A perforation gun includes an external gun barrel in the interior of which perforators are located which can be ignited via a fuse extending through the gun barrel and which, after ignition, pierce the gun barrel with perforation holes. A sliding tube or a swellable two-component foam is provided which automatically closes the perforation holes. The swellable two-component foam can be provided in a cartridge located inside the gun barrel and can be broken up by the ignited fuse, thereby allowing foam to escape from the cartridges, allowing it to swell and obliterate the perforation holes. The sliding tube can be displaced after perforation by an adjusting device by at least the diameter of the perforation hole, the sliding tube being located coaxially between the perforators and the gun barrel.