Bump-firing is a method of firing a semiautomatic weapon very rapidly, exactly mimicking fully automatic fire. The Colt M1911 semiautomatic pistol is a classic firearm, used as the standard-issue sidearm by the U.S. armed forces from 1911 through 1985. The Colt M1911 semiautomatic pistol can be bump-fired using an improvised tool, but it takes a bit of preparation and practice to perform it well—and to do it safely.
Grip the pistol in your strong hand. Extending your gun arm, aim downrange toward the target as usual. The difference is you'll only have one hand gripping the pistol for bump-firing.
Extend your weak hand out, palm down, next to the pistol. Hold the bump-firing tool--it can be a permanent marker or a wood dowel of similar diameter--horizontally in the fist of this hand like it's a bicycle handlebar, with the writing end of the capped marker pointed away from the gun. Now move your hands together so the the other end of the marker is inserted between the trigger and the trigger guard of the M1911.
Rest the pistol on the marker. Remember that your non-firing hand and arm must be kept rigid, but the firing hand must be kept relaxed, but with a secure enough grip on the pistol for aiming and control.
Push the pistol forward when you're ready to shoot. As you do this, the trigger should be slowly pressed against the rigidly held marker. When the gun fires, don't fight the recoil in your gun hand. The recoil will cause the gun to push back until it hits the rigidly held marker. The gun's trigger guard will then instantly bounce off the marker, forcing the gun back into the trigger, which will fire another round. The cycle will then repeat. With practice, you can empty the magazine downrange in a second or two.
You can also perform this trick just using your off-hand thumb as a substitute for the marker, but it can be a bit more tricky, and possibly injurious to your thumb.
Do not attempt this trick unless your are confident you have a very clear and safe field of fire, as this method of shooting is notoriously inaccurate. Make sure you do not have such a loose grip on the gun that the repeated recoil causes it to come loose from your hand.