A worn Sear or Bolt will make your gun 'rapid fire' like a machine gun, but too fast for it to work properly. The gun may not stay cocked either. These are both caused by the rear bolt slipping off of the Sear which is supposed to catch it and keep it back in the cocked position.
If either the Sear or rear Bolt is worn, Tippmann suggests replacing both of them at the same time. A worn Sear will wear down a rear bolt faster than normal and vice versa.