The FN 509 is a semi-automatic, locked-breach pistol. With the chamber and magazine loaded, the pistol will fire a single shot each time the trigger is pulled until the magazine and chamber are empty. The slide will remain locked to the rear after the last cartridge is fired.
The FN 509 is equipped with four passive safety systems to prevent the pistol from firing unless the trigger is pulled and the slide and barrel are in the locked position.
The Striker Block prevents the tip of the striker from protruding from the breach face unless the trigger has been pulled to the rear (Figure 25).
The Drop Safety prevents the sear from moving down out of engagement with the striker unless the trigger has been pulled to the rear (Figure 26).
The Trigger Disconnect Safety is actuated when the disconnect cam is pushed out of alignment with the sear preventing the sear from releasing the striker. This safety feature prevents the pistol from firing out of battery (Figure 27).
The Trigger Safety remains engaged unless the shooter’s finger is on the trigger and blocks the rearward movement of the trigger, preventing the trigger from moving rearward under inertia should the pistol be dropped (Figure 28).
Some FN 509 pistols may be equipped with a manually activated safety that prevents the pistol from firing unless it is deactivated.
On FN 509 pistols equipped with a manual safety the safety levers will be located near the rear of the frame.
When the safety levers are moved to the up position, the safety is engaged and blocks the movement of the sear carrier and trigger assembly.
When the safety levers are moved down the red dot indicating that the pistol will fire is exposed and the firing mechanism is free to operate.
The safety lever is retained in the selected position by a detent and will snap into location when engaged or disengaged.
If the pistol is equipped with a safety, it is recommended that the safety be disengaged only when ready to fire the pistol or for disassembly.
FIELD STRIP (DISASSEMBLY FOR NORMAL MAINTENANCE)
1. Completely unload the pistol and remove the magazine. Inspect the chamber and the magazine well to verify that the pistol is completely unloaded (Figure 38).
2. Retract the slide and lock it in its rearward position using the slide stop (Figure 39).
3. Remove the thread protector or muzzle device if the pistol is equipped with a threaded barrel (Figure 40).
4. Rotate the takedown lever approximately 100 deg. clockwise (Figure 41).
5. While holding the slide with one hand, release the slide from the slide stop and ease it forward (Figure 42).
6. While keeping the rear of the slide and rear of the frame in alignment, point the muzzle in a safe direction and press the trigger to release the striker. The slide will move forward slightly when released (Figure 43).
7. After releasing the striker, you can remove the slide by pulling the slide forward and away from the frame. If the striker is inadvertently recocked, return to Step 5 (Figure 44).
8. Hold the slide upside down, grasp the small spring of the recoil spring assembly then lift the recoil spring assembly up and out of the slide (Figure 45).
9. Remove the thread protector or muzzle device if the pistol is equipped with a threaded barrel
10. Grasp the barrel by its lug, lift it up and around the extractor and slide the barrel rearward out of the slide (Figure 46).
REASSEMBLY FROM THE FIELD STRIPPED CONDITION
1. Install the barrel into the slide by grasping the lug of the barrel and sliding the muzzle of the barrel through the barrel hole in the slide from the inside. Allow the barrel to drop down into the slide and slide the barrel back to the breach face until the barrel drops into the locked position (Figure 47).
2. Install the thread protector or muzzle device if the pistol is equipped with a threaded barrel (Figure 48)
3. Place the large end of the recoil spring assembly against the recess in the front of the slide. Compress the recoil spring assembly and slide the back of the recoil spring guide onto the recess until centered on the front of the barrel lug (Figure 49).
4. Guide the slide and barrel assembly onto the frame and pull the slide to its rearmost position and lock the slide to the rear using the slide stop (Figure 50).
5. Rotate the takedown lever upward locking the frame and slide together (Figure 51).
6. Release the slide and allow it to travel forward. Test the functions of the pistol to ensure the slide stop, trigger, magazine release and manual safety, if provided, are functioning correctly (Figure 52).