The FN 509 MRD is a full-size 9mm pistol chambered in 9mm Luger (9x19 Para) with a Flat Dark Earth PVD slide finish and black polymer frame. It runs Double Action Only and ships with a 17+1 round capacity. 
 

Key Specifications 

• Brand: FN 
• Model: 509 MRD 
• Caliber: 9mm Luger (9x19 Para) 
• Action: Double Action Only (DAO) 
• Barrel Length: 4.5 inches 
• Overall Length: 7.9 inches 
• Capacity: 17+1 rounds 
• Weight: 27 oz (1.75 lbs) 
• Finish: Flat Dark Earth PVD on the slide; black barrel finish 
• Grip Material: FDE Polymer 
• Sights: Co-Witness Iron Sights 
• Safety Features: No manual safety; fully ambidextrous controls 
   

Detailed Features 

The optics system uses FN's Low Profile Optics Mounting System, which accepts most common red dot footprints without adapter plates. The cold hammer-forged stainless steel barrel has a recessed target crown. Grip texture is aggressive enough for fast strings without being abrasive at rest, and three interchangeable backstraps let you dial in the fit. Both the slide stop lever and magazine release are fully ambidextrous.

The FN 509 MRD in FDE draws a mix of positive and critical feedback.

On the positive side, users consistently cite solid build quality and durable materials. The ergonomics get high marks -- most shooters find it comfortable for extended range sessions. The optic-ready mounting system is a real draw for competitors and tactical shooters who want to run a red dot without extra hardware. Accuracy is frequently noted as a strength, with tight groups reported at typical handgun distances. The 17-round standard capacity is well-regarded for a full-size gun.

The common criticisms: the full-size frame puts it on the heavier end for carry use, and the trigger pull gets mixed reviews -- some shooters find it heavier or less crisp than they'd prefer. Price comes up occasionally, with a few users feeling comparable pistols undercut it. Aftermarket holster and accessory selection is thinner than for higher-volume models like the Glock 17.