NEW FN 509 Midsize Review – Contender to the Throne?

The FN 509 Midsize, FN’s new 15-round do everything pistol.

FN has launched a new version of the FN 509, this time in a midsize package that will compete directly with the Glock 19. Does the FN 509 Midsize have a chance at taking on the champ? I think so.

The Elephant In the Room

First, why do I think the FN 509 M has a strong chance at competing with the well established Glock 19?

Using Brownells prices, the FN 509 M should come out to $559 on Brownells, $20 less than the Standard 509. A Glock 19 with metal sights is $599.99 as a point for comparison. We are $40 cheaper on the FN 509 M, throw in a mag and you are within a few dollars of the Glock and get real ambi-controls, forward serrations, and a nice zippered case.

There are some other things to consider like the much larger Glock aftermarket and magazine costs, but for professional users, those won’t be much of a factor. The aftermarket should grow quite quickly as it did after the FN 509 Tactical’s release. That said, there already is a great trigger on the market and more stuff coming out fast for the FN pistols.

All of that said, the FN 509 Midsize is a touch larger than the Glock 19. While the size is something that should be mentioned, it isn’t noticeably larger.

FN 509 Midsize First Look

The new FN 509 Midsize is almost identical to the FN 509 released at back in 2017 with the exception of the 15-round capacity and some other small parts. Same 4″ barrel, same glow in the dark metal sights, same trigger.

The new FN 509 Midsize in front of a Tactical and Standard FN 509.

I do have 1,200 rounds through the gun though, so at least I can tell you what I think of the pistol. I do want to mention my largest gripe about the gun, the lack of FN’s excellent optics mounting system. More on that in the conclusion.

The FN 509 M uses standard glow in the dark 509 sights.

The FN 509 M starts to step away from the standard FN 509 when you look at the shorter frame with some enhancements, 15-round magazines, a reduced power recoil spring, and the same slide release found on the FN 509 Tactical.

Original FN 509 slide release on the frame stippled by TXT Custom Gun Works, the new Midsize on the left in stock form.

What most people are going to focus on is the shorter frame, and rightly so. Some people have had issues concealing the full-size grip of the Standard FN 509, the Midsize frame is only a touch shorter, but makes a world of difference.

The FN 509 Midsize is on par with the Glock 19’s frame size.

Internally the new Midsize is identical to the full-size pistol and retains full parts compatibility. All of that long-term testing that I have done with both the FN 509 Standard and the Tactical models apply to the Midsize, I expect the same kind of performance without question.

One of the most important changes to the pistol is a redesigned frame that is not only shorter but also addresses the complaints that some had with the FN 509 Standard’s sometimes stiff magazine release. FN accomplished this by reshaping the fence around the magazine button so it is easier accessed.

The reshaped fence around the magazine release compared to the standard frame.

The reshaped fence around the mag button means that the FN 509 Midsize can use the standard 509 mag release without the issues some saw on the standard.

Tactical mag release on left, Midsize center, Standard right.

FN also used the yellow reduced power spring that ships with the FN 509 Tactical to make the pistol easier to rack. No worries though, FN tells me that they see similar lifespans on the two spring weights as long as you are shooting ONLY +p ammunition. While I will talk more about it in the shooting section, the pistol no longer feels oversprung with 115-grain ammunition like the Blaser Brass Black Pack ammo I have a ton of.

The FN 509 Midsize slide detail stripped next to a detail stripped FN 509 Tactical slide.

The magazine is nearly identical, the only difference being the mag spring length, baseplate, and length of the magazine body.

FN 509 Standard/Tactical mag on the left, FN 509 Midsize on the right.

One of the things that I feel the FN 509 series did exceptionally well was slide serrations. The Midsize is no different and shares the same grippy, but not overly sharp front and rear serrations that are dang near as good as those found on an ATEi Dougified pistol.

The 509 probably the best slide serrations on the market. Also, notice the lack of the optics mount that should have been an option.

If you are curious if there is a threaded barrel that works with the Midsize for suppressors or compensators, you are in luck. The Tactical’s barrel fits into the Midsize without issue since the slide shares internal dimensions with all other current 509 models.

A quick swap of barrels allows the use of suppressors or compensators.

Like the other 509s, the Midsize uses interchangeable backstraps. I seem to prefer the flat backstrap personally, but you do have the option of a curved one that bulks the grip up a bit for those with larger hands. I do wish that FN included a tool for this as many won’t have a punch that is long enough or a punch at all.

Interchangeable backstraps are easy to swap out.

