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FN 509C MRD Review

The new FN 509C MRD compact checks every box in today's semiauto pistol market.

FN 509C MRD Review

The 509C MRD comes with a 12-round magazine with finger hook as well as a 15-round mag with grip sleeve. Arched and flat backstraps are included.

If there is an official industry list of hot trends in pistols, FN’s new 509C MRD checks every box. It’s a striker-fired, polymer-frame 9mm with an accessory rail; it’s the right size for concealment; it’s red-dot ready; it comes with interchangeable backstraps; and it’s available in black and a color other than black.

The newest version of FN’s 509 pistols series, the 509C MRD is a compact pistol (hence the “C” in its designation) that’s capable of mounting a mini red dot (hence the “MRD”). It’s smaller than the original duty-size 509 but not subcompact-small because FN wanted this pistol big enough to accommodate any slide-mounted optic and any standard weapon light.

The original 509—which started out life as a submission for the U.S. military’s Modular Handgun System contract—had a four-inch barrel and a frame long enough to accommodate a flush-fitting 17-round magazine. It was followed by the 509 Tactical that had an extended threaded 4.5-inch barrel and then the 509 Midsize, which combined the original’s four-inch barrel with a shorter frame that took flush-fitting 15-round magazines.

The new 509C MRD pairs a 3.7-inch barrel with an even shorter frame. The frame on the 509C MRD is roughly a half-inch shorter than that of the full-size 509. It comes with two magazines. The shorter magazine has a finger-hook extension and holds 12 rounds; the extended 15-round magazine features a grip sleeve. FN also offers 10-round magazines for those living in restrictive states.

I wish they offered a true flush-fitting 12-round magazine for this pistol because the finger-hook extension makes it nearly as long as the 15-round magazine and is only slightly more concealable. However, the pistol accepts any 509 magazine, including the extended 24-rounders.

You’ll see a three-slot Picatinny rail on the front of the pistol, and the engineers at FN went with a 3.7-inch barrel in part because this made the pistol and its rail long enough to accommodate every common full-size handgun-mounted light on the market.

The 509C MRD can be had either in black or flat dark earth. As mentioned, the frame features interchangeable backstraps, and you get two with the pistol: one flat and one arched. There is not a huge size difference between the two, but there is some.

The 3.7-inch barrel is cold hammer forged. The slide has aggressive, flat-bottomed serrations front and back for a sure grip in all situations. With the 12-round magazine in place, this pistol is 6.8 inches long, 1.25 inches wide (at the slide release) and 5.1 inches tall. Weight is 25.5 ounces.

Both the magazine and slide releases on the 509 are ambidextrous, steel and black. On the FDE model, the color contrast between the small black parts and the FDE frame and slide looks very nice.

You’ll notice the frame and slide aren’t exactly the same color on the FDE model. Trying to color match polymer and PVD-coated steel is almost impossible, so FN deliberately goes for a two-tone look. The frame is FDE, whereas the slide is darker, almost bronze.

The 509C MRD has four safeties, although only the trigger safety lever is externally visible. The remaining three are a striker block, drop safety and trigger disconnect safety.

The trigger is hinged to provide insurance against an accidental discharge if the pistol is dropped, and it’s here you’ll see another difference between the 509C MRD and previous models. Listening to user suggestions, FN has reshaped the trigger so it has a flatter face. This is supposed to provide the user a little more control.


With the 509C MRD, FN has changed the trigger profile to more of a flat face, although Tarr thought the pull was excessively heavy. The black controls contrast nicely with the flat dark earth finish.

While I really like the looks and features of the 509C MRD, the only thing I don’t like about the 509 series is the trigger pull. Of all the newer polymer-framed striker-fired pistols on the market, its trigger pull is just about the heaviest—with the official specs calling for a pull between 5.5 and 7.5 pounds.

The pull on my sample was 6.75 pounds, but by the time I weighed it I’d already put more than 500 rounds through it at a media event, and I’m sure it lightened up and smoothed out with that use. A lot of people don’t notice or care about a trigger this heavy, but this is an FYI for those of you who do.

A nice, padded, zippered case that has an internal pocket large enough for a spare magazine ships with the pistol. You also get a plastic blister pack with 12 pouches containing everything you need to mount the red dot of your choice on this pistol, including a reference guide to let you know which plate works with which optic.

FN’s MRD optics mounting system allows you to mount the red dot directly to the slide of your pistol, which is a more reliable system. The company provides different adapter plates and the necessary screws, but the screws securing the red dot go straight from the optic, through the adapter plate, into the slide. The plates exist solely to mate the profile of the red dot to the profile of the slide and are just sandwiched between the red dot and slide.

The pistol’s adapter plates mount directly to the top of the slide, and the gun comes with plates and screws to accommodate most popular red dots.

The adapters fit the three most common mounting patterns and allow you to direct mount at least 10 different optics, pretty much everything on the market except for the new Aimpoint Acro P-1. FN has a separate adapter available for that optic.

To introduce its new pistol to the media, FN invited several gun writers to Oak Grove Technologies in Hoffman, North Carolina, to attend an all-day training seminar put on by Sage Dynamics, a well-known and respected tactical training group. While I first shot a red dot-equipped pistol back when Bill Clinton was president and have run them competitively quite a bit, I’ve never had any formal training on how to employ a red dot-sighted pistol defensively. I found the experience enjoyable and instructive.

