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Review of FN 509 Midsize and Compact MRD: Excellent Carry Guns

The FN 509 pistols, specifically the Midsize MRD and the Compact MRD models, are two great 9mm pistols for concealed carry. The “MRD” stands for “Micro Red Dot” as both models come with the company’s patented Low-Profile Optics Mounting System for mounting reflex optics.

Size Comparisons

The FN 509 Midsize MRD with its four-inch barrel and full grip frame is roughly the size of a Glock 19. But it’s more contoured, not as blocky as the Glock. The 509 Midsize comes with two 15-round magazines.

The FN 509 Compact MRD is fitted with a slightly shorter 3.7-inch barrel. It’s roughly the size of a Glock 26. It comes with one 12-round mag and one 15-round extended mag.

Ten-round magazines are available for both guns. FN’s 17- and 24-round mags will work too and grip spacers are available for those longer mags.

The length of the grip on the Midsize model is just .4-inch longer. But it makes for the biggest difference between the two pistols when it comes to handling characteristics.

The FN 509 Midsize MRD (top) is about the same size as the Glock 19. The FN509 Compact MRD is about the size of a Glock 26.

The extended floorplate on the Compact allows me to get my pinky finger on the grip. But the longer grip on the Midsize just feels more comfortable to me.

These Two Pistols Have Lots In Common

That being said, other than the slight size differences, these FN 509 pistols are more alike than different. Both are polymer-frame, striker-fired semi-autos. And both feature bilateral slide stop and magazine release levers.

These pistols have large, reliable external extractors that poke out just enough when a round is chambered to serve too as visual and tactile loaded chamber indicators.

Both have forward and rear cocking serrations on the slide. Each comes equipped with black metal high-profile sights. The sights are high enough to use should your reflex sight fail. 

While they co-witness, their black finish doesn’t distract you when using a red dot sight.

Each features a very usable MIL-STD 1913 accessory rail, not just a rudimentary add-on that’s just for show. I tried my Streamlight TLR-8 light/laser combo on each of them as well as a Crimson Trace CMR-209 Rail Master Universal Pistol Light. Each fit well on these pistols.

The barrel on each pistol is cold hammer-forged and features a recessed crown with polished chamber and feed ramp. I’ve yet to experience any type of failure after 100’s of rounds through each gun.

The pistols are available in matte black or with an FDE (flat dark earth) slide and frame.

Each pistol comes in a soft-sided case with two magazines and an interchangeable backstrap panel.

Unique Mount Keeps Optics Low

FN’s reflex sight mounting system eliminates the need for adaptor plates that run the full length of the slide cut. The cut in the slide actually is a two-tiered setup. Several small adaptors are included for use with your optic of choice. They look like small puzzle pieces. You place one in the lower part of the slide cut.

Then, you attach the reflex sight directly into the slide. You’re not fastening a plate to the slide and then the sight to the plate. The FN system is very strong and it keeps the sight closer to the line of the bore.

Burris Fastfire 3 For The FN 509 Midsize

For the FN 509 Midsize pistol, I chose the Burris Fastfire 3. It’s very compact. My sample came with a large 8 MOA red dot that proved to get my gun on target quickly at close range. The sight is available with a 3 MOA red dot as well.

The Burris Fastfire 3 has a single control button. It’s used to power it on or off and to cycle from the auto brightness setting through the three manual brightness settings.

One CR1632 battery powers the Fastfire 3 for up to 5,000 hours of run time.

The author mounted a Burris Fastfire 3 to the FN 509 Midsize. Its large 8 MOA red dot was fast to acquire at close range.

The unit shuts down automatically after nine hours of inactivity. A good feature is that you can access the battery compartment from the top of the unit without the need to remove it from the pistol. The price on this sight is $240.

Truglo Tru-Tec Micro For the FN 509 Compact

I chose a TruGlo Tru-Tec Micro red dot for use on the FN 509 Compact. It has a 3 MOA dot. This sight has no automatic brightness mode. No loss there. I normally find the auto mode too bright with many sights.

The TruGlo does have 10 manual settings, however. So, you’ll have no trouble finding a setting that’s bright enough to acquire quickly without being too bright, fuzzy and distracting. When you power it on, it reverts to the last setting used. 

This sight features a good sized window for a large field of view. Naturally, I found the smaller dot to be more precise for longer shots.

