The FN 509 Midsize MRD pistol in 9mm and black finish (brand part no. 66-100587) trims the full-size 509 down to a midsize frame while keeping the mini red dot optics mounting system, giving shooters a more concealable platform with red-dot compatibility. FN America builds the pistol with a 4-inch barrel and co-witness iron sights that align with a mounted red dot. The double-action-only trigger runs with no manual safety, and two 15-round magazines plus a soft pistol case ship with the pistol. Among optic-ready semi-auto handguns, this 509 Midsize configuration favors carry and duty shooters who want higher capacity in a smaller frame.

Key Specifications

• The chambering is 9mm.
• The capacity is 15+1 rounds.
• The barrel measures 4 inches.
• The slide is optic ready and serrated, with co-witness iron sights.
• The trigger action is double-action-only, with no manual safety.
• Two 15-round magazines and a soft pistol case ship with the pistol.
• The unloaded weight is 26.5 ounces.
• The rifling twist rate is 1:10-inch.
• Overall length measures 11.5 inches.

Frequently Asked Questions

Do the iron sights co-witness with a red dot? Yes, the co-witness iron sights align with a mounted optic.

How does this compare to the full-size 509? The Midsize trims frame dimensions for better concealment while keeping the optic-ready slide.

Buy the FN 509 Midsize MRD Pistol, 15-Round

Higher capacity in a more concealable midsize frame is exactly what this 509 delivers. Order it from our Lubbock, Texas gun shop for fast, insured shipping to your FFL.