How an AR-15 Trigger Works: Standard vs FRT vs Binary, in 3D

Three parts on two pins do the work. The hammer sits on the rear pin under spring tension, held back by the trigger's sear on the front pin. Pull the trigger and the sear slips off the hammer's hook; the hammer swings up and strikes the firing pin through the bottom of the bolt carrier.

As the carrier runs back it rolls the hammer down again. Your finger is still on the trigger, so a small spring loaded hook on top of it, the disconnector, catches the hammer. Let the trigger forward and the disconnector hands the hammer back to the sear. That handoff is the reset you feel and hear. See the most picked ones in the AR-15 trigger guide.

A forced reset trigger drops the disconnector. Instead, as the carrier rolls the hammer back, the hammer pushes the trigger forward into its reset against your finger. A locking bar, worked by the carrier, holds the trigger there until the bolt is fully home, so it can't fire out of battery.

When the bar lets go, a shooter who is still pressing pulls the trigger again and the rifle fires again. Each shot still takes its own function of the trigger, which is the argument the makers won in the 2025 settlement with the Department of Justice. It needs a full auto profile carrier to work the bar, and usually a heavier buffer. Check what your rifle needs in the FRT and binary trigger picker and whether your state allows one in FRT legality by state.

A binary trigger adds a third selector position. In it, a second sear catches the hammer after the shot on the pull, and lets it go when you release the trigger, so the rifle fires once each way. In semi auto it behaves like a standard trigger, and safe is still safe.

It works with any standard carrier. Remember the release fires: if you change your mind with the trigger held back, switch to semi before you let go, which most models are built to allow. See which states ban them in binary triggers by state and how the three compare in FRT vs binary vs Super Safety.