Prior to hitting the range, we mounted red dots on our pistols. We had our choice of Holosuns, Trijicon SROs and Aimpoint Acro P-1s, and I chose one of the latter. We also mounted Streamlight weapon lights on our guns and were provided holsters that accomodated the lights. We used the iron sights as reference when rough zeroing the red dots in the classroom.

FN states that the iron sights “co-witness” with the red dots, but my experience was that while you could use the iron sights through the very bottom of the red dot’s window, I don’t consider it a true co-witness setup because your irons are nowhere near the center of the optic window. You can drift the rear sight in the dovetail to adjust your windage, but that’s it.

The barrel length is such that there’s enough room on the frame for a rail that can handle all common lights/lasers. The tall sights can be seen through the red dot but don’t truly co-witness.

This training class was not fluffery. We began shooting around 11 a.m. and finished around 9 p.m., taking breaks only for meals and water. We started by zeroing our pistols at 25 yards to make sure they were on at distance, then moved up closer to the targets.

Most of our shooting was done at realistic defensive distances, from three yards to 10 yards. Some of it was minute-of-bad-guy speed shooting, while other drills involved precision shooting, such as aiming for the eyebox of the silhouette target.

I found the texturing on the pistol was more than aggressive enough for all situations, although the trigger’s heavy pull was a handicap to pinpoint accuracy. I had no problems operating the controls of the pistol even with tired hands and shooting in the dark.

The instructor demonstrated a simple draw stroke that he found helped people get on their dot quicker and more consistently. He preached, “Bring it up to your nose and push it out.”

I also learned you don’t need tritium night sights when you’ve got a red dot because it works in all lighting conditions, although I discovered that with a 25-yard zero, at three yards your shot will hit about an inch low.

While this article is about the new FN pistol, I did learn or relearn a few other things about red dots. A few of the sights, which were brand new, experienced wandering zeroes, and one wouldn’t turn on at all.

Our Sage Dynamics instructor was a huge proponent of red dots on defensive handguns, but even he admitted he’d had every brand and type of red dot on the market either break or had the batteries die unexpectedly—and this is a guy who meticulously maintains his equipment. Definitely something to keep in mind if you’re buying any red-dot-capable pistol and plan to use such a sight on a gun you’re betting your life on.

For accuracy shooting back at home, I mounted a Trijicon SRO on my sample pistol. This red dot has a large window, which helps you more quickly reacquire that dot as the pistol comes down out of recoil, something increasingly important when you’re shooting a compact pistol with more muzzle jump. The larger window of the SRO overhangs the ejection port of the pistol a bit, but I didn’t experience any problems, and neither did any of the people running them at the Sage Dynamic class.

I did most of my shooting with the larger backstrap, and even with that in place, the grip of the 509C was not large. With the smaller backstrap installed, the back of the grip feels a little flat to me, but because it is so aggressively textured once you pick the backstrap that fits you, the gun won’t move in your hand when shooting. And I preferred the feel of the extended 15-round magazine with its grip sleeve, but that’s really no surprise. Bigger grips are more comfortable to hold and shoot.

There are three different kinds of texturing on the frame of the 509C, and the resulting surface is very aggressive.

Being a “compact” rather than a subcompact pistol, this is not anywhere close to a pocket gun, especially if it’s wearing a red dot. You’ll need a holster, a good belt and a covering garment, but its size also means that it handles and shoots better than a tiny pocket gun or even a subcompact.

The precision of the SRO’s 2.5-m.o.a. dot was offset by my pistol’s near seven-pound trigger pull, but at the FN event I was still able to do a fist-size group at 25 yards, bent over, while shooting off someone’s unsteady backpack.

While I prefer a flat-faced trigger, it provides only a slight advantage, perhaps equivalent to half a pound off your trigger pull. Running this pistol at speed was more about how fast you could work the trigger than trying to muscle the gun because it is large enough for just about everybody to get their entire hand on—even with the shorter magazine.

Spoiled gun writer whining about heavy trigger pulls aside, the 509C MRD is more than accurate enough for defensive use and holds sufficient ammo to get the job done. Considering I observed no malfunctions with my gun or the others fired at the class—going through 5,000 rounds in all—the design has proved itself to be eminently reliable, which is the most important consideration in a defensive pistol.

With its tall black sights the 509C MRD is obviously intended to be wearing a red dot, and FN’s optics mounting system is as good or better than anything else on the market. The rest of this pistol is just as tough, as you would expect from FN, whose tag line is “The most battle-proven firearms.”

Reliable and small enough to conceal but big enough to shoot comfortably, capable of direct mounting a red dot and a full-size pistol light, the 509C MRD seems to me to be the ideal pistol for those people who want the option of a red-dot carry gun.

Notes: Accuracy results are the averages of four five-shot groups at 25 yards from a sandbag rest. Velocities are averages of 10 shots measured with an Oehler Model 35P 12 feet from the muzzle. Abbreviation: JHP, jacketed hollowpoint

FN America 509C MRD

  • Type: striker-fired semiauto
  • Caliber: 9mm
  • Capacity: 12-, 15-round magazines supplied (where legal)
  • Barrel: 3.7 in. stainless steel
  • OAL/Height/Width: 6.8/5.1/1.25 in.
  • Weight: 25.5 oz. w/12-round magazine
  • Construction: flat dark earth polymer frame, flat dark earth PVD-finished carbon steel slide (as tested)
  • Sights: tall black front and rear; adapter plates for red dot mounting
  • Trigger Pull: 6.75 lb. pull (measured)
  • Safety: trigger lever, striker block, drop, trigger disconnect
  • Price: $799
  • Manufacturer: FN America,

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