FN 503 Subcompact 9mm Pistol Review

The new 503 is FN's take on a popular 9mm handgun size.

March 25, 2021 By Keith Wood

During my three decades as a shooter, handgun trends have changed considerably. The passage of so-called “shall-issue” concealed-carry laws in most states has legalized the practice of carrying a concealed firearm for ordinary citizens. The 1970s and ’80s brought us large double-stack handguns with lots of firepower that became extremely popular. Folks learned quickly, though, that many of these large, heavy wonder-nines were unsuitable for everyday carry. On the other hand, existing compact handguns such as five-shot revolvers and .380 ACPs weren’t necessarily ideal for defensive use.

As the ranks of concealed-carry permit holders grew, so did the hunger for a better handgun solution. Though it took many years, that demand for lightweight, compact and concealable yet reasonably powerful handguns has led the way for a more recent trend: the single-stack 9mm subcompact. Among the guns in that category is the FN 503, a polymer-framed handgun built with concealment in mind.

Fabrique National is a relative newcomer to the modern subcompact 9mm scene, but this isn’t the firm’s first single-stack handgun. Though there were several models, the FN 1910, designed more than a century ago and chambered in .380 and .32 ACP, was arguably the most successful.

The company itself is more than 130 years old and has produced some of the most influential firearm designs in history. FN developed the groundbreaking P35 Hi Power 9mm, produced the legendary FAL battle rifle and has provided small arms and crew-served weapons to the U.S. military for many years.

Based in McLean, Virginia, and with a manufacturing facility in Columbia, South Carolina, FN America produces a variety of firearms for the domestic civilian, law enforcement and military markets. Though the company has an international reach, the 503 is built right here in the USA.

FN America offers numerous handgun variants, but the 503 is the smallest and most concealable of the lot, making it an attractive choice for concealed carry. Much of the 503’s design heritage evolved from the earlier FN 509, a handgun designed to compete in the U.S. military’s handgun trials five years ago.

The 509 is available in full-size/tactical, midsize and compact formats, with dimensional decreases along the way. Even the most compact of these handguns are double-stack designs, though, so the 503 is 0.25 inch narrower, 4.5 ounces lighter and 0.9 inch shorter than anything in the 509 series. Like all of the 509s on the market, all 503s are chambered in 9mm Luger only.

fn 503 — The controls on the FN 503 consist of a slide stop and magazine catch. Both were easy to reach and simple to operate.

The 503 is a chassis gun, meaning the polymer grip frame is just that: a grip that can be replaced without serial number problems. Presumably, this paves the way for OEM and aftermarket grip alternatives to suit different hand sizes.

The standard grip is comfortable and well designed, though the configuration puts the bore axis at a higher level than some of the 503’s competitors. Stippled panels on the sides of the grip offer good purchase, as does the pattern that is molded into the front and rear surfaces of the frame. The exterior of the pistol is devoid of any unnecessary sharp edges, which is a good thing on a carry gun.

The 503 ships with two stainless steel and polymer magazines; one holds six rounds while the other holds eight. With the more compact six-round magazine inserted, the shooter’s little finger rides below the grip.

The larger magazine uses a more generous base pad and allows for a full-fingered grip on the pistol. Clearing malfunctions can sometimes mean forcibly stripping the magazine out of a handgun, and the grip frame and base pad design on the 503 offer a positive surface to pull on if the need arises.

There is no manual safety on the 503, although there are numerous passive-systems included in the handgun’s design. A striker-block ensures the striker’s nose does not cross the plane of the breech face unless the trigger is pulled, effectively preventing the gun from discharging if dropped. The trigger disconnect prevents the trigger bar from contacting the sear if the slide is not into battery. More on that later.

Finally, a trigger safety prevents rearward travel of the trigger unless the center blade is depressed. It probably goes without saying that with all of these features in place I would not hesitate to carry this—or any other modern striker-fired handgun—in a secure holster with a round in the chamber. The 503 will fire without a magazine, another plus in the defensive-use column.

Since there is no safety lever, the controls on the 503 are simple and minimal. There is an all-metal trigger, a reversible magazine release and a slide stop. Both the mag release and slide stop were easy to reach and operate without shifting my grip.

The trigger on my sample broke at 5.25 pounds with a longish pull, which I don’t mind on a handgun with no manual safety, as it provides an extra margin of conscious action to fire. The reset is longer than one would expect and takes a little getting used to if you’re accustomed to something shorter. That said, I never missed a reset while shooting the 503.

The metal components of the 503, including the slide, are ferritic nitrocarburized, a finishing process better known as black nitriding. The finish is hard, durable and very resistant to corrosion.

