The FN 509C MRD is a compact 9mm Luger semi-automatic pistol. It has a 3.7-inch cold hammer-forged barrel, holds 10+1 rounds, weighs 25.50 oz (1.6 lbs), and measures 6.8 inches overall. The frame and slide are Flat Dark Earth polymer and steel respectively. Two magazines included. The MRD designation indicates it accepts miniature red dot sights directly. 
 

Key Specifications 

• Brand: FN 
• Model: 509C MRD 
• Caliber: 9mm Luger 
• Action: Double Action Only (DAO) 
• Capacity: 10+1 rounds 
• Barrel Length: 3.7 inches 
• Overall Length: 6.8 inches 
• Weight: 25.50 oz (1.6 lbs) 
• Grip Type: Flat Dark Earth Interchangeable Backstrap 
• Sights: Iron sights with contrast styling 
• Frame Material: Polymer with Flat Dark Earth finish 
• Slide Material/Finish: Flat Dark Earth Steel 
• Includes Magazines: Yes (2 magazines) 
   

Detailed Features 

• Cold Hammer-Forged Barrel: Consistent bore geometry and extended service life. 
• MRD-Compatible Slide: The slide has a direct optic mounting footprint, no adapter plate required for many common red dot sights. 
• Ambidextrous Controls: Magazine release and slide stop work from either side. 
• Interchangeable Backstraps: Three sizes included to fit different hand dimensions. 
• Trigger Pull: Approximately 5.5 to 7.5 lbs, consistent pull weight shot to shot.

The FN 509C MRD in FDE gets solid feedback overall, with a few specific points coming up regularly.

Ergonomics lead the positive comments. The grip texture is described as secure without being abrasive, and the interchangeable backstraps let most shooters dial in a comfortable fit. The compact dimensions carry well, and the balance feels natural for most users. Reliability with common 9mm loads gets consistent praise, and performance at typical defensive and range distances is well-regarded.

The optic-ready slide is a draw for those who want to run a red dot without extra hardware. The ambidextrous controls also come up favorably in discussions from left-handed shooters, who don't always have that option at this price point.

The DAO trigger system is a dividing point. Some shooters prefer the consistency and safety of a DAO pull; others find heavier pull weights tiring over long sessions and wish for a shorter reset. The 10+1 capacity is workable for carry but gets compared to higher-capacity compacts. Aftermarket support exists but is less developed than for Glock or S&W, which comes up when shooters want holster options or custom parts. Price sits slightly above some competitors, though most buyers find it justified by build quality.