Jeremiah Espino, 52, of Sanger, suffered severe injuries in the April 17 blast and died at a hospital on Monday afternoon, the Fresno County Sheriff's Office said.
The explosion sent 11 people to the hospital, including eight jail inmates who were doing cleanup work at the range and a county employee operating a front-loader. Two other inmates and the county worker are still hospitalized, sheriff's spokesman Tony Botti said.
The blast occurred while the employee was using the front-loader to build a dirt berm to confine gunfire to the range.
The explosion sent flames towering over a nearby highway and warped 400 feet of nearby railway line, shutting down both.
Pacific Gas & Electric Co. has said it appears the employee ruptured its pipeline. But sheriff's officials have disputed that, saying the county equipment operator was smoothing dirt, not digging, near the line and was merely driving on the road near the berm when the line ruptured.
The blast is now being investigated by a host of agencies, including the sheriff's office, the California Public Utilities Commission, PG&E and the Fresno Fire Department.