GatCrankRapidfire Trigger Actuator. Fires Three Shots Per Revolution.
Works on AR-15, AK-47, 10/22, and others.
Another common modification is the so-called gat crank, where this small silver crank is inserted into the trigger mechanism of a semiautomatic weapon, making it act like a fully automatic one.PBS
A simple bolt-on device, which allows the attached firearm to be fired by turning the crank. … it is highly effective for rapid-fire. Federal officials only consider a gun automatic ― and thus illegal to own without government clearances ― if it can fire multiple rounds with a pull of the trigger. That definition allows such devices, which do not involve physically pulling the trigger, to skirt current regulations.Huffington Post
A “trigger crank” or “gat crank” attaches onto the trigger guard, and the shooter then rotates the crank, which will the pull the trigger about 3x per rotation. … You can’t modify the internal components of the gun to make it fully automatic, but these workaround accessories are perfectly legal.Time