A mechanical linear actuator in an aircraft brake may include a ball nut, a ball screw, and an actuator drive unit housing. The ball screw may rotate to drive the ball nut axially. The ball screw and the actuator drive unit housing may form a series of annular raceways. The ball screw may have a first window corresponding to a first raceway and a second window corresponding to a second raceway. Balls may be inserted into the first raceway through the first window and into the second raceway through the second window.