F-35’s Gun That Can’t Shoot Straight Adds to Its Roster of Flaws

Add a gun that can’t shoot straight to the problems that dog Lockheed Martin Corp.’s $428 billion F-35 program, including more than 800 software flaws.

The 25mm gun on Air Force models of the Joint Strike Fighter has “unacceptable” accuracy in hitting ground targets and is mounted in housing that’s cracking, the Pentagon’s test office said in its latest assessment of the costliest U.S. weapons system.

A U.S. Air Force F-35A stealth fighter jet

Photographer: SeongJoon Cho/Bloomberg

The annual assessment by Robert Behler, the Defense Department’s director of operational test and evaluation, doesn’t disclose any major new failings in the plane’s flying capabilities. But it flags a long ...