FN 509 Midsize MRD: No Rounds Fired Non-Review

FN 509 Midsize MRD: No Rounds Fired Non-Review
FN 509 Midsize MRD: No Rounds Fired Non-Review

USA – -(AmmoLand.com)- I have to be upfront, I have not pulled the trigger on FN 509 Midsize MRD with a round in the chamber yet. How could I possibly write a review of a pistol that I have never shot? Pretty easily it turns out. Heck, I can even review the FN 509 Midsize MRD as though I have had months of time carrying and shooting one.

The three things I hope you get from this is a better understanding about how hard releasing a product is without leaks, the modularity of the FN 509 platform, and an idea what the 509 Midsize MRD brings to the table.

I guess I should give you some backstory as to how this non-review came about.

Launching A Product Is Freakin’ Hard

If you haven’t noticed, launching a pistol these days seems to be near impossible. As a journalist, I understand the desire to find that scoop where someone leaked the new thing but I also see the other side of the coin where product embargoes allow those same journalists the ability to provide valuable information to consumers at the time a product launches. To be entirely honest, the last successful launch of a gun that I can recall was the Springfield Armory Saint back in 2016. Some manufacturers guard new releases so closely that sometimes they are so focused on preventing leaks the company keeps everything internal until time for it to hit the market.

NOTE: FN America has sent a factory FN 509 Midsize MRD to me for review, I will absolutely be writing a proper review. Until then the Franken509 Midsize MRD spurred some thoughts I felt worth talking about. Besides, the only thing that makes my gun different from the factory Midsize MRD is a tan slide, an Apex trigger, and night sights.

The Franken509 Midsize MRD (R) next to a factory 509 Midsize MRD (L).

I have covered almost every iteration of the FN 509 since it was launched, this makes the first iteration of the platform that I, like everyone else, missed the chance to review under embargo. Normally I am well aware of when a new FN product is about to be dropped onto the market but somehow the FN 509 Midsize MRD not only made it to distributors, but it even made it to retail stores without me being aware of its existence.

The FN 509 Midsize frame from the Franken509 Mid MRD on bottom, factory 509 Mid MRD frame on top.

I want to be very clear about something. The fact that the 509 Midsize MRD launch was so quiet is a direct result of the media’s inability to work with manufacturers. The fault doesn’t fall completely on the media’s shoulders though. While FN has historically done an outstanding job with product launches, there are other companies have been less enjoyable to work with. Heck, some companies could be described as impossible to work with. I am not going to point fingers, but I want to stress that the FN crew has been nothing short of amazing to work with since my introduction to them at a media event for the first iteration of the FN 509 at SHOT 2016.

What it boils down to is the inability of some manufacturers to trust that much of the media want a successful product launch costs the consumer valuable information.

A Zero Round “Review”?

How is it possible? The only reason that I am able to speak with any amount of authority about the FN 509 Midsize MRD is the modularity of the 509 platform. Before you go beating your fists against the keyboard about chassis systems, let’s take a closer look at 509 series.

In a 2019 SHOT Show interview with Miles Vining, FN’s Pistol Product Manager Tom Victa stated that the slide of the previous versions of the FN 509 will interchange with the 509 Midsize. Victa also stated that the 509 family will continue to expand and that new additions will be reverse compatible. Since I have been playing gun legos with the 509 series since the launch of the Tactical, I can attest to Tom’s claim of reverse compatibility.

Swapping slides between the Tactical and the Midsize in an earlier review.

If you recall the review I wrote about the FN 509 Midsize, I showed you that the slides were interchangeable with the Tactical. What I didn’t tell you is that once I learned this prior to the official launch of the midsize, I placed a call to Andrew Henry of Henry Holsters and asked him to come up with an AIWB holster for the FN 509 that was set up for the excellent Streamlight TLR 7. Since the 509 Midsize is effectively the same size as the Glock 19, I started to think about how a factory iteration of the Franken509 Midsize could potentially be close to on par with the highly modified Glock 19 that I generally prefer to carry and surpass an MOS Glock handily.