The steel sights are dovetailed into the slide and use the same dovetail dimensions as the 509 series of handguns. The non-illuminated three-
dot sights are visible, rugged, snag-resistant and are drift-adjustable for windage. A half-moon relief cut is milled into the rear of the barrel hood, acting as a visual loaded-chamber indicator.

An external extractor is pinned into the slide and is actuated with a coil-spring imbedded within. This is one of the notable carryovers from the 509 series of pistols.

Internally, the 503 mirrors most common striker-fired designs. It uses a Browning tilt-barrel locking system, which has proven itself as reliable, durable and safe. The 1:10 twist barrel is ramped, and the chamber is fully supported.

A dual captive-spring recoil spring system, similar to that of other subcompacts on the market, rides on a full-length steel guide rod. Recoil was mild, likely due to this spring design. The metal chassis that is the core of the handgun provides a rigid surface for the integral frame rails.

In theory, the 503 can be fieldstripped without tools, though a small punch makes the task far easier. To take down the unloaded pistol, the slide is retracted until the half-moon notch on the slide is aligned with the slide stop. The slide stop can then be pulled, pried or pushed outward—the latter requires a small punch that can be fed through a hole on the right side of the frame.

With the slide stop removed, the trigger is pulled to allow the slide to come forward and away from the frame. Reassembly would be simple but for a pesky spring leg that protrudes behind the slide stop opening. I found that twisting the stop as it’s inserted solves this problem.

I tested the 503 with a wide variety of defensive and full-metal-jacket factory loads ranging in bullet weight from Super Vel’s speedy 90-grain solid copper hollowpoint to Hornady’s 147-grain Subsonic XTP.

Accuracy testing was conducted from a rock-steady benchrest that has proven capable of producing excellent accuracy. My results at 15 yards are available in the accompanying table and were about what one would expect of a subcompact pistol with a short sight radius. Most notable is the consistency of the accuracy; this handgun seemed to shoot all brands and loads into similar-size groups.

I experienced one persistent malfunction with the test sample, one that concerned me. During my third magazine through the gun, I experienced a “dead trigger.” I quickly determined the slide had failed to return to battery, stopping a fraction of an inch from its home. Since the gun was not in battery, the trigger disconnect feature did its job.

Assuming that this hiccup was part of breaking-in a brand-new gun, I bumped the back of the slide with my palm and continued shooting. Unfortunately, the problem worsened as testing progressed and did not appear to be ammunition or magazine-dependent. By the end of the test, I was manually returning the slide to battery after every shot—the gun effectively working like a single-action revolver.

At first, I was unable to diagnose or correct the malfunction. The gun was relatively clean and well lubricated, and all of the ammunition was from factory sources. I paid careful attention to ensure my hands and the rest were not interrupting the slide’s travel in any way.

Back at my shop, I stripped the 503 down and gave it a close inspection. With the barrel removed, I dropped several loaded rounds into the chamber and they slid in with no resistance.

After fiddling with the pistol for several minutes, I decided the recoil spring mechanism could interrupt the slide if the guide rod was not properly seated to the barrel lug. Hoping I’d found the culprit, I cleaned and lubricated the gun and reassembled it carefully.

Back on the range, I put several magazines of Winchester and SIG full-metal-jacket ammunition with zero malfunctions. I’ve not heard or read of this problem on other 503s, so it is possible that we just drew the short straw with this individual gun. A colleague of mine tested another 503, and his was 100 percent reliable. This is a great example of why any handgun, regardless of the reputation of the brand or model, should be tested extensively before being carried for defensive use.

Once the gun was assembled correctly, round after round went into a steel target at 15 yards, and I was finally able to appreciate its handling qualities. The sights were well zeroed out to 25 yards, which was the farthest distance that we tested the 503.

For a subcompact, I would rank the sights as above average in terms of my ability to acquire a fast and reasonably precise sight picture. The trigger had some rolling creep that didn’t seem to hamper performance, a common thread among many guns in this category.

As mentioned, recoil was relatively soft with all of the ammunition used. I found the 503 to be easy to shoot and simple to operate. Early reliability issues aside, I would not hesitate to carry this handgun for defensive use.

I had emailed the folks at FN to let them know I was having some problems. The response was admirable and immediate. In a period of days I had a shipping label emailed to me so I could return the pistol for one of the company’s engineers to inspect.

Type: striker-fired semiautomatic
Caliber: 9mm Luger
Capacity: 6-, 8-round magazines supplied
Barrel: 3.1 in.
OAL/Height/Width: 5.9/4.5/1.1 in.
Weight: 21 oz.
Construction: black polymer frame, black-nitride metal components
Grips: chassis-style polymer grip module
Sights: 3-dot drift-adjustable steel
Safeties: striker block, trigger disconnect, trigger lever
Trigger: 5.25 lb.
Price: $549
Manufacturer: FN America, FNamerica.com