An onboard combustion-gas-powered engine supplies power to a paintball marker or other projectile launcher by generating gas pressure pulses for propelling paintballs and other projectiles. The combustion gases produced by the engine can be allowed to rise in pressure within a confined volume of space before being released through a valve into a barrel for applying enhanced pressure pulses to the projectiles. A loading system is linked to a combustion accelerating system for automatically loading projectiles into the launcher.