The FN 509 Midsize Tactical is a striker-fired semi-automatic pistol chambered in 9mm Luger (9x19 Para). It has a 4.5-inch threaded barrel, 10+1 round capacity, and weighs 1.74 lbs. The slide is optics-ready (MRD Ready) and the pistol ships with suppressor-height three-dot night sights. Finish is matte black with black interchangeable backstraps. 
 

Key Specifications 

• Brand: FN 
• Model: 509 Midsize Tactical 
• Caliber: 9mm Luger (9x19 Para) 
• Action: Striker Fire 
• Capacity: 10+1 Rounds 
• Barrel Length: 4.5 inches (Threaded) 
• Weight: 1.74 lbs 
• Finish: Matte Black 
• Grip Type: Black Interchangeable Backstrap 
   

Features 

 
The striker-fire action delivers a consistent pull on every shot. The threaded 4.5-inch barrel allows direct suppressor attachment. Suppressor-height three-dot night sights remain visible above most cans and work in low-light conditions without a light source. The MRD-ready slide accepts micro red dot optics directly without additional milling. Interchangeable backstraps let users adjust grip thickness for different hand sizes. The midsize frame hits a balance between concealability and the longer sight radius of a full-size pistol. 
 

Usage 

 
The 509 Midsize Tactical is aimed at users who want a suppressor-ready platform without modification. The 4.5-inch threaded barrel, night sights, and optics-ready slide make it suited for home defense, nighttime range use, and tactical applications. At 1.74 lbs it's manageable for all-day carry, though the midsize frame is thicker than a slim-line carry pistol.

The FN 509 Midsize Tactical gets consistently positive reviews. Ergonomics are the most praised trait — the grip fits a range of hand sizes, the texture holds up during extended sessions, and interchangeable backstraps let owners dial in the fit. Accuracy gets strong marks, with owners reporting tight groups at distance for a striker-fired pistol. The threaded barrel for suppressor use is a major draw, and night sights are appreciated for low-light capability without additional accessories. Reliability across ammunition types is reported as high by most owners.

On the critical side, weight and bulk are the most common concerns for those considering it as a carry pistol — it runs heavier than competing slim-line options. Trigger feel draws some scrutiny, with a portion of owners wanting a crisper break or shorter reset. Holster compatibility is noted as occasionally awkward due to the threaded barrel profile. Price comes up in comparisons to competing 9mm pistols, with some buyers viewing it as a premium over similar-spec guns from other manufacturers.