Andrew and I had a very cryptic conversation where I asked him to make something that had no use to any 509 model he was aware of, he agreed to make it for some reason. Andrew nailed the holster and after adding a pair of Discrete Carry Concepts clips, it proved to be so good that after zeroing the pistol and confirming reliability it became one of two carry guns the I gravitated to depending on how I was dressed.

509 Tactical and Mid MRD slides compared. Note the use of a non-threaded barrel in the Tactical slide.

The result of the experiment was a pistol that I truly feel to be damn near on the same level as the highly modified ATEi Glock 19 pistol I have been carrying at a much more attractive price point. There was also a perfect holster on the market for the 509 Midsize MRD that I suspected would be hitting the market later in the year.

Is It The Best Pistol On The Shelf Today?

Prior to the launch of the FN 509 Midsize MRD, I fully believed the FN 509 Tactical to be the single best all-around off the shelf pistol to hit the market in the last decade. Between the forward-thinking optics mount, the crazy good controls, and accuracy that put most other pistols on the market to shame it wasn’t hard to say about the gun. Once you add in FN’s reputation for brutal R&D that generally results in soldier proof firearms built to take the very worst punishment, the 509 Tactical was a home run in my eyes.

FN used the same outstanding serrations on the Midsize MRD as they have on all 509s to date.

Now that the FN 509 Midsize MRD is a thing and brings everything you get with the Tactical to the table with the exception of the threaded barrel, it looks to be the best handgun on the shelf of your local gun store. I can’t think of a more capable pistol on the market, please let me know if you can think of one because I am drawing a blank. Before you go shooting from the hip, there are several pistols out there that appear to be on par with the 509 series, but nothing truly comes close to the brilliance of FN’s new optic mount.

More Value Than You Expect

To get a sense of why I think the FN 509 Midsize MRD is the best value, we need to take a look at the competitors in the same space. I have long been of the belief that the plate style mounting system found on most optics ready pistols today is less than optimal. It was a great starting point, but it has some large drawbacks like optic height and the plate coming loose from the slide while the optic remains tight due to an error installing the plate.

The cover plate changed on the Midsize MRD to a more traditional style.

Every single optics ready pistol on the market with the exception of the SIG Sauer P320 XCompact uses some variation of the MOS style plate mount. Even though the XCompact comes damned close to being on the same level as the 509 Midsize MRD, the fact that it is limited to DeltaPoint Pro footprint optics from the factory means it falls just short. After all, the Trijicon RMR is the gold standard for a reason.

Now I know that most people don’t modify their carry pistols to the extreme as I have in the past, but for the sake of conversation, let’s take a look at what it would cost to build an FN 509 Midsize MRD that mimics my absurdly expensive but finely machined $2,300 (that hurt to type) Glock 19 Gen 3. I will also spec out a Gen 5 Glock 19 MOS since that is the closest competitor to the Midsize MRD and the defacto pistol that all else is compared to.

A closer look at FN’s optic mount from the 509 Tactical review last year.

Every effort will be made to get the pistol on the same playing field as the others. Even though I generally use a Tenicor SAGAX LUX when carrying the Glock 19, I am going to use the Henry Holsters Glock 19 / TLR 8 holster for the breakdown for the Glock and the FN 509 / TLR 7 holster for the 509 Mid MRD.

FN 509 Midsize MRD:

Base Pistol Cost – $625
Apex Trigger – $142.45
Optic – $220 for Holosun HS407C to $450 for Trijicon RMR RM06 Type 2
Streamlight TLR7 – $111 on Amazon
Henry Holsters FN 509 / TLR 7 Holster – $85
Discreet Carry Concepts Clips Mod 4 Universal – $23.98 for 2
Spare Mag To Bring Total To 3 – $49

Total With Stock Trigger & Holosun – $1,113.98
Total With Apex Trigger & Trijicon RMR – $1,486.43

Glock 19 Gen 5 MOS With Forward Serrations:

Note: Some things like the slide stop and mag catch on the FN 509 Midsize are more like aftermarket parts, we will factor in replacing these with parts that perform identically to keep the pistols on a nearly level playing field. 

