The FN 509 Midsize Tactical is a semi-automatic pistol chambered in 9mm Luger, built around a striker-fired action and sized between FN's compact and full-size 509 variants. The threaded 4.5-inch barrel accepts suppressors and standard muzzle devices without adapters, the optics-ready slide is machined for RMR-footprint red dots, and tritium night sights come installed from the factory so the gun is usable in low light right out of the box. 
 

Key Specifications 

• UPC: 845737017392 
• Caliber: 9MM LUGER (9X19 PARA) 
• Action: Striker Fired 
• Capacity: 24 Rounds 
• Barrel Length: 4.5 inches 
• Weight: 1.7 lbs (26.5 oz.) 
• Sights: Tritium Night Sights 
• Optic Mount: RMR Compatible 
• Muzzle Type: Threaded for Suppressor Use 
• Finish: Flat Dark Earth (FDE) 
   

Features 

 
The striker-fired mechanism gives a consistent trigger pull shot to shot. At 24+1 capacity the magazines hold more rounds than most duty-size pistols in the same caliber. Ambidextrous controls and interchangeable backstraps let left- and right-handed shooters dial in the grip without aftermarket parts. The FDE finish resists corrosion and everyday wear. 
 
At 26.5 oz. unloaded the gun is on the heavier side for a midsize frame, which suits range and home-defense use better than all-day concealed carry. That weight does absorb recoil well, and the 4.5-inch barrel extracts a bit more velocity from 9mm loads than a shorter compact would.

The FN 509 Tactical draws consistent praise for build quality and reliability — FN Herstal's track record with military contracts carries weight here, and the pistol's fit and finish back it up. Shooters frequently call out the ergonomics: the grip texture, control placement, and backstrap options make it comfortable to run for extended sessions.

The night sights and suppressor-ready barrel are the most talked-about selling points. Owners who run cans appreciate that the threading is done at the factory, and the RMR-cut slide means no gunsmithing to mount a red dot.

The main criticism is size and weight. At over 26 oz. unloaded, it's harder to justify for concealed carry when slimmer options exist. Magazine compatibility and availability also come up occasionally, though this tends to vary by region and market conditions.

Overall sentiment leans positive. Most owners treat it as a home-defense or range gun and are happy with that role. Those who wanted a suppressor host or an optics-ready duty pistol tend to be especially satisfied.