Why can a submachine gun fire bullets continuously? What is its power?

Submachine guns are generally fired by the hammer striking the firing pin. Power: 1. Gas-guided type, which uses the gas fired from the bullet to push the piston through the gas tube to drive the bolt movement. 2. Bolt-recoup type: directly uses the recoil force of the bullet fired to drive the bolt movement: the bolt moves backward and unlocks. Pull out the cartridge case, reset the hammer, and then move forward under the action of the recoil spring, grab the bullet and push it into the gun chamber, lock it, and prepare for the next firing cycle (closed chamber and ready to fire). When the chamber is open and ready to fire, the bolt is recoiled. Without resetting, wait until the trigger is pulled, then grab the bullet, push the gun into the chamber, and lock the shot.