiautomatic
  • Cartridge: 9mm
  • Capacity: 6+1 rds.; 8+1 rds.
  • Barrel: 3.1 in.
  • Overall Length: 5.9 in.
  • Weight: 1 lb., 5 oz. (with unloaded flush-fit magazine)
  • Width: 1 in.
  • Height: 4.4 in.
  • Finish: Black nitride (steel)
  • Trigger: 5 lbs., 8 oz. (tested)
  • Sights: Three dot; front and rear drift adj. for windage only
  • MSRP: $550
  • Manufacturer: FN America, 800-635-1321, fnamerica.com

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