FN 503 Subcompact 9mm Review

FDE FN 503 chambered in 9mm

Throwback to early 2020, and FN released their smallest handgun in decades: the FN 503. Geared towards conceal-ability, FN states that “compromises in shootability, accuracy, and reliability with slim CCW handguns are solved.” This pistol utilizes single stack magazines to give it a total width of 1.1 inches. The slim design makes concealed carrying easier and more comfortable than other large options. 

Coming in at 21oz, having a length of 5.9”, and height of 4.6” the FN 503 balances comfort-ability and shoot-ability well. Its small enough carrying isn’t quite as burdensome as larger options, but it still maintains a large enough frame for me to get a solid grip to control when shooting fast. Ergonomically, FN did about as good as one could do for a compact handgun. The slide serrations are deep enough to easily rack the slide with or without gloves. I am personally a huge fan of the texturing they use on multiple pistols in their lineup. The 503 utilizes aggressive texture where it needs to and molded-in mild texture the rest of the way around the grip. When shooting, I found this texturing to be more than adequate for a solid grip that doesn’t slip when firing.

Nice balance of textured and molded grip

This pistol comes with standard low profile white 3 dot iron sights which are tried and true. These sights utilize the same dovetail as the FN 509 series of pistols and are made from metal unlike those from some other manufactures in this space who use plastic “iron” sights.

A solid set of iron sights

The slide release is oversized to aid in easy activation. It feels good, and the lever works well. Coming straight out of the box the slide release was tough to activate, but over time this has smoothed up some to be what I would call reasonable. At first, my wife couldn’t activate it at all, but after a first-range session, she could occasionally release the slide one-handed with the slide release lever. If it was still too difficult, she would just rack the slide and be good to go. The more I have used this, the smoother it has gotten.

FN boasts their all-metal trigger in this 503 which supposedly breaks cleanly at 5.5lbs. The trigger’s contour feels good and pulls smoothly back into the wall. However once at the wall of the trigger, there is a decent amount of mush before the trigger actually breaks. I have not found my particular 503 to have a clean break like so many other reviewers have praised. The trigger in the FN 503 I received is very comparable to most other subcompact pistols on the market. Once the trigger breaks, there is a decent distance for a reset which leaves for more overall finger movement than I would like, but again comparable to other subcompact pistols. The best way to compare would be to find a local gun store that has multiple models in stock to try out for yourself.  

All-metal trigger

This 9mm was designed to contain beefier metal parts to reduce felt recoil. FN did a good job balancing the weight which helps tune down perceived recoil. While it still has a higher bore line than say the Glock 43, the FN 503 handles well. 

The standard magazine can hold 6 rounds while sitting flush with the bottom of the handgun frame. The 8 round magazine adds about half of an inch to the grip which is ideal for people willing to sacrifice a slight amount of conceal-ability for more rounds and a larger gripping surface. Both of these magazines are single stacked which allows the frame to be thinner. I found the 6 round mag to work without issue, but when trying to use the 8 round mag my wife had some troubles. After topping off the 8 round mag, she couldn’t rack the slide. I also found this to require way more force than normal. Racking the slide when downloaded to 7 rounds or with the fully loaded 6 round mag was no problem. However, when racking the slide with the 8th round in the force to overcome was substantial and almost more than my wife could physically do on a cold winter day. This issue has become much less troublesome throughout testing, and after loading the mag many times the springs have gotten worn in and work just fine. While not being too difficult for me, the fact that my wife couldn’t rack the slide when the 8 round magazine is fully loaded out of the box is worth being noted. It seems to have been resolved after about 150 rounds and loading/unloading 20ish times.

8 round magazine

During testing I had one round fail to go off which was with 124gr Magtech ammunition. It could have been a light primer strike or a hard primer. After re-chambering and pulling the trigger for a second time it went off. Looking at the picture, it seems the indent is plenty deep so I will attribute this to being a hard primer and bullet issue not something regarding the reliability of the FN 503.

Possible hard primer or light primer strike

While shooting 50 steel-cased Red Army Standard 115gr bullets, I had one stovepipe as seen below. Brass all worked without issue, so this may or may not be firearm-related. Steel cased ammo is known for being dirty and less reliable, but this is still noteworthy.

