Owner’s Manual 2020

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8. FUNCTION OF THE FN 509
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.
8.1 FIRING CYCLE
When the trigger is pulled the striker block and trigger safety are
disconnected and the striker is released to move forward and strike the
primer of the loaded cartridge, firing the pistol. The energy generated from
the firing of the cartridge moves the slide and barrel rearward, the barrel is
unlocked from the slide after a short distance and stopped. The slide then
continues rearward under inertia compressing the recoil spring and ejecting
the fired cartridge case. As the breach face of the slide passes the back of
the magazine in its rearward travel, the cartridges in the magazine rise
under spring tension until the top round is in contact with the magazine
feed lips. As the slide is returned forward by the recoil spring the top
cartridge is stripped from the magazine by the slide and pushed into the
chamber of the pistol. Releasing the trigger will allow the firing mechanism
to reset and the process can be repeated until the magazine is empty. Upon
firing the pistol with an empty magazine inserted, the magazine follower
will push the slide stop into engagement with slide and lock the slide to the
rear of its travel.
9. FN 509 FEATURES
9.1 PASSIVE SAFETY SYSTEMS
The FN 509 is equipped with four passive safety systems: a striker block;
drop safety; trigger disconnect; and trigger safety lever, 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).