Gas circuit breaker

A gas circuit breaker comprising:

• a tank filled with an arc extinguishing gas;
• a fixed side arc contact and moving side arc contact in the tank;
• a puffer chamber formed with a puffer cylinder including the moving side arc contact at an end and a fixed piston;
• and
• an insulating nozzle, attached to the end of the puffer cylinder, surrounding the moving side arc contact, that forms a flow channel to guide the arc extinguishing gas from the puffer chamber to the contacts,
• wherein the arc extinguishing gas in the puffer chamber is compressed in accordance with opening operation of the contacts and blown to an arc between the contacts,
• wherein a hollow cylindrical moving side main contact is provided at a breaker part side end of the puffer cylinder,
• wherein a hollow part is provided at a breaker part side end of the hollow cylindrical moving side main contact,
• wherein an end of the insulating nozzle is disposed in the hollow cylindrical moving side main contact,
• wherein the hollow part of the moving side main contact has an engagement member that engages the insulating nozzle, and
• wherein the engagement member has a long hole in which a position of the engagement member in the hollow part is adjustable in a diameter direction of the insulating nozzle.