The FN 509 Compact is a 9mm DAO pistol with a 3.70-inch barrel, 10+1 capacity, and a polymer frame. At 25.50 oz it is on the heavier side for a compact, but that weight contributes to a controlled shooting feel. HiViz front sights and low-profile rear sights aid quick target acquisition. The black serrated steel slide and polymer frame are straightforward for a working carry gun. 
 

Key Specifications 

• Model: FN 509C 
• Caliber: 9mm Luger 
• Barrel Length: 3.70 inches 
• Overall Length: 6.80 inches 
• Capacity: 10+1 rounds 
• Weight: 25.50 oz 
• Action Type: DAO (Double Action Only) 
• Finish Color: Black 
• Frame Material: Polymer 
• Slide Material: Serrated Steel 
• Sights Configuration: HiViz Front & Low Profile Rear Sights 
• Safety Feature: Loaded Chamber Indicator 
   

Features 

 
The HiViz front sight gives a bright aiming point in varied lighting, and the loaded chamber indicator provides a visual confirmation of chamber status. The interchangeable backstrap system lets you adjust grip size. FN's striker-fired DAO system requires no manual decocker and gives a consistent pull every shot. The slim profile at 6.80 inches overall is reasonable for concealed carry.

The FN 509C is well-regarded for its ergonomics and overall feel in hand. Owners regularly mention comfortable grip geometry and the HiViz sights as practical upgrades over plain black sights. Reliability across ammunition types gets positive marks in most reviews.

The weight at 25.50 oz unloaded is the most common point of hesitation -- it is heavier than sub-compact competitors like the SIG P365. Some buyers also mention that the 10+1 standard capacity feels modest given the gun's size. Pricing is discussed too, with a few reviewers noting it sits higher than comparable options. For buyers who prioritize the FN build quality and the bright sights, those concerns tend not to be dealbreakers.