Slide/Frame & Magazine Compatibility

I am sure this is a question that you are asking yourself if you happen to own an FN 509 already, the answer is yes you can swap slides around. I function tested this with 200 rounds, 150 was FMJ Blazer Brass 115-grain with the last 50 being 124-Grain +p Federal HST.

The FN 509 Tactical slide not only fits but functions perfectly as well.

I will caution the use of 17 or 24-round magazines in the FN 509 Midsize at this time. The 509 series of pistols use either the baseplate of the magazine or the spacer sleeve to prevent over insertion. While you might not think this is a big deal, it can cause serious damage to your firearm.

Notice the gap on the Midsize frame, this can cause damage to your firearm.

If you look closely at the rear slide rails, you see that the Midsize on the left has an upward cant. This can cause the slide rails to bind in the slide as well as cause damage to the ejector. Like previously mentioned, this is because magazine over-insertion is prevented with the floorplate or spacer sleeve. The easy solution is to use magazines designed for the Midsize for the time being, sleeves for the 24-round mag will be coming soon according to FN.

The reason that you don’t see this on some other guns like Glocks is their magazine has an over-insertion stop built into the body of the magazine preventing over-insertion with an internal frame feature.

The result of using a magazine that does not have a means of preventing over-insertion can cause the sear housing and ejector to tilt up.

Replacing The Trigger After 500 Rounds

While there is nothing wrong with the stock trigger, why not replace it with an improved one when you have one laying around? I just so happen to have an Apex FNS trigger that I hadn’t installed in my early run FN 509 Standard and figured what the hell, why not. We reviewed the Apex FN 509 trigger a while back, you can read it here.

The stock trigger after a single 200-round range trip was only 5 pounds 6 ounces, hardly heavy. I find the factory trigger to be rather shootable but do like the Apex more if given the choice.

Stock trigger pull was 5 pounds 6 ounces.

With the flatty installed the trigger weight was now 4 pounds 6 ounces with a much smoother takeup, more positive wall, crisper break, and shorter reset.

Trigger pull after the Apex flat trigger was installed was 4 pounds 6 ounces.

What You Get In The Box

FN ships the 509 Midsize with a spare backstrap to give you the choice of curved or flat like were included with the original 509. The zippered pistol case is the same one that FN has been shipping for some time, same with the lock. You also get a second magazine and a sticker.

Stickers are cool, right?

What you get with the new FN 509 Midsize.

Shooting The FN 509 Midsize

With over 1,200 rounds down range with the FN 509 Midsize and not a single malfunction, I can say that the Midsize is every bit as reliable as the standard FN 509. I don’t feel as though I lose any control over the gun with the shorter grip, especially when shooting quickly. I would like to replace the sights or more likely, have ATEi mill the slide for an RMR since the three dot sights are functional, but easy to outrun.

I don’t know why, but the FN 509 Midsize really agreed with me on the range. Both groups shown below were shot unsupported, in a standing position. No Ransom Rest here, I wanted to know what the gun would so in my hands. That said, I spent a metric ton of time at the range shooting B8 repair centers at 25-yards using as many ammo types as I could find in my stash. Normally I don’t do accuracy testing since it isn’t really telling without a Ransom Rest and every type of ammo you can find, but what the heck.

The 10-yard groups were pretty impressive, the best group being on par with most pistols in this segment. Surprisingly, the 1.725″ group was shot with 115-grain Blaser Brass Black Pack ammo. You know, the cheap stuff.

Other 10 round groups at 10-yards were 1.976″ with S&B 124-grain FMJ, 2.135″ with Federal HST 147-grain JHP, and 2.773″ with Winchester 9mm NATO 124-grain.

10 rounds fired at 10-yards with the FN 509 Midsize

As I mentioned, most of my shooting with the FN 509 Midsize has been at 25-yards and most of it has been about what I would expect from a modern service pistol, with the group below being the exception. Everything else that I shot through the 509 M produced good, but not as stellar groups. Federal 147-grain HST JHP produced a 4.395″ 10-round group at 25-yards, Blaser Brass 115-grain gave me a 4.895″ group at 25-yards, and the 124-grain S&B being the worst at 5.083″ at the 25-yard line.

The best group was shot with Precision Delta PDP Pro 124-grain JHP at 3.163″. Sadly I only had 10 rounds of it left, I would have liked to shoot more of it to see if it was a fluke with this gun. I do know that the PDP Pro is extremely accurate in other guns that I have shot it in, but over a 1″ improvement at 25-yards is nothing to sneeze at.

