The FN 509 Tactical is a semi-automatic 9mm Luger pistol with a 4.5-inch threaded barrel, 10+1 capacity, and a Flat Dark Earth finish. It weighs 27.9 oz and runs a 12-inch overall length. Fixed 3-dot night sights are standard, and the optic-ready slide accepts common red dot mounts. The barrel is threaded at 1/2"-28 tpi for suppressors and muzzle devices. 
 
Key Specifications 

• Brand: FN 
• Model Name: 509T (Tactical) 
• Caliber: 9mm Luger 
• Action Type: DA/SA (Double/Single Action) 
• Capacity: 10+1 rounds 
• Barrel Length: 4.5 inches 
• Overall Length: 12 inches 
• Weight: 27.9 oz 
• Sights: Fixed 3-Dot Night Sights 
• Grip Type: FDE Interchangeable Backstrap 
• Finish Color: Flat Dark Earth (FDE) 
• Condition: New in Box 
   
  Detailed Features 
   
  The threaded 1/2"-28 tpi barrel allows direct attachment of suppressors and compensators without an adapter. The optic-ready slide has machined cuts for direct mounting of red dot sights, which eliminates adapter plates and keeps the optic low. Fixed 3-dot night sights remain usable in low-light conditions with or without a suppressor. The FDE interchangeable backstrap adjusts grip circumference to fit different hand sizes. A Picatinny rail below the frame accepts lights and lasers. The polymer frame keeps the pistol at 27.9 oz without sacrificing durability.

The FN 509 Tactical FDE with night sights and threaded barrel draws solid feedback for its build quality and accuracy. The threaded barrel is a standout feature for suppressor-compatible configurations, and the 3-dot night sights add low-light capability that owners find practically useful. Most users describe the grip as comfortable and the controls as intuitive for both newer and experienced shooters.

The main criticisms are weight and trigger. At 27.9 oz it runs heavier than compact pistols, which is a relevant factor for extended carry. The trigger pull is described by some as heavier or grittier than comparable options, prompting a few owners to seek aftermarket trigger work. Pricing gets weighed against alternatives, though most buyers in this category consider it fair for the feature set. Holster availability and aftermarket accessories specific to the 509 platform are occasionally noted as more limited than for more common platforms.