My sample was compatible with RMR-style mounts. It also came with a Picatinny rail mount for use on a long gun. Another model comes with a 45-degree offset Picatinny mount. The sight is available too with a green dot.

The sight runs on a single 3-volt CR2032 lithium battery. It shuts down automatically after four hours of inactivity. The MSRP for the Truglo Tru-Tec Micro is $235.99.

The TruGlo Tru-Tec Micro sight the author mounted on the FN 509 Compact proved to be an excellent sight.

Carrying In Muddy River Tactical Holsters

While attending a media event for the FN 509 Compact MRD, we all carried the small pistols in an outside-the-waistband rig from ANR Design Kydex Holster, paired with their single mag carriers for spare magazines.

This setup worked well, but I generally prefer to use an inside-the-waistband holster when carrying concealed. The selection of holsters isn’t as great for these FN pistols compared to some other brands. That’s especially true when you factor in that you want an IWB holster for a gun that also has an optic mounted on it.

I turned to Muddy River Tactical. I use one of their rugged water buffalo leather rigs regularly for one of my other pistols. This time, I chose two of their custom-molded Kydex holsters.

Their tension is adjustable. So too is the cant to some extent. They’re available in a variety of colors with several attachment options. Service is great and turn-around is fast.

In working with these pistols, I found the holsters to be well made. They held the guns securely, while allowing for comfortable carry and quick access.

The author chose Kydex inside-the-waistband holsters cut for optics from Muddy River Tactical for the FN pistols. The company also makes great holsters of water buffalo leather.

Both FN 509 Pistols Performed Well

Both pistols performed very well at the range. Function was flawless with both full metal jacket and hollowpoint ammo. With a small pistol such as the FN 509 Compact, I normally do my accuracy testing at 15 yards from a rest. 

This was no challenge for these pistols. Group size ranged from 1.0 to 1.75 inches.

Off-hand the pistols were fun to shoot. I find the double-stack pistols normally spread the recoil better and don’t torque in your hand the way some single-stacks want to do. There are usually more magazine options for the double-stacks too. Yet, don’t think for a minute that these pistols are too fat to conceal. They measure just 1.35 inches wide.

Both FN pistols feature ambidextrous slide lock and magazine releasse levers.

Which One Should You Choose?

If you want an accurate, reliable pistol, but favor a short grip for concealment, the FN 509 Compact MRD might be the way you lean. And the Compact shoots great.

I personally favor carrying a slightly larger gun simply because I shoot them better. And I have no trouble dressing accordingly to conceal the FN 509 Midsize MRD.

To make the decision easier, I bought them both. It looks like I’ll be keeping the Midsize.

My son – who followed in the “family business,” namely law enforcement – will probably latch on to the Compact.

The FN 509 Midsize ships with two 15-round magazines (shown), while the FN 509 Compact comes with a flush-fit 12-rounder and one extended 15-rounder.

Key Features: FN 509 Midsize MRD and FN 509 Compact MRD

Model: FN 509 Compact MRD

Type: Striker-fired semi-auto pistol

Caliber: 9mm Luger

Magazine Capacity: 12 and 15 (10, 17, and 24-round magazines available)

Frame: Black or FDE polymer with full accessory rail

Slide: Optics-ready

Barrel: 3.7 inches

Overall Length: 6.8 inches

Height: 4.8 inches (with 10-round magazine)

Width: 1.35 inches

Weight: 25.5 ounces

Sights: Suppressor-height metal sights

Sight Radius: 5.6 inches

MSRP: $799

The FN 509 Compact comes with a cover plate for the slide in case no optic is used.
The FN 509 Compact MRD comes with the hardware needed to mount several brands of optics.
The FN 509 Midsize MRD sells for the same price as the Compact model and offers a slightly longer grip.
The FN 509 Midsize MRD is sized right for an all-around carry gun.

Model: FN 509 Midsize MRD

Type: Striker-fired semi-auto pistol

Caliber: 9mm Luger

Magazine Capacity: 15 (10, 17, and 24-round magazines available)

Frame: Black or FDE polymer with full accessory rail

Slide: Optics-ready

Barrel: 4.0 inches

Overall Length: 7.4 inches

Height: 5.2 inches

Width: 1.35 inches

Weight: 26.5 ounces

Sights: Suppressor-height metal sights

Sight Radius: 5.79 inches

MSRP: $799

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