Base Pistol Cost – $620
Trigger – $134.95 for Agency
Optic – $220 for Holosun HS407C to $450 for Trijicon RMR RM06 Type 2
Ameriglo Suppressor Sights – $43.99
Vickers Mag Catch – $17.99
Slide Stop – $50 for Kagwerks
Streamlight TLR7 – $111 on Amazon
Henry Holster Glock 19 / TLR 8 Holster – $85
Discreet Carry Concepts Clips Mod 4 Universal – $23.98 for 2

Total With Stock Trigger & Holosun  – $1,171.96
Total With Agency Trigger & Trijicon RMR – $1,536.91

The obvious conclusion is that the FN 509 Midsize MRD has some distinct advantages that make it a winner in the value category. You can put together a P10 C Optics Ready or IWI Masada a bit cheaper, but the P10 C still suffers from the limitations of the MOS style optics mount. I didn’t see the $80 or so savings worth overlooking the plate system limitations.

The Best Factory MRDS Mount Out There

So I mentioned the limitations of the MOS style system found on all other pistols in the same segment with the exception of the SIG P320 XCompact which is cut for the DeltaPoint style footprint, what is the biggest limitation?

The main issue with the MOS style mount is that even when the plate is installed just right it, can be prone to vibrating loose causing the optic to lose zero. You can check the visible screws that secure the dot body to the plate 1,000 times and miss the plate screws coming loose until the dot is loose enough that the deviation is larger than the group you can normally shoot.

Thankfully, FN used all black sights on the Mid MRD.

Depending on skill level, the dot may need to visibly rattle on the slide before you notice the lost zero but I was able to see a shift in zero with a freshly installed ACRO optics plate that was torqued to 15 in-lb and had Vibratite VC3 on the screws holding the plate to the slide. While this may seem like a non-issue, the roughly 0.5-degree rotation of the Aimpoint ACRO which I was able to replicate a 6″ or so deviation in POI by twisting the optic body. The fun thing about the shift? You couldn’t tell the optic was loose.

The Franken509 Midsize MRD was shot with the Aimpoint ACRO, Trijicon RMR, Holosun HS407C, and the Leupold DeltaPoint Pro. I ended up settling on the Trijicon RMR for my use as a carry gun. The housing of the RMR is less bulky making concealment easier when carrying AIWB but I would be perfectly happy with the Holosun if I was looking for a more cost-effective solution.

With the exception of the new cover plate, flatter trigger face, and standard mag release you might mistake this for a black 509 Tactical.

I really like the ability to run whatever optic I want with no worry about the red dot coming loose from the slide with the exception of the ACRO which forces an MOS style attachment with either Apex Tactical’s ACRO plate or the one the FN America ACRO plates that will be on the market soon.

Addressing Perceived Problems

Now there have been some limited reports of strikers breaking and while I don’t mean to be dismissive of those reports, I have three separate FN 509s with more rounds through them cumulatively than the average gun owner puts through firearms of any kind in a 20-year period without a single parts breakage. The Tactical slide and internals that I will be showing you in this review has north of 12,000 rounds of 9mm through it in one configuration or another and is still going strong.

Aside from the striker, there is a lot of talk about hydro locking when the pistol has been submerged in water. Personally, I don’t feel it is an issue since the demonstrater often either tries to shoot the pistol far faster than the average person could draw a firearm or even retrieve it from water and aim the gun.

The internals appear to be identical on the Franken509 and the 509 Mid MRD.

Now, if these perceived problems are an issue for you, there is a fix. Apex’s Heavy Duty striker should fix the hydro locking issue because it has two cuts at 3 and 9 ‘o’clock that when combined with the cuts at noon and 6 o’clock should function like Glock’s maritime spring cups. When I get my Apex striker installed in one of my 509 slides that is absolutely something I intend to test.