Stovepipe while using Red Army Standard 115gr steel cased ammo

The ejection pattern for the FN 503 was sporadic and landed anywhere from -10 degrees back over my left shoulder to about 80 degrees to the right (90-degree difference) for all of the different rounds I used. Most of these shells were landing on or near my right shoulder. Originally I found the slide to only lock back in an empty magazine about half of the time. Many times after firing the last round in a magazine, the slide would return back into battery instead of locking back on the empty mag. This did not improve as I continued testing. From 6 different brands and 4 different bullet weights, I consistently had issues with the slide locking to the rear. However, looking back on my two different range trips, I think I may have been riding the slide release with my thumb. I normally have a very high and tight grip, and with this compact handgun, this is more than probable.

I shot 6 round groups at 7 yards standing up unsupported in the cold and windy Oklahoma tundra. While my groups were not that impressive, I believe this pistol is much more capable than I was that day. The accuracy of this pistol is good, but the compact size of the 503 makes it harder to squeeze out every ounce of performance that this barrel is capable of. 

Top two left: Red Army Standard 115gr FMJ, Bottom two left: Blazer 124gr FMJ, top and bottom right targets: Magtech 124 gr. FMJ

The next range trip was a calm and warm day. I shot 8 round groups at 7 yards with a variety of well-known self-defense ammo options. I had no performance issues and was still happy with the accuracy provided by this 3.1″ barrel. The Hornady 100gr FTX, 124gr +P XTP, and 147gr XTP all performed well, but I seemed to get a few more flyers when shooting the 147gr. As I previously stated, this compact handgun makes it hard to squeeze out every ounce of performance, but for what it is, I will take it.

From left to right: Hornady 100gr FTX, Hornady 124gr +P XTP, Hornady 147gr XTP

Overall for the subcompact category, the FN 503 is a good contender. I personally am a proponent of carrying full-sized guns for concealed carry, but subcompacts have their place. After about a 100 round break-in period, some original reliability concerns have been dampened, and the 503 has been pushing on. The current MSRP for the FN 503 is $549 and you can read more about it here.


  • CALIBER: 9mm
  • OPERATION: Striker fired
  • MAG CAPACITY: 6 or 8 Rd.
  • WEIGHT: 21 oz.
  • TWIST RATE: 1:10 RH
  • HEIGHT: 4.6″
  • WIDTH: 1.1″
  • TRIGGER PULL: 5 – 7 lb.

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About the author: Mitchell Graf is passionate about hunting and competition shooting. During college he was the shooting instructor for Oklahoma State’s Practical Shooting Team, and these days he spends as much time as he can chasing after pigs and coyotes with night vision and thermals. You can follow Mitchell’s adventures over at his Instagram @That_Gun_Guy_

{ 4 comments… add one }
  • Tony May 13, 2022, 6:51 am

    While this is typical great FN build quality, it was 10 years out of date when they brought it to market.

    It is, essentially, a Springfield XDs package. Just built by FN.

    When the XDs came out it was very innovative, but times have changed and newer, better, higher capacity, smaller, guns have been released since the XDs.

    We had one in the shop for a year and eventually sold it at cost just to get it out the door. No one wanted it.

  • Mario May 9, 2022, 5:47 pm

    When you think about how much thought S&W, Sig, and Ruger have put into their entries in this category, it sure seems like FN mailed it in.

  • Jim May 9, 2022, 3:28 pm

    Looks good, but I’ll stick with my Bond Arms Bullpup 9. I still have to be careful of the ammo I use, but have the same barrel length with a shorter overall length. 7 + 1 is enough ammo with a spare mag.

  • Doug May 9, 2022, 12:36 pm

    I like my Ruger EC9s better, carry’s more rounds with both the standard mag and the extended mag, looks like it’s slimmer too. The FN 503 does have nice looking sights, the one and only draw back I see in my EC9s, I really wish my Ruger had night sights on it, my Taurus G3C has the factory night sights and I like them a lot.

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