Semi-auto

Semi-auto (semi-automatic) is a firing mode where the weapon fires one round per trigger pull. After firing, the action cycles on its own – it ejects the spent casing and chambers a fresh round. The shooter must release the trigger and press it again for each follow-up shot.

How semi-auto works

When fired, the slide or bolt travels rearward and then forward. During this cycle, a part called the disconnector comes into play. As the slide moves back (after roughly 2.5 mm of travel), the disconnector separates the trigger from the sear. This prevents the gun from firing again until the shooter releases and re-presses the trigger. The disconnector also blocks firing if the slide is not fully closed – a safety feature that prevents out-of-battery fire.

In airsoft, semi-auto works differently depending on the power source. In electric guns (AEGs), a cutoff lever stops the gearbox after one cycle. In gas blowback pistols (GBB), a mechanical disconnector works much like the one in real firearms.

An experienced shooter can fire 3–6 rounds per second in semi-auto mode.

Related terms: blowback, double action, single action, AEG