Time On The Range

I presume that the FN 509 Midsize shoots exactly like the non-optics ready Midsize that we already reviewed. In fact, I suspect that the Midsize MRD shoots identical to the Franken509 that I put together since I only spotted two changes between it and the factory Midsize MRD I detail stripped at a local gun store. The Midsize MRD uses all-black sights (which I would personally prefer) and the Midsize MRD uses a more conventional cover plate design than the Tactical’s cover with the rear sight protection wings.

As I said before, a FN 509 Midsize MRD has been shipped to my FFL for a proper review. As soon as I get it in hand an RMR and TLR 7 will be mounted and the testing process will begin. 

The 509 line’s largest downside is the absurdly expensive magazines.

So, how does the Franken509 shoot? Like a modern 4″ optics ready pistol with a compact grip. The slide is super easy to manipulate thanks to the standard reduced power recoil spring and the best slide serrations I have seen on a factory pistol. Since the components are the same as they use in the 509 Midsize and 509 Tactical there is no question in my mind that the pistol will be perfectly reliable just as the Franken509 Mid MRD was.

I lost track of how many rounds the Franken509 Midsize MRD saw, but it was a lot and I didn’t experience a malfunction. When I get the factory Midsize MRD in for review proper round tracking will be part of the review.


When I was told that the FN 509 Midsize was coming, I asked FN if I could get it with a tactical slide before I even saw the pistol. Unfortunately for me, FN was selling Tacticals like crazy at the time so I used the slide off of my 509 Tactical. I am super thankful that the Midsize MRD is out, now I can stop reconfiguring my Tactical slide every other week to test a new part.

From the top, the two slides look nearly identical.

The sad reality is that the FN 509 Midsize MRD will likely be overlooked by many because gun store employees are often undertrained on the pros and cons of the products they are selling. While many other industries ensure their employees are well trained on the product, for some reason the gun industry routinely expects their salespeople to educate their self which rarely happens. The fact that not a single gun store employee I spoke with understood how different the new FN mounting system is and the benefits of it make me think that undereducation is going to stifle sales of this fantastic pistol.

The controls on the Midsize frame are near perfect out of the box for me. The trigger is a bit stiff, but I find it easy to stage.

The other hurdle to the 509 platform is the magazine prices, they must drop so that high magazine prices are no longer an objection for potential buyers. With left-leaning lawmakers relentlessly pushing one form of ban or another, the ability to stock up on as many mags as possible is absolutely a point of consideration that FN should revisit. A $49 magazine is absurd. If Smith & Wesson, CZ-USA, and Springfield Armory can all keep their mag cost about $35 or less, there is no reason FN can’t.

Where To Find More Info

The FN 509 Midsize MRD carries an MSRP of $799 but I was able to locate the pistol pretty easily for $625 to $650 at online retailers. Look for more information and specs on the FN 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 FirearmRack.com as well as on the YouTube channel Firearm Rack or Instagram at @thepatrickroberts.

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“$2300.00” spent on a Glock 19?

“A fool and his money be soon at debate,
which after with sorrow repents him too late.”
Thomas Tusser


tl;dr;dh (didn’t happen)

Wild Bill

@Patrick Roberts, What the hell is Agg even saying?


It’s too bad that the trigger lbs and slide retraction of the G19 5 and the MRD weren’t compared. Even w/o shooting, that would be helpful. Since he shot the earlier pistol, listing those results, and saying that he expected something similar, would also be helpful.

Facts are always better than opinions, to me!!


I was wondering when FN would come out with this. Fortunately or unfortunately I bought the Midsize when they first came out. I only paid $399, such a deal! Then the tactical was released and I thought that the cost was too high andBut I wanted to put a red dot on and started to add up all the costs. I wonder if I should trade in my non- MRD and get this one?