The FN 509 LS Edge is a full-size semi-automatic pistol chambered in 9mm Luger with a 5-inch barrel and DAO action. It ships with the Vortex Viper Red Dot already mounted, which is a meaningful inclusion at this price point. 
 

Key Specifications 

• Model: FN 509 LS Edge 
• Caliber: 9mm Luger 
• Barrel Length: 5 inches 
• Capacity: 10+1 rounds 
• Weight: 31 oz (approximately 1.94 lbs) 
• Overall Length: 8.20 inches 
• Frame Material: Polymer with a matte black finish 
• Action Type: Semi-Automatic (DAO) 
• Safety Features: Ambidextrous controls; no manual safety 
• Sight Configuration: Fiber optic front sight and blackout notch rear sight 
   

Features 

The extended slide is longer than a standard 509, which helps with recoil management and gives you a longer sight radius before you even factor in the optic. The Vortex Viper Red Dot mounts via FN's proprietary system on the slide. The flat-face trigger breaks at 90 degrees with a clean pull, which suits shooters who prefer that geometry over a curved trigger shoe. 
 
Textured interchangeable backstraps let you adjust grip circumference to fit your hand. The fiber optic front with blackout notch rear still works as a backup if the optic goes dark. No manual safety — the DAO action and ambidextrous controls handle the safety side.

The FN 509 LS Edge gets consistently good marks for ergonomics and build quality. Shooters like the grip texture and how balanced the gun feels in hand, and the Vortex Red Dot inclusion draws frequent praise for the practical benefit it adds to target acquisition speed.

The fiber optic sights are appreciated as a backup to the red dot and for shooters who want to transition between the two. For competition use, the combination works well and the pistol handles dynamic scenarios cleanly.

The main criticisms come down to weight — with the red dot mounted, some shooters find it heavier than similar-class pistols — and price, which is on the higher end. Aftermarket support is reasonably good but some owners wish for more options specific to this model. Adjusting to red dot shooting on a pistol takes time for those new to the setup, which is worth mentioning for buyers coming off iron-sight-only guns.