To solve the problem in a caseless type gas gun or air gun that the appearance is poor since a bolt, a bolt carrier or a slide is simply modeled after the appearance of an engine part to shield the engine part, the engine part differed in shape from an actual gun is fully exposed even if it is movable, or a cover is attached thereto and, further, a feeding or charging cannot be performed.

When a member such as the bolt, the bolt carrier, or the slide is moved to a bolt-action position, the interlocking of a feeding nozzle for performing feeding by its longitudinal movement in interlocking with a trigger is released by the moving operation to the bolt-action position.