FN 509 Midsize MRD 9mm Luger 4" 15+1 FDE Semi-Auto Pistol - Optic Ready

The FN 509 Midsize MRD is a striker-fired, double-action-only 9mm Luger service pistol built around a midsized polymer frame and a four-inch recessed-crown barrel. This variant ships with a Flat Dark Earth PVD-coated optic-ready steel slide featuring front and rear serrations, paired with a matching FDE polymer frame machined with an integrated Picatinny accessory rail. The 15+1 capacity lands this midsize offering between the compact FN 509 and the full-size FN 509 Tactical, giving shooters a balance of concealability and shootability comparable to a Glock 19 in overall footprint.

The MRD (Miniature Red Dot) configuration adds the FN Low Profile Optics Mounting System, allowing direct mounting of more than ten popular micro red dots without the need for adapter plates. Black co-witness iron sights come installed from the factory so the pistol is range-ready even before an optic is added. The slide is cut with a precision optic pocket, and the slide plate is easily swapped to match the footprint of the chosen dot.

Fully ambidextrous controls include a reversible magazine release and ambidextrous slide stop levers, making the 509 Midsize MRD equally intuitive for left- and right-handed shooters. There is no manual external safety; instead the pistol relies on its DAO trigger system with a built-in trigger safety for carry. The grip features FDE interchangeable backstraps so the hand fit can be tuned without tools. Overall length is 7.4 inches.

Whether you are looking for a do-it-all defensive pistol, a home-defense platform that will accept a red dot out of the box, or a duty-grade handgun built on FN's combat-proven striker platform, the 509 Midsize MRD delivers the features modern shooters expect in a package sized for daily carry.

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