Two interchangeable backstraps

Two 15-round magazines

Owner’s manual

Locking device

FN logo soft pistol case

FN 509 Midsize MRD 9mm 66-100587

Out of Stock


New in box and with soft case. Two 15 rd. capacity magazines. 4 in. cold hammer forged barrel. Trigger pull 5.5-7.5lb. Ambidextrous magazine and slide releases. Optics ready. Ships with two additional backstraps. Lock and manual also included.

MDR Stands for Mini Red Dot

Your EDC just got better with the all-new FN 509® Midsize MRD.

This evolution of the FN 509 Midsize, now featuring the FN Low Profile Optics Mounting System, gives you the option of direct mounting more than 10 different miniature red dot optics to your concealed carry pistol. The FN 509 Midsize MRD features a four-inch barrel and slide with optics mounting package, a midsized frame, standard 15-round capacity and is compatible with larger capacity FN 509 magazines with use of a sleeve. The improved controls aid in manipulation, the new improved texturing on the two included backstraps provides better recoil management, and a new flatter faced trigger allows for more controllable trigger press and cleaner break.


  • Caliber: 9mm
  • Operation: Double-action
  • Mag Capacity: 15 Rd.
  • Weight: 26.5 oz.
  • Barrel Length: 4.0"
  • Overall Length: 7.4"
  • Twist Rate: 1:10" RH
  • Height: 5.2"
  • Width: 1.35"
  • Trigger Pull: 5.5 - 7.5 lb.
  • Sight Radius: 5.79"

Primary Features

Full-sized performance in a concealed carry package

Striker-fired autoloader

Double-action operation

Fully ambidextrous controls

FN Low Profile Optics Mounting System with plate adapters for direct mounting of more than 10 optics

All-black co-witness iron sights



Easily racked, combat-style sights

External extractor; loaded chamber indicator

Improved front and rear cocking serrations



Cold hammer-forged stainless steel

Recessed target crown

Polished chamber and feed ramp



Polymer construction with replaceable steel frame/slide rails

Enhanced grip textures which enables faster follow-up shots in all conditions

Interchangeable backstraps

MIL-STD-1913 accessory mounting rail

Improved flatter face trigger



Fully ambidextrous slide stop lever and magazine release



High visibility, low-friction follower; polymer base with black finish

Compatible with FN 509 17-round and 24-round
magazines with appropriate magazine sleeves



Two interchangeable backstraps

Two 15-round magazines

Owner’s manual

Locking device

FN logo soft pistol case


Condition: New
Manufacturer: FN America
Model: 509 MRD
Caliber: 9mm Luger
SKU: 845737010737
MPN: 66-100587
UPC: 845737010737
Vendor: Gunprime
Reviews (6)
By EM on 10/09/20
Good experience

Fair price and quick delivery.

By Jonathan Oertle on 09/29/20
Great firearm, great service!

First off, the service at Gunprime was top notch, I had my new FN 509 Midsize in less than a week, which is saying a lot during these times. The firearm itself is more than expected. Super smooth action, great trigger, and perfect ergonomics. Fits like a glove, with great texturing. Fired 100 rounds flawlessly and accurately. Couldn’t be happier!

User uploaded images:

By Ozzy on 09/01/20
Awesome experience

This review is more geared towards GunPrime than it is towards the FN509. Although the FN509 is a great handgun, there is not a lot to brag about than people don't already know. Nevertheless, the communication and customer service from GunPrime is second to none. Not only they gave a fair price but the shipping was lightning fast and kept updated all the way. In addition, they already had my preferred FFL on file which was a huge plus. Thank you GunPrime, this won't be my last transaction with you.

By Tyler on 08/25/20
Best experience in long time.

What drew me to this site was the pricing on this firearm. The sale was better than anywhere else. They shipped very quickly as well. Very smooth transaction. I will be purchasing from them in the future. The gun was flawless and in perfect condition. They responded to my question very quickly as well.

By EL on 07/16/20
Love the FN 509

I have been through Glock’s, SIGs, S&Ws and now have this FN 509. The FN is my favorite. Installed an Apex trigger and striker, added a Trijicon RMR, and swapped out the suppressor height sights for the regular 509 sights (I’m not a fan of the cowitness). Feels great in the hand, acquires picture quickly and shoots great. Thanks for the great price, Gunprime.

By DBank57 on 06/16/20
I love this pistol

I am totally satisfied with this pistol. I shot five major brands of tier one striker fired pistols when making my decision on my purchase. My best grouping was with a 509 Tactical. I chose the 509 Midsize MRD for my EDC. It hides well carrying IWB and packs 15+1. I have owned my 509 for three months now and have taken two pistol shooting courses so during those courses plus range time I have run over 2500 rounds through this pistol with not one malfunction or misfire. It runs like a high dollar pocket watch. When I first began shooting this pistol I inadvertently dropped a couple mags out of it while firing. I discovered the pad of the first knuckle on my trigger finger was depressing the mag release on the right side. Once I determined the cause it has not happened again. I recommend this pistol without reservation. I got a great deal through Gunprime and will continue using them for purchasing firearms.

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