A paintball marker for launching a paintball using a bolt with an internal impact ring for contacting a power tube sized to fit within the bolt. The power tube has an internal gas passage for supplying launching gas to the paintball and an external striking surface that is contacted by the bolt's impact ring. A main seal is positioned selectively seal the internal passage of the power tube from a gas supply. Movement of the bolt causes the impact ring to contact the striking surface to unseat the power tube from the main seal to release gas from the main gas chamber through the internal passage into the breach to launch the paintball.