A magazine and tube dispensing method is provided. The magazine includes a receiving compartment for temporarily receiving unfilled tubes intended for filling with a flowable product, the compartment being formed with a movable outer rail wall. A gate assembly downstream from the receiving compartment includes a constriction passageway formed between a lateral inner wall and a lateral member wall allowing downward gravity feed of tubes only in a single file. The lateral member wall is movable in a direction toward or away from the lateral inner wall and integrally movable as a member of the outer rail wall, thereby adjusting a cross-sectional dimension of the passageway to accommodate processing of different diameter tubes.