Abstract: A semiautomatic firearm having a rotating cylinder is provided. The cylinder has a plurality of chambers adapted to receive a cartridge and is rotatingly supported in a housing by a cylinder pin whereby each of the chambers of the cylinder is positionable in one of a loading position, a firing position, and an ejecting position. The cylinder pin is reciprocally movable between a retracted position wherein the cylinder pin is disengaged from a firing mechanism and an extended position wherein the cylinder pin engages the firing mechanism so as to cock the firing mechanism. The cylinder pin is movable from the retracted position to the extended position in response to gas pressure generated by the firing of a cartridge disposed in the chamber of the cylinder positioned in the firing position acting on the cylinder pin so as to move the cylinder pin from the retracted position to the extended position.