An automatic recoiler for converting a firearm into a simulator includes a sealed cylinder with a piston. A piston rod extends from the piston through the rebound chamber and out of the cylinder. A gas block at the end of the rebound chamber has a pressure relieve valve for allowing fluid to enter and exit. The cylinder includes an inlet port in communication with the compression chamber. The piston rod has an end face sized to contact a front surface of the slide for recoiling the slide backward. A power source moves the piston thereby extending the piston rod from the cylinder. A controller controls the power source thereby controlling the extension of the piston rod from the cylinder. Whereby, when a user presses the trigger, the controller controls the power source to move the piston thereby extending the piston rod from the cylinder and recoiling the slide backward.