A method of operating a gas operated automatic or semi-automatic weapon that has a bolt that locks by a partial rotation of the bolt with respect to a bolt carrier, the bolt carrier in communication with a gas port on the barrel of the weapon, the method comprising utilizing the gas pressure from a cartridge received from a port in the barrel to unlock the bolt, and utilizing the expansion of a telescoping cartridge in the chamber to recycle the weapon after the bolt is unlocked. In embodiments the cartridge is a 5.56 mm cartridge. In embodiments, the propellant driving the projectile does not provide enough gas pressure to recycle the weapon and the telescoping cartridge supplements the needed power for recycling sufficient to accomplish the recycling. The invention include the telescoping cartridge providing a projectile with lethal energy and recycle capability for gas operated rifles. The subsonic cartridge may have at least 80 ft lbs of energy and operates subsonically.