Abstract: A method seals a projectile having a wall against propellant charge gas pressure occurring during firing of the projectile. A propellant charge is ignited and the projectile is acted upon from the outside by the propellant charge gas pressure. In order reliably to seal the projectile, during the firing thereof, against penetration by propellant charge gas from the outside into the interior thereof, it is proposed that a contact connection of an electrical interface arranged in a channel in the wall is moved in the channel by the propellant charge gas pressure and presses a seal into a sealing seat.