The best 25-yard group from the FN 509 Midsize.

Carrying The FN 509 Midsize

Once I had about 600 rounds through the gun and had function checked it, I sent a message to my friend Jon at PHLster and asked him if he had a Spotlight I could buy for the FN 509. The PHLster was a natural choice since I normally carry a Glock 19 with a TLR-7 in a Spotlight (If you would like to read the PHLster Spotlight review it can be found on Firearm Rack) with an Ares Gear Aegis Enhanced belt.

While the holster is a bit longer than I prefer, the gun carried well and I didn’t have much issue concealing it thanks to the shorter grip. In the past, I would struggle with keeping the gun from printing as a result of the full-size grip. Not anymore.

My FN 509 Midsize in a PHLster Spotlight.

Once I function checked the FN 509 Midsize with the Tactical slide and barrel, I swapped slides since I prefer a red dot on my carry gun. Once I get the slide cut for an RMR or get an optics ready slide, the gun will get its own slide back permanently.

The Frankin509 as it is carried.

Once the holster is on, you would never know I was carrying a 4″ gun with 16-rounds of 124 +P Federal HST with a 15-round reload. Is this setup comfortable for long hours sitting? Sorta.

As you can see, the 509 M, Surefire X300 Ultra, and holster all disappear under my shirt.

Truthfully I would have preferred a holster that was no longer than the gun, preferably for a Streamlight TLR-7. Why? simply put because I am a shorter guy that has less vertical real estate to stuff a gun. The good news is that Henry’s Holsters is currently finalizing an FN 509 holster that not only mimics the Spotlight in many great ways but also has the potential to be better for me personally because of the shape of the built-in wedge Andrew uses.

Make sure to look into Henry’s Holsters, they are great people and make some seriously good holsters. I imagine the FN 509 / TLR-7 holster will look a whole lot like his Glock 19 / TLR-8 holster if I had to guess.

The Aegis Enhanced belt does a great job at keeping the gun well supported.

Final Thoughts

I really like the FN 509 Midsize a lot, but I have been a fan of the 509 platform since the first time I got the gun on the range and really wrung it out. I guess it isn’t much of a surprise that when FN introduces the pistol that I was longing for from the start, I am going to like it. Could I be a bit bias? Maybe? The fact remains that it is a pistol that has far better features than the Glocks I normally gravitate towards, shoots better, and frankly has a better aftermarket trigger option than anything that I have felt on the Glock platform.

I have two gripes about the FN 509 Midsize, the first being magazine cost. With 509 mags north of $40, that is going to be offputting to most consumers. I really wish that either FN included a one or two more mags from the factory or more preferably, dropped the price of the mags to the low to mid $30 range. My second giant gripe is that for whatever reason, FN didn’t launch an optics ready variant of the Midsize. It isn’t like it would have been hard to do since the FN 509 Tactical Black was introduced at the same time (I decided I didn’t want to review a new color) and all they really needed to do was pop the non-threaded barrel on the tactical slide. Instead of two SHOT releases, they could have and probably should have had three, if not four had tan also been an option for the Tactical Timmys out there.

All of that said, I fully intend to buy at least one FN 509 Midsize, possibly two since I like the idea of having a duplicate of my carry gun. They will go to ATEi so Doug can work his magic sinking a red dot as far into the slide as possible. Seriously, the guy is a wizard.

Everything about the gun tells me that if there was a gun that actually had a chance at being a “Glock killer,” it’s the FN 509 Midsize. Not only does it check all the boxes and then some, but it is also built by a brand that has just as much attention from LEOs as Glock does. Other pistols have been in the position to overtake Glock but have had their fair share of problems, I don’t think that will be an issue with the FN 509 Midsize.

The Fn 509 Midsize is currently available at FN dealers and carries an MSRP of $649, a bit cheaper than the 509 Standard’s MSRP. I fully expect the pistol to street for about what the Standard 509 is currently selling for, if not a few dollars less.

Find more information on the FN America website.

About Patrick R.Patrick Roberts

Patrick is a firearms enthusiast that values the quest for not only the best possible gear setup but also pragmatic ways to improve his shooting skills across a wide range of disciplines. He values truthful, honest information above all else and had committed to cutting through marketing fluff to deliver the truth. You can find the rest of his work on as well as on the YouTube channel Firearm Rack or Instagram at @thepatrickroberts.

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JP Jones

Gen 4 Glock 19 ships with 3 magazines. There’s your $40 difference in MSRP. I like the FN 509 also, but am sceptical that it will over take the G-19 as the best selling pistol in the free world.