Trigger group for semi-automatic firearms

A trigger group for a firearm, the trigger group comprising:

• a hammer movable between a cocked position and a striking position;
• the hammer being biased toward the striking position;
• the hammer having a first hammer hook;
• the hammer having a second hammer hook;
• a trigger element movable by a user between a rest position and an actuated position;
• a movable sear responsive to movement of the trigger element and operable to engage the first hammer hook to restrain the hammer in the cocked position when the trigger element is in the rest position, and in response to pulling the trigger element to the actuated position to release the hammer to the striking position to discharge the firearm;
• a selector movable between at least a first position, a second position, and a third position;
• a disconnector assembly operably connected to the selector and having first and second hammer retention facilities, each configured to engage the second hammer hook;
• the first hammer retention facility operable when the selector is in the first position to retain the hammer in the cocked position in response to release of the trigger element to the rest position subsequent to discharge of the firearm by pulling the trigger element;
• the second hammer retention facility operable when the selector is in the second position to release the hammer to the striking position in response to release of the trigger element to the rest position subsequent to discharge of the firearm by pulling the trigger element, such that the firearm discharges once per cycle of the trigger element when the selector is in the first position, and twice for each rearward-forward motion sequence of the trigger element when the selector is in the second position;
• and
• the disconnector assembly being operable when the selector is in the third position to prevent discharge of the firearm in response to an application of force on the trigger.