Abstract: A self-locking telescoping device including an outer tube, an inner tube telescoped into the outer tube having a cone-shaped ramp at an inboard end, and a plurality of metal spheres between the ramp and the outer tube. The metal spheres wedge between the ramp and the outer tube when the inner tube is thrust into the outer tube in a collapse direction thereby locking the tubes together. When the thrust is attributable to a severe impact, the spheres plastically deform the outer tube by plowing tracks therein thereby to absorb energy. The self-locking telescoping device further includes an actuator rod, a driver which translates the actuator in the collapse direction and in an expansion direction, a first clutch which translates the inner tube with the actuator rod in the expansion direction, a second clutch which translates the inner tube with the actuator rod in the collapse direction, and a tubular retainer on the actuator rod having a plurality of closed-ended slots around the metal spheres.