The FN 509™ is built on the proven architecture of the FNS™ Compact, FN made changes internally and externally to meet the rigorous performance standards of the MHS requirements and further developed the platform into the FN 509 with the help from industry experts. Over the course of development, the platform has been tested extensively for reliability, ammunition compatibility and durability – totaling more than one million rounds.
Standing 5.5″ tall and 7.34″ long with a 4″ barrel, and weighing 25.3 ozs. with an empty magazine, the 509 is a tilting-barrel, locked-breech autoloader with barrel-hood-to-ejection-port lockup. A captive, dual-nested recoil spring assembly returns the slide to battery once the pistol is fired, this configuration being used because it reduces stress on the springs and increases the service life of these parts. The gun’s steel magazines have a standard capacity of 17 rounds, although 10-rounders will be available for those jurisdictions that require them.
The 509 uses a partially pre-cocked, double-action-only striker system, whereby pulling the trigger first completes the process of cocking the striker before disengaging the striker block and releasing the striker to impact the cartridge’s primer. Designed as a duty pistol with military and law enforcement customers in mind, FN calibrated the 509’s trigger to break between 5 lbs., 8 ozs., and 7 lbs., 8 ozs., of pressure—light enough to be easily manageable, but heavy enough to discourage accidental discharges during high-stress situations.