The FN 509 is a full-size semi-automatic pistol chambered in 9mm Luger with a double action only (DAO) trigger. It carries 10+1 rounds through a 4" cold hammer forged barrel, weighs 26.90 oz, and measures 7.40" overall. The flat dark earth finish is applied to a polymer frame with an interchangeable backstrap system. 
 

Key Specifications 

• Brand: FN 
• Model Name: 509 
• Caliber: 9mm Luger 
• Action: Double Action Only (DAO) 
• Capacity: 10+1 rounds 
• Barrel Length: 4 inches 
• Frame Material: Polymer 
• Grip Type: Standard with interchangeable backstrap options 
• Safety Feature: No manual safety 
• Weight: 26.90 oz (1.68 lbs) 
• Overall Length: 7.40 inches 
• Height: 5.56 inches 
• Width: 1.35 inches 
• Sight Configuration: Three-dot fixed sights 
   

Detailed Features 

The cold hammer forged barrel delivers consistent accuracy and holds up well over high round counts. Interchangeable backstraps let shooters dial in grip fit for different hand sizes. The three-dot fixed sight system is straightforward for fast alignment in dynamic situations. The flat dark earth finish provides corrosion and wear resistance alongside its tactical appearance. 
 
There is no manual safety on this model -- the DAO mechanism itself is the primary operational safety, which some users prefer for simplicity and speed. 
 

Usage 

The FN 509 suits law enforcement and civilian users looking for a reliable 9mm platform. It works for home defense, concealed carry (though its full-size dimensions make this a tradeoff), and competitive or recreational shooting.

User feedback on the FN 509 in flat dark earth centers on a few consistent themes.

Build quality and durability draw frequent positive comment -- owners describe it as solid in the hand and well-constructed. The flat dark earth finish gets credit for its appearance and its tactical practicality. Accuracy is generally rated well, with owners reporting effective performance at both short and longer ranges.

The DAO trigger is a topic that splits users. Those who prefer a consistent, straightforward pull appreciate it for home defense and duty use. Others feel it could be lighter or crisper for precision work and suggest it needs some rounds downrange before it smooths out.

Ergonomics are broadly liked. The grip texture generates some disagreement -- some owners want more texture for better purchase in adverse conditions, while others find it too aggressive for extended range sessions.

Magazine capacity in the 10+1 configuration is seen as competitive with similar pistols in its class. On price, the 509 sits above budget options, and most owners consider the performance worth the cost.