A circuit interrupting device has a stationary contact. A movable contact is carried by a movable double-walled conductive tube which is telescoped and electrically continuous with a stationary tube. The tubes carry all of the current through the device. A piston carried by the stationary tube defines a piston-cylinder with the movable tube. When the movable tube moves to open the contacts, the piston-cylinder forces dielectric gas to and past the gap therebetween. In a two-gap version of the device the stationary tube is also double-walled and carries a second stationary contact. A piston carried by the movable tube defines a piston-cylinder with the stationary tube. When a second movable contact jointly moves with the first movable contact to open the contact pairs, both piston cylinders force dielectric gas to and past both gaps.