What internal safety feature prevents the M9 service pistol from firing fully automatic?

The disconnector is an essential internal safety feature in the M9 service pistol that prevents the firearm from firing automatically. It plays a crucial role in ensuring that the pistol operates in semi-automatic mode. When the trigger is pulled, the disconnector allows the hammer to fall and strike the firing pin, but it also ensures that the trigger can only release the sear for one shot at a time. After the trigger is released, the disconnector resets, preventing the hammer from being released again until the trigger is pulled once more.

This mechanism is vital for controlling the firing cycle, maintaining the intended operation of the pistol as a semi-automatic firearm rather than allowing it to function as a fully automatic weapon, which could pose significant safety risks and make it difficult for the shooter to maintain